Biology Chapter 14

Types of Pre-Reproductive Barriers

geographic isolation, ecological isolation, temporal isolation, behavioral isolation, mechanical isolation, gametic isolation

Reduced Hybrid Fertility

hybrids cannot reproduce because they are sterile

Reduced Hybrid Viability

hybrids do not develop fully or die at a young age

Gametic Isolation: Example

in some different species of fish, reproduction is prevented because the sperm cannot penetrate the egg

Post-Reproductive Barriers

prevent hybrid offspring from developing into viable, fertile adults

Gametic Isolation: Definition

reproduction is prevented because gametes are not compatible with each other

Behavioral Isolation: Definition

reproduction is prevented because members of a species only respond to certain mating calls and dances

Ecological Isolation: Definition

reproduction is prevented because species live in distinct habitats and rarely encounter each other

Temporal Isolation: Definition

reproduction is prevented because species mate at different times of day, seasons, or years

Geographic Isolation: Definition

species are separated by a geographical feature and a physical barrier prevents reproduction

Punctuated Equilibrium

states that speciation occurs in rapid bursts of change mixed with long "static" periods of little or no change

Gradualism

states that speciation occurs over a long time through a gradual accumulation of small changes

Behavioral Isolation: Example

the Blue Footed Booby only mates after a courtship display that is unique to the species

Hybrid

the offspring of two different species

Speciation

the process in which one species splits into two

In order for new species to form, populations must __________

become isolated

Ernst Mayr

created the Biological Species Concept

Biological Species Concept

defines a species as a population whose members can interbreed and produce viable, fertile offspring

Reduced hybrid fertility is often caused by __________

different number of chromosomes in the parents

Geographic Isolation: Example

different species of antelope squirrel on either side of the Grand Canyon

Ecological Isolation: Example

different species of garter snake rarely encounter because one species lives on land and the other lives in water

Temporal Isolation: Example

different species of spotted skunks do not mate because one species breeds during Winter and the other breeds during Summer

Mechanical Isolation: Example

many insects cannot mate because their sex organs do not fit together, which prevents the transfer of sperm

Pre-Reproductive Barriers

obstacles that prevent mating or fertilization

Mechanical Isolation: Definition

physical differences between species prevent reproduction