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Transcript of Australian Biota
Australian Biota 1. Evidence for the rearrangement of crustal plates and continental drift indicates that Australia was once part of an ancient super continent 1.2.1 Identify and describe evidence that supports the assertion that Australia was once part of a landmass called Gondwana, including: Matching continental margins Position of mid-ocean ridges Spreading zones between continental plates Fossils in common on Gondwanan continents, including Glossopteris and Glangamopteris flora, and marsupials Similarities between present-day organisms on Gondwanan continents Crustal Plates move over time Theory of plate tectonics states: Earth crust is divided into several big, rigid plates that are made up of continents and ocean basins. Plates can move apart, slide past one another or collide Continents were once part of an ancient super continent. Over time they drifted apart and split. Part of evidence of continental drift theory comes from study of Gondwana Gondwana was a large landmass of southern continents (including Australia) that split from the super continent Evidence that Australia was once part of Gondwana Evidence comes from evidence that supports crustal plate movement and continental drift Matching of continental margins Evidence of rifting & drifting comes from ways continents fit together and continuity of rocks between their opp edges. The geometric & geological fit can be seen between South America and Africa. Shaded areas show areas of matching rock that have been radiometrically dated to an age more than 2 bil yrs. The position of mid-ocean ridges and spreading zones between continental plates Mid-ocean ridges form the boundaries of Earths crustal plates where the plates move apart. Crusts move cos lava (hot molten rock) is added at these ridges Active volcanoes and shallow earthquakes occur here too Seafloor spreading occurs where 2 crustal plates move apart. Hot molten material rises into the gap. When this material cools and becomes rigid it forms part of the plates on either side of the spreading zone. Earth doesnt seem to be expanding. So if new crust is being added at spreading zones, it must be destroyed at other places. Fossils in common on Gondwana continents Glossopteris and Gangamopteris are distinctive Plants from the Permian age- fossil remains of these plants have been found on all Gondwana continents. Not found on others. Similarities between present day organisms on Gondwana continents The floras of southern continents- South America, South Africa, Australia and New Zealand have many features in common. E.g. the family Myrtaceae includes the plant genera Eucalyptus, Callistemon, Melaleuca and Leptospermum. Myrtaceae are widespread through AUS (50 genera), South America (27 genera) and southern Asia. The family Proteaceae includes the plant genera Banksia, grevillea and Telopea. Proteaceae are found in New Zealand, South America and South Africa.
1.2.2 Discuss current research into the evolutionary relationships between extinct species, including megafauna and extant Australian species Mammals Monotreme: mammals that lay eggs eg. platypus Marsupial: have a pouch, baby born undeveloped eg. kangaroo Placental: higher order organism, slightly more advanced Evolution of species in Australia Flora & fauna that associate w Australia are restricted to continents of southern hemisphere. Australia unique/distinct environmental pressures/conditions|evolution in isolation isolation of Aus. as island continent = monotreme/marsupial survival (lacking competition from placentals) also reduced competition amongst themselves by occupying different niches and often developed specialised diets fossil evidence mammals evolved from reptiles 200m mya Aus. marsupials evolved in isolation until 50mya ( up till humans) great number different types, wide range environments Evolution of life has give rise to about 500mil animal species since life began. Extant species number about 3-4mil. Examples of extinct megafauna Wonambi- a giant snake, megalania- a lizard which grew up to 6-7m in length, diprotodont- a large wombat like marsupial, at least as big as a rhinoceros. during last 1.64my many backboned animals (marsupials, reptiles) became very large megafauna some megafauna survived until last 20,000years; now EXTINCT megafauna NOT believed to be direct ancestors of present marsupials/reptiles related; evolved from COMMON ANCESTOR in distant past 1.3.1 Solve problems to identify the positions of mid-ocean ridges and spreading zones that infer a moving Australian continent Evidence that the Aus continent is moving at 5-6cm per year in a North-East direction has been obtained using modern technology. Before this, the movement of the continent was inferred from the position of the mid-ocean ridges, particularly those to the south of Aus and the fact that the sea floor was spreading on either side of the ridge. The fact that Aus and Antarctica split up fairly recently supports the explanation.
1.3.2 Identify data sources, gather, process and analyse information from secondary sources and use available evidence to illustrate the changing ideas of scientists in the last 200 years about individual species such as the platypus as new information and technologies became available The platypus Was first described in 1799 in Shaws Naturalists Miscellany along with the koala, kangaroo, wombat, emu. Since first discovered-lots of debate as to whether its a mammal and how it should classified. Platypus primitive mammal lays eggs absence of true teeth absence of true mammary glands BUT special glands that secrete milk fur BUT has horny beak [like the bill of a duck] webbed teeth tail like a beaver Up until 1884 there was uncertainty about how the platypus reproduced. Caldwell solved the problem by capturing a female with eggs About 1904- the scientific American reported that there are many mammals that do not possess teeth when adults
2. The changes in Australian flora and fauna over millions of years have happened through evolution 2.2.1 Discuss examples of variation between members of a species Variations: small differences btwn organisms belonging to the same species features size/colour various body parts biochemical differences important in evolutionary terms when environmental change occurs variation in population = chance some members will be able to survive White-naped honeyeater Melithreptus lunatus eastern Australia short bill, orange-red eye patch lunatus western Australia larger bill, white or green eye patch whitlocki, chloropsis cannot interbreed (geographically isolated), subject to different environmental conditions. They might evolve eventually into a different species 2.2.2 Identify the relationship between variation within a species and the chances of survival of species when environmental change occurs environmental change climate hot/cold/wet/dry distribution/abundance living things changes organisms w favourable variations may survive changes and bring about change in species by natural selection 2.2.3 Identify and describe evidence of changing environments in Australia over millions of years Changing climate 65mya: when AUS and Ant. Were still joined together, climate=cool and wet temperate rainforest 45mya Aus. completed separation from Antarctica WIND PATTERNS CHANGED, became cooler/drier As Aus drifted nth, gradually became warmer rainforest area shrank, other types vegetation increased As AUS moved north of tropic of Capricorn, climate in north became tropical. warmer, wetter periods when forests expanded | cooler, drier periods where grasslands increased overall Aus. has become warmer/drier, particularly inland In last 120 000 years has been a warm period during which fire is significant environmental feature.
Changing landscape sea levels risen and fallen Tasmania joined mainland 8 times in past 30my erosion continued, lowering land surface Australia flattest continent 35mya volcanic activity created extensive lava flows around east coast 20mya Eastern Highlands uplifted Changes in distribution and abundance warmer/drier = living things evolved w adaptations to survive increasing aridity adaptive radiation: transforming of species to survive in new environment e.g. acacias (wattles) and eucalyptus 950 species acacias found almost everywhere, 800 species eucalypts found mainly in forests/open woodlands 35 types Proteaceae endemic to Australia banksias, grevilleas, hakeas, waratahs 3 types mammals placentals, marsupials, monotremes fossil record = placental mammals, apart from bats, died out placentals didnt reach AUS until AUS drifted close to Asia for colonisation to occur in north. marsupials diversified and flourished, now 141 species frogs wide variety habitats lack of dependence on H2O breed in temporary pools brief tadpole stage Theories about changes to Australian species Riversleigh, NW QLD rainforests to dry habitats fossils dating from Miocene to Pliocene period Naracoorte, SA [fossils from Naracoorte and pollen data from nearby Wylie swamp] during Quaternary, inland lakes dried up, vegetation changed from forest to open woodland fossils found give clearer picture of evolution of ecosystems to warmer and drier conditions world heritage areas b/c fossils already found and continuing research will greatly contribute to knowledge. 2.2.4 Identify areas within Australia that experience significant variations in temperature and water availability Australia surrounded by ocean w greatest land width along tropic of Capricorn, 5.6m km2 Temperature inland temp range wide bc heat from day rapidly lost at night generally sub or tropical temp only in SE and SW are mild and temperate conditions inland deserts/grasslands summer 40C day, cool night winter 20C day, sub-zero night Rainfall Aus is worlds driest continent 75% receives lass than 800m