Evolution and Ecology Core Concepts

Evolution

Change in heritable characteristics of biological populations over successive generations.

Natural selection

Differential survival and reproduction of individuals due to phenotypic differences.

Variation

Differences in physical traits or genetic makeup among individuals in a population.

Mutation

A permanent change in the nucleotide sequence of an organism's DNA.

Microevolution

Evolutionary change below the species level, involving changes in allele frequencies.

Macroevolution

Major evolutionary change resulting in the formation of new species and higher taxa.

Survival of the fittest

Phrase meaning reproductive success rather than physical strength.

Gene

A basic unit of heredity made of DNA that determines specific traits.

Genotype

An organism's complete genetic makeup or allele combination.

Phenotype

The observable physical or biochemical characteristics of an organism.

Allele

One of two or more alternative forms of a gene.

Dominant

An allele that expresses its phenotypic effect even when heterozygous.

Recessive

An allele whose phenotypic effect is masked in heterozygotes.

Levels of organization (individual, population, etc)

Hierarchical structure of biological systems from individual to biosphere.

Hypothesis (null and alternative)

Null assumes no effect; alternative proposes a significant effect or relationship.

Complete dominance

A relationship where the dominant allele completely masks the recessive allele.

Incomplete dominance

A genetic condition where neither allele is fully dominant, blending traits.

Phylogenetics

The study of evolutionary relationships among biological entities.

Extinct/extant

Extinct means no longer living; extant means currently existing.

MRCA / tips / nodes

Most recent common ancestor, terminal taxa, and branching points on a tree.

Phylogram

A phylogenetic tree where branch lengths are proportional to evolutionary change.

Cladogram

A tree showing branching relationships without proportional branch lengths.

Chronogram

A phylogenetic tree where branch lengths represent absolute time.

Occam's Razor

The principle that the simplest explanation is usually the best.

Maximum parsimony

Selecting the phylogenetic tree that requires the fewest evolutionary steps.

Trait data

Observable morphological or physiological characteristics used in analysis.

Molecular data

Genetic sequences used to infer evolutionary relationships.

Homology

Similarity resulting from shared ancestry.

Homoplasy

Similarity due to convergent evolution, not shared ancestry.

Light microscope

Microscope using visible light and lenses to magnify specimens.

Stereoscope

Microscope providing a low-magnification 3D view of solid specimens.

Abundance

The total number of individuals of a species in an area.

Richness

The total number of different species in a community.

Evenness

A measure of the relative abundance of different species in an area.

Shannon Diversity Index

A measure of biodiversity that accounts for both abundance and evenness.

Simpson's Diversity Index

Measures the probability that two randomly sampled individuals belong to different species.

Margalef's Diversity Index

A species richness index accounting for total individuals.

Faith's PD

Phylogenetic diversity calculated as the sum of branch lengths on a tree.

Ecological levels of organization (individual to biosphere)

Hierarchy from single organisms up to the entire global ecosystem.

Mesocosm

An experimental tool that encloses a part of a natural ecosystem.

Transect

A line or strip used to sample biological communities across an environment.

Alpha, beta, and gamma diversity

Local diversity, change between habitats, and regional diversity respectively.

Obligate vs facultative vs aerotolerant

Strict requirement, optional usage, or tolerance of specific conditions like oxygen.

Niche (fundamental vs realized)

Potential environmental conditions versus actual conditions an organism occupies.

Ecological succession

The process by which the structure of a biological community evolves over time.

R vs K selection

Selection for high reproductive rate versus efficient resource use in stable environments.

Competitive exclusion

Principle that two species competing for the exact same resources cannot coexist.

Niche partitioning

Differentiation of niches that enables similar species to coexist.

Grinnellian, Eltonian, and Hutchinsonian Niche definitions

Focus on habitat, trophic role, and multidimensional hypervolume respectively.

Intermediate disturbance hypothesis

Local species diversity is maximized at intermediate frequencies and intensities of disturbance.

Trophic cascades (top-down vs bottom-up)

Ecological effects controlled by top predators or primary producers respectively.

Ecological extinction

Reduction of a species to low abundance so it no longer plays its ecological role.

Steady state

An unvarying condition in a physical or ecological system over time.

State shift

A large, abrupt, and persistent change in the structure and function of an ecosystem.