Notes on Descent With Modification: Darwinian View of Life

Evolution

Descent with modification, change in genetic frequencies over time, and change with inheritance.

Lamarck's Use and Disuse Theory

Organisms could adapt to their environment, and modifications acquired during a lifetime could be passed to offspring.

Uniformitarianism

Proposed by Charles Lyell, stating that the mechanisms of change on Earth are constant over time and result from slow, continuous actions still operating today.

Natural Selection

The core idea proposed by Darwin, where individuals with favorable traits are more 'fit' (better suited to their environment) and leave behind more offspring, leading to changes in favorable traits across generations.

Thomas Malthus's Principle

Populations tend to grow faster than resources, leading to competition and a struggle for existence.

Phenotype

The product of an inherited genotype and environmental influences; natural selection acts on phenotypic variation that has a genetic component.

Mutation

A change in the nucleotide sequence of DNA, which is a source of new genes and alleles. Only mutations in gamete-producing cells can be passed to offspring.

Homologous Structures

Anatomies inherited from a common ancestor (e.g., the bone structure of a human arm, cat leg, whale flipper, and bat wing).

Analogous Structures

Structures that have similar functions but different evolutionary origins (e.g., the wings of a bird and the wings of an insect).

Vestigial Structures

Reduced or no longer functional structures in a species but homologous to functional structures in relatives (e.g., the human coccyx or wisdom teeth).

Biogeography

The study of how geography and dispersal influence evolution, often exemplified by island species diverging from mainland ancestors.

Directional Selection

A mode of natural selection that favors one extreme end of the phenotypic range, shifting the population mean toward that extreme.

Sexual Dimorphism

Marked differences between sexes in secondary sexual characteristics, resulting from sexual selection (a form of natural selection focusing on mating success).

Heterozygote Advantage

A condition where some heterozygous individuals have higher fitness than either homozygote, thereby helping to preserve genetic variation in a population (e.g., sickle-cell allele providing malaria resistance).

Hox Genes

Genes that control basic body plans; they show deep similarities in gene expression across distantly related species, indicating developmental similarities.