AP Biology

Charles Darwin’s book is called

Charles Darwin’s book is called

On the Origin of Species

What did Darwin argue?

Descent with Modification and Modification by Natural Selection

Descent with Modification

The idea that species change over time, give rise to new species, and share a common ancestor.

Modification by Natural Selection

As traits are passed through generations, there is modification.

Causes of Genetic Variation

Mutation,

Sexual Reproduction,

Rapid Reproduction

Changes in Allele Frequencies

Gene Flow,

Genetic Drift,

Natural Selection

Gene Flow

The transfer of genetic material from one population to another.

Genetic Drift

The change in frequency of an existing gene variant in the population due to random chance.

Bottleneck Effect

A sharp reduction in the size of a population due to environmental events such as famines, earthquakes, floods, fires, disease, and droughts; or human activities such as genocide.

Founder Effect

The loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population.

Similarities of Bottleneck and Founder

They reduce the amount of genetic diversity in a population. They are the result of catastrophes. They lead to a small population.

Heterozygote advantage

Have a higher relative fitness than either the homozygous dominant or homozygous recessive genotype.

What is fitness in relation to evolution?

Reproductive success and reflects how well an organism is adapted to its environment.

Explain how sickle cell disease demonstrates heterozygote advantage?

Heterozygotes are therefore more resistant to the debilitating effects of malaria than the normal homozygotes. This heterozygote advantage in many sickle-cell carriers outweighs the severe reproductive disadvantage of the rarer sickle-cell homozygotes.

What are the conditions needed for Hardy-Weinberg?

No mutation,

random mating,

no gene flow,

infinite population size,

no selection.

Sexual Selection

Sexual selection is a mode of natural selection in which members of one biological sex choose mates of the other sex to mate with, and compete with members of the same sex for access to members of the opposite sex

Intrasexual Selection

Members of the same sex attempt to outcompete rivals, often during direct encounters.

Intersexual Selection

Involves individuals of one sex choosing among members of the opposite sex based on the attractiveness of certain traits that those individuals possess.

Sexual Dimorphism

A difference in secondary sexual characteristics between males and females of the same species.

Homology

Similarity of the structure, physiology, or development of different species of organisms based upon their descent from a common evolutionary ancestor.

Three Types of Homology

Anatomical

Molecular

Embryological

Anatomical Homology

Organisms that are closely related to one another share many anatomical similarities.

Molecular Homology

Similarities between species on the molecular level.

Embryological Homology

Embryos of different species can have similarities that are not visible when the organisms are fully formed. They have homologous structures called pharyngeal arches, or gill arches.

Causes in Allele Frequency Changes

Selection, mutation, migration, and genetic drift

Stabilizing Selection

Is a type of natural selection in which the population mean stabilizes on a particular non-extreme trait value.

Direction Selection

Is a type of natural selection in which one extreme phenotype is favored over both the other extreme and moderate phenotypes.

Disruptive Selection

Both extreme phenotypes have a higher fitness than intermediate phenotypes.

Analogous

Features of different species that are similar in function but not necessarily in structure and which do not derive from a common ancestral feature