Biol 106 Lecture 11: Evidence of Evolution & Population Genetics

Vocabulary flashcards summarizing key terms and definitions related to population genetics and evidence for evolution from Biol 106 Lecture 11.

Allele Frequency

Proportion of a specific allele (0–1) among all copies of the gene in a population.

Genetic Structure

The combined distribution of allele and genotype frequencies within a population.

Hardy–Weinberg Equilibrium

Idealized state in which allele and genotype frequencies remain constant across generations.

Mutation (HW Context)

Change in DNA sequence that introduces new alleles; must be absent for HW equilibrium.

Natural Selection

Differential survival and reproduction of genotypes; must be absent for HW equilibrium.

Gene Flow

Movement of alleles into or out of a population via migration; violates HW equilibrium.

Genetic Drift

Random fluctuation of allele frequencies, strongest in small populations; absent in infinite populations.

Random Mating

Condition in which mate choice is independent of genotype; required for HW equilibrium.

Fossil Record

Physical remains of past organisms preserved in rock layers, documenting extinction and change.

Biogeography

Study of the geographic distribution of species and the patterns that result.

Comparative Morphology

Comparison of body plans, structures, and embryonic stages among organisms to infer relationships.

Molecular Biology (Evidence)

Use of DNA and protein sequence comparisons to reveal evolutionary relationships.

Lab & Field Experiments

Direct observation of evolutionary processes under controlled or natural conditions.

Radiometric Dating

Technique that determines fossil age by measuring radioisotope decay and calculating half-lives.

Radioisotope

Unstable form of an element whose nucleus decays at a constant rate into daughter products.

Half-Life

Time required for half the atoms of a radioisotope to decay into its daughter element.

Tiktaalik

Transitional fossil showing features of both fish and early tetrapods, bridging aquatic to terrestrial life.

Vestigial Structure

Reduced or non-functional anatomical feature that was functional in an ancestor (e.g., human appendix).

Convergent Evolution

Independent evolution of similar traits in distantly related lineages adapting to similar niches.

Analogous Structures

Body parts that perform the same function but evolved separately and are not from a common ancestor (e.g., bird vs. bat wings).

Homologous Structures

Anatomical features inherited from a common ancestor, may differ in function (e.g., vertebrate forelimbs).

Marsupials

Mammals whose young develop briefly in the uterus and complete growth in a pouch; share closer relation to each other than to placentals.

Placentals

Mammals whose offspring develop fully in the uterus with a placenta; show convergent forms with marsupials.

Molecular Similarity

Degree of DNA or protein sequence identity between species, reflecting relatedness and divergence time.

Microevolution

Small-scale changes in allele frequencies within populations over a few generations.

Macroevolution

Large-scale evolutionary changes that give rise to new taxa, often over long time periods.

Allele Counting Method

Procedure for estimating allele frequencies by tallying each allele across all individuals and dividing by 2N.

Heterozygote (Aa)

Individual carrying two different alleles at a locus.

Homozygote (AA or aa)

Individual carrying two identical alleles at a locus.

Constraints on Evolution

Limits on adaptive change due to lack of variation or developmental/mechanical restrictions.

radiometric dating

A method for determining the age of an object by measuring the presence of radioactive isotopes.

missing link

a transitional fossil — a species that shows traits intermediate between an ancient ancestor and a more modern organism.