Biology Module 2- Natural Selection and Evolution

Who is Charles Darwin?

Father of evolution

Comparative Anatomy

Presence of homologous (shared) structures and shared embryonic development between species indicates descent from common ancestors

Vestigial Structures

A structure that is present in an organism but no longer serves its original purpose

Artificial Selection

selective breeding of plants and animals to promote the occurrence of desirable traits in offspring

Darwin's contribution to evolution

He wrote The origin of species. His main points were organisms inhabiting Earth today descended from ancestral species.

Natural selection is the mechanism for descent with modification.

Darwin's 4 observations of natural selection

1. high reproductive capacity

2. heritable variation

3. limits on population growth, or a struggle for existence (most species produce more offspring than survive)

4. differential reproductive success (survival & reproduction is not random)

Misconceptions about natural selection

1. Natural selection does not create alleles

2. Evolution by natural selection never stops

3. Natural selection does not lead to perfection

Who is Jean Lamarck?

A french zoologist who made a theory based on the vertical hierarchy, the property of use and disuse, and the inheritance of acquired characteristics

Who is Alfred Wallace?

He sent Darwin his findings of evolution, having the same ideas about evolution as Darwin

Stabilizing Selection

Natural selection that favors intermediate variants by acting against extreme phenotypes

Directional Selection

occurs when natural selection favors one of the extreme variations of a trait

Disruptive Selection

favors individuals at both extremes of the phenotypic range

Sexual Selection

A form of natural selection in which individuals with certain inherited characteristics are more likely than other individuals to obtain mates.

Genetic Drift

random change in allele frequencies that occurs in small populations

Bottleneck Effect

A change in allele frequency following a dramatic reduction in the size of a population

Founder Effect

change in allele frequencies as a result of the migration of a small subgroup of a population

Adaptation

A trait that helps an organism survive and reproduce

divergent evolution

evolution of one or more closely related species into different species; resulting from adaptations to different environmental conditions

Variation

differences in physical traits of an individual from the group to which it belongs

homologous structures

Structures in different species that are similar because of common ancestry.

natural selection

A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits.

convergent evolution

Process by which unrelated organisms independently evolve similarities when adapting to similar environments

bionomial nomenclature

Classification system in which each species is assigned a two-part scientific name

Parts of a phylogenetic tree

root, branch, node, clade

Root (phylogeny)

common ancestor of all organisms in the tree

branch (phylogeny)

a line representing a population through time

unrooted phylogenetic tree

show relationships but not a common ancestor

rooted phylogenetic tree

single lineage (at base) represents common ancestor

branch point on phylogenetic tree

represents the divergence of two species

sister taxa (sister group)

groups that are more closely related to each other than either of them is to any other group

Gene

A segment of DNA on a chromosome that codes for a specific trait

Allele

Different forms of a gene

allele frequency

Proportion of a specific allele in a population.

gene pool

All the genes, including all the different alleles for each gene, that are present in a population at any one time

Population

A group of individuals that belong to the same species and live in the same area

Phenotype

An organism's physical appearance, or visible traits.

membrane bound organisms

Eukaryotic

No membrane bound organisms

Prokaryotic and bacteria