4.1 Gondwana Questions and Answers

4.1 – Gondwana – Questions and answers

Q1.

Bk Ch4 S4.1 Q1

Draw up a timeline that illustrates the key events in the formation and position of the Australian continent, from its supercontinent origins to the present.

A1.

Bk Ch4 S4.1 A1

Original supercontinent: Pangaea

160 million years ago Pangaea splits into two smaller landmasses, Laurasia (north) and Gondwana (south)

Gondwana consists of South America, Africa, Madagascar, India, Antarctica, Australia, New Zealand

60 million years ago Gondwana begins to break up. Antarctica and Australia split from South America and begin drifting northwards.

55–45 million years ago Australia breaks away from Antarctica, becoming a separate continent

Present time Australia continues to move northwards at a rate of about 6 cm per year

Q2.

Bk Ch4 S4.1 Q2

Describe the geographical and biological evidence that supports the theory that Australia was once connected to the supercontinent called Gondwana.

A2.

Bk Ch4 S4.1 A2

Geographical evidence: Rock strata in Australia and other landmasses that formed Gondwana are perfectly matched in some places; the contours of the continents resemble the pieces of a jigsaw puzzle and suggest the way the continents might have fitted together in the past; deep-sea surveys of mid-ocean ridges (where plates are moving apart and mantle material rises to the surface forming the ocean floor) between the continents show that the further away from the ridge, the older the rock forming the ocean floor, suggesting that the plates carrying these continents have been moving apart for a long time.

Biological evidence: Fossils of plants such as Glossopteris found in rock dated at the same age in Australia, Africa, India, South America, New Zealand and Antarctica. The fossil record shows that marsupials, now only prevalent in Australia, were present on all of the continents that made up Gondwana. Present-day organisms found in Australia are also indigenous to other continents; for example, the southern beech tree Nothofagus is also found in New Guinea, New Zealand and South America. Fossils of Nothofagus have also been found in Antarctica. Many animal species that are native to Australia have close relatives on other continents, for example parrots, and flightless birds—Australian emu, African ostrich, South American rhea.

Q3.

Bk Ch4 S4.1 Q3

a Make a list of extinct Australian megafauna.

b Outline the two theories that have been proposed to account for the extinction of these organisms.

A3.

Bk Ch4 S4.1 A3

a Extinct Australian megafauna include the marsupial lion, diprotodon, giant kangaroo, giant echidna, giant Tasmanian devil, giant Australian python, giant goanna, giant Australian megapode, Genyornis.

b Climate change: As the last Ice Age ended during the Pleistocene Period climatic conditions in Australia changed from cold and dry to warm and dry with water becoming less abundant. Unsuitable conditions may have led to the decline and extinction of the megafauna.

Arrival of humans in Australia: The megafauna were large and probably relatively slow and therefore vulnerable to hunting. Hunting by the first human inhabitants is thought to be a factor related to their extinction.

Q4.

Bk Ch4 S4.1 Q4

Outline some of the similarities and differences between present-day Australian native animals and their ancient relatives.

A4.

Bk Ch4 S4.1 A4

Present-day relatives of Australia’s extinct megafauna exist, for example kangaroo, wombat, Tasmanian devil, echidna. Similarities between the megafauna and their present-day descendants include their general form and lifestyle as well as special characteristics such as those associated with being a marsupial or monotreme. The single most pronounced difference is in their size—present-day species are as much as 30% smaller than their ancient relatives.

Q5.

Bk Ch4 S4.1 Q5

a Explain what is meant by ‘extant Australian species’.

b Identify some plant and animal examples of living fossils that are endemic to Australia.

A7.

Bk Ch4 S4.1 A7

a Extant fossils are species that exist today and have remained unchanged for millions of years.

b Australian living fossils include stromatolites, plum pines, huon pines, Wollemi pines, velvet-worms, Queensland lungfish, crocodiles.

4.1 Gondwana QA page 1 of 2