VCE Biology Unit 4 AoS 2: How Do Humans Impact Biological Processes? — Flashcards & Quiz

Q1: What is a phylogenetic tree and how is it constructed?

A phylogenetic tree is a branching diagram showing the evolutionary relationships between species based on shared characteristics or molecular data. Construction methods: 1) Morphological comparison — shared derived characters (synapomorphies). 2) Molecular comparison — DNA/protein sequence similarity. 3) Computational analysis — algorithms align sequences and build trees based on similarity. Branch points (nodes) represent common ancestors; branch lengths may indicate time or genetic change.

Q2: What are homologous and analogous structures?

Homologous structures: similar underlying anatomy inherited from a common ancestor but adapted for different functions (divergent evolution). Evidence of common descent. Analogous structures: similar function but different evolutionary origin (convergent evolution). NOT evidence of common descent — they evolved independently in response to similar selection pressures.

Q3: How does molecular evidence support evolutionary relationships?

Molecular evidence includes: 1) DNA sequence comparison — more similar sequences indicate closer relatedness. 2) Protein sequence comparison — amino acid differences correlate with evolutionary distance. 3) DNA hybridisation — degree of binding reflects similarity. 4) Immunological comparison — cross-reactivity indicates protein similarity. 5) Shared pseudogenes — non-functional DNA sequences shared by related species provide strong evidence of common ancestry (no selective reason to be similar).

Q4: What is a molecular clock and what are its limitations?

A molecular clock uses the rate of molecular change (mutations accumulating in DNA or protein sequences) to estimate the time of divergence between species. Assumption: mutations accumulate at a roughly constant rate over time. Calibration: known fossil dates are used to calibrate the clock. Limitations: 1) Mutation rates vary between genes, lineages and over time. 2) Natural selection can accelerate or slow changes. 3) Requires calibration with fossil dates (circular reasoning risk).

Q5: How do fossils provide evidence for evolution?

Fossils provide evidence by: 1) Showing morphological changes over time in lineages. 2) Revealing transitional forms between groups (e.g., Tiktaalik — fish to tetrapod). 3) Documenting past biodiversity and extinctions. 4) Showing biogeographic patterns (distribution matching continental drift). 5) Allowing relative dating (stratigraphy — older rocks = lower layers) and absolute dating (radiometric — using radioactive decay). The fossil record provides direct evidence of organisms that once lived.

Q6: What are the key trends in hominin evolution?

Key evolutionary trends from early hominins to modern humans: 1) Bipedalism — upright walking (foramen magnum moves to base of skull, pelvis widens). 2) Brain size increase — ~400 cm³ (Australopithecus) to ~1400 cm³ (Homo sapiens). 3) Jaw and tooth reduction — smaller jaw, reduced canines, changes in tooth enamel (diet shift). 4) Tool use and complexity — Oldowan → Acheulean → Mousterian → Upper Palaeolithic. 5) Language and symbolic thought. 6) Extended childhood and social complexity.

Q7: Compare the "Out of Africa" and multiregional hypotheses of modern human origins.

Out of Africa (Recent African Origin): modern Homo sapiens evolved in Africa ~200,000 years ago and migrated outward, replacing other hominin populations (Neanderthals, Denisovans) with limited interbreeding. Supported by: greater genetic diversity in African populations, mitochondrial DNA evidence, oldest H. sapiens fossils in Africa. Multiregional hypothesis: modern humans evolved simultaneously across multiple regions from local H. erectus populations connected by gene flow. Current evidence overwhelmingly supports Out of Africa with some interbreeding.

Q8: What are vestigial structures and how do they provide evidence for evolution?

Vestigial structures are reduced or non-functional remnants of structures that were functional in ancestors. They provide evidence for evolution because they indicate descent from ancestors where these structures had a function. The structures have been retained but reduced through evolution because they no longer provide a selective advantage.

Q1: A phylogenetic tree shows that species sharing a more recent common ancestor are more closely related.

Answer: TRUE

In a phylogenetic tree, species that share a more recent branching point (common ancestor) are more closely related than species whose lineages diverged earlier. The tree represents evolutionary relationships.

Q2: Analogous structures provide evidence of common ancestry between two species.

Answer: FALSE

ANALOGOUS structures result from convergent evolution — similar function but different evolutionary origin. They do NOT indicate common ancestry. HOMOLOGOUS structures (same origin, different function) provide evidence of common ancestry.

Q3: The molecular clock assumes that mutations accumulate at a perfectly constant rate in all genes and all lineages.

Answer: FALSE

The molecular clock assumes a roughly constant rate, but acknowledges that rates vary between genes, lineages and over time. This variation is a key limitation, which is why calibration with fossil evidence and statistical methods are essential.

Q4: Transitional fossils show intermediate features between ancestral and descendant groups.

Answer: TRUE

Transitional fossils exhibit characteristics of both ancestral and descendant groups. For example, Tiktaalik has fish features (scales, fins) and tetrapod features (flat head, neck, wrist-like bones), showing the transition from aquatic to terrestrial vertebrates.

Q5: Large brain size evolved before bipedalism in the hominin lineage.

Answer: FALSE

BIPEDALISM evolved BEFORE significant brain expansion. Australopithecus afarensis (Lucy, ~3.2 MYA) was bipedal but had a brain size similar to a chimpanzee (~430 cm³). Major brain expansion occurred later in the Homo lineage.

Reproductive Strategies

Organisms use asexual and sexual reproduction to maintain continuity of life. Understanding the advantages and disadvantages of each strategy, including genetic variation through meiosis and fertilisation, is fundamental. Comparing reproductive strategies across different organisms and linking them to environmental conditions is a common VCAA exam question.

DNA Technologies and Gene Cloning

Techniques such as PCR, gel electrophoresis, restriction enzymes, DNA sequencing and gene cloning allow scientists to analyse and manipulate genetic material. Understanding how these tools work together in processes like genetic profiling, gene therapy and the production of transgenic organisms is essential for exam responses according to the VCAA study design.

Genetic Engineering and Its Applications

Genetic engineering involves modifying an organism's DNA to introduce new traits or remove undesirable ones. Applications include GM crops (herbicide and pest resistance), gene therapy for genetic disorders, and production of biological molecules like insulin. Being able to explain the steps involved and evaluate the benefits and risks is a core exam skill.

Bioethics and Social Implications

Advances in DNA technologies raise ethical questions about genetic modification, cloning, gene therapy and genetic screening. Understanding different ethical frameworks and being able to construct balanced arguments about the social, environmental and economic implications of biotechnology is valued in VCAA extended-response questions.

What does VCE Biology Unit 4 AoS 2 cover?

AoS 2 explores how humans impact biological processes through reproductive technologies, DNA manipulation and genetic engineering. Key topics include reproductive strategies in organisms, DNA technologies (PCR, gel electrophoresis, restriction enzymes, gene cloning), genetic engineering applications in medicine and agriculture, and the bioethical implications of biotechnology.

What DNA technologies do I need to know for VCE Biology Unit 4?

Key technologies include PCR (polymerase chain reaction) for DNA amplification, gel electrophoresis for separating DNA fragments, restriction enzymes for cutting DNA at specific sequences, DNA sequencing, gene cloning using vectors, and genetic profiling. You must understand how these tools work together in applications like gene therapy, forensic analysis and transgenic organism production.

How are bioethics assessed in VCE Biology?

VCAA expects you to evaluate the social, ethical and environmental implications of DNA technologies and genetic engineering. This includes constructing balanced arguments about GM crops, gene therapy, genetic screening, cloning and stem cell research. Extended-response questions require you to consider multiple perspectives and apply ethical frameworks to real-world biotechnology scenarios.