Microevolution and Population Genetics (module 2)

Adaptation

Inherited characteristics of organisms that enhance their survival and reproduction in specific environments.

Behavioral Adaptations

Actions or behaviors that help an organism survive in its environment.

Structural Adaptations

Physical features of an organism's body that help it survive.

Biochemical Adaptations

Chemical or metabolic processes within an organism that aid survival.

Physiological Adaptations

Internal systemic responses to external stimuli to help an organism maintain homeostasis.

Evolution

Change in heritable traits in a population over generations; broadly defined as change over time.

Jean Baptiste Lamarck

Proposed that life evolves by use and disuse and the inheritance of acquired characteristics.

Lyell's Principles of Geology

Influenced Darwin by suggesting the Earth is very old and shaped by slow, continuous processes.

On the Origin of Species

Darwin's 1859 book presenting descent with modification and evolution by natural selection.

Natural Selection

Differential success in survival and reproduction of individuals resulting from variable inherited traits.

Observation 1 for Natural Selection

Individuals in a population vary in their inherited traits, many of which are passed on to offspring.

Observation 2 for Natural Selection

A population can produce far more offspring than the environment can support.

Evolutionary Adaptation

The accumulation of favorable inherited traits in a population over time.

Artificial Selection

The selective breeding of domesticated plants and animals by humans.

Evolution by Natural Selection (Definition)

The adaptive change in a population's genetic makeup through successive generations.

Key Point: Individuals vs. Populations

Individuals do not evolve; populations evolve over generations.

Key Point: Heritable Traits

Natural selection can only amplify or diminish heritable traits, not acquired characteristics.

Key Point: Direction of Evolution

Evolution is not goal-directed and does not lead to perfection.

Rosemary and Peter Grant

Researched Darwin's finches in the Galápagos, observing beak size changes based on wet and dry years.

Pesticide Resistance

Example of natural selection where pesticide application favors resistant insects, increasing their frequency over time.

Antibiotic Resistance

Public health concern where excessive antibiotic use selects for resistant bacteria, especially in hospitals.

Fossil Record

Historical sequence of organisms found in sedimentary rock layers showing how life evolved.

Whale Evolution Fossils

Documented transition from land mammals (Pakicetus) to aquatic forms (Rhodocetus, Dorudon) and recent whale ancestors (Balaena).

Comparative Anatomy

Comparison of body structures in different species to study evolutionary relationships.

Homology

Similarity in characteristics resulting from a shared common ancestry.

Comparative Embryology

Comparison of early developmental stages showing embryonic homologies like tails and pharyngeal pouches in vertebrates.

Vestigial Organs

Remnants of features that served important functions in an organism's ancestors (e.g., whale pelvis and hind-leg bones).

Molecular Biology Evidence

Comparisons of DNA and amino acid sequences revealing evolutionary relationships; all living things share a common DNA code.

Phylogenetic Tree

An evolutionary tree that uses homologous structures and genes to show branching patterns of descent.

Population

A group of individuals of the same species living in the same place at the same time.

Gene Pool

The total collection of genes in a population at any one time.

Microevolution

A change in the relative frequencies of alleles in a gene pool over time.

Population Genetics

The study of how populations change genetically over time.

Modern Synthesis

Connects Darwin's theory of evolution with population genetics.

Mutation

Change in the nucleotide sequence of DNA; the ultimate source of new alleles.

Chromosomal Duplication

Source of genetic variation where duplicated genes can mutate without harming original functions (e.g., olfactory receptors).

Sexual Reproduction

Shuffles existing alleles into new combinations during meiosis and fertilization without changing overall allele frequencies.

Hardy-Weinberg Principle

States that allele and genotype frequencies within a sexually reproducing, diploid population will remain in equilibrium unless acted upon by outside forces.

Hardy-Weinberg Equation

p² + 2pq + q² = 1.0, where p² is homozygous dominant, 2pq is heterozygous, and q² is homozygous recessive.

Hardy-Weinberg Conditions

Five conditions required to maintain equilibrium: very large population, no gene flow, no mutations, random mating, and no natural selection.

Main Causes of Evolutionary Change

Natural selection, genetic drift, and gene flow.

Genetic Drift

A change in size and genetic makeup of a small population due to chance events.

Bottleneck Effect

Genetic drift resulting from a disaster or drastic reduction in population size, leading to loss of genetic diversity (e.g., northern elephant seals).

Founder Effect

Genetic drift that occurs when a few individuals colonize a new habitat, forming a distinct gene pool.

Gene Flow

The movement of individuals, gametes, or spores between populations, altering allele frequencies.

Evolutionary Fitness

An individual's contribution to the gene pool of the next and subsequent generations.

Stabilizing Selection

Favors intermediate phenotypes and acts against extreme phenotypes, common in stable environments.

Directional Selection

Acts against individuals at one phenotypic extreme, common during environmental change or migration.

Disruptive Selection

Favors individuals at both extremes of the phenotypic range, common in patchy habitats.

Sexual Dimorphism

Distinctly different phenotypic appearances between males and females in an animal species.

Intrasexual Competition

Competition for mates among members of the same sex, usually involving males.

Intersexual Competition (Mate Choice)

Selection where individuals of one sex (usually females) are choosy in picking mates, often selecting flashy traits.

Diploidy (Preserving Variation)

Preserves genetic variation by hiding recessive alleles in heterozygotes.

Balancing Selection

Maintains stable frequencies of two or more phenotypes, including heterozygote advantage and frequency-dependent selection.

Heterozygote Advantage

When heterozygotes have greater reproductive success than homozygotes (e.g., sickle-cell anemia).

Frequency-Dependent Selection

Maintains two different phenotypes in a population based on their relative abundance (e.g., African scale-eating fish).

Neutral Variations

Variations that provide no apparent advantage or disadvantage (e.g., human fingerprints).

Constraints on Natural Selection

Evolution is limited because selection acts only on existing variations, is constrained by history, involves compromises, and interacts with unpredictable environments.

Speciation

The evolutionary process in which one species splits into two or more species.

Allopatric Speciation

Speciation that occurs when populations of a species are geographically isolated.

Sympatric Speciation

Speciation that occurs without geographic isolation, often through polyploidy or habitat differentiation.

Prezygotic Barriers

Reproductive barriers that impede mating or hinder fertilization between species.

Postzygotic Barriers

Reproductive barriers that prevent hybrid zygotes from developing into viable, fertile adults.

Biological Species Concept

Defines a species as a group of populations whose members have the potential to interbreed and produce viable, fertile offspring.

Morphological Species Concept

Characterizes a species by body shape and other structural features.

Gradualism

The model of evolution in which speciation occurs slowly and steadily over long periods of time.

Punctuated Equilibrium

The model of evolution in which species diverge in brief periods of rapid change, followed by long periods of stability.

Adaptive Radiation

The evolution of many diverse species from a common ancestor upon introduction to new environmental opportunities.

Macroevolution

Evolutionary change above the species level, including the origin of new taxonomic groups over geological time.

Exaptation

Structures that evolve and function in one context but can become co-opted for another evolutionary use.

Paedomorphosis

The retention in an adult organism of juvenile features of its evolutionary ancestors.

Evo-Devo

Evolutionary developmental biology; the field that studies how genetic changes affecting development can lead to major morphological novelties.

Mass Extinction

A widespread and rapid decrease in the biodiversity on Earth, often resulting from catastrophic global events.

Prezygotic Barriers Examples

Habitat, temporal, behavioral, mechanical, and gametic isolation.

Postzygotic Barriers Examples

Reduced hybrid viability, reduced hybrid fertility, and hybrid breakdown.

Ring Species

Populations that can interbreed with neighbors, but whose extremes cannot interbreed.

Horizontal Gene Transfer

The movement of genetic material between unicellular and/or multicellular organisms other than by parent-to-offspring transmission.

Adaptive Radiation Example

Hawaiian silverswords or Galápagos finches evolving rapidly from a common ancestor.

Cladistics

An approach to systematics in which organisms are placed into groups called clades based primarily on common descent.

Clade

A group of species that includes an ancestral species and all its descendants.

Biogeography

The study of the past and present geographic distribution of species.

Molecular Clock

A method that uses mutation rates in DNA to estimate the length of time that two species have been evolving independently.

Systematics

A discipline focused on classifying organisms and determining their evolutionary relationships.