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18 Cards in this Set

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a population of individuals that can breed and produceviable offspring . This is Biological Species Concept

Morphological Species Concept

classification based on phenotype

Ecological Species

Concept-based on living in same habitat

Phylogenetic spcies

based on taxonomy

Reproductive barriers

-Divided into two groups:

1. Prezygotic barriers

2. Postzygotic

Prezygotic barriers

A. Temporal isolation

B. Habitat isolation

C. Behavioral isolation


A. Hybrid inviability (hybrids do not survive to maturity)B. Hybrid sterility (hybrids survive but are sterile)

How do species start?

Most often a geographic barrier prevents gene flow

Mutation and genetic drift occur

Called allopatric speciation

Allopatric speciation

Several geologic processes can isolate populations.

A mountain range may emerge and gradually split a population oforganisms

A large lake may shrink until there are several smaller lakes

Continents themselves can split and move apart.

How large must a geographic barrier be to keep allopatricpopulations apart?

Answer depends on the ability of the organisms to move.

Birds, mountain lions, and coyotes can easily cross mountain ranges.

How do reproductive barriers arise?

The environment of an isolated population may include:

different food sources

different types of pollinators

different predators

Result of natural selection acting on preexisting

Other ways for species to arise

New species can arise right next to parent population

Known as Sympatric speciation

Reproductive isolation keeps parental and new species apart

of all living plant species are descendants of ancestors that formed bypolyploid speciation.


Polyploid plants

• cotton• oats• potatoes• bananas• peanuts• barley• plums• apples•sugarcane• coffee• wheat

Even more ways for new species to arise..

If an individual is introduced into a new environment

Must adapt to changes

If leads to new species is called adaptive radiation

Common when individuals reach an island

What happens when separated populations of closely relatedspecies come back into contact with each other?

Biologists try to answer such questions by studying hybrid zones

How does evolution “move along”?

-Two major theories:

1. Gradualism Model

2. Punctuate evolution

Gradualism Model

species gradually change over time, evolutionruns at constant slow rate