Evolution, Microevolution, and Population Genetics

Flashcards covering key vocabulary related to evolution, microevolution, population genetics, mechanisms of evolution, variation, evolutionary evidence, and historical context based on lecture notes.

Evolution

The change in the genetic makeup of a population over time; specifically, the change in allele or genotype frequencies in populations over time.

Biological evolution

Describes change in allele or genotype frequencies in a population over time.

Population

A group of individuals of a species at the same place and at the same time.

Phenotype

The expressed physical, behavioral, and biochemical traits of an individual (e.g., height, eye color).

Genotype

The genetic makeup of a cell or organism.

Phenotypic variation

Refers to the physical, behavioral, and biochemical differences within a population.

Genetic variation (Heritable variation)

Refers to the differences in genotype among individuals in a population.

Gene Pool

The sum of all alleles at all gene loci within a population, characterizing its genetic makeup.

Microevolution

Evolution within a species.

Macroevolution

Changes between species.

Heritability

The proportion of the total population variation in a trait that is due to genetic differences among individuals.

Continuous variation

Where the variable has a range and intermediates (e.g., mass, height), controlled by multiple genes or different loci.

Discontinuous (quantitative) variation

Where the variable falls into distinct groups with no intermediates (e.g., eye color), controlled by a single gene or few genes on the same loci.

Polymorphism

Describes two or more variants of a trait on a gene.

Genotype frequency

The proportion of a specified genotype among all the genotypes for a specific gene or set of genes in a population.

Allele frequency

The proportion of a specified allele among all the alleles of a gene in a population.

Mendelian segregation

A universal law stating that only one of the two gene copies present in an organism is distributed to each gamete (egg or sperm cell) it makes, and the allocation is random.

Fixed allele

When a population only exhibits one allele at a particular gene (e.g., if a human population only exhibits brown eyes, the allele for brown eyes is 'fixed').

Hardy-Weinberg Principle

Suggests that there is an equilibrium of alleles within a population, where allele and genotype frequencies do not change in the absence of evolutionary change.

Hardy-Weinberg Equilibrium

A state where allele and genotype frequencies do not change, provided that only Mendelian segregation and recombination of alleles is at work.

Null model (Hardy-Weinberg)

A theoretical genetic makeup of a population if it were not evolving at a specific gene locus, used for comparison with real populations.

Mutation

A spontaneous evolutionary mechanism that leads to genetic or heritable variation, introducing new alleles into a gene pool.

Gene flow

The movement of alleles across different populations.

Genetic Drift

A change in allele frequencies due to a chance event.

Population/evolutionary bottleneck

The reduction in alleles due to sudden population reductions caused by factors like disease, starvation, or drought.

Founder effect

Change in allele frequency due to a few individuals starting a new population.

Natural selection

The process by which a given trait in a population with genetic variation, causes variants best suited for growth and reproduction in a given environment to contribute disproportionately to future generations, leading to adaptation.

Selection pressure

An environmental factor that disfavors some members of a population while favoring others.

Relative fitness

The extent to which an individual's genotype is represented in the following generation, describing how well an individual survives and reproduces in a particular environment.

Stabilizing selection

A type of natural selection that favors the mean phenotype.

Directional selection

A type of natural selection that favors one of the extreme phenotypes.

Disruptive selection

A type of natural selection that favors both extreme phenotypes, often resulting in polymorphisms.

Artificial selection

A form of directional selection where humans intentionally breed for specific traits.

Negative selection

Natural selection that reduces the frequency of a deleterious allele.

Positive selection

Natural selection that increases the frequency of an advantageous allele.

Balancing selection

A form of natural selection that acts to maintain two or more alleles in a population, reaching an equilibrium state.

Heterozygous advantage

A mechanism of balancing selection where heterozygotes have higher fitness than either homozygote, thus maintaining both copies of the gene in the gene pool (e.g., Sickle Cell Anemia and Malaria).

Frequency-dependent selection

A mechanism of balancing selection where the relative fitness of genotypes varies with their frequencies in the population, with fitness often highest when rare.

Sexual selection

A form of natural selection defined as the competition for mates.

Intrasexual selection

Sexual selection involving interactions between individuals of one sex, as when members of the same sex compete for the opposite sex.

Intersexual selection

Sexual selection involving interactions between males and females, as when females choose from among males.

Adaptive traits

Products of selection that increase relative fitness.

Adaptations

The accumulation of adaptive traits over time.

Vestigial structures

Currently useless structures of organisms, also called 'evolutionary leftovers'.

Natural history

The biological study of organismal form and variety in natural environments.

Natural theology

A field of study that sought to catalog God's creation, promoting the investigation of living organisms.

Taxonomy

The biological classification of organisms.

Biogeography

The study of the world distribution of organisms.

Comparative morphology

The study that revealed structural similarities in 'dissimilar' anatomies.

Fossils (Stratification)

Preserved remains or traces of organisms found in horizontal layers of sedimentary rocks, with different fossils in different layers indicating age.

Paleobiology

The study of ancient organisms.

Catastrophism

The theory of fossil formation by catastrophe.

Descent with Modification

Darwin's idea that present-day species are descendants of common ancestors that were modified through evolution.

Principle of succession

The observation of similarity between fossil and living forms in the same geographical area (e.g., Patagonia fossils).

Divergence in Isolation from a Common Ancestor

The idea that similar physical conditions across different islands (e.g., Galapagos) can lead to distinct species evolving from a common ancestor due to isolation.

Monogenism

The belief that all human races originated from a single source, often implying race as a social construct.

Polygenism

The belief that human races originated from multiple independent sources, often supporting racial essentialism.

Alfred Russel Wallace

A co-developer of the theory of evolution by natural selection with Charles Darwin, known for discovering Wallace's line.

Wallace's line

An imaginary boundary separating Asian animals from Australian ones across the Malay archipelago, based on observed differences in life forms.

Theory (scientific)

A supposition or system of ideas intended to explain something, especially one based on general principles independent of the thing to be explained; explains why.

Law (scientific)

A statement of fact, deduced from observation, to the effect that a particular natural or scientific phenomenon always occurs if certain conditions are present; describes what.

Transitional forms

Fossils or organisms that show intermediate states between an ancestral form and that of its descendant (e.g., dinosaurs with birds).

Per-mineralization

A fossilization process where an organism is buried, filled with mineral-rich waters, turning tissue to stone, sometimes in exceptional detail.

Trace fossil

A track or trail (e.g., dinosaur track, feeding trails) left by an animal as it moves or buries into sediments.

Molecular fossil

Biochemicals (like sterols, bacterial lipids, or pigment molecules) relatively resistant to decomposition that can be preserved in sedimentary rock.

Geological dating

Determining the age of fossils by dating rock strata, where deeper layers are generally older.

Radiometric data

Determining the age of fossils using the half-lives of isotopes, such as Carbon-14 for recent periods or uranium and lead for older periods.

Carbon-14 tracing

A radiometric dating method for more recent periods (up to 50,000 years ago), based on the decay of Carbon-14 with a half-life of 5730 years.

Cyanobacteria

The earliest life form detected by humans so far.

Atavism

A modification of a biological structure whereby an ancestral genetic trait reappears after having been lost through evolutionary change in previous generations.

Retrodiction

A prediction of the past based on the laws known today that are assumed to govern them; the explanation or interpretation of past actions or events inferred from assumed governing laws.

Vestigial genes

Non-functional genes that once served a purpose in ancestral organisms but are now useless (e.g., human genes for making yolk proteins or vitamin C).