Lecture 6 - Forces of Evolution

Flashcards covering key vocabulary related to the forces of evolution, including population genetics, speciation, mutation, gene flow, genetic drift, and natural selection.

Population Genetics

The study of genetic variation within and between populations, with an emphasis on microevolution (generation to generation changes within a species).

Population

Members of a species that regularly mate with each other and exchange alleles, sharing a gene pool.

Biological Species Concept

Defines a species as a group of interbreeding organisms reproductively isolated from other organisms.

Allopatric speciation

A type of speciation where populations evolve independently after geographic isolation interrupts gene flow, eventually leading to reproductive isolation.

Mutation

A change in the sequence of bases in a gene, representing the only source of completely new genetic variation (creates new alleles).

Point Mutation

A change in a single DNA base, potentially altering a codon for one amino acid to a codon for a different amino acid.

Sickle Cell Disease

An autosomal recessive genetic disorder caused by a single base change (point mutation) that codes for abnormal hemoglobin.

Silent/Synonymous Mutation

A type of point mutation where the DNA code for an amino acid is converted to a sequence that specifies the same amino acid, having no effect on the protein.

Nonsense Mutation

A type of point mutation where the DNA code for an amino acid is converted to a code for a chain-terminating codon.

Frameshift Mutation

An insertion or deletion of a base that changes all codons 'downstream' from the mutation, severely altering the protein.

Chromosomal Mutations

Larger-scale changes in chromosomes including deletions, duplications, inversions, and translocations.

Gene Flow

The exchange of genes between populations, influenced by factors like physical distance and social structures, tending to decrease variation between populations.

Genetic Drift

Changes in the frequency of alleles due to chance, having the greatest impact in small populations and can lead to complete loss of alleles.

Founder Effect

A subset of a larger population migrates and establishes its own gene pool, carrying only a portion of the alleles present in the original population, leading to different allele frequencies by chance.

Genetic bottleneck

A sharp reduction in the size of a population due to environmental events or human activities, resulting in a loss of genetic diversity as only a small fraction of the population survives to reproduce.

Natural Selection

An evolutionary force that removes unfavorable variations and preserves favorable ones by acting on the organism's phenotype, with the environment serving as a filter.

Balanced polymorphism

A situation where a harmful allele is maintained in certain populations because natural selection favors the heterozygous state (e.g., sickle cell trait providing malaria resistance).

Polymorphism

A trait for which two or more distinct phenotypes exist within a population, with frequency and distribution shaped by gene flow, genetic drift, environment, natural selection, and culture.

Lactase persistence

The ability to digest lactose into adulthood, common in some human populations due to selective advantage after the domestication of dairy animals.

Lactose Intolerance / Lactase Impersistence

The typical mammalian condition where lactase production decreases with age, leading to the inability to digest lactose and its accumulation in the intestines.