Evolution Final Flashcards (GRAHHH)

A comprehensive set of vocabulary flashcards covering the key concepts of evolutionary biology, including population genetics, speciation, selection mechanisms, and historical scientific cases as detailed in the lecture transcript.

Vestigial organs

Organs, traits, or features that once served a purpose in an ancestor but no longer do so in a descendant, such as the palmaris longus muscle or tailbones in humans.

Biological species concept

Defines different species based on their ability to interbreed and produce fit, fertile offspring.

• This is opposed to the morphological species concept and the phylogenetic species concept

• It has downsides when trying to define species based on fossil evidence

Archaeopteryx

A transitional fossil representing the evolutionary transition between non-avian feathered dinosaurs and modern birds, providing evidence for macroevolution.

Homologous structures

Physical structures or features in different species that share similarities due to common ancestry.

Pseudogenes

Mutated or non-functional remains of genes from common ancestors used to trace genetic lineage and analyze when genes lost function.

Natural selection

The mechanism theorized by Charles Darwin by which individuals better adapted to their environment tend to survive and reproduce at higher rates.

Epperson v. Arkansas, 1968

A case where the Supreme Court overturned an Arkansas law prohibiting the teaching of evolution, ruling it a violation of the First Amendment.

State of Tennessee v. John Thomas Scopes, 1925

A case where a teacher was found guilty of teaching evolution in violation of the Butler Act, though the verdict was later overturned on a technicality.

Kitzmiller v Dover Area School District, 2005

A case that found the teaching of intelligent design as an alternative to evolution in public schools to be a violation of the First Amendment due to its religious nature.

Genetic variation

Heritable variation resulting from differences among individuals encoded in their DNA.

Environmental variation

Variation that arises when external factors influence the amount or structure of proteins made from a particular gene.

Genotype-by-environment variation

Differences among individuals encoded in DNA that result in different sensitivities or reactions to environmental influences.

Reaction norm

The pattern of phenotypes an individual may develop upon exposure to different environments.

Ex: The scale of fur color an Arctic Fox might change to in winter

Transition

A type of DNA substitution where a purine is swapped for another purine ($A-G$) or a pyrimidine is swapped for another pyrimidine ($C-T$).

Transversion

A mutation wherein a purine ($A, G$) is swapped for a pyrimidine ($C, T$) or vice versa.

Paralogous genes

Genes evolved from a common ancestral gene that were split by a gene duplication event.

Orthologous genes

Genes evolved from a common ancestral gene that were split by a speciation event.

Overdominance

Also known as heterozygote advantage, it is a condition where being a heterozygote carries higher fitness than being a homozygote.

Polyploidy

The condition of containing more than two sets of chromosomes.

Clines

The variation in a trait within a species across its inhabited geographical scope.

Synonymous mutation

A mutation that codes for the same amino acid during transcription and translation, resulting in no change to the protein.

Non-synonymous mutation

A mutation that changes the amino acid coded for during transcription and translation.

Hardy-Weinberg equilibrium

A null model assuming no evolution, defined by the equations $p + q = 1$ (allele frequency) and $p^2 + 2pq + q^2 = 1$ (Genotype Frequency), assuming random mating, no mutation, no selection, infinite population, and no gene flow.

• It’s a null model assuming no evolution!

• p²= Homozygote Dominant

• 2pq= Heterozygote

• q²= Homozygote Recessive

Frequency-dependent selection

A mode of selection where the fitness of a genotype or phenotype depends on its frequency in the population.

Mutation-selection balance

An equilibrium where the rate of new copies of alleles created by mutation is exactly equal to the rate at which they are eliminated by selection.

Founder effects

A situation where a new population consists of a small number of individuals, leading to allele frequencies that differ by chance from the ancestral population.

Genetic drift

The fluctuation in allele frequencies within a population caused by random chance.

Migration-selection balance

An equilibrium reached between migration, which homogenizes populations, and selection, which increases genetic differences

Ex: those dumbass banded snakes (banded phenotype perpetuating in islands where unbanded phenotype is selected for due to migration from mainlands)

Fitness

An organism’s ability to survive and reproduce.

Modern Synthesis

The integration of Mendelian Genetics with Darwin’s Theory of Evolution by natural selection.

Linkage disequilibrium (LD)

The nonrandom association of alleles at different loci within a population

• Increases in cases of inbreeding!

Red Queen Hypothesis

The theory that organisms must constantly adapt and evolve to survive when pitted against other constantly-evolving organisms in a changing environment.

Twofold cost of sex

The disadvantage of sexual reproduction where males cannot produce offspring, making it theoretically less efficient than asexual reproduction.

Quantitative traits

Consistently variable or fluctuating measurable traits that are often polygenic, such as height and weight.

Qualitative traits

Categorizable phenotypic traits usually encoded by fewer genes that are not continuously variable, such as flower color.

Narrow-sense heritability ($h^2$)

The proportion of phenotypic variation due to additive genetic variation, often calculated via midparent-offspring regression ($h^2 = ext{additive variance} / ext{total phenotypic variance}$).

Sexual dimorphism

The phenomenon where different sexes within a species exhibit different morphological characteristics.

Phylogenetically independent contrasts

A statistical method used to compare trait differences among species while accounting for the lack of independence due to common ancestry.

Intrasexual selection

Selection involving competition among members of the same sex (typically males) for access to mates.

Intersexual selection

Selection involving members of the limited sex (typically females) choosing mates from the less limited sex.

Altruism

Actions that benefit a recipient at a potential cost to the actor.

Kin selection

Natural selection that leads to the spread of alleles that increase the indirect component of fitness by benefiting relatives.

Inclusive fitness

The sum of an individual's direct fitness (reproductive success) and indirect fitness (reproductive success of relatives).

Genetic hitchhiking

A change in the frequency of an allele due to positive selection on a different, linked locus.

Eusociality

The highest level of social organization characterized by cooperative brood care, overlapping generations, and specific reproductive castes.

Selection gradient

Calculated as selection differential divided by the variance of a trait, representing relative fitness as a function of variation.

Selection differential

The difference between the mean trait value of selected parents and the mean trait value of the base population.

Breeder’s Equation

An equation used to predict evolutionary change: $R = h^2 S$, where $R$ is the response, $h^2$ is narrow-sense heritability, and $S$ is the selection differential.

Muller’s ratchet

The process by which asexual populations irreversibly accumulate deleterious mutations over generations.

Hamilton’s rule

The principle that altruistic behavior is favored when Br > C, where $B$ is the benefit to the recipient, $r$ is relatedness, and $C$ is the cost to the actor.

Parent-offspring conflict

A conflict arising from disagreements in fitness interests, particularly regarding the amount of parental investment.

Synapomorphy

A shared trait derived from a common ancestor that defines a group.

Monophyly

A taxonomic group that includes an ancestor and all of its descendants.

Paraphyly

A taxonomic group that includes an ancestor and some, but not all, of its descendants.

Polytomy

A multifurcation in a phylogeny where more than two lineages diverge from a single ancestral point, often indicating unknown relationships.

Senescence

The permanent state of non-division in cells or the general process of biological aging.

Antagonistic pleiotropy hypothesis

The theory that alleles with early fitness benefits but detrimental effects later in life can be selected for because more individuals reap the benefit than suffer the cost.

Grandmother hypothesis

Suggests that menopause evolved because it is more beneficial for older females to care for relatives than to produce their own young.

Lack’s hypothesis

The theory that selection favors the clutch size that leads to the most living offspring, suggesting an intermediate optimal size.

Implies either/or: 

-There must be trade-offs between a parent’s reproductive effort in one year 

and its survival or reproductive performance in future years (ex: female parental investment in current clutch affects future reproduction) 

-there must be effects of clutch size on offspring besides effects on survival

OR: (Data re-analyzed— found wrong control groups were initially used, birds might generally have had right # eggs given capacity)

Optimal foraging hypothesis

Although obtaining food provides the animal with energy, searching for and capturing the food require both energy and time. The animal wants to gain the most benefit (energy) for the lowest cost during foraging, so that it can maximize its fitness.

Virulence

The harm done by a pathogen to its host during the course of an infection.

Coincidental hypothesis

The idea that the virulence of certain pathogens is not a direct target of selection but a byproduct of selection on other traits.

For example, tetanus is caused by a soil bacterium, Claustridium tetani. When tetanus bacteria find themselves inside a human wound, they can grow and divide. They also produce a potent neurotoxin, making tetanus infections highly lethal. However, tetanus bacteria ordinarily do not live in humans and are not transmitted by humans. The ability of these bacteria to produce tetanus toxin is probably the result of selection during their ordinary life in the soil, not selection inside human hosts.

Shortsighted evolution hypothesis

The idea that traits enhancing the within-host fitness of a pathogen may rise to high frequency even if they are detrimental to transmission to new hosts.

Allopatry

The existence of species or populations in different geographic areas that prevents consistent gene flow.

Sympatry

The existence of species or populations within the same geographic area where they can interact or interbreed.

Vicariance

The split of one geographic location into two or more parts, leading to forced allopatry for resident populations.

Prezygotic isolation

Barriers to gene flow that operate prior to the formation of a zygote, such as behavioral or mechanical differences.

Ex: Different shaped genital systems in snails, cryptic isolation (like sperm selection)

Postzygotic isolation

Barriers to gene flow that operate after a zygote has formed, often involving low fitness or sterility in hybrids.

Ex: Mules (hybrids between horse and donkey) are sterile due to chromosome mismatch, polyploid speciation

Adaptive radiation

The rapid formation of many new species from a single common ancestor due to colonization of new niches.

Cambrian Explosion

A period approximately $542-488$ million years ago characterized by the rapid appearance of most modern animal phyla.

Incomplete lineage sorting

A situation where a gene tree differs from the species tree because common ancestors were polymorphic and different alleles were preserved in different descendants.

Coalescent theory

A mathematical framework in population genetics that traces lineages backward in time to the most recent common ancestor ($MRCA$).

Age of Earth

• About 4.5 Billion Years

• Evidence: Radiometric Dating Techniques can trace ages of certain minerals using ratio of parent/daughter isotopes

Gregor Mendel

“Father of Genetics,” developed theory of genetic inheritance (dominant/recessive traits) independently from Darwin’s evolutionary theory. His theories originally disregarded but eventually became recognized for their significance in evolution

Charles Darwin

Introduced natural selection as a primary evolutionary mechanism, explained natural diversity through “descent with modification” aka evolution

Alfred Russel Wallace

Independently conceived natural selection alongside Darwin spurred him to write/publish Origin of Species and contributed to the field of biogeography, emphasizing the role of environmental factors in species distribution.

Galapagos Finches

Different finches on different islands exhibit different traits/adaptations—provide evidence for natural selection, selection as a mechanism by which evolution (change in allele frequencies over time) occurs

Variation

Total phenotypic variation is made up of genetic variation, environmental variation, and genotype-by-environment variation

Substitution

One base being “swapped” for another

Transition

A purine is swapped for another purine (A-G) or a pyrimidine is swapped for another pyrimidine (C-T)

Transversion

A mutation wherein a purine (AG) is swapped for a pyrimidine (CT) or vice version

Homologous Genes

Genes derived from a common ancestor

Punnett Square

A table which allows one to assess the possible genetic outcomes from a cross between two individuals with known genotypes

Homozygote

An organism inheriting two identical alleles for a specified gene (either dominant or recessive)

Heterozygote

An organism that inherits one dominant allele and one recessive allele of a gene

Heterozygote advantage (Overdominance)

A phenomenon where being a heterozygote for a specific gene carries fitness advantages over being a homozygote

• Individuals heterozygous for the sickle cell trait (one sickle cell allele, one normal allele) gain resistance against malaria without developing severe sickle cell disease. (Homozygotes for the normal allele lack malaria resistance, while homozygotes for the sickle cell allele develop sickle cell disease)

Diploid

Contains 2 sets of chromosomes

• Somatic cells in humans

Haploid

Containing one set of chromosomes

• Sex Cells

Point Mutations

Mutations that occur at one base (in/del, substitution)

Insertion/Deletion Mutations

Insertion or deletion of a base along the genetic code

Frameshift Mutation

Caused by indels in multiple not of 3

Gene duplication events

Gene duplication events occur when a segment of DNA containing a gene is duplicated, resulting in two copies of that gene. This can lead to evolutionary diversification, as one copy may retain its original function while the other can accumulate mutations and potentially develop new functions

Inversion

A type of mutation involving a segment of DNA that is reversed end to end, which can affect gene expression or function.

Genome Duplication

A phenomenon where an organism's entire genetic material is duplicated, resulting in multiple sets of chromosomes. This event can lead to significant biological diversity and complexity, as it provides raw material for evolution by allowing one copy of genes to mutate and acquire new functions while retaining the original gene's function

Hardy-Weinberg Conditions

• Random Mating

• No Mutation

• No Selection

• No Gene Flow

• Infinite Population Size

Gene flow

Gene flow can help small populations by introducing new/unrelated genetic material, helping to reduce inbreeding, depression, and accumulation of deleterious mutations

Ex: Florida Panthers were caught in an extinction vortex, introducing pumas from Texas has helped their population sizes grow

Inbreeding

Breeding between closely related population, increases rates of linkage disequilibrium

Artificial Selection

Intentional breeding of plants or animals in order to enhance or produce certain traits

Ex: Dog breeding

Experimental Evolution

The study of evolutionary processes occurring in experimental populations in response to conditions imposed by the experimenter. This research approach is increasingly used to study adaptation, estimate evolutionary parameters and test diverse evolutionary hypotheses.