Heritable variants already differ.
🐚AP BIOLOGY STUDY GUIDE
Unit 7: Natural Selection Study Guide
Review evolution, population genetics, evidence for common ancestry, speciation, and phylogeny.
8 key ideas8 flashcards5 practice questions
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Variation comes first. Sorting follows.
Local conditions affect survival and reproduction.
Allele frequencies can shift across generations.
Key ideas to know
Start with the relationships between ideas. Then close the notes and explain each one from memory.
- 01
Natural selection acts on heritable variation in a population.
- 02
Evolution is a shift in allele frequencies across generations.
- 03
Genetic drift has stronger effects in small populations.
- 04
Gene flow transfers alleles between populations.
- 05
Speciation requires reproductive isolation and accumulated divergence.
- 06
Hardy-Weinberg equilibrium supplies a null model for a nonevolving population.
- 07
Fossils, homology, biogeography, and molecular data provide evidence for common ancestry.
- 08
Phylogenetic trees are hypotheses about relationships, not ladders of progress.
PART OF THE AP BIOLOGY GUIDE
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Open the full AP Biology guide →Two ideas worth correcting now
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→Organisms evolve because they need a trait
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Selection sorts existing heritable variation. Need does not direct a useful mutation.
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→The fittest organism is always the strongest
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Fitness means leaving more viable offspring in a specific environment.
Flashcards
Answer before opening each card. The effort to retrieve is part of the learning.
1What is fitness in evolutionary biology?Show answer ＋
Relative reproductive success in a particular environment.
2What does Hardy-Weinberg equilibrium describe?Show answer ＋
A population in which allele and genotype frequencies remain constant under stated conditions.
3What is a bottleneck effect?Show answer ＋
A sharp population reduction that changes allele frequencies by chance.
4What is homology?Show answer ＋
Similarity due to shared ancestry.
5What does a phylogenetic node represent?Show answer ＋
A common ancestor where lineages diverged.
6What is gene flow?Show answer ＋
Movement of alleles between populations through migration and reproduction.
7What condition is represented by p + q = 1?Show answer ＋
The frequencies of two alleles at one locus sum to one.
8What is reproductive isolation?Show answer ＋
A barrier that prevents or reduces gene exchange between populations.
Explain it in your own words
Use the answer as a check after you have written or spoken your response.
01Why does an individual not evolve during its lifetime?
Evolution refers to genetic shifts in populations across generations.
02How can antibiotic resistance increase without antibiotics causing useful mutations?
Resistant variants already arise through mutation, and antibiotics favor their survival and reproduction.
03Why can two unrelated organisms look similar?
Similar environments can favor similar traits through convergent evolution.
04How could a storm alter allele frequencies without favoring a phenotype?
If survival is random with respect to phenotype, genetic drift can shift allele frequencies.
05Why are sister taxa more closely related to each other?
They share a more recent common ancestor with each other than with the other taxa shown.
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