Gondwana Flashcards
identify and describe evidence that supports the assertion that Australia was once part of a landmass called Gondwana including:
Matching continental margins
Positions of mid-ocean ridges
Spreading zones between continental plates
Fossils in common on Gondwanan continents, including Glossopteris and Gangamopteris flora, and marsupials
Similarities between present day organisms on Gondwanan
continents
Identify the role of cell division in growth, repair and reproduction in multicellular organisms:
Living things are made up of cells
In multicellular organisms new cells are produced by cell division for growth
repair and reproduction
In unicellular organisms, cell division divides the organisms into 2 new organisms
The four main points of Darwin‟s Theory of Evolution by Natural Selection are:
In any population, there are variations
In any generation, there are some individuals that do not reach maturity and
reproduce; the characteristics of these individuals are removed from the
population
The individuals that survive and reproduce are well adapted to the
environment; they have favourable conditions (survival of the fittest)
Favourable conditions are passed on to offspring; they become more and more
common in the population
Discuss evidence that suggests that crustal plates move over time:
the age of the sea floor around mid-oceans ridges
the matching edges of continents
fossils of similar organisms found in different parts of the world
how was Gondwana formed
All landforms were originally joined together in a giant landmass called Pangaea
In the Jurassic, 160 million years ago, Pangaea split into two super continents:
Gondwana and Laurasia
Gondwana: Australia, Africa, Madagascar, New Zealand, South America, India
Laurasia: Europe, North America, Asia (except India)
when did Australia split from Gondwana
60 million years ago
geological evidence that Australia was once part of Gondwana:
- The rock strata around continental margins match exactly in many places,
eg: 1) South Australia & Australia, 2) West Africa & east South America. - Mid-ocean ridges are formed where plates are moving apart
- When plates move apart, molten rock rises up and forms new sea floor.
- In these areas, called spreading zones, the new rock that forms is older the
further it is from the ridge - This proves that the plates have been moving apart steadily for a long time
biological evidence that Australia was once part of Gondwana:
The fossil record and present day organisms provide evidence that Australia was part of Gondwana
- Fossil Evidence:
o Glossopteris and Gangamopteris are fossil plants found in rocks of the same age in Australia, Africa, India, South America, Antarctica and New Zealand
o Fossils of marsupials have been found on all the continents that were part of Gondwana
o This is evidence that the continents were once joined
Extant Organisms:
o Nothofagus, or the southern beech trees, are found in forests of Australia, New Guinea, New Zealand and South America
o Many plants and animals exist only where the Nothofagus still live; e.g. a parasitic fungus, a moss and bugs which depend on the moss
o Many groups of animals in Australia have close relatives in South America, Africa, India and New Zealand, but not in Northern Asia, Europe or North America
o These animals include: parrots, ratites (flightless birds) etc
Why have megafauna become extinct
- Climate Change:
Megafauna were mainly suited to glacial conditions. Their large bodies enabled them to live in extreme conditions. In Australia, the temperature changed from cold-dry to warm-dry. As a result, water sources began to dry up, and many animals lost their habitat and died out. - Human Expansion:
The time of the extinction of megafauna matches very closely the pattern of human migration into these areas. Megafauna are also large and slow, which makes them susceptible to hunting. In Africa, humans evolution occurred there, so hunting increased slowly, allowing animals to adjust. That is why there are still megafauna there. However, in places where humans arrived as skilled hunters, the most extinction occurred.
what are spreading zones
the new areas of floor created at ridges where molten rock
rises out from the mantle and solidifies
how do we know Australia is moving North
There are spreading zones on the southern side of the Indo-Australian plate, and
collision zones on the northern side
spreading zones are created at ridges where molten rock
rises out from the mantle and solidifies
illustrate the changing ideas of scientists in the last 200 years about the platypus as new information and technologies became available
- 1798: A dried platypus skin sent to England considered to be a fake; the bill was thought to have been stitched on (observation and dissection)
- 1988: their chromosomes resemble those of reptiles (advanced microscopic techniques, genetic fingerprinting)
- 2001: (radio-telemetry) to record body temperatures year round
Examples of variations include:
- The white-naped honeyeater:
In Australia, eastern populations have a short
bill and an orange eye-patch. These belong to lunatus. Populations in western Australia have larger bills and white or green eye-patches. - The common heath:
This flower show remarkable variations in the colour of
the flowers, from pure white, to pink, to deep red.
The greater the variation within a species…
…the greater the chance that it will be able to survive in a situation of environmental change.
what happened as Australia moved north
it became warmer
rainforests shrank
sclerophyll and grasslands increased
in what period were there many ice ages
Quaternary period
Other environmental changes that have shaped ecosystems, besides climate are:
Sea levels have risen and fallen; mainland Australia and Tasmania have been joined and parted at least 8 times in the past 30 million years
Erosion continues, making Australia the flattest continent
35 mya, volcanic activity created extensive lava flows around the east coast of
Australia
Identify changes in the distribution of Australian species, as rainforests contracted and sclerophyll communities and grasslands spread, as indicated by fossil evidence:
- As Australia became warmer and drier, rainforests shrank, and grasslands and sclerophyll communities increased
- Organisms well suited to these conditions undertook “adaptive radiation”
- Two groups that are part of the sclerophyll family are eucalypts and acacias
- Both forms have adapted to survive in dry hot conditions
- The 950 species of acacia are found almost everywhere, from tropical to
temperate, arid and semi-arid.
- The 800 species of eucalypts are found mainly in open woodland and forests
describe some Australian fossils, where these fossils were found and use available evidence to explain how they contribute to the development of understanding about the evolution of species in Australia:
Riversleigh (North-western Queensland)
- 6 species of thylacine (Tasmanian tiger) have been found
- Size ranged from Burmese cat to Doberman
- Giant Rat-Kangaroo (proleopines) were found in 1888. They were carnivorous.
- A jaw from a possum - representing the Striped Possum
- A complete skull of monotreme obdurodon
- Fangaroo, A small herbivorous kangaroo with huge teeth
Present information from secondary sources to discuss the Huxley- Wilberforce debate on Darwin’s theory of evolution:
- Darwin‟s book The Origin of Species caused great uproar in the community, especially among religious clergy
- Several debates happened, each side arguing they point of view of evolution
- The most famous of these is the debate between Thomas Huxley (Darwin‟s Bulldog) and Bishop Samuel Wilberforce (Soapy Sam).
- Wilberforce: “Rocks pigeons were what rock pigeons had always been”
- Wilberforce asked Huxley whether it was his grandmother or his grandfather that
came from a monkey. - Huxley replied that he would rather have an ape for an ancestor than a person who
uses their intelligence to „introduce ridicule into a grave scientific discussion‟.
describe mitosis
- cell division, where two daughter cells are produced that are identical to the parent cell
- It is used for growth and repair
- Also basis of sexual reproduction
- Division occurs only once
- The stages are Interphase, Prophase, Metaphase, Anaphase and Telophase
- Cells produced are diploid
describe meiosis
- produces 4 haploid cells
- These cells are sex-cells; also called gametes
- Gametes fuse together during fertilisation to form a zygote, which multiplies
by mitosis to form a new organism - Human males produce gametes called sperm, females produce ova or eggs
- When two gametes join, the normal number of chromosomes is achieved
- Similar chromosomes can be paired up, and are called homologous
- In homologous chromosomes, one is from the mother, one from the father
- Random segregation is, during meiosis, the separation of chromosomes by
chance into the resulting daughter cells. This means that the gametes produced
can have any combination of chromosomes. This results in increased variation
similarities of mitosis and meiosis
Both are types of cell division
Chromosomes are replicated before both types of divisions
Conditions needed for fertilisation:
- Both male and female gametes need to be produced and ready at same time
- Arrangements need to be bring the gametes in contact with each other
- Water needs to be present (male gametes must swim to the female gamete)
