Evolution Flashcards
Homologous Structures
Body parts that resemble each other in different species
Evolved from common ancestor
Analagous Structures
Resemble each other because evolved due to similar environments
Darwin’s Argument For Natural Selection
Populations posses an enormous reproductive potential
Population sizes remain stable
Resources are limited
Much variation in heritable
Only the most fit individuals survive
Stabilizing Selection
Common traits favoured
Directional Selection
Favours one extreme
Disruptive Selection/Diversifying Selection
Favours extreme traits, selection against common traits
Sexual Dimorphism
Difference in appearance of males and females
Sexual selection is a form of disruptive selection
Outbreeding
Mating with unrelated partners
Increases the possibility of mixing different alleles and creating new allele combinations
Hybrid Vigor/ Heterosis
Superior quality of offspring resulting from crosses between 2 different inbred strains of plants
Superior hybrid quality results from a reduction of loci with deleterious homozygous recessive conditions and an increase in loci with heterozygote advantage
Frequency-dependent selection/minor advantage
Least common phenotype has selective advantage
Will increase in frequency
Phenotypes alternate between low and high frequencies
Gene Flow
Introduction or removal of alleles from the population when individuals leave (emigration) or enter (immigration) the population
Genetic Drift
Random increase or decrease of alleles by chance
Greater effect in smaller populations
Founder Effect
Allele frequencies in a group of migrating individuals are (by chance) not the same as their population of origin
Bottleneck effect
□ Population undergoes a dramatic decrease in size
□ Resulting population becomes severely vulnerable to genetic drift
Conditions For Genetic Equilibrium
All traits are selectively neutral (no natural selection)
Mutations do not occur
Population must be isolated from other populations (no gene flow)
Population is large (no genetic drift)
Mating is random
Allopatric Speciation
Population divided by geographical barrier
Sympatric Speciation
New species formed without geographical barrier
Adaptive Radiation
Relatively rapid evolution of many species from a single ancestor
Hybrid Inviability
Zygote can’t develop
Hybrid Sterility
Hybrid is sterile
Hybrid Breakdown
Hybrid produce produces offspring with reduced viability or fertility
Divergent Evolution
2 or more species originate from a common ancestor and becomes increasingly different over time
May be a result of allopatric or sympatric speciation or by adaptive radiation
Convergent evolution
2 unrelated species that share similar traits
analagous traits
Parallel Evolution
2 related species or 2 related lineages that have made similar evolutionary changes after their divergence from a common ancestor
Coevolution
Evolution of one species in response to new adaptations in another species
Phyletic gradualism
Evolution occurs by the gradual accumulation of small changes
Argues fossil record is incomplete
Punctuated Equilibrium
Long periods of little/no evolution that is interrupted/punctuated by geologically short periods of rapid evolution
Argues that absence of fossils revealing intermediate stages of evolution is considered data that confirms rapid evolutionary events
Uniform Dispersion
Individuals spaced evenly
i.e. Plants secrete toxins to inhibit growth of nearby individuals
Animal species stake out and defend territories
Commensalism
One party benefits, no effect on other party
Form of symbiosis
Allelopathy
Production of biochemicals by an organism that influences the growth, survival, and reproduction of other organisms
Form of interference competition
Interference Competition
Occurs directly between individuals via aggression
Other individuals are prevented form physically establishing themselves on a shared habitat
Exploitation Competition
Occurs indirectly through depletion of a common resource
i.e. Lions and cheetahs both hunt for gazelles
If lions eat all the gazelles, will affect cheetahs
Apparent Competition
Occurs when 2 species are preyed upon by the same predator
i.e. Spider and beetles hunted by owls
If spider population increases, owl population will increase, and will hunt more beetles
Intraspecific Competition
Types of competition that occurs between members of the same species
Ecological Succession
Predictable process of ecosystems changing and developing over time
Occurs in a new habitat or after a disturbance
Primary Succession
Occurs after a large disturbance in an area that has never supported live
Begins with pioneer species (lichen, fungi, algae)
Order of Colonization
Pioneer species—> thin soil—> vascular plants—> larger plants—> animals
Climax Community
Community that has reached steady state
Secondary Succession
Has supported life previously, but has had destruction following a disturbance
Similar pattern of colonization as primary succession, but begins with grasses and shrubs
Keystone Species
Maintains ecological balance despite low abundance (i.e. predator)
Anagenesis
Differentiation process which causes one species to evolve into a new one
Cladogenesis
Speciation event allowing for the introduction of novel species from an ancestor
Opportunistic Relationship
Bacteria, virus, protozoan or fungus takes advantage of opportunities to cause disease
Parasitism
One organism benefits but the other is harmed
Cryptic Colouration
Organism using colouring to avoid detection by its predators
Batesian Mimicry
Prey animal mimics a warning signal of an animal that possesses strong defenses
Molecular Mimicry
Structural, functional, or immunological similarities shared between macromolecules found on infectious pathogens and in host tissues
Mullerian mimicry
2 species that are equally unpalatable evolve to look like each other
Predator learns to avoid one, will avoid both
