Biological Species Concept and Speciation

These flashcards cover key concepts related to the Biological Species Concept, various types of reproductive barriers, speciation processes, and models of evolution.

Biological Species Concept

A species is a group of populations whose members can interbreed in nature and produce viable fertile offspring, but do not successfully breed with other groups.

Reproductive Barrier

Biological factors that prevent species from interbreeding and producing fertile offspring, maintaining species boundaries by blocking gene flow.

Prezygotic Barriers

Factors that prevent mating or fertilization before a zygote forms.

Postzygotic Barriers

Factors that occur after fertilization that prevent the hybrid from developing properly or reproducing.

Habitat Isolation

Species live in different environments and rarely meet, e.g., snakes that live on land vs. in water.

Temporal Isolation

Species breed at different times such as season, day, or year, e.g., skunks that mate in winter vs. summer.

Behavioral Isolation

Different courtship rituals or mating signals, e.g., fireflies with unique light patterns.

Mechanical Isolation

Physical differences prevent mating, e.g., insects with incompatible reproductive parts.

Gametic Isolation

Sperm and egg are incompatible, e.g., sea urchin gametes that can't fuse.

Reduced Hybrid Viability

Hybrid embryo doesn't develop properly or dies early, e.g., salamander hybrids that don't survive.

Reduced Hybrid Fertility

Hybrid lives but is sterile, e.g., mule (horse x donkey) that is sterile.

Hybrid Breakdown

First-generation hybrid is fertile, but later generations are weak or sterile, e.g., hybrid crops losing fertility in later generations.

Allopatric Speciation

Occurs when populations are geographically separated, stopping gene flow and allowing populations to evolve independently, e.g., Grand Canyon squirrels on north vs south rim.

Sympatric Speciation

New species form in the same area, often due to genetic changes like polyploidy or behavioral isolation.

Polyploidy

When an organism has extra sets of chromosomes (more than 2n), common in plants.

Pollinator Choice

Different pollinators prefer certain flower shapes, colors, or scents, leading to reproductive isolation, e.g., red tubular flowers attract hummingbirds, while blue flowers attract bees.

Adaptive Radiation

The evolution of many diverse species from a common ancestor, often after new habitats or resources become available, e.g., Darwin's finches evolving different beak shapes.

Gradual Model of Speciation

Species evolve slowly and steadily over time, showing smooth, continuous change.

Punctuated Model of Speciation

Long periods of little change (stasis) interrupted by short bursts of rapid speciation.