Evolutionary Theory and Mechanisms of Change

Evolution is…

descent with modification over time.

Natural Selection

Mechanism for evolution via heritable traits.

Common Ancestor

All species share a single ancestral origin.

Phenotypic Variation

Differences in traits among individuals.

Descent with Modification

Species change through inherited trait alterations.

Linnaeus

who organized biodiversity into nested sets?

Great Chain of Being

Historical concept of life's hierarchical organization.

Nicolaus Steno

Identified tongue stones as fossilized shark teeth.

Mary Anning

who discovered extinct marine reptile fossils?

Jean Baptiste de Lamarck

Proposed early ideas on evolution and adaptation.

Phylogeny

Evolutionary history and relationships among species.

Phylogenetic Tree

Diagram illustrating species' evolutionary relationships.

Homology

Shared ancestry of traits across different taxa.

Analogy

Similar structures in unrelated species.

Vestigial Organs

Rudimentary traits with functions in relatives.

Pseudogenes

Non-functional genes from reverse-transcribed mRNA.

Speciation

Gradual divergence of populations into new species.

Ring Species

Connected populations that can interbreed, except endpoints.

Stickleback Evolution

Freshwater colonization led to species adaptation.

Radiometric Dating

Method to determine Earth's age, ~4.5 billion years.

Oldest Fossils

Stromatolites, approximately 3.7 billion years old.

Convergent Morphology

Similar form and structure of organisms evolve independently in different species.

Darwin's Blind Spot

Question of heritable variation origins in traits.

Heritable Variation

Differences in traits passed from parents to offspring.

Mendel's Law of Segregation

Alleles segregate during gamete formation.

Mendel's Law of Independent Assortment

Genes for different traits segregate independently.

Mendel's Law of Dominance

Dominant alleles mask recessive alleles in phenotypes.

Discrete Traits

Traits that exhibit distinct categories or classes.

Continuous Traits

Traits that show a range of phenotypes.

Mutation

Change in nucleotide sequence in the genome.

Genetic Variation

Diversity in gene frequencies within a population.

Point Mutation

Single nucleotide change in DNA sequence.

Synonymous Mutation

No change in amino acid sequence of protein.

Non-synonymous Mutation

Change in amino acid sequence of protein.

Cis-regulatory Elements

DNA sequences regulating gene expression nearby.

Indel Mutation

Insertion or deletion of nucleotides in DNA.

Gene Duplication

Copying of a gene resulting in two copies.

Genome Duplication

Doubling of an organism's entire genome.

Recombination

Mixing of parental genes during meiosis.

Transcription Factor

Protein regulating gene expression by binding DNA.

Repressor

Protein that inhibits gene expression by binding DNA.

Enhancer

DNA sequence where activators bind to increase expression.

Intron

Noncoding section of RNA transcript.

Exon

Coding section of RNA that translates into proteins.

MicroRNAs

Small RNA molecules that silence gene expression.

Allele Frequency

Proportion of a specific allele in a population.

Genotype Frequency

Proportion of individuals with a specific genotype.

Evolution

Shift in allele frequencies across generations.

Genotype dependent survival rate

Survival influenced by specific genotype.

Genotype dependent reproductive rate

Reproduction influenced by specific genotype.

Genetic drift

Random change in allele frequency.

Smaller populations experience…

stronger genetic drift

Genetic bottleneck

Drastic reduction in population size affects genetic variation.

Founder effect

Loss of variation from small founding population.

Gene flow

Movement of alleles between populations.

A mutation is a…

source of genetic variation for evolution.

Hardy-Weinberg principle

Model predicting allele frequency stability under specific conditions.

Random mating

Males and females pair independently of genotypes.

Non-random mating

Mating influenced by genetic similarity.

Inbreeding

Mating among closely related individuals.

Homozygotes

Individuals with identical alleles at a locus.

Null model

Assumes no evolutionary forces acting on a population.

Genotype frequency

Proportion of a specific genotype in a population.

Heterozygote

Individual with two different alleles for a gene.

Fitness

Reproductive success of a genotype or phenotype.

Absolute fitness

a measure of how well an organism or genotype is able to survive, reproduce, and pass on its genes to the next generation

Relative fitness

Fitness compared to other genotypes.

Selection

Process favoring certain genotypes over others.

Negative selection

Selection against a specific genotype.

Relative fitness

Fitness of genotypes compared to each other.

Selection coefficient (s)

Difference in relative fitness between genotypes.

Evolutionary forces

Factors influencing evolutionary change.

Mutation

Random changes in DNA sequence.

Selection

Process favoring advantageous traits.

Genetic drift

Random changes in allele frequencies.

Migration

Movement of individuals between populations.

Average Excess of Fitness

Difference in fitness of allele carriers.

Mutation-selection balance

Equilibrium between mutation and selection rates.

Cystic fibrosis

Lung disease from a loss-of-function mutation.

Mutation rate

Frequency of new mutations occurring.

Local adaptation

Traits evolved in response to local conditions.

Gape width

Mouth opening size related to feeding habits.

Piscivory

a carnivorous animal that feeds primarily on fish.

Trait-environment correlations

Relationships between traits and environmental factors.

Convergent evolution

how similar traits evolve independently in different species

Phylogenetic comparative methods

Analyzing traits considering evolutionary relationships.

Goldenrod gall fly

Insect that induces growth on goldenrod plants.

Selective agent

Organism influencing survival and reproduction.

Gall size distribution

Variation in size of galls produced.

Fitness distribution

Variation in reproductive success among individuals.

Historical contingencies

Past events influencing current evolutionary paths.

Adaptation

Trait enhancing survival and reproduction in environment.