STUDY GUIDE: EVOLUTIONARY
BIOLOGY
Topic: Mechanisms, Evidence, and Outcomes of Evolution
Prepared by: Study Master
1. DEFINITION
Evolution is defined biologically as the change in the genetic composition of a
population over successive generations.
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Crucial Distinction: Individuals do not evolve; populations evolve.
Scale: It can be micro (small changes within a species) or macro (speciation
over long periods).
2. THE MECHANISM: NATURAL SELECTION
Proposed by Charles Darwin, this is the primary engine of evolutionary change. It acts
as a filter for traits.
The 4 Pillars (V.I.S.T.)
1. Variation: Genetic differences exist within every population.
2. Inheritance: Traits are passed from parents to offspring.
3. Selection: Environmental pressures lead to differential survival and reproduction
("Survival of the Fittest").
4. Time: Over generations, advantageous traits become dominant in the gene pool.
Key Concept: "Fitness" refers strictly to an organism's reproductive success and ability
to survive in a specific environment, not physical strength.
3. EVIDENCE OF EVOLUTION
Evidence is drawn from multiple scientific disciplines to support the theory of evolution.
A. The Fossil Record
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Chronological collection of life's remains in sedimentary rock layers.
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Shows transitions from simple to complex life forms.
B. Comparative Anatomy
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Homologous Structures: Structures in different species that are similar
because of common ancestry (e.g., the arm of a human, wing of a bat, and
flipper of a whale).
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Vestigial Structures: Remnants of organs or structures that had a function in an
early ancestor (e.g., human appendix, whale pelvic bones).
C. Molecular Biology
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All living things share the same genetic code (DNA/RNA).
Protein and DNA sequence comparisons reveal how closely related two species
are.
D. Embryology
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Similarities in the early development of embryos across different species imply a
common ancestor.
4. MECHANISMS OF CHANGE (NON-SELECTION)
Natural Selection is not the only force changing gene pools.
Mechanism Definition
Impact
Mutation
Random change in DNA
sequence.
The ultimate source of new genetic
variation.
Genetic
Drift
Change in allele frequencies Significant impact on small populations
due to chance.
(e.g., Bottleneck Effect).
Gene Flow
Movement of genes into/out
of a population.
Reduces differences between populations
(e.g., migration).
5. SPECIATION & PHYLOGENY
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Speciation: The formation of new and distinct species in the course of evolution.
This usually requires reproductive isolation (populations stop breeding with each
other).
Phylogeny: The evolutionary history of a species or group of related species.
Cladogram: A branching diagram showing the cladistic relationship between a
number of species.
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6. THE HARDY-WEINBERG PRINCIPLE
A mathematical model used to measure if a population is evolving. If a population is in
equilibrium (not evolving), allele frequencies remain constant.
The Equation:
$$p^2 + 2pq + q^2 = 1$$
$$p + q = 1$$
Variables:
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$p$ = Frequency of the dominant allele
$q$ = Frequency of the recessive allele
$p^2$ = Percentage of homozygous dominant individuals
$2pq$ = Percentage of heterozygous individuals
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$q^2$ = Percentage of homozygous recessive individuals
7. KEY VOCABULARY
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Adaptation: An inherited characteristic that increases an organism's chance of
survival.
Artificial Selection: Selective breeding of plants and animals to promote the
occurrence of desirable traits in offspring.
Convergent Evolution: Process by which unrelated organisms independently
evolve similarities when adapting to similar environments (e.g., sharks and
dolphins).
Coevolution: The influence of cl