NY Regents Life Science: Biology Module 5 evolution: a complete overview of natural selection, evidence, common ancestry, speciation and biodiversity

What Module 5 actually demands

Module 5 is the evolution core of the Life Science: Biology Regents. Under the New York State Science Learning Standards it is disciplinary core idea LS4, Biological Evolution: Unity and Diversity. It explains the mechanism (natural selection), the evidence, how species are related (common ancestry), how species form and die out, and why diversity matters. The dominant crosscutting concepts are cause and effect, patterns, and stability and change. Many clusters give you a scenario (a changing environment, an isolated population) or a model (an evolutionary tree) to reason about.

This guide ties together the matching dot-point pages, each with its own practice questions: natural selection and adaptation, evidence for evolution, common ancestry and phylogeny, speciation and extinction, and biodiversity and its value.

Natural selection

Natural selection changes the proportion of traits in a population over generations. The logic has four steps: individuals vary (originally from mutation); populations overproduce, causing competition; individuals with favorable, inherited traits survive and reproduce more (differential survival); and they pass those traits on, so the favorable trait spreads and the population becomes adapted. Crucially, selection acts on variation that already exists; organisms do not adapt on purpose. The Beaks of Finches lab and antibiotic resistance are the standard worked contexts.

Evidence for evolution

Several independent lines of evidence point to common ancestors. The fossil record shows change over time and transitional forms. Comparative anatomy reveals homologous structures (same plan, different function), best explained by inheritance from a shared ancestor. Embryology shows similar early development. Molecular evidence, the strongest, shows that more closely related species have more similar DNA and proteins. Their power is that they all agree, which is exactly what the Relationships and Biodiversity lab demonstrates.

Common ancestry and trees

Common ancestry means species descended from shared ancestors. An evolutionary tree represents this: each branch point is a common ancestor, and species sharing a more recent common ancestor are more closely related (and have more similar DNA). The key skill is to judge relatedness by where branches join, not by how near the tips are drawn. The exam tests this almost entirely as a model-reading task.

Speciation and extinction

A species is a group that can interbreed to produce fertile offspring. Speciation happens when a population becomes reproductively isolated (often geographically), then diverges through independent natural selection and mutation until the groups can no longer interbreed. Extinction happens when the environment changes faster than a species can adapt, so too few survive. Genetic variation raises the chance that some individuals cope with change, reducing extinction risk.

Biodiversity

Biodiversity is the variety of species and the genetic variation within them. It matters for resilience: a genetically diverse population is more likely to survive a disease or climate change, and a species-rich ecosystem is more stable because other species can fill the roles of those that decline. Human activity (habitat loss, pollution, climate change, overharvesting) reduces biodiversity and raises extinction risk.

Check your knowledge

A mix of recall and application questions covering Module 5. Attempt them under timed conditions, then check against the solutions.

1. State the four steps of natural selection. (2 marks)
2. State the original source of the variation natural selection acts on. (1 mark)
3. Define a homologous structure and give an example. (2 marks)
4. Explain why similar DNA between two species is evidence they are closely related. (2 marks)
5. On an evolutionary tree, how do you decide which two species are most closely related? (2 marks)
6. Explain how a new species forms after a population is split by a geographic barrier. (3 marks)
7. Explain why a species may become extinct when the climate changes rapidly. (2 marks)
8. Define biodiversity. (2 marks)
9. Explain why a genetically diverse population is more likely to survive a new disease. (2 marks)