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Preliminary Biology Topic 4
EVOLU LUT TION OF AUS AUST TRALIAN BIO BIOT TA
What hat is this t his topi t opic c abou about? t? To To keep it as sim simple as po possi ssib ble, le, (K.I.S.S.) K.I.S.S.) this topic involve lves th the stu study of: 1. PLATE TECTONICS & THE FORMATION OF AUSTRALIA 2. EVOLUTION IN AUSTRALIA 3. ADAPTATIONS FOR REPRODUCTION 4. MAINTAINING BIODIVERSITY
but firs f irst, t, an introd int roduct uction ion.... More on Evolution...
Plate Tectonics & Moving Continents You may already be aware that a map of the world would not always have looked as it does today.
In the previous topic you learned some of the “ Facts Facts of Evoluti on” ... ... the evidence evidence that life on Earth Earth has changed over million s of years. years.
The science sci ence of Plate Tectonics ectonic s has revealed revealed that the Earth’s crust is made up of a number of separate “plates” which slowly move the continents about, splitting up and colliding over millions of years.
In this topic you will learn about the process of “ Natural Natural Selection” Selection” which is believed believed to be the driving force that causes evolution evolution to happen
? In this topic you y ou will consider some of the evidence evidence for the moving continents, conti nents, and and learn learn how Australia Aust ralia came to be the “island continent”.
Au A u s t r ali al i a’s Uni Un i q u e Bi B iota “ Biota” means means all the plants (“ (“ Flora”) and animals animals (“Fauna” (“Fauna” ) of a particular region. You already know that Australia’s native plants and animals are sometimes cute, sometimes deadly deadly dangerous dangerous and always i nteresting nteresting for their unique appearance and habits. In this topic you will find out a little about some of the earlier inhabitants of Australia, and what happened to them. You will also study s ome of the ways that our biota is superbly adapted adapted to A ustralia’s harsh and unpredictable cli mate. mate. 1 -2
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CONCEP CONCEPT T DIAGRAM DIAGRAM (“ Mind Map” ) OF TOPI TOPIC C Some students find that memorising the OUTLINE of a topic helps them learn and remember the concepts and and important facts. As you proc eed eed through th e topic, come back back to thi s page regularly regularly to see how each each bit fits t he whole. At the th e end of th e no tes yo u w il l fi nd a bl ank versi ver si on of th is “ Min d Map ” to pract pr act is e on . Evidence for fo r Plate Tectonics
Changing Ideas Ideas abou t Au st ral ian An imals im als
The Evid Evid ence for Climate Change
Structure of the Earth
Natural Selection, Variation and Evolution
Plate Tectonics & the Formation of Australia
Evolution of Au st . Plants Pl ants
Evolution in Australia
EVOLUTION o f AUSTRA A USTRAL L IAN IA N B IOTA IOTA
Megafauna & Extinction
As exu al v Sexual Sexu al Mitosis v Meiosis External v Internal Fertilization
Ad aptat ap tatii o n s f o r Reproduction
Maintaining Biodiversity
Case Study Study : Extinction of the Thylacine
When Asexual Reproduction is Useful
Value o f Biodiversity
How Palaeontology Can Help -2
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Reproductive Ad aptat ions io ns of Au st ral ian An im als
Reproductive Ad aptat io ns of Au st ral ian Plants
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1. PLATE TECTONICS & THE FORMATION OF AUSTRALIA The Stru ctu re of th e Earth Earth Seismology Seismology is the study of earthquakes earthquakes and and the behaviour behaviour of t he shock waves they they produce. During the 20th 20th century, seismology revealed revealed that the Earth Earth is not a soli d ball of rock, but made up of a number of layers. -S
Furthermore, we have come to realize that the crust is not a single solid “skin” on the outside of the Earth. Earth. Rather, Rather, it has fractured int o about a dozen dozen “ plates” wh ich slide around as as the mantle currents push from below. Since they are all touc hing o n the surface of a sphere, as the plates move they must: • move apart from each other o r, r, • s lili de de s id id ew ew ay ay s pas t eac h o th th er er o r, • c o l l id id e w i t h ea eac h ot ot h er. -F As plates move apart, apart, new
of higher density rock
of lower density rocks
rock fills the gap, creating a “mid-ocean ridge”
Ocean Solid iron & nickel
Liquid iron & nickel
C
nen t t in Con t i
We now know that the outer layer, the “crust” is not tightly attached to the “mantle” below it. Also, the mantle is not rigid and solid, but “plastic”, and can slowly flow in huge convection currents that are bringing heat energy outward from the Earth’s core. These convection currents push against the crust.
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push crust plates apart
As th e plates pl ates move, mo ve, th ey carry car ry th e co ntin nt inents ents , and the crust under the oceans, oceans, with them.
Au A u s t r alia al ia was n ’ t alway al way s t h e island continent of today.
The Evidence for Plate Tectonics The Shape Shape of th e Cont Cont inents The continents of the Earth are like jigsaw puzzle pieces... pieces... they fit togeth er quite well, especially along the lines of the “continental shelf” rather than the actual coastline.
Edge of continental shelf
Africa India
Modern coastlines
The continental shelf is the true edge of each each cont inent. In In most cases cases it is under w ater today. Antarctica South America
The evidence evidence sug gests that abou t 130 milli on years years ago all the southern cont inents (pl us Indi a, New New Zealand Zealand and New New Guin ea) ea) were join ed togeth er in a si ngle super-continent called “ Gondwana” Gondwana” . Forces Forces under the crust, however, caused Gondwana to begin to break apart. -2
a i l a r t s
Moving at a rate of a few cm per y ear, ear, Gondwana broke apart and the fragments moved gradually gradually to t heir modern-day modern-day positi ons. 3
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The Mid-Ocean Mid-Ocean Ridges It’s not just t he shapes shapes of the continents that convince scientists of “ Continental Continental Drift” . On On the ocean ocean floo rs, under several kilometers of water, the mid-ocean ridges show strong evidence of sea-floor spreading where plates are moving apart. The rocks of the parallel ridges are youngest in the middle and get progressively older as you move outward.
In a few places on Earth, spreading zones are visible on dry land too. The “ Great Great African Rift Rift Valle Valley” y” is a spreading spreading zone which will one day make most of east east Afric a into an island.
Symmetrical patterns patterns of magnetism on either side of central rif t
Parallel undersea ridges Central Rift
Youngest rocks
Older rocks
The Rift Valley contains many deep lakes between parallel escarpments. There There are several active v olcanoes, and the area is an acti ve earth earth quake zone.
Older rocks
New molten rock fills the rif t
The “ residual magnetism” magnetism” in the rocks (which was aligned as the rock hardened from molten lava) shows a symmetry on either side of the central ridge. Each matching band of magnetism r epresents a lin e of new rock formed as the crust plates moved apart. Later, these bands were separated by even newer rock injected from below as the crust plates continued to move.
Fossil Evidence for Moving Continents Continents The distribution of certain fossils gives us more evidence of the moving continents. One particular fossil is a plant called Glossopteris. It has been been disc overed overed in rocks in many parts of the southern hemisphere, including Antarctica. Africa
A numb nu mber er o f ani mal fo ss il s, dat ing in g f rom ro m 100-200 million years ago, have been found only in S.America & Africa, or in Africa, India & Au st ral ia. The c ro co di l e-li e-l i ke Mes os aur us is known from fossil s in Africa & South America. America.
Oz
These places are now w idely s eparated, eparated, and it is very unlikely th at these plants plants or animals could cross an ocean. The explanation is that these organisms l ived in a united Gondwana, Gondwana, and their fossils have been separated by later continental movement.
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India
South America
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Evidence from Distribution of Modern Species There are some living species which show th e same same pattern pattern of di stribut ion as the fossils such as Glossopteris.
Marsupial mammals which are found only in Australia, New Guinea & Am eri ca. (Fos si ls are fo un d in Af r ic a) An t arc t ic Beec h trees found only in Au st r ali a & Sout Sou t h Am eri ca (& fo ss il s in An tarct tar ct ic a).
Lungfish Flightless birds
Marsupials
Large flightless birds; birds ; emu, ostrich, rhea & the recently extinct moa (New Zealand) & elephant bird (Madagascar).
Antarctic beech
The explanation is that these groups evolved in Gondwana, and then were carried to their current locations by the drifting continents.
Freshwate Freshwaterr lungfi sh in Australia, Africa & S.America.
The BreakBreak-up up of Gond ondwana wana Is Australia Still Moving? Ap parentl paren tl y s o! The ocean o cean fl oors oo rs hav e now no w b een well mapped so we know where the mid-ocean ridges are. The positions of frequent earthquakes and active volcanoes identify the plate boundaries. The volcanic islands to our north indicate that this is a “ collis ion zone” zone” between between the IndoIndo Au st ralian ral ian plate pl ate an d the th e As ian pl ate.
India Africa
How fast is the movement? movement? Australia South America
Antarctica Antarc tica
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It averages between 2-5 cm per year. This means about 50km per million years. As volcanoes add to the islands, and the plate slides north, it is likely you will be able to walk to China in 5-10 million years... but you’ll have to clim b over some serious serious mountains!
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Changing Ideas deas About Ab out Australian Anim als When When the first specimen of a platypus platypus was sent sent back to England after after the European European settlement settlement of Aust ralia, it w as thought to be a hoax. The platypus seemed an impossible animal, with a duck-like bill, fur like an otter, webbed webbed feet and a sharp, sharp, poisono us spur on its leg. That perception is changing. Fossil discoveries in South America of platypus-like animals prove that monotremes did not just evolve in Au st r ali a, but b ut i n wi der Gon dw ana.
It was eventually accepted as real, but when it became known that it reproduced by laying eggs, it and the echidna were classif ied int o a separate separate sub-class of mammals... the “Monotremes”.
For more than a century, the monotremes were considered as “ living fossils” fossils” and thought to be extremely “ primitive primitive”” and therefore, somehow inferior to mainstream placental mammals.
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Furthermore, the more research is done on the platypus and other native Australians animals, the mor e scientis ts realize that th ese are are not “ primit ive” creatures. creatures. Yes, they have have an an ancient lineage, but they are highly adapted to the unpredictable Australian climate, and have thrived through millions of years of ecological changes in one of the harshest harshest environm ents on Earth.
The marsupials were thought to b e only slightly more advanced, and the consensus was that Australian fauna, like the nation itself, was a bit “backward”.
It was thought that the only reason such “primitives” had survived into the modern era, was because Australia had been isolated so that they faced no competition from superior, more advanced mammals.
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They had already faced competition competition from “advanced” placental mammals mammals before Au st ral ia bec ame iso lated... lated... and they won!
Au st r ali an nati n ati ve pl p l ants ant s an d an im als are now being seen as ancient, but highly sophisticated life forms.
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Work sheet 1
Plate Plate Tectoni cs & Aust ralia’s Formation
Fill in the blank spaces The study of earthquakes is called a).................................. This science has revealed revealed that t he Earth Earth has a number o f layers. On the outside is a thin b)....................... and under it is the thick c)....... c)........... ....... ....... ........ ...... .. The crust cr ust is fr actured actu red into a number of d)...................... which can slide around, driven by e).................... currents in the mantle. This whole concept is referred to as “ Plate Plat e f).................... f)............................. ...........” ..”
More evidence for plate movement comes from fossils such as the plant r)......... r)............ ....... ........ ....... ....... ....... ... Its fossi fo ssi ls are f ound ou nd on all southern continents and India. The explanation is that it lived in areas right across s)....................................., and the fossils have been separated by plate movement. The distribution of some modern species can also be explained by continental drift. Marsupials are found in Australia and t)................................. Lungfish are in Australia, u)........................ and ................................ Other examples are the v)................................ (e.g. emu, ostrich) and th e w)..................... w)..................... ............. ................... ...... tr ee.
The continents fit together like jig-saw pieces, especially if you fit them along their thei r g)....... g)........... ....... ....... ........ ....... ..... .. shelf sh elf rath er t han coastline. The continents of Australia, Af r ic a, h)........... h). ...................., .........., .................... .......... ................ ...... and .................................... were once connected forming the super-continent i)...............................
The ancestors of each of these groups are thought to have lived throughout Gondwana, and the various populations were separated separated when th e plates moved.
From about 75 MYA MYA i)......... i)............. ........ ........ ....... ....... ...... began to break up forming the separate continents of today. Australia separated from fr om j)......... j)............. ........ ........ ........ ...... about abo ut 40 MYA MYA and spent k)................ million years totally isolated. It It was in this time that many of Au st ral ia’s ia’ s pl ants ant s and ani mal s evol evo l ved from Gondwanan Gondwanan ancestors. ancestors.
Au A u s t r al i a i s c u r r ent en t l y b ein ei n g c ar r i ed x)........................ (direction) on the y)..................... y)............................. ................ ................. ............ ... p late lat e at a speed sp eed of about z)..... z)......... ........ ....... ... cm p er year y ear.. Au st ral ian nat i ve ani mal s are mai nl y aa).................................. (pouched) plus the platypus and ab)............................... whic wh ich h are egg -layin g ac)....... ac)........... ........ ........ ........ ....... ...
Evidence for “Continental Drift” includes the l).................................. ridges, found along th e ocean ocean floors all around the Earth. These are zones where crustal plates are m).................... m)............................. .............. ..... The ocean-fl oc ean-fl oor oo r crust sho ws a series series of ridges which are youngest n)........................... and get older as you go further in each direction. The rocks show matching patterns of o).......................... on either side of the central rift. As the plates move apart, new crust is formed from p)............................... coming up from the th e q).................... q)............................ ..........
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They were con sidered si dered ad)...... ad).......... ........ ....... ....... ....... ... and inferior to placentals, but are now being seen as ancient, but highly ae)..................................
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Work sheet 2 Practi Practi ce Questi Questi ons section 1 Multiple Choice Longer Response Questions Mark values given are suggestions only, and are to give you an idea of how detailed an answer is appropriate. appropriate. Answer in the spaces spaces provided.
1. The movement movement of t he “ Tectonic Plates” Plates” is driven by: A. the th e pl ates push pu sh ing in g o n eac h o th er. B. movements movements of t he liquid core. C. thrusting of earthquakes earthquakes at pl ate boundaries. D. convection currents in the mantle.
5. (4 marks) Indentify and describe TWO pieces of evidence that support the assertion that Australia was once part of a larger landmass called Gondwana.
2. Which present-day landmass was NOT part of Gondwana? A. India Ind ia B. Europe C. New Zealand D. Africa
6. (3 marks) Outline how the ideas of scientists about Au st ral ian speci sp eci es, such su ch as th e p lat ypus yp us , hav e changed ov er the past 200 years. years.
3. Of the following, the youngest youngest rocks would be found: A. near the th e cent c entre re o f a mi d-ocean d-o cean ri dge. dg e. B. at the conti nental nental sh elf. C. on the ocean floor, well away from the mid-ocean ridge. D. under folded cont inental inental mo untains.
4. The distribution of fossils of the plant Glossopteris provide evidence that: A. plant pl ant seeds seed s can drif dr iftt acros acr oss s an o cean and survive. B. the southern c ontinents were once all jo ined in ed t ogeth og eth er. C. dinosaurs were widespread in Gondwana. D. modern Australian plants evolved from Glossopteris.
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7. (3 marks) The “ ratites” are a family of flight less birds such as the emu, emu, ostrich and kiwi . None of this group are native to the northern hemisphere, but are found throughout the south. Being flightless, and poor swimmers, it is impossible that they spread spread by crossi ng the oceans. Ac coun co untt for fo r their th eir presenc pr esenc e on all the th e maj or landmasses landmasses of the southern hemisphere. hemisphere.
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2. EV EVOLUTIO LUTION N IN AUST AUSTRALIA RALIA Natural Selection & Evolution
How Natur Natur al Selection Selection Works
Th e f ac ac t t h at at l if i f e o n Ea Ear t h h as as undergone a sequence of changes was dealt dealt wit h in the previous topic. The scientific theory to explain explain how and and why evolution occurs all hinges on the concept of “ Natural Natural Selection” Selection” , and and the key key to this is the “ variation” variation” within each each species... the simple fact that individuals are not the same as each other. “Natural Selection” refers to the way that the conditions of nature constantly select who survives and who dies. If survival depends depends on sp eed eed to r un from a predator, then the faster individuals survive and the slower ones get eaten. In a drought those plants with slightly thicker cuticle on their leaves conserve water and survive, while others die.
The Impor Impor tance of Variation It is vital vital for the on-going survival of a species that it has variation among the individuals of the population.
It may seem seem as as if Evoluti Evoluti on is an intelligent force which directs organisms in an appropriate direction. In our fictitious population of animals, the climate became became colder and it would seem that some evolutionary force caused an appropriate change in the population... they became squat & hairy to conserve body heat better.
When changes occur in the environment, a species with a lot of variation has more chance to survive, because out of all the different “types” there is a good chance that at least some will sur vive to breed breed and continue the species.
But of course “squat” and “hairy” were already in the population. They simply became more common, and finally predominant, because these types survived in greater numbers and reproduced to pass on their characteristics to their offspring.
A sp eci es wi th li tt l e var iat io n wi th in i t, might have no survivors from an environmental change, and become extinct. What constitutes an environmental change? It could be... • a change change of c lim ate. • a new disease, predator or competitor in t he ecosystem. ecosystem. • a change in availability of a food resource, or any other factor. -2
Evolution is not intelligent. Nature selects the survivors from the different “types” available. Survivors breed... if you’re dead, you can’t reproduce! 9
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Evolution volut ion of o f Australian Australian Biota Over the past 100 100 mill ion years years Au st r ali a has h as go ne fr om bei ng part of Gondwana to a separate island continent...
The Sclerophyl l Plants Scleropylls are those plants which are adapted to dry climates. They are characterized by thin, small leaves with a very thick waxy cuticle and are very resistant resistant to drying out. In drought, when other leaves would wilt and wither, scleropyll leaves maintain their shape, and when water is available again they quickly regain their normal functioning.
India Africa
Australia South America
Au st r ali an f lo ra to day is do mi nat ed by three main main scl erophyll typ es: • Eucalypt Eucalypt (Gum (Gum trees) trees) • Banksia Banksia (Bottle brush and and Gre Grevillia) villia) • Acacia (Wattle (Wattle & mul ga)
Antarctica Antarctica
... so t here has been been a lot of environmental change, ... and a lot of evolution!
The Evid Evid ence for Climate Change Change Fossils dated dated betwee between n 50-1 50-100 00 million years old show that most of central Au st ral ia was on ce co ver ed by l us h forests. Some of the common plants included the seedseed-fern fern Glossopt Glossopt eris and the rainforest rainforest species “ Antarctic Beech”. This proves that at that time much of Au st ral ia (and mu ch of Gon dw ana) had a much wett er cli mate than today. When sea-levels rose about 40 million years ago, parts of central Australia were covered by an inland sea.
Fossils of leaves and pollen in New Zealand and South America show that the Eucalypts and Banksias were already Gondwana inhabitants befor e 50 50 million years ago, but must have been relatively rare and unimportant during the time of the great rainforests in Au st r ali a.
An A n i m al f o s s i l s i n c l u d e t h o s e o f crocodiles, flamingos and tortoises which indicate extensive water environments.
However, as the climate dried the rainforest plants (like Antarctic Beech) struggled and the sclerophylls thrived. Ab ou t 25 mi ll i on year s ago sc l ero ph yl l pollens suddenly become very common in the fossil record.
As Gon dw ana sp li t up , and Au st r ali a moved north, the climate gradually became drier. The evidence is the appearance appearance in the foss il r ecord, at about about 25 million years ago, of sclerophyll plants beoming beoming very comm on. -2
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From 2 MYA MYA to Today Today
Ad A d apt ap t ati at i o ns o f B ank an k s ias t o Fir e
By about 2 million years ago, the rainforests had lost the battle west of the Great Dividing Range. Central Au A u s t r al i a w as par t l y d eser es er t environment, with open gr asslands asslands and sclerophyll forests surrounding the deserts. The rainforests still dominated the mountains and many valleys along the east coast.
The Banksia plants of Western Australi a are more “ primi tive” and resemble resemble the fossil s and their modern day Gondwana Gondwana relatives in South Africa and New Zealand. In Eastern Australia the Banksias are more distantly related and there are many different species, with many different ways of dealing with fire in their environment. This seems seems t o be the result of natural selection acting on the variations that were present in ancestral Banksia populations.
The sclerophyll forests contained eucalypts, banksia and acacia and a number of other types such as Casuarinas. Then about 100,000 years ago another environmental factor changed... fire became more common. We find layers of charcoal and ash in the sediments from these times. Presumably, the fires were initially caused by lightnin g strikes in the dry bushland, but after about 40,000 years ago the evidence for fire becomes even more noticeable.
Some adaptations to cope with fire are: • Thick, corky bark with epicormic buds underneath. The buds are stimulated by fire, and so the blackened trunk soon sprouts new shoots after a fire. • Lignotub Lignotube ers - thicke thickene ned d roots, roots, from which new shoots sprout after fire destroys everything above ground.
We think the Aboriginal people had arrived by then, and and part of their cul ture was to deliberately set fires. They knew that fire encouraged encouraged the growth of m ore open grassland, which attracted more grazing animals (e.g. large kangaroos) and this meant better hunting for the people.
• Ha Hard, wood woody y see seed pods (“ Banksi Banksia a men” ) which split op en after after being being scorched by fire, dropping seeds into the fertile ashes and germinate rapidly after after any sli ght r ain.
Fire also also altered the composition of th e sclerophyll woodlands. Some of the sclerophyll plants (especially Banksia) can surv ive and regenerate regenerate quickl y after fire. They became more common. Others, such as Casuarina do not survive fire as well, and became less comm on. Today Today,, the Casuarin Casuarin as (“ sheoaks” ) are are common i n swampy areas, areas, and along creek margins where fires have less less im pact, but th ey are are no lon ger a dominant type in the bush as they once were.
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Meanwhile, the Animals... When Australia became isolated from other Gondwana fragments about 40 millio n years ago its fauna was dominated by the marsupials (pouched mammals) and reptiles.
There were also many other species of huge kangaroos, wombats, snakes and crocodiles, but it seems that Australia’s megafauna were not as big as in o ther parts parts of t he world, possibly because the developing sclerophyll flora, and the ancient, poor soils could not support as much biomass as (say) Europe.
As happen hap pened ed in many parts part s of the th e worl wo rl d in the th e past 20-30 million years, some animals evolved to be very, very large... large... the “ megafauna” . In the Northern Hemisphere it was species like mammoth, sabre-tooth cats and huge rhin oceros species. In Aust ralia, the megafauna included:
It is also notable that the top predators seemed to be reptiles rather than mammals. One plausible theory is that reptiles, which do not need need to constantly “ burn” food to maintain maintain body temperature, need less food and can eat less often. Reptiles can survive as top predators in food pyramids that contain less total biomass. A mammal predator needs to eat more often and needs needs a food pyramid containing more biomass.
• Diprotodon Diprotodon - a 2 tonne wombat wombat relative. • Procoptodon Procoptodon - a 3 metre tall tall kangaroo. kangaroo. • Megalania Megalania - a 7 metre, 1,00 1,000 0 kg g oanna.
What Happened to t o t he Megafauna? Megafauna?
In Europe, Asia and North & South America there is convinci ng evidence that humans contr ibuted to the extinction of t he large mammals. mammals. Climate Climate change at at t he end of the last “ Ice-Age Ice-Age”” probably helped too, but there is no doubt that early early humans hunted large mammals, like the mammoth, in large numbers.
Human-Ca Human-Caused used Extin cti on?
Climate Change Change Exti Exti nct ion?
In Australia, most of t he megafauna megafauna species disappeared between 35,000 and 10,000 years years ago. Aborigines were well established by thos e times and and undoub tably lived at the same tim e as these mega-species. However, there is no evidence of them hunting these species... no animal bones in human camp sites, no tool cuts on the animal bones.
Perhaps Perhaps the megafauna megafauna just co uld not cope with the climate changes, including the severe cooling and drying duri ng the last i ce-age ce-age? ? But then, these animals, and their forebears had survived many previous ic e-age e-ages s ov er 25 million years. The most recent ice-age ice-age was not as severe as some previous. We await more evidence to settle this debate!
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A Timel Tim elii n e of o f A u s t r ali al i an Evo Ev o l u t i o n ary ar y His Hi s t o r y -
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Charles Charles Darwi Darwin n and Evolu tio nary Theory Theory
In the 1830 1830’s ’s a young Englis h natur alist, Charles Darwin, sailed around the world on board the navy survey ship HMS Beagle. He studied the plants and animals, and and ro cks and fo ssils in many places, especially in South America. He became convinced that life on Earth had changed, and was capable of evolving by Natural Selection. He devoted devoted his life to developing developing his t heory, heory, and collecting more evidence to support his ideas. He knew that his theory would not be readily accepted accepted by the conservative society society of the time.
The Huxley - Wilberforce Debat Debate e of 1860 1860
Darwin in Aust ralia On its journey around the world, the Beagle called into Sydney, and Darwin spent time ashore, travelling overland to Bathurst and collecting and studying Austr Aus tralia’s alia’s flora fl ora and fauna. f auna.
Darwin published his evidence and ideas on evolution in 1859, but it took some time for people to become aware of th em. On On fir st r eading eading , Darwin’s Darwin’s i deas are not easy to absorb and fully understand, so it took time for the theory to “ sink-in” . To To this d ay, ay, it remains one of the least understood of all the major theories of Science.
He noted how well suited the plants were to the dry Australian climate. He was later to link this to his idea of Natural Selection, explaining the sclerophyll characteristics as adaptations adaptations to t o the cli mate. He also noticed similarities between some Australian plants and species he had seen in S.America and in Africa. He could not explain this except by seeds drifting across oceans, and he carried out many experiments immersing plant seeds in sea-water to test if it was possible.
One of th e events events that foc used attentio n on thi s new theory w as a famous famous d ebate ebate at Oxford University in 1860. The main speakers were Thomas Huxley, who argued the case for Darwin’s theory, and Archbishop Samuel Willberforce who was vehemently opposed to it, on both scientific and religious grounds.
(He (He had no knowledge of “ Continental Continental Drift” .)
He was fascinated by the marsupial fauna, fauna, but considered them as as “ inferior” to the placental mammals of other continents, and believed they had only survived because of lack of competition from “ real” real” mammals. mammals.
It has generally been considered that Huxley got the better of the debate and this event helped establish the Theory of Evolution as a credible credible scientific idea. idea. Probably Probably w hat was more important was that the debate sparked interest in evolution among scientists and led to much more study, experiment and debate over the following years. 150 years later we are still researching and learning about the evolution of life on Earth.
In terms of evolution he believed the marsupials were bound to lose the “ Survival of the Fittest” co mpetition and would eventually eventually b ecome extinct. extinct. The city of Darwin, Northern Territory, was named named in his his honour. -2
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Worksheet orksheet 3 Evolution volu tion in Australia Fill in the blanks spaces. When the natural environment “chooses” which organisms survive to reproduce, and which do not, we say that a)................................................ is at work. The more b)................................... among the members of a species, the better better ch ance the species species has to survive when wh en c).................... c)............................. ................. ............ .... ............. .............
Ab A b o u t 100,000 100, 000 y ear s ago ag o a n ew enviro nmental factor became imp ortant... s).................... At first it was probably start ed by t)......... t)............. ........ ........ ....... ...... ... but later t he Ab or ig in al peo pl e set it del i ber atel y in or der to u)..................... u)............................. ................ ................ ............... ....... which improved hunting. Regular fires altered the balance of the different plant types: the v)................................. became less common, while fire resistant types became predominant.
We know that Australia was largely covered by rainforest between 50-100 MYA, because of fossils of d)....................................... (seed fern) and e)...................................... Beech. At one time central Australia was covered by an inland f)...................... Animal fossils, including g)........................................ indicate many water environments.
Some of the adaptations shown by Banksias Banksias to cope with fire include w).............................. which are thickened roots which sprout new shoots after after fir e, and x)............................. seed pods which release release seeds seeds on ly after fi re.
Au A u s t r al i a s epar ep ar at ed fr om h)................................... about i)................ MYA, and became totally isolated. As it drifted north the climate gradually became bec ame j)..................... j).............................. ............... ...... By abou t k)..... k)........ ..... ..... ...... ..... .. MY MYA the fo ssil pol len fr om l)....................................... plants becomes common. Sclerophylls are characterized by m)............................ leaves with a thick n)............................ which resists water loss. The main three types are o)............................, ............................ and ................ ........................ ................. ........... Two of th ese ty pes evolved in Gondwana, but the p)........................ probably came from As ia.
The animal life, or y)......................, was dominated by reptiles and z).................................. (type of mammal). Some very large animals, collectively known as aa)................................ evolved. The largest was a 2-tonne relative of the wombat called ab)...................................... Al A l l t h e m egaf eg af aun au n a b ec ame am e ext ex t i n c t between 35,000-10,000 years ago. It may be their extinction was caused by ac)........................ .............................. or simply that they could not cope with ad)..............................................................
By 2 MYA, most of Australia was dominated by q)........................................ forest with rainforest only remaining along the mountains and the r)........................ coast.
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Charles Darwin studied the Australian biota during his voyage on HMS ae)........................... in the 1830’s. He noted how well adapted to the climate the af)................................. were and linked that to his theory of evolution by ag)........................... ............................ However, he thought the animals were ah).................................... and believed they would soon become ai)....................................... in competition with aj)....................................... mammals.
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Workshee ork sheett 4 Practice ractic e Questions uestio ns secti secti on 2 Multiple Choice
Longer Response Questions An sw er o n back, bac k, if in suff su ff ic ient ien t spac e.
1. “ Natural Natural Selection” Selection” is the process when: A. li vi ng thin th in gs ch ange to su it th eir environment. B. the organisms with “ better” characteristics characteristics live longer. C. the conditi ons of t he environment environment determine determine which “ variations” surv ive. D. the surviving i ndividuals are the ones which breeed.
9. (2 marks) Identify Identify the relationship relationship betwee between n variations within a species and the chances of survival of the species, when the environment changes.
2. For long-term survival of a species, it is an advantage to have: A. a lo t of geneti gen eti c variat var iat ions io ns in the th e po pulat pu lat ion. io n. B. a lot of indiv iduals who are very similar. C. a lot of very large and and stro ng indiv iduals D. a fast-changing environment.
10. (5 marks) Discuss the changes that occurred to the Au st ralian ral ian cl im ate, and to the th e fl ora or a ov er t he past 50 million years. In your answer, describe the evidence for the changes you describe.
3. The fossil evidence shows that 50-100 MYA most of Aus tralia was was covered by: A. desert des ert B. ocean C. rainforest D. sclerophyll forests 4.Which of the following would considered a sclerophyll plant? A. Red g um B. Golden wattle C. Bottle-brush D. Morton Bay fig
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11. (5 marks ) a) How would you identify a plant as a “sclerophyll”?
b) Identify two common types of sclerophylls in the modern Australian flora.
5. According to the fossil evidence, the sclerophyll plants became became signifi cant members of Australian flora about: A. 2 MYA MYA B. 25 MYA MYA C. 40 MYA D. 100 MYA
12. (4 marks) a) Identify a member of Aust ralia’s extinc t “ megafa megafauna una”” known from its fossils.
6. A significant significant factor factor in the Australia Australian n environm ent for the past 100,00 100,000 0 years has been: A. wi despr des pread ead r ain fores fo res t. B. fire. C. an inland sea. D. heavy rain and flooding.
b) List s imilarities and diff erences erences between between the named example in (a) (a) and any any related livin g species.
7. A “ lignotuber” is an adapta adaptation tion of the Banksia Banksia plants to help them: A. repro rep rodu duce ce as exuall exu all y B. attract pollinating animals C. survive a bushfire D. achieve internal fertilization.
13. (4 marks) Discuss Charles Charles Darwin’s observations of Au st ralian ral ian biot bi ota a and rel ate t hese hes e to t o h is theor th eory y of evolution.
8. Aus tralia’s “ megafauna” were not as as large as the megafauna that evolved in other parts of the world. One One possible explanation explanation for this is: A. human hu mans s hunt hu nted ed an d ki ll ed t he l argest arg est ones. on es. B. the larger larger animals could not outrun fi res. C. being marsupials, they grew more slowly. D. the soils and plant life could not suppo rt so much biomass. -2
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3. ADAPT ADAPTATIONS ATIONS FOR REPRODUC REPRODUCTION TION As A s ex exu u al Rep Reprr o d u c t i o n Unicellular Unice llular Re Reproduct product ion
As A s ex exual ual Rep Reprr o d uc t io n in Multicellular Life
Single-celled organisms such as bacteria reproduce by simply dividing in two by mitosi s. The offspring cells are genetically genetically identical to each other, other, and and to t he “ parent parent cell” .
Many multi-cellular organisms are able to reproduce asexually.
Fungi , such as mushrooms, reproduce by releasing releasing “ spores” . Each Each spore is a single cell which can grow into a new fungus. The spore cells are produced by mitosi s, and release released d from a singl e “ parent” parent” .
Regardless of the details, asexual asexual reproducti on always: always:
Many Plants can reproduce asexually by sending sending out “ runners” runners” .
• requires only one parent. • involves mitosis cell division. • produces offspring which are genetically genetically identical to the parent and to each other.
Ad A d v ant age Ase A sex x ual ua l repr re pr od uc t i on c an pr od uc e larg la rg e numbers of off spring qu ickly, to take advantage advantage of a sudden or temporary increase in some environmental environmental resource such as food.
Disadvantage By producing genetically identical offspring, there is less less varia variation tion in the population. population. If an environmental change occurs, a low-variation species is at at risk of extinction.
These same plants can also reproduce sexually sexually with their flowers.
Sexual Repro Reproduc ductio tion n Sexual Sexual reproduction always always in volves 2 parents parents who com bine part part of t heir genetic genetic information t o produce offspri ng which are different different to both parents. parents.
Male Parent
Female Parent
v ( v v
v
meiosis
Zygote
Embryo
(first cell of the offspring)
(developing offspring)
Ad v an antt ag age e
Disadvantage
Sexual Sexual reproduction produces more variation in a population, by mixing genes in new combinations. This helps a species survive when environments change. -2
Sexual Sexual reproduction is mo re complex, and often takes more time and energy to achieve. 17
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External and Internal Fertili Fertili sation Sexual Sexual reproduction always always inv olves the process of fertilisation... when egg egg and sperm sperm fuse together together forming one new cell (the (the “ zygote” zygote” ) which con tains tains genetic information f rom bot h parents. parents. For fertilisation to oc cur, the sperm cells must swi m to th e egg. egg.
External Fertilisation
Each species may have some str ategy to ensure that male and female parents release their gametes at the same time and in the same place:
Organisms such as corals and sponges release gametes when a certain “ environmental environmental trigger” trigger” occurs, such as a full Moon, or an especially especially high tide.
Most fish species have have “mating rit uals” and visual signals wh ich st imulate a mating pair to release gametes tog ether.
Either way, external fertilisation is to some extent a “hit -and-miss” -and-miss” strategy, strategy, often involving millions of gametes, gametes, many of whi ch are wasted. wasted.
For organisms that live in water, fertilisation is generally achieved by both parents simply releasing eggs and sperm into the water environment. Since fertilisation occurs outside the orga organisms’ nisms’ bodie bodies, s, this this is exte externa rnall fertilisation.
Internal Fertilisation For organisms which l ive on land, an an unprotected egg or sperm cell would rapidly dry out and die. Al so, so , t he s perm cel ls canno can nott “ sw im ” thro th roug ugh h t he ai r, or acros acr os s th e gr ound ou nd surf su rf ace... t hey need water to swim through. To To solv e these problems, problems, terrestrial organisms use internal fertilisation.
Terrestrial A nimals
Terrestrial Pla Plants nts
The male male uses his penis (or si milar struc ture) to deposit sperm inside the female’s reproductive tract. The sperm cells are never exposed to the drying outsi de environment. environment.
• produce their male gametes wrapped in a protective capsule to prevent dryi ng... ng... a pollen grain.
The female system is lined with tissue with a film of moisture always present, so the sperm cells can swim to find and fertilise the egg(s) inside the female’s female’s body.
• use either either the wind , or animal pollinators (e.g. bees) to carry the pollen to a flower. • the pollen grain then releases its sperm cell into a fluid-filled tube (the pollen tube). The sperm sperm can swi m down to reach the egg, inside the ovary ovary of t he flower. flower.
There are a number of strategies for development development of the zygote after after fertilis fertilis ation:
Birds & Most Reptiles Reptiles The female lays eggs and the embryos develop outside her body and hatch from the eggs.
Some Reptiles The female keeps the fertilized eggs within her body. When they hatch, the babies emerge from her body vent as if being born.
Marsup Marsup ial Mammals After Af ter a very ver y shor sh ortt gestat ges tatio ion, n, the th e fo etus etu s is born bo rn and crawls into a pouch. It feeds on milk, while developing fully in the pouch.
Placental Placental Mammals Mammals The foetus foetus develops for a relatively long ti me inside the female’s body, nourished via the placenta. When When fully developed, the baby baby is “ born” .
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As part par t of yo ur st ud ies in th i s sec ti on , the syllabus requires you to compare the 2 cell cell di visions , Mitosis Mitosis & Meiosis. Meiosis.
The syllabus also requires you to “ compare & contrast” internal and external external fertili sation. This means means t o fi nd simil arities and differences. differences.
Comparison Compa rison of Mitosis and Meiosis Meiosis MITOSIS Single ingle cellcell-div divisi ision on,, produce produces s 2 “daughte “daughterr cells
Internal & External Fertilisation
MEIOSIS Double ouble divisi division on,, produ produce ces s 4 egg egg or spe sperm cells cells
Similarities Both involve sperm fertilising the egg in sexual reproduction. The sperm must swim to the egg in both cases.
Chromosome Chromosomes s line up Chromosome Chromosomes s line up in singly singly durin during g divisio division n pairs pairs duri during ng divis division ion
Differences
Daughter Daughter cells identical Gamete Gamete cells cells are all to parent parent cell, and to different diff erent to each each other each each other o ther Number of chromosomes is maintained
Number of chromosom chro mosomes es halved (so that ch chromos. number is restored at fertilisation)
Occu ccurs in asexu sexua al reproduction reproduc tion and in growth an and re repair
Ex t er n al
In t er n al
Sperm & eggs both released released int o outside environment.
Sperm released released insi de female body.
Sp er m s w i m i n t he he water of the en v i r o n m en t .
Sp er m s w i m i n f l u i d in female female reproductive t r ac t .
Us ua ual ly ly ma man y eg eg gs gs Us ua ual ly ly fe few er er eg eg g s produc produce ed to improv improve e beca because use ferti fertilis lisa ation tion chance chance of fertilis fertilisa ation. is more more likely likely..
Occu ccurs only to make gametes gametes for sexual reproduction
How Ferti Ferti lis lisation ation Method Re Relates lates to Habita abitatt The great great suc cess of sexual reproduction is t hat it g reatly reatly increases increases the amount of variation variation i n a species. species. This This gives Natural Natural Selection Selection more opportuni ty when the environment changes, and and mo re chance for species survival and evolution. The big prob lem with sexual reproduction is achieving achieving fertil isation.
The Evoluti on o f Sex In the previous topic it was shown that sexual reproduction was “invented” by living things about 1 billion years ago, in the aquatic environment. The process evolved in a watery environment where the cells could not dry out, and where one gamete cell, if equipped with a flagellum tail, could actively swim to seek out the other gamete. The result is that external fertilisation is totally suited to the aquatic environment where it fir st evolved.
The first land vertebrates were the amphibians. They never really mastered the terrestrial environment and 300 million years later, their descendants descendants sti ll return to water to breed so that their external fertilisation will work. The true colonisation of the terrestrial environment came only when i nternal nternal fertilisation was first invented:
The first land plants to evolve were mosses and later ferns. To this day, both these types rely on very moist conditions for the sexual stage of their complicated reproductive cycles. Both types are confined to relatively wet habitats, or to places where there is a “ wet season” season” during which their male gametes can swim to find the eggs.
• in plants by the cone-bearing cone-bearing “ conifers” • in animals by the reptiles, and later later bir ds and mammals.
Internal fertil isation is an an ada adaptatio ptatio n to the terrestri al environ ment -2
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Reprodu ctive Adaptation Adaptations s of Australian Au stralian Flora
For a terrestrial terrestrial plant the first st ep toward achieving achieving fertilisation i s to su ccessfully transfer pollen from one plant to the flow ers of another. another. After fertilisation, the big problem is to di sperse the seeds seeds so they can germinate and and gr ow.
Ad A d ap aptt at atii o ns f o r Seed Dis per s al
Ad ap aptt at atii o n s f o r Pol li n at atii on
Once again, some Australian plants have adapted adapted to use the wind, wh ile others enlist t he help of animals to disperse their seeds. seeds.
Some Australian plants, such as the Acacia (wattles) (wattles) rely on the wind to achieve pollination. They They prod uce large amounts amounts of fine, light p ollen which blows easily easily on th e breeze breeze..
Some of the desert grasses, such as feather spear spear grass, produce ti ny seeds which have fine hairs attached. Being so light and “fluffy” they can be picked up on the slightest breeze. In stronger winds they can be transported hundreds of kilometres.
Their flowers have protruding stigmas, which catch any incoming, wind-blown pollen. Many other plants rely on animals to carry pollen from plant to plant. Unlike the northern hemisphere, where the honey bee is the major pollinator, many Australian plants rely on vertebrate animals such as birds, bats and possums.
The familiar bindii plant relies relies on animals. animals. Its Its seeds have a sharp point which penetrates any foot that steps on them, (or shoe or bicycle tyre) so they are carried some distance away before falling out or being picked out. The dispersed seed lies dormant in the soil until it germinates in the followi ng season. season.
The Callistemons (Bottle brushes) and Grevilli Grevilli as mainly depend depend on t he many “ honeyeaters” eaters” and parrots parrots w hich f eed eed on nectar.
In the “burr ” plants, such as as sheep’s sheep’s burr, the seed is covered in small spikes and hooks. These These will st ick to the fur of any passing animal and be carried off to a new location. Eventually the animal will groom itself or shed its fur, thus depositing the seed possibly many kilometres from the parent parent pl ant.
They produce flowers which lack petals, but have masses of stamens to produce pollen, and stigmas to receive receive pollen from another flower. flower. They have brightly coloured flowers, producing huge quantities quantities of sugary nectar, nectar, to attract birds.
Many of Australia’s rainforest plants, such as native rasberry, produce their seeds inside a fleshy fruit which is highly attractive as food for the fruit bats and various birds. The seeds are eaten eaten too, but are not digested and pass throu gh the digestive system intact. Eventually the seeds are deposited in a new location, and with the added bonus of a rich manure fertilizer.
Their pollen grains are sticky, or covered with tiny hook s, so they cling to bi rd feathers. feathers. As the th e bi rds rd s move mo ve from fr om plant pl ant to plant pl ant feedin feed ing, g, they accidentally pick up masses of pollen grains and later deposit some on receptive flowers of the same species. species. Many Many of t he Melaleucas Melaleucas (pape (paperbarks) rbarks) rely on “ flying-foxes” for poll ination. Since these these fruit bats are nocturnal, and relatively heavy animals, th e paperbark paperbark flowers:
Some plants have a tough seed coat which only allows germination after being softened by an animal’s digestive system.
• are carried on strong branches, to support feeding feeding bats. • grow in large clusters, so at least least som e will survi ve being eaten by the bats. • are white or pale yellow to be seen seen better in moonl ight.
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Reproductive Adaptations of Australian Fauna Adaptati Ad aptations ons to Ensur Ensure e Ferti Fertilis lisatio ation n
Au s t rali ra li a i s t he on l y c on t i nen t wh ere er e t he mammal fauna is almost exclusively marsupials... the pouched mammals. For over a century the opinion of most biologists was that marsupials were “primitive”.
Like mammals mammals in many other parts parts of the world, in many Australian species the males compete with each other for the right to mate with the females.
However, we now realize that the marsupials domi nate the Aust ralian scene because they are superbly adapted to survive in the harsh and unpredictable climate. One of the major aspects of their adaptation to the environment is their method of reproduction.
Al l th e lar ger kangaroo and wallaby species compete with “boxing” matches among the males. This competition ensures that that only th e strongest and healthiest males get to father the babies. This behaviour helps to ensure successful fertilisation and healthy, healthy, robust offsp ring.
Short Gestation Marsupi Marsupi als have a very shor t gestation perio d and the baby is bo rn in a very und eveloped state. This can be an advantage under conditions of drought and severe food sho rtage. If If th e baby dies, then at least the mother has not “ wasted wasted”” a lot of her own body resources as a placental mammal would in a much longer gestation. This gives the adult a greater greater ch ance to survive until conditions improve, and breeding can recommence.
Am ong on g nat iv e roden ro dents ts,, su ch as the th e sp inif in if ex hopping mouse, a male male secretes secretes a “plu g” of mucous into t he female’s female’s vagina after after his s perm has been deposited. This helps ensure fertilisation of the eggs, and prevents other males mating with the female. In many parts of the world, where the seasons are highly predictable, many species have a “ breeding breeding season” season” so that the young will be born in spring when food is plentiful. In Au st ral ia th is tec hniq hn ique ue is us ed (e.g. th e many man y “ Christmas beetles” beetles” ) but many amphibians, amphibians, reptiles and mammals mammals breed breed not by t he seasons, seasons, but by the rains.
High Birth Rate Under good conditions, when there is plenty of food, a marsupial can breed rapidly and increase the population more quickly. For example, example, the red kangaroo kangaroo can have have an an older jo ey at foot fo ot , but bu t st il l feedin feed ing g from fr om th e milk mi lk glands in th e pouch, while having a younger one in the pouch, and another embryo in the womb awaiting awaiting its t urn.
They might not breed for several years during drought, but w hen rain falls in the desert there is a sudden burst of plant growth and animal matings . Females Females ovulate and become become receptiv e and the males become sexually active and seek out their mates. mates.
Suspended De Development velopment The development of a marsupial embryo can also be suspended suspended (“ embryonic diapause” diapause” ) if times are tough. When conditions improve, the embryo continues its development and is born when conditions are better for its survi val.
This instinctive behaviour helps to ensure successful fertilisation, and that the offspring will be born while there is ample food. An example example is t he “ water-holding” water-holding” desert desert f rog, which lies dormant for years, buried deep in sandy soil, surounded by a waterproof layer of mucous. Within hours of heavy rain, thousands of frogs emerge to mate and lay eggs in the short-lived desert desert pools .
Under extreme conditions, it has been known for the lone female survivor from a kangaroo mob to raise her male joey, who was in “ suspended animation” animation” for 2 years, years, then mate with h im and re-establish re-establish the population. No placental mammal could ever do that. -2
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Ad A d ap aptat tatii o n s t o En Ens s u r e Off Of f s p r i n g Su Surr v i v al Many Many of the examples already already giv en not only help ensure successful fertilisation, but also that the offspring will have a better chance of survival.
An ot her adap tati tat i on th at hel ps ens ur e survival of offsp ring is th e territori al and and family behaviours in many Australian s p ec ec i es es s u ch ch as as k o ok ok ab ab u rr rr as as a n d magpies.
For example:
By living in family groups which hold and defend a territory against others of the same species, they ensure that the offspring can be well fed from the resources within the territory, as as well as being protected and nurtured by a supportive family group.
• males competing to mate ensures that offspr ing get genes genes from st rong and healthy healthy fathers. • timing reproduction to the conditions ensures that babies are born at times of good foo d supply.
When Asexual Reprodu Reproducti ction on is i s Useful Useful As A s exu ex u al A n i mal s
Sexual reproduction has the advantage of producing genetic variation in the population. The dis advantage is t hat it co sts mo re, in energy energy and time, to make all all th at pollen, or the nectar to attract pollinators, or for animals to find their mates, compete with others or defend a territory.
A few si mp l e anim an im als can do so met hi ng similar. Among the insects, the aphids can reproduce asexually to produce enormous numbers of offspring in a short time, to take advantage of a shortterm abundance of food. The female aphids are able able to pr oduce hundreds of unfertilised eggs which develop into a clone of identical female female offspring .
Sometimes it is an advantage to be able to reproduc e asexually. asexually. Many Many Aus tralian pl ants are able to reproduce by both methods.
Sturt’s Desert Pea This plant grows in arid areas of central Australia. It reproduces sexually, producing seeds which can lie dormant in the soil f or many years years waiting for suitable condition s to germinate. It can also reproduce asexually asexually by sending out “ runners” runners” . In In the occasional periods of good rain in the desert, a single plant can send out many runners and rapidly produce dozens dozens of off spring, whic h cover large areas areas of ground. By usi ng both methods, the desert desert pea gains gains t he advantages of both... the ability to reproduce cheaply and rapidly to take advantage of good conditions, and achieve the genetic variations which help a species survive when the environment c hanges. hanges.
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At A t o t h er t i m es, es , t h e f em al es m at e sexually with males to produce offspr ing with greater greater genetic genetic variety. variety.
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Work sheet 5
General General Adaptations for Repro Repro duct ion In n).......................... environments, fertilisation often occurs outs ide the organisms body. This This is called o).................................. fertilisation. In terrestrial environments, most organisms have evolved to use p)................................ fertilisation.
Fill in t he blank spaces. spaces. As exua ex uall repr re pr od uc t i on in v ol v es a)... .... .... .... . parent(s). The offspring are genetically b)............. b).................... .......... ... to thei r c).............. c)..................... ............ ..... and to each other. They are a d)........................... The advantage of asexual reproduction is that it allows e).................................................................. to take advantage of good conditions. The disadvantage is lack of f)................................., which helps a species survive when g)...........................................................................
Land plants have adapted to have the male gamete, cal led q )........... )................. ............. ............, ....., enc enclos los ed in a capsule. This can be transported by the r)........................... or carried by various animals. Once it reaches a receptiv e flower, the “ sperm” cell is released to swim along the s).............. s)..................... .......... ... t ube to the t).............. t).................... ............. ......... .. o f the flower where the eggs are.
Al l form fo rms s of asex ual repro rep rodu duct ct ion io n invo in vo lv e the th e cell division called h).......................................
In animals, the female reproductive system is kept u)......................... so that sperm can swim to the eggs. In most cases of internal fertilisation, v)...................... (more/less) eggs are produced compared compared t o external fertilisation.
Sexual reproduction involves the cell division i)............................. to produce the reproductive cells or j)........................ Each gamete is genetically k)........................... and the number of l).............. l)..................... ............. ............ .......... .... has been h alved, so that th at the correct number is restored when m)..................................................... occurs.
Worksheet 6 Australian Adaptations Adaptations for Reproduction Reproduction An im als
Plants Am ong on g Aust Au st ral ian fl ora or a there th ere are a variet var iet y of adaptations to achieve pollination and seed dispersal.. Wind pollination is used by the a)............................ plant group. The pollen grai ns are b)............. b)................... ............. ............. ........ and t he fl ower s have stigmas which c)..................................... so as to catch pollen better.
The marsupials all give birth to babies that are very t)............................ This is an advantage in time of drought because u).......................... .................................................................................. Many marsupials are able to suspend the development of the embryo in the uterus, and delay the birth until v)................................... ......................................
The bottle-brushes and Grevillias rely on d)................... to carry pollen. They produce large amounts of e)................. to attract birds, and the pollen is f).................. so that it g)...................... to the feathers. Many of the Melaleuca plants rely on h)...................... for pollination. Their flowers are light coloured so that i)................................. They grow in large masses so that j)...................................... and they grow on stro ng b ranches s o k )..... )......... ....... ...... ...... ...... ..... ....................
In many species the males w)......................... for the r ight to x)...... x)......... ...... ...... ....... ...... .. wit h t he females. This helps ensure that the health health iest, stro ngest males pass on y)........................ to the next generation. Rather Rather than having a regular “ breeding breeding s eason” eason” , many Australian animals are stimulated to breed when z)............................... ..................................
For seed-dispersal, the feather spear grass relies on l).......................... Its seeds have many m)............................ attached which means it can be n)............... n)..................... ......... ... even on a li ght breeze. Other plants such as o)................. and p)...................... have seeds seeds covered covered in s pikes or hook s so they will be q).......................... by animals. Many rainforest plants produce fruit which are eaten by r)................ and ................ The seeds survive digestion and are deposited elsewhere. Some seeds will only germinate after s)....................... ..................................................
Many plant s, s uch uc h as ac )........... )................. ............. ............. ............. ........... .... can reproduce both ad)................................. and sexually. When conditions are good, the plants send out ae)............................... to rapidly build up the population. When conditions are tough, the sexually produced seeds survive until af)............................ By using both reproductive strategies, the plant gains the advantages of bot h. It can ag)........... ag).................. ............. ......... ... when wh en con diti di tions ons are good, and has genetic ah)........................ which helps a species survive when ai)............................................................................
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Many species such as aa).................................. live in family groups and and hold a “territory ” . This This helps ensure that offspring ab).............................
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4. MAINTAINING MAINTAINING BIODIVERS BIODIVERSITY ITY The Value of Biod iversit y
How Palaeontology Can Help
Biodiversity refers to the variety of different species of plants and animals. In all ecosystems, the greater the biodiversity, the more stable and resilient the system is... the better able it is to survive and adjust when changes changes occ ur or disasters happen. happen.
Palaeontology, the study of fossils, provides information about about plants and animals animals of the past, how they evolved and in s ome cases cases how they became extinct extinct . This can give us pointers about modern plants and animals, and allow us to make predictions about how they may evolve in the future, and what factors might threaten them with extinction.
The greatest threat to biodiversity is human activities. Humans:• destroy habitats to create space for agriculture, roads, etc. • introduce exotic species to habitats where they have no natural predators or diseases. They over-populate and out-compete the natives. • pollute environments environments with i ndustrial chemicals or pesticides which k ill species and upset the balance of the ecosystem.
For example, recent research on the fossil teeth of k angaroos angaroos gi ves some evidence that some of the modern, living species seem to have become smaller over the past 30,000 years or so. One explanation is that the aborigines have tended to take the larger individuals when hunting, thereby leaving more smaller individ uals to breed breed the next generation. generation.
We need to maintain biodiversity in order to help the natural ecosystems survive in a sustainable form.
Over thousands of years this “selective hunting” has acted just like Natural Selection, causing changes in the populations... in this case a “ shrinking” of the average average size of the animals. animals.
Current Efforts to Monitor Biodiversity To have any chance of maintaining biodiversity we first need need information about about things like:
This helps us to predict the effects of human activities on species. For example, when we catch fish we tend to keep the largest, and release the smaller ones. Will this cause the fish populations to evolve to be smaller? Fisheries scientists are already finding evidence for this occurring in some fish species.
• how many species live in each each ecosyst em. • the abundance of species, especially those . thought to be rare or endangered. s t c • how the abundance changes over time.
e j o r gathered by p This sort of information can only be gathered r e people setting out to observe, measure and e t count or ganisms in their natural habitats. habitats. n u l o v At any gi ven mo men t th ere are do zens of t n projects running all over NSW. These projects e r r are organized and run by government agencies, u NSW National Parks & Wildlife Service, c e Universities and “ wildli fe organizations” organizations” . e s o t
Palaeontology has revealed how the flora and fauna of Australia changed in its relative abundance abundance and in its distributi on as the continent underwent cl imate change over over the past 50 mill ion years. For example, we understand reasonably well how, as the climate dried, the rainforests contracted to the mountains and east coast and rainforest species, such as the antarctic beech declined from being a dominant species to near extinction.
Many Many proj ects are not jus t done by professional
g r scientists, but rely on amateur volunteers. A o . h couple of interesting projects running at the c t time of writ ing are: a w h t r • NSW Fisheries Dept. are tagging grey nurse a sharks, and asking for any sightings to be e . w reported. reported. They They hope to build up information about w shark movements and population size. w t u o • The NSW Wader Study Group are seeking k c volunteers to “ adopt” an estuary estuary and carry carry out e h regular regular counts of s horebirds. C
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Meanwhile, the sclerophyll plants expanded their distribu tion to become the dominant flora. We now f ace a major cl imate change in the for m of “ Global Global Warming” Warming” . The knowledge gained gained from palaeontology allows scientists to make predictions about the future changes to distribution of our modern plants and animals as climate changes changes occ urs. 24
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Case Stud tudy: y: the Thylacine Thylacin e
Reasons for Thylacine Survival The Thylacine possessed a number of adaptations adaptations which may have allowed it to thrive as top predator predator for t ens of millions of years.
Evolutio n, S Survival urvival & Extinct ion of a Species
It had an enormously wide and powerful bite. The Thylacine jaw could open to almost 180 o , and it possessed powerful jaw muscles. This allowed it to deliver skull-crushing bites to its prey, prey, so this relatively relatively small animal animal could take relatively large prey. It could also eat every part of its prey, including large bones. This was a major advantage in the tough Australian conditions.
The Thylacin e or “Tasmanian “Tasmanian Tiger” was once one of the major marsupial carnivores in Au st ral ia. It bec ame ext inct in ct on th e mainl mai nl and about 3,000 3,000 years years ago, but surv ived i n Tasmania Tasmania until about 70 years ago. The last known individual died in Hobart Zoo in 1936. There have been a number of unconfirmed reported sightings since then, but it is generally generally b elieved elieved to be extinct extinct .
It was also a solitary animal. The Thylacine could not afford to hunt in packs because the low productivity of the sclerophyll forests and poor soils could not support herds of grazing prey animals which a hunter group need. need. Thylacines kept a solitary existence, coming together only to mate. mate. This helped helped this small but deadly deadly predator to thrive in the low-producti vity Au st ralian ral ian bush bu sh..
Reasons for Thylacine Extinction The Thylacine died out on the Australian mainland about 3,000 years ago. This was probably due to the introduction of the dingo from Asia, possibly by Malay fishermen who visit ed the northern coasts by boat.
Reasons for Thylacine Evolution
The dingo’s abundance rose as that of the Thylacine declined... a classic example of what happens when 2 species compete.
Ac co rdin rd ing g to t o th e fos si l reco r eco rd (admi (ad mitt tt edly edl y rath r ath er sparse) ancestral Thylacines evolved about 50 million years ago. Related to the quolls, the successful evolution of the species can probably be attributed to:
) E C N A D N U B A ( e z i S n o i t a l u p o P
The extinction of the dinosaurs left an “ ecological vacuum” vacuum” which allowed mammals mammals and birds to undergo a huge diversification and radiation radiation of different types
The general success of marsupials on
-C Dingo Thylacine Original population reasonably stable
Dingo introduced
Thylacine Extinct
TIME
the Australian continent, especially after it became isolated from other parts of Gondwana.
The dingo never got to Tasmania, and there the Thylacline survived. However, when the European settlers arrived, the Thylacines quickly learned to hunt sheep. This prompted the government to place a bounty on them in 1888. Thousands were shot, and an epidemic of an int roduc ed disease kil led even more.
As pec ts of th is su cc ess have hav e already alr eady been discussed, but certainly the marsupial reproductive method seems especially well suited to the uncertainties of an irregular climate like Aus tralia’s. tralia’s.
Ironically, in the year that the last Thylacine died, the species was given given “ protected” status. -2
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Workshee ork sheett 7 Practice ractic e Questions uestio ns
sections 3 & 4
Multiple Choice
Longer Response Questions
1. Which Which s tatement tatement about mitosi s is INCORRECT? A. the th e chr c hrom omos osom ome e nu mber mb er i s halved hal ved . B. the daughter cells are genetically identical C. is the basis for all asexual asexual reproduction. D. produces 2 daughter daughter cells from a single division.
An sw er o n b ack if in suff su ff ic ient ien t spac e. 9. (4 mark s) Distinguish between between the processes of Mitosis and Meiosis Meiosis in terms o f the daughter cells produced.
2. A “ pollen pollen grain” can be thought of as: as: A. an eg g i n a sh ell . B. a plant s eed. C. a sperm cell in a waterproof capsule. D. an asexual spore
10. (6 marks) a) Compare and contrast internal and external fertilization.
3. Internal fertilization, when compared to external external f ertilization, ertilization, usually: A. invo in volv lv es f ewer eggs egg s bei ng prod pr oduc uced. ed. B. is less likely to be successful. C. wastes a lot of gametes. D. occurs in the aquatic aquatic environment.
b) Discuss the relative success of these forms of fertilization in relation to the colonization of the terrestrial and aquatic environments.
4. A plant plant which relies on the wind for pollination is likely to produce: A. large lar ge s ti ck y poll po ll en g rains rai ns . B. small flowers with protruding stigmas. C. large, large, colourful flowers. D. large amounts amounts of n ectar. ectar.
11. (4 marks) Describe the conditions under which asexual asexual reproduction is advantageous, advantageous, with reference reference to a s pecific Aust ralian example. example.
5. A plant plant which produces masses masses of white flowers supported on stro ng branches may may be relying on which pollinator? A. an i ns ect B. a bi rd C. t h e w i n d D. a f r u i t b at
12. (5 marks) For many years Australian marsupials w ere considere considered d “ primitive” primitive” and and “ inferior” inferior” to placental mammals. Explain how the marsupial method of reproduction is actually an an advantage advantage under under Aust ralian conditi ons.
6. The sharp sharp “ prickles” of the “bindii” plant plant is an adaptation for A. poll po ll in ati on B. seed disp di sp ersal ers al C. internal internal fertilization D. fire resistance resistance 7. Many Many Australian animals improv e the chances of survival of their offspring by: A. repro rep rodu duci ci ng rapid rap idly ly by asex ual means when conditions are tough. B. holding them in a pouch during development. C. timing reproduction to rain and good food suppy D. competing competing wi th each other for the right t o mate.
13. (6 marks) Describe, with named examples, TWO diff erent mechanisms mechanisms f ound in Australian flora for pollination.
14. (3 marks) Outline the reasons reasons for the extincti on of a named Australian animal.
8. Which of the follow ing i s NOT an an adaptation adaptation possessed by the extinct Thylacine? Thylacine? A. Camou fl age s trip tr ip es an d c olou ol ourat rat ion. io n. B. Extremely Extremely po werful bit e. C. Solitary habits. D. Gave Gave birth to hi ghly developed offspring.
15. (4 marks) a) Explain the need to maintain Biodiversity. b) Discuss Discuss a current effort effort to monitor biodiversity.
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CONCEP CONCEPT T DIAGRAM DIAGRAM (“ Mind Map” ) OF TOPI TOPIC C Some students find that memorising the OUTLINE of a topic helps them learn and remember remember the conc epts and and impo rtant facts. Practise Practise on thi s blank version.
EVOLUTION o f AUSTRA A USTRAL L IAN IA N B IOTA IOTA
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An A n s w er Sect Sec t i o n
Work sheet 3
a) s ei s m o l o g y b) c ru s t c ) m an t l e d ) p l at es e) c o n v ec t i o n f ) Tec t o n i c s g) continental h) South America, Antarctica Antarctica & India i ) Go n d w an a j ) A n tar c t i c a k ) 25 l ) m i d -o c ean m) moving moving apart/ part/spr spre eading ding /growin growing g n ) i n th th e m i d d l e o ) (r es i d u al ) m ag n et i sm sm p) molten rock / lava / magma q ) m an t l e r ) Gl o s s o p t er i s s ) Go n d w an a t ) A m er i c a u) Africa & S.America S.America v)flightless v)flightless birds (ratites) (ratites) w ) an ta tar ct ct ic ic b ee eec h x ) n or or th th wa war ds ds y ) In do do -A us us tr tr al ia ian z) 2-5 c m aa) m ar s u p i al s ab ) ec h i d n a ac ) Mo n o t r em es ad ) p r i m i t i v e ae) adapted / sophisticated
a) Na Natura tural Se Selecti lection on b) varia variatio tion n c) the environment changes d ) Gl o s s o p t er i s e) A n tar c t i c f ) s ea g ) c r o c o d i l es /f l am i n g o s h ) A n tar c t i c a i ) 40 j) drier dr ier k) 25 l ) s c l er o p h y l l m ) t h i n , s m al l n) cuticle (waxy covering) o) Eucalypts, Banksia, Acacia p ) A c ac i a q ) s c l er o p h y l l f o r es t r ) eas t s) fire t) lightning u) encouraged encouraged growt h of grasslands v ) Cas u ar i n a w ) l i g n o t u b er s x ) h ar d , w o o d y y ) f au n a z) m ar s u p i al s aa) m eg af au n a ab ) Di p r o t o d o n ac ) h u n t i n g b y hu hu m an s ad) clim clima ate cha change nge ae) Bea Beagle gle af ) p l an ts ag ) n at u r al s el ec t i o n ah ) p r i m i t i v e ai ) ex t i n c t aj) placental
Work sheet 2
Work sheet 4
Work sheet 1
1. C 5. B
1. D 2. B 3. A 4. B 5. (1) (1) The The shapes of th e contin ents are like jig-saw pieces. They fit together almost perfectly if the “ continental shelf” is used as the actual actual edge of each continent. Such fitting together suggests strongly that Australia was once joined to An tarc ti ca & Ind ia.
3. C 7. C
4. D 8. D
9. The greater the amount of variation in a species, the better the chance of the species surviving when the environment changes. If all the members of a species are very similar (little variation) then there is a good chance there would be no survivors of an environmental change, and the species would become extinct.
(2) Fossils & rock layers match up perfectly on different continents. For example, example, fossils of the extinct seed seed fern “Glossopt eris” are found across S.America, Africa, India, Antarctica and Au st ral ia. The exp lanati lan ati on i s that t hat t his hi s pl ant o nce nc e lived right across Gondwana, and its fossils have been carried to their current locations by the drifting of the continents. 6. Initially specimens of the platypus w ere thought to be fakes. Later it came to be considered as “primitive” and inferior to “real” (placental) mammals. As more evidence and knowledge accumulates, it is now realized that the platypus, and other Australian animals, are ancient, ancient, but highly adapted adapted to t he unpredictable unpredictable Au st . env ir onmen on ment. t. 7. It is thought that the ancestors of the ratites evolved in Gondwana when it was still one continent. As Gondwana split up, populations of flightless birds were carried away on each fragment. Each population, now isolated from others, evolved evolved int o the modern species on t he separate continents... ostrich in Africa, emu in Au st ral ia et c.
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2. A 6. B
10. Between Between 50-1 50-100 00 MYA MYA much of Aust ralia was was covered with rainforest, wetland environments, and partly by an inland sea at one time. The evidence is the fossil record, which shows that rainforest species, such as Antarctic Beech were widespread, and the animal life included many crocodiles, flamingos and turtles... all evidence of a wet climate. Ab ou t 25 MYA t he f os s i ls sh ow a mar k ed increase in pollens from sclerophyll plants. These are adapted to survive drought, and show that the climate must have become drier. A decrease in pollens from rainforest species shows that these habitats habitats were shrinking. By 2 MYA, the rainforests had disappeared from most of Aus tralia. After about 100,000 100,000 years ago, a lot of ash and charcoal in the sediments indicates the increasing increasing occ urrence of fire in the environment, indicating that the modern, dry & drought-prone climate was in place. 28
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Work sheet 4 (cont) 11. 11. a) Sclerophylls are characterized by small, thin leaves with a thick, waxy cuticle. Unlike nonsclerophylls, their leaves do not wither under dry conditions. They retain their shape, and simply resume normal operations when water becomes available again. b) Eucalypts (gum trees) & Acacias (wattles)
Worksheet 6 a) A ca cac ia ia (w at at tl tl e) e) b ) f in in e o r l ig ig ht ht c) protrude from the flow er d ) an i m al s / b i r d s e) n ec tar f) sticky / have hooks g) sticks / clings h) bats/flying bats/flying foxes i) they can be seen seen at night / in moonli ght j) some so me s urvi ur vi ve being bei ng eaten k) the weight of the bat can be supported l ) w i nd m ) f i n e h ai r s n) picke picked d up / carrie carried d o) bindii bindii p ) bu rr s q ) c ar r i ed aw ay r) birds & bats s) passing passing through an animal animal gut t) undeveloped/immature u) if the baby dies, little has been been “ wasted”, and the adult can survive until conditions improve. v) conditions get better / more food & water is available w ) f i g h t / c o m p et e x ) m at e y) their characteristics / their genes z) rains rains oc cur / foo d is available available aa) kook aburra/magpie ab) well fed ac) Sturt’s desert desert pea pea ad) asexually asexually ae) r u n n er s af ) c o n d i t i o n s i m p r o v e ag) increase increase numbers qu ickly ah) variations ai) the environment changes
12. a) Diprotodon was a “giant wombat” , weighing weighing about 3 tonnes. Several fossil part-skeletons have been discovered, allowing accurate reconstruction. b) Diprotodon Diprotodon w as similar to living w ombats. • both were/are marsupials, with same body plan. • both were herbivorous... plant eaters. D. was was diff erent erent to l iving w ombats in • body size being approx 50 times bigger. • modern wombats burrow and spend a lot of time underground. D’s size may have made this impossible. • D was was probably a “ browser” of leaves leaves and vegetation, while modern wombats eat a lot of plant roots and tubers. 13. Darwin noted that many Australian plants seemed well-suited to the dry climate. He later linked this to his Theory Theory of Evolution by arguing that the ancestors ancestors of modern sclerophylls were “ selected” by nature because because they had had characteristics that helped survival in the dry climate. By this “ natural natural selection” selection” t he plants had evolved evolved to thrive in the harsh climate.
Worksheet 7 1. A 5. D
3. A 7. C
4. B 8. D
9. Mitosis involves a single cell division which produces 2 daughter cells which: • are identical to each other. • are identical to the parent cell. • have the same number of chromosomes. Meiosis is a double division which produces 4 cells which: • are all different genetically to each other. • are different to the parent cell. • have only half the number of c hromosomes.
He noted that the animals too, were well suited to the environment, but never fully understood ju st how ho w wel l. He th ough ou ghtt th e marsu mar su pials pi als and monotremes were were “prim itive” and would not survive if faced with competition from “more advanced” advanced” mammals. mammals. In line wi th his theory, theory, Darwin assumed that the marsupials would eventually eventually become extinct, just as the dinosaurs had, as more advanced types took over.
10. a) External fertilization is when the egg & sperm unite in the outside environment. Internal fertilization occurs i nside the body of t he female female parent. b) External fertilization evolved in the aquatic environment and still wo rks well th ere. ere. Since the environment is water, the gamete cells cannot dry out, and the sperm cells can swim to fi nd the eggs.
Work sheet 5 a) o n e b ) i d en t i c al c ) par en t d) c l one e) rapid increase in the population/ rapid reproduction f) genetic variation g) the environment changes h) m i t os i s i ) m ei o s i s j) g ametes amet es k) diff di ff erent / un ique iq ue l ) c h r o m o s o m es m ) f er t i l i s at i o n n ) aq u at i c o ) ex t er n al p ) i n t er n al q ) p o l l en r) wi nd s ) p o l l en t u b e t ) o v ar y u) moi s t v) less (fewer)
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2. C 6. B
Internal fertilization evolved to suit the terrestrial environment where gametes could rapidly dry ou t, and sperm would not be able to swim to the egg. The inside of the female reproductive system is kept moist (simulating the aquatic environment) to keep sperm alive and swimming t owards the eggs. 29
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Work sheet 7 (cont) 11. 11. As exu al repro rep rodu duct ct ion io n is an advantag adv antag e when wh en conditions suit a rapid increase in numbers, to take advantage of a temporary increase in food supply or other resources. It allows rapid reproduction of many offspring without the expenditure of energy and resources that sexual sexual reproducti on requires.
14. The Thyl Thyl acine, or “ Tasmanian Tiger” , was once the top predator across much of the continent. It became extinct on the mainland approximately 3,000 years ago probably due to the arrival of a new competitor, the dingo. Dingos were probably introduced by humans, became feral and spread spread over most o f the continent.
An exampl exam pl e is Sturt Stu rt ’s desert des ert pea wh ic h can rapidly send out “ runners” to populate an an area area after after th e occasional desert rain. This allows t he plants to take advantage of temporary good conditions. Under normal dry conditions it reproduces sexually, sexually, producing seeds which lie dormant for years awaiting suitable conditions for germination.
Dingos never reached Tasmania, so there the Thylacine survived. When the European settlers arrived, the Thylacines began taking sheep, so the government put a bounty on them, and many were shot. Many others died from a disease epidemic in the 1890’s. The last nown specimen died in the Hobart Zoo in 1936.
12. Marsupials have a very brief gestation and give birth to a partly developed embryo which matures inside the pouch. This can be an advantage under extreme drought. If the baby dies, which may well happen, then at least the mother has has not “ wasted” much of her body resources. This gives her more chance to survive, and she can rapidly begin breeding again again when condit ions imp rove.
15. a) It has been found that the greater the variety of dif ferent ferent species in any ecosystem, the more stable the system is, and the more able it is to cope with changes. Maintaining biodiversity is important in order to help natural ecosystems to surviv e in a sustainable form. b) The NSW Wader Study Group is enlisting the support o f interested amate amateurs urs to “ adopt an estuary” and carry out regular counts of shore bird popul ations. The data will help moni tor the biodiversity of these ecosystems, and keep track of changes to various species populations.
Some marsupials, such as the red kangaroo, can even even “ suspend” the development development of an embryo in the uterus and hold it t here for many months until conditions improve. 13. (1) The Acacias (wattles) rely on the wind for pollination. The plants produce l arge quantities quantities of fine, light-weight pollen whic h can be carried carried long distances by any breeze. The flowers have a number of stigmas which protrude from the flowers to catch any incoming pollen. (2) (2) The “ bottle brushes” and Grevillias Grevillias rely on “ honey-eater” honey-eater” bir ds and lorikeet parrots parrots for pollination. The flowers lack petals, petals, but produce large amounts amounts of nectar nectar for the birds to f eed eed on. They have many stamens producing large pollen grains which are sticky, or covered with small hooks, so the grains adhere to the feathers of the feeding birds and are carried on to other receptive receptive flowers for poll ination.
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