bio exam 1 (real)

Evolution

Change in genetic composition of a population across generations; descent with modification

Macroevolution

Evolution on a broad scale across species

Fitness

Number of surviving offspring an individual leaves behind

Natural Selection

Mechanism of evolution where advantageous traits become more common

Heritable Trait

Trait passed genetically from parent to offspring

Phenotypic Plasticity

Ability of a genotype to produce different phenotypes based on environment

Developmental Plasticity

Environment determines phenotype early in life and it stays

Seasonal Plasticity

Phenotype changes during lifetime due to seasonal environmental shifts

Genetic Variation

Differences in gene/DNA sequences within a population

Point Mutation

Random error in DNA sequence

Chromosomal Mutation

Large-scale mutation like insertion or deletion of chromosomal sections

Crossing Over

Exchange of genetic material during meiosis, increases variation

Alleles

Different forms of a gene (e.g., A or a)

Gene Pool

Total collection of genes/alleles in a population

Hardy-Weinberg Principle

Principle stating allele frequencies remain constant in absence of evolution

Directional Selection

One extreme phenotype is favored

Stabilizing Selection

Intermediate phenotypes are favored

Disruptive Selection

Both extremes are favored over intermediates

Genetic Drift

Random change in allele frequency; affects small populations more

Bottleneck Effect

Drastic reduction in population size leading to reduced genetic variation

Founder Effect

New population started by small number of individuals, reducing genetic diversity

Gene Flow

Movement of alleles between populations via migration

Assortative Mating

Mating based on trait similarity, not at random

Sexual Selection

Selection based on traits increasing mating success

Intrasexual Selection

Competition among same sex (usually males)

Intersexual Selection

Mate choice (usually by females) based on traits

Balancing Selection

Maintains multiple alleles in a population

Heterozygote Advantage

Heterozygotes have higher fitness than either homozygote

Frequency-Dependent Selection

Fitness depends on how common the phenotype is

Positive Frequency-Dependent Selection

Common phenotypes favored

Reinforcement

Hybrids are less fit, reproductive isolation strengthens

Fusion

Hybrids are more fit or equal, species merge

Stability

Hybrids are more fit in certain zones, hybrid zones persist

Species

Group of interbreeding organisms that are reproductively isolated

Biological Species Concept

Species defined by reproductive isolation

Prezygotic Isolation

Barriers before fertilization (habitat, time, behavior, mechanics, gametes)

Postzygotic Isolation

Barriers after fertilization (inviability, sterility, breakdown)

Hybrid Breakdown

Hybrids viable initially but less fit in future generations

Allopatric Speciation

Speciation with geographic barrier

Sympatric Speciation

Speciation without geographic barrier, via mutation or trait divergence

Autopolyploidy

Chromosome duplication within a species; leads to new species

Allopolyploidy

Chromosome duplication following hybridization between species

Polyploidy

Organism has more than 2 sets of chromosomes

Adaptation

Trait favored by natural selection that increases fitness

Acclimation

Individual, non-heritable physiological adjustment to environment

Local Adaptation

Populations evolve traits specific to local environments

Extinction

Disappearance of a species

Mass Extinction

Global, large-scale species loss

Species Radiation

Rapid diversification of species into new forms

Cambrian Explosion

Rapid diversification of animal life ~540 MYA

Coevolution

Reciprocal evolutionary influence between two interacting species

Red Queen Hypothesis

Coevolving species must constantly adapt to maintain status

Phylogeny

Hypothesis of evolutionary relationships

Clade

Group including a common ancestor and all its descendants

Node

Branching point in phylogeny, represents common ancestor

Taxa

Groups of organisms (species, genus, etc.)

Sister Taxa

Two taxa that share the most recent common ancestor

Homology

Similarity due to shared ancestry

Analogy (Homoplasy)

Similarity due to convergent evolution, not ancestry

Cladistics

Method of building phylogenetic trees using shared derived traits

Monophyletic Group

Group with a common ancestor and all descendants

Paraphyletic Group

Common ancestor and some, but not all, descendants

Polyphyletic Group

Group lacking common recent ancestor

Parsimony

Simplest explanation (fewest evolutionary changes) is most likely

Molecular Clock

Method of estimating evolutionary timing using DNA mutation rates

Punctuated Equilibrium

Rapid evolutionary changes followed by long stasis

Gradualism

Evolutionary change occurs slowly over time

Stasis

Period with little evolutionary change

Synapomorphy

Shared derived trait used to define a clade