Bio Diversity: Speciation and Phylogeny – Chapter 2

Evolution

— A change in allele frequency in a population over time.

Population

— A group of individuals of the same species that interbreed and share a common gene pool.

Allele frequency

— The relative abundance of a particular allele in a population.

Population genetics

— The study of genetic variation within populations and how it changes over time.

Genetic diversity

— The variety of alleles and genotypes present within a population.

Mutation

— A change in DNA sequence that introduces new alleles into a population.

Genetic recombination

— The reshuffling of genetic material during sexual reproduction that increases genetic diversity.

Immigration

— The movement of individuals into a population, increasing genetic diversity.

Emigration

— The movement of individuals out of a population, decreasing genetic diversity.

Genetic drift

— Random changes in allele frequencies that occur due to chance events, especially in small populations.

Selection

— A nonrandom process by which individuals with certain traits have higher reproductive success.

Genotype

— The combination of alleles an individual possesses.

Phenotype

— The observable traits of an organism produced by the interaction of genotype and environment.

Nonrandom mating

— Mating patterns in which individuals do not pair randomly with respect to genotype or phenotype.

Assortative mating

— A form of nonrandom mating in which individuals preferentially mate with others that are similar to or different from themselves.

Hardy-Weinberg model

— A mathematical model describing the expected genotype frequencies in a population under conditions of random mating and no evolutionary forces.

Hardy-Weinberg equilibrium

— A state in which genotype frequencies in a population remain constant from generation to generation.

Hardy-Weinberg equation

— p² + 2pq + q² = 1

p

— The frequency of one allele in a population.

q

— The frequency of the other allele in a population.

p + q

— Equals 1, representing all alleles in the population.

p²

— The frequency of homozygotes for the p allele.

q²

— The frequency of homozygotes for the q allele.

2pq

— The frequency of heterozygotes in the population.

Purpose of Hardy-Weinberg equilibrium

— To provide a baseline for detecting evolutionary change in populations.

Violation of Hardy-Weinberg assumptions

— Indicates that evolution is occurring due to selection, drift, migration, mutation, or nonrandom mating.

Gene flow

— The exchange of genes between populations through interbreeding.

Genetic isolation

— A condition in which gene flow between populations is reduced or prevented.

Speciation

— The process by which new species arise from populations of pre-existing species.

Prezygotic barrier

— A reproductive barrier that prevents mating or fertilization from occurring.

Postzygotic barrier

— A reproductive barrier that reduces the viability or reproductive success of offspring.

Allopatric speciation

— Speciation that occurs when populations are geographically separated.

Sympatric speciation

— Speciation that occurs without geographic separation.

Quantitative characters

— Traits influenced by multiple genes that vary continuously across a range of values.

Directional selection

— Selection that favors one extreme phenotype, causing the mean to shift.

Stabilizing selection

— Selection that favors intermediate phenotypes and reduces variation.

Disruptive selection

— Selection that favors both extreme phenotypes over intermediate ones.

Importance of disruptive selection

— It is particularly likely to split a population into two species.

Adaptive radiation

— Rapid diversification of a single ancestral species into many new species.

Cause of adaptive radiation

— The availability of new ecological opportunities and unoccupied niches.

Example of adaptive radiation

— Darwin's finches of the Galápagos Islands.

Species concept

— A framework used to determine what constitutes a species.

Morphological species concept

— Defines species based on physical characteristics.

Biological species concept

— Defines species based on reproductive compatibility.

Genetic species concept

— Defines species based on genetic similarity and phylogenetic relationships.

Difficulty defining species

— No single species definition applies universally across all forms of life.

Phylogeny

— The evolutionary history and relationships among species.

Phylogenetics

— The study of evolutionary relationships among organisms.

Phylogenetic tree

— A branching diagram that represents patterns of ancestry.

Branch point (node)

— Represents a common ancestor in a phylogenetic tree.

Monophyletic group (clade)

— A group consisting of a common ancestor and all of its descendants.

Tree of life

— The complete phylogenetic tree representing the diversification of all life on Earth.

Closely related species

— Species that share a more recent common ancestor.

Phylogenetic trees as hypotheses

— Phylogenetic trees represent proposed relationships that may change with new evidence.

Convergent evolution

— Independent evolution of similar traits in distantly related species.

Parsimony principle

— The preferred phylogenetic tree is the one requiring the fewest evolutionary changes.

Molecular phylogenetics

— The use of DNA sequences to infer evolutionary relationships.

Most parsimonious tree

— The tree that requires the fewest genetic mutations to explain observed data.

Conserved genes

— Genes that change very slowly over time and are useful for phylogenetic analysis.

Fossil record

— Preserved remains or traces of organisms from the past.

Radiometric dating

— A technique used to determine the age of fossils or rocks using radioactive decay.

Radioisotopes

— Unstable isotopes that decay into daughter products at a predictable rate.

Daughter product

— The stable isotope produced by radioactive decay.

Radioactive decay

— The spontaneous conversion of an unstable isotope into a more stable form.

Molecular clock

— A method that estimates divergence time based on the rate of DNA mutation.

DNA mutation rate

— The speed at which mutations accumulate in a DNA sequence over time.

Importance of molecular clocks

— They allow estimation of when species diverged from a common ancestor.

Finish this statement: "Evolution is a _"

— change in allele frequency in a population over time.

Finish this statement: "Speciation requires _"

— genetic isolation.

Finish this statement: "Phylogenetic trees are_"

— hypotheses.

Finish this statement: "The most __ tree is preferred."

— parsimonious

Finish this statement: "_ is particularly likely to split a species

— Disruptive selection