Evolutionary Biology Key Terms

Flashcards covering key vocabulary and concepts related to evolutionary biology.

Typological Thinking

Classifying things only by their ideal type; variation is considered trivial.

Plato’s Ideal Essence

The belief that each species has a perfect form and individual variations are unimportant.

Aristotle’s Great Chain of Being

A hierarchy ranking life from simple to complex (minerals → plants → animals → humans).

Species

A group of organisms that can interbreed and produce fertile offspring.

Lamarck’s Use and Disuse Hypothesis

Traits used become stronger; unused traits deteriorate over time.

Inheritance of Acquired Characteristics

Traits gained during an organism’s life are passed to offspring (incorrect).

Lamarck’s Contribution

Proposed that species change over time and pass traits to offspring.

Darwin’s Descent with Modification

All species share common ancestry and change through branching lineages.

Natural Selection

Individuals with advantageous traits survive and reproduce more successfully.

Darwin vs. Lamarck

Darwin → populations evolve; Lamarck → individuals change in their lifetime.

Evolution (modern definition)

Change in allele frequencies within a population over time.

Microevolution

Small genetic changes within populations.

Macroevolution

Large-scale evolutionary changes that lead to new species.

Hardy-Weinberg Principle

Describes a population that is not evolving.

Hardy-Weinberg Conditions

Random mating, large population, no natural selection, no mutation, no migration.

Allele Frequency Equation

p + q = 1.

Genotype Frequency Equation

p^2 + 2pq + q^2 = 1.

Meaning of p

Frequency of the dominant allele.

Meaning of q

Frequency of the recessive allele.

Meaning of 2pq

Frequency of heterozygous genotype.

Mutation

Random change in DNA that creates new alleles; source of all genetic variation.

Gene Flow

Movement of alleles between populations due to migration; makes populations more similar.

Genetic Drift

Random changes in allele frequencies, stronger in small populations.

Founder Effect

New population formed by a small group with different allele frequencies.

Bottleneck Effect

Population size drastically reduced, changing allele frequencies randomly.

Natural Selection

Non-random survival and reproduction based on phenotype.

Requirements for Natural Selection

Variation among individuals. Trait must be heritable. Differential survival and reproduction. Fitness differences linked to phenotype.

Fitness

The ability to produce viable offspring compared to others.

Adaptation

Trait that increases survival and reproductive success.

Positive Assortative Mating

Similar individuals are more likely to mate; increases homozygosity.

Negative Assortative Mating

Dissimilar individuals mate; increases heterozygosity.

Inbreeding

Mating between related individuals; reduces genetic variation.

Effect of Non-Random Mating on Evolution

Changes genotype frequencies but not allele frequencies directly.

Directional Selection

One extreme phenotype is favored.

Stabilizing Selection

Intermediate phenotype is favored; extremes selected against.

Disruptive Selection

Both extremes favored; intermediate has lower fitness.

Sexual Selection

Evolution due to mating success rather than survival.

Intersexual Selection

Mate choice between sexes; one sex prefers specific traits (e.g., bright feathers).

Intrasexual Selection

Competition within one sex for mates (e.g., male combat).

Result of Sexual Selection

Evolution of showy or competitive traits.

Myth 1: Evolution happens in individuals

❌ It happens in populations.

Myth 2: Natural selection is goal-directed

❌ It acts on existing variation.

Myth 3: Natural selection leads to perfection

❌ There are fitness trade-offs.

Myth 4: Natural selection is the only mechanism

❌ Drift, gene flow, and mutation also cause change.

Speciation

Process where new species form.

Genetic Isolation

Populations separated by barriers preventing gene flow.

Genetic Divergence

Populations evolve independently via mutation, selection, drift.

Reproductive Isolation

Populations can no longer interbreed.

Biological Species Concept

Species are reproductively isolated (can interbreed and produce fertile offspring).

Morphological Species Concept

Species defined by differences in physical traits.

Phylogenetic Species Concept

Species identified as smallest monophyletic group on a tree.

Reinforcement

Selection for traits that prevent hybridization (when hybrids are unfit).

Fusion

Two populations rejoin due to continued gene flow.

Hybrid Zone

Geographic area where hybrid offspring are common.

Phylogeny

Evolutionary history of species or groups.

Systematics

Study of evolutionary relationships.

Taxonomy

Naming and classifying organisms.

Root

Most ancestral lineage of a tree.

Branch

Represents evolution of a species through time.

Node

Point of common ancestry; where branches split.

Tip

Represents a species or group.

Sister Taxa

Two closest relatives that share a recent ancestor.

Outgroup

Species that branched off earlier; used to root the tree.

Monophyletic Group (Clade)

Common ancestor + all descendants.

Paraphyletic Group

Common ancestor + some descendants.

Polyphyletic Group

Group with similar traits but no common ancestor.

Anagenesis

One species evolves into another over time.

Cladogenesis

One species splits into two or more.

Ancestral Trait

Trait found in ancestor.

Derived Trait

Modified version in descendants.

Synapomorphy

Shared derived trait from a common ancestor.

Homology

Similarity due to shared ancestry.

Homoplasy

Similarity due to independent evolution (not common ancestry).

Convergent Evolution

Independent evolution of similar traits due to similar environments.

Parsimony

Simplest explanation (fewest evolutionary changes) is most likely correct.

Fossil Record

Collection of all known fossils.

Fossil Bias

More likely for organisms with hard parts and large populations to fossilize.

Limitation of Fossil Record

Represents less than 5% of all species that ever lived.