Hello hello tubes!
Ah, human evolution question! My [least] favourite! 🙃
I will try to give some tips, advice, and some suggested answers. However please note that I am not a teacher, so other advice (i.e. from your VCE Biology teacher) is highly recommended.
a) Which currently known hominin species is most likely the ancestor of Aboriginal Australians? Explain
your response by referring to the different species and other information presented in the article. (3 marks)
a) Homo heidelbergensis that evolved into Homo sapiens 300,000ya in Africa and then migrated to Australia 50,000 ya. Already present before the arrival of the ancestors of Indigenous Australians was Homo erectus - an earlier hominin- that had previously migrated out of Africa and had diverged into Homo floresiensis in Indonesia also coexisted with Homo sapiens.
You should make it clearer which hominin species you are selecting for your answer (e.g. "Homo heidelbergensis, evolved into Homo sapiens...").
The question stem specifically asks for an explanation using hominin species referenced in the provided article, you made a tangent which references hominins referenced in the article; these are very different things.
In this question/example, Homo denisova would have been the best hominin species to reference in your answer, because we are told (presented information) that Aboriginal Australians share some common DNA with H. denisova. Even more compelling evidence presented in the article is that it specifically states no other currently known ancestral species shares similar nuclear DNA with Aboriginal Australians.
b) Comparisons of genomes of Aboriginal Australian populations on the west coast and east coast suggest
that there were two distinct pathways of migration across Australia.
Using supporting evidence from the article, explain likely reasons for the differences seen in the
genomes of the populations. (2 marks)
tubes b) Migration to Australia occurred in 2 distinct pathways, were one group reached and travelled along the East coast 40,000 ya and the 2nd group travelled across the western coast and settled 41000, because the 2 main groups were geographically isolated by Australia's mainland, gene flow was limited and hence different mutations occurred and accumulated in each population's genome
This is good, you have the main guts of it down; as you mentioned gene flow is limited and accumulation of different mutations lead to differences. I would only suggest polishing it up a little bit.
E.g.
- Migration to Australia, by who?
- Be more precise in how gene flow is limited, mainland is usually a means of gene flow.
- Also be more precise that a large amount of time has elapsed in order for the mutations to accumulate.
Overall pretty good answer for this part, goodjob 😁 👍️
c) Analysis of mtDNA from Aboriginal Australians and phylogeographic patterns support the contention
that there was a continuous presence of distinct populations in discrete geographic areas for up to
50000 years.
i) Identify two types of artefacts that may be found in a particular geographic area if Aboriginal
Australians had lived in that area for long periods of time (thousands of years)? (2 marks)
i) Evidence of art (cultural evolution) such as cave paintings. The presence of stone tools.
VCAA has specifically stated in their 2022 VCE Biology FAQs that "...ability to distinguish between biological evolution and cultural evolution is not required."
So I think this is a typical case of VCAA blunder, and am not so sure you will encounter such questions on the end of year exam.
However, in the case that it does show up, answers such as cave paintings, burial sites... etc. are perfectly fine, I think (stress "I think" 😅 ).
ii) Explain how mtDNA phylogeny provides evidence for the continuous presence of Aboriginal
Australian populations in discrete geographic areas. (3 marks)
ii) The large genetic variation in mtDNA indicates that a long time had elapsed since migration hence the time for mutations to accumulate, supporting a continuous presence in Australia as well as in discrete areas as many different mutations occurred in specific isolated population and hence accumulated because of the lack of gene flow leading to 111 mtDNA genomes to diverge
This is a hard question. I had to think about it for a while. What do they mean by continuous presence?
The question asks for an explanation, you need to give a structured and logical line of thought in order to explain this.
Perhaps you could say "When Aboriginal Australian populations formed in discrete geographic locations, they became isolated from other populations; which then limited gene flow between these populations. Consequently, over long (and continuous) periods of time, differences in their gene pools from mutations, natural selection and genetic drift accumulated. MtDNA phylogeny can serve as evidence of these differences, and hence the continuous presence of these populations."
Or perhaps we can take a different angle of attack and say "Large differences between genetics of Aboriginal Populations of discrete geographical areas illustrated in mtDNA phylogeny, evidence that these populations have been established a very long time ago and have been continuously present. As those are the conditions required for these differences to arise, conditions required for factors such as lack of gene flow, different mutations, different natural selection pressures acting, and genetic drift to act on these populations; and create such differences."
Feel free to add anything to these "suggested" answers (or dispute their validity), I feel like VCAA expects a fairly meaty answer for this type of question; perhaps some more information from the article can be utilised?
Be careful, as it is very easy to fall into the trap of making an answer which uses false logic/circular reasoning for this sort of question, yuck 🙃 .
Hope this helps!
(Apologies if I may have used harsh wording.)
