HE: CH4 Speciation and Phylogeny

Life can be clustered into distinct types called-

-species.

Species

• Potential to interbreed and produce fertile offspring

• Reproductively isolated from other such groups

• Connected through gene flow

• Species and subspecies can be difficult to differentiate

Anagenesis:

a single population evolving through time the descendant population (B) will evolve to significantly diverge from its parent population (A)

Cladogenesis:

• one population (A) evolves into two populations (B and C)

• the descendant populations live at the same time and are different enough and reproductively isolated enough for taxonomists to classify them as different species

Reproductive Isolation

• Reduces or eliminates successful interbreeding between populations

• Contributes to genetic divergence

Mechanisms of reproductive isolation:

Prezygotic—before formation of a zygote

Postzygotic—soon after formation of a zygote

Examples of prezygotic mechanisms:

• Species do not encounter one another

• Species have different courtship behaviors or preferences

• Species have bodies or genitals that differ too much

• Species have incompatible sperm and egg cells

Examples postzygotic mechanisms:

• Set of chromosomes of hybrid embryo cannot match up correctly

• Embryo does not carry a complete set of genetic information

Allopatric Speciation

New species form because populations are geographically separated (physical barrier like a mountain, river, or distance)

-Combination of reproductive isolation and natural selection

Parapatric Speciation

New species form in adjacent populations that have limited gene flow, often due to different environmental conditions along a gradient.

Sympatric Speciation

New species form within the same geographic area, without physical separation.

Ecological niche

The way an organism “makes a living”

More niches leads to more species.

Adaptive radiation

Rapid diversification fills niches

The Comparative Method

• Function of behavior or morphology deduced

• Independent evolutionary events counted

DNA in noncoding regions changes at a constant rate (T/F)

True

when a population is divided by some type of barrier, such as a geographical barrier, and different parts of the population adapt to different environments, this is called-

-allopatric speciation.

Cultivated crops such as wheat, corn, and tobacco have undergone speciation due to human intervention in their breeding and cultivation. These are examples of -

-sympatric speciation

The technique of deducing the function of morphological features or behaviors by comparing the traits of different species is known as-

-comparative method.

Based on genetic distances among noncoding sequences of DNA, humans are most closely related to-

chimpanzees.

A single kind of animal or plant diversifies to fill many available niches in the process called-

-adaptive radiation

adaptive radiation

an evolutionary process where a single ancestral species rapidly diversifies into a variety of new forms, each adapted to a different ecological niche