Evolutionary Theory Part 2: Forces and Debates

Flashcards covering the history of evolutionary thought, the mechanisms of evolution, and modern debates such as Selectionist vs. Neutral Theory.

Evolution

A change in the gene frequencies of a population over time.

Charles Darwin (1809-1882)

Scientist who voyaged on the Beagle and concluded that all Galapagos finches descended from a common ancestor, publishing his findings in 1859.

Alfred Russel Wallace (1823-1913)

Scientist who proposed in 1855 and 1858 that species descended from other species and that evolution is a process driven by competition and a struggle for existence.

On the Origin of Species

The book published by Charles Darwin in 1859 describing the preservation of favoured races in the struggle for life through natural selection.

Patrick Matthew (1790-1874)

Scottish landowner who proposed evolution by natural selection based on trees in his 1831 work 'Naval Timber and Arboriculture'.

Al-Jahiz (776-868)

Author of 'The Book of Animals' who described how animals had different traits to survive their environment and outlined the concept of natural selection.

Malthusian competition

Concept by Thomas Robert Malthus involving geometric population growth and limited resources leading to a struggle for survival.

Mendelian inheritance

The principle that offspring receive two copies of each gene, one from each parent, as established by Gregor Mendel.

Modern Synthesis of Evolution

The early 20th-century integration of natural selection, mutation, genetic variation, and Mendelian inheritance to explain changes in allele frequencies over time.

Natural Selection

Occurs when individuals with certain genotypes are more likely to survive and reproduce, passing their alleles to the next generation.

Fitness

A relative measure that changes with environmental conditions; natural selection can only act on traits that affect this value.

Sickle Cell Anemia

A human evolutionary example where the heterozygous (AS) genotype provides protection against malaria, while the homozygous (SS) genotype is highly anemic.

Sexual Selection

A type of natural selection where members of one sex choose mates or compete with members of the same sex based on specific characteristics.

Mutation

Small changes in individual characteristics that exist on a continuum of being advantageous, neutral, or deleterious.

Genetic Drift

A neutral evolutionary force where gene variant frequencies change due to random sampling, having a stronger effect in small populations.

Tay-Sachs Disease

A disorder resulting from a mutation in the HEXA gene that is more common in small, isolated populations like Ashkenazi Jews, French Canadians of southeastern Quebec, and Old Order Amish.

Founder Effect

A special type of genetic drift that occurs when a small group from a mother population establishes a new population.

Gene Flow

The exchange of genes between two populations, such as the interbreeding between humans and Neandertals in Eurasia between ~45,000-65,000 years ago.

Selectionist hypothesis

The proposal that most genetic variation is caused by the process of natural selection.

Neutral Theory

The theory by Motoo Kimura stating most molecular variation is due to random processes and neutral mutations rather than natural selection.