Microevolution, Speciation, and Evolutionary Concepts

microevolution

Change in the gene pool of a population from one generation to the next.

speciation

The process by which one species splits into two or more species.

biological species concept

A group of populations whose members can interbreed and produce fertile offspring.

reproductive isolation

Different species cannot produce viable, fertile offspring.

morphological species concept

Defines species based on observable physical traits.

ecological species concept

Defines a species by its ecological niche.

phylogenetic species concept

Defines a species as the smallest group sharing a common ancestor.

reproductive barrier

Biological features preventing species from interbreeding.

prezygotic barriers

Barriers that prevent mating or fertilization.

postzygotic barriers

Barriers where zygotes fail to develop into fertile adults.

habitat isolation

An example of a prezygotic barrier.

temporal isolation

Species breed at different times.

behavioral isolation

Different courtship rituals.

mechanical isolation

Reproductive structures are incompatible.

gametic isolation

Sperm cannot fertilize the egg.

reduced hybrid viability

Offspring fail to develop properly.

reduced hybrid fertility

Offspring are sterile.

macroevolution

Evolutionary change above the species level.

fossil record

Sequence of fossils appearing in rock strata.

geologic record

Chronology of Earth's history based on fossil ages.

theory of plate tectonics

Earth's crust is divided into floating plates.

Pangaea

Supercontinent formed 250 million years ago.

mass extinctions

Five documented mass extinctions.

adaptive radiations

Periods when many new species evolve from a common ancestor.

taxonomy

Branch of biology for naming and classifying organisms.

binomial

Two-part scientific name (genus + specific epithet).

phylogeny

Evolutionary history of a species or group.

phylogenetic tree

Hypothesis about evolutionary relationships.