Evolution

Evolution

Evolution

the process of biological change in populations over time that makes descendants genetically different from their ancestors (microevolution, macroevolution)

Population

number of individuals in a group/species

Species

animals in the same group that have similar morphology, mating behavior, environment/habitat, and can produce fertile and viable offspring with each other

Natural Selection

organisms with the best traits for their environment will live longer and reproduce more causing a change in the population of a species in a certain environment

Artificial Selection / Selective Breeding

variation exists in domesticated plants and animals, humans take advantage of these differences, we select which traits are more favorable to be passed onto the next generation

Homologous Structures

similar in structure but have different functions (ex: arm of human and wing of bird have similar bones but have different functions)

Analogous structures

structures are different but have similar functions (ex: wing of bee and wing of a bat)

Vestigial Structures

Structures that have no purpose and are an evolutionary remnant of an ancestor

Fitness

Ability to survive and reproduce in a given environment

Adaptation

An inheritable characteristic that enhances an individual's fitness

Microevolution

Evolutionary change WITHIN a species (same species), change in allele frequency in a population

Macroevolution

Evolutionary change across species

Speciation

the evolutionary process by which populations evolve to become distinct species

Coevolution

When two or more species evolve in response to changes in one another (ie snake and newt)

Gene pool

All the genes (alleles) in a population

Allele frequency

Frequency of an allele in a population IMPORTANT: Each organism has 2 alleles for each trait

Disruptive selection

splits the population into two groups, favoring the extremes

Directional selection

when a single extreme phenotype is favored over other phenotypes

Stabilizing selection

natural selection favors the average phenotype, selecting against the extremes. The average expression leads to higher fitness

Sexual selection

occurs when certain traits increase mating success, females are choosy about their masters because their investment in offspring is higher (in most cases) (competition between males) (males display certain traits that attract the female)

Sexual Dimorphism

a trait that differs between males and females

Adaptive Radiation

same as divergent evolution, is when new environments cause differences to evolve in populations (one common ancestor evolving into many different species)

Reproductive Isolation (with speciation)

the inability of a species to breed successfully with related species due to geographical, behavioral, physiological, or genetic barriers or differences

Prezygotic barriers

Temporal, geographic/habitat/ecological, behavioral, mechanical, gamete isolation

Postzygotic barriers

Hybrid inviability, hybrid infertility, hybrid breakdown

Conditions for Genetic Equilibrium

1. Population is large

2. Random mating

3. No migration

4. No mutations

5. No natural selection

(IF AT LEAST ONE OF THESE CONDITIONS IS NOT MET THEN THE POPULATION IS EVOLVING)

Genetic Drift

Changes in frequency of genotypes through random events, especially in small populations, ie randomly a tree falls on and kills 3 of the 4 animals with red spots, drastically reducing their share of the gene pool

Bottle Neck

When population is drastically reduced in size, limiting genetic diversity

Founder Effect

a loss of genetic diversity when a small group of individuals establish a new population (a few individuals from a population start a new population with a different allele frequency than the original population)

Non-random mating

also known as sexual selection, occurs when certain traits increase mating success, females are choosy about their mates because their investment in offspring is higher (in most cases) (ex: competition between male bighorn sheep, the winner gets to mate with the female)(ex: males display certain traits that attract the female, male peacock fan out their tails)

Mutations

Random changes in DNA that can cause changes in phenotype, one of the drivers of evolution

Gene flow

movement of genes into/out of a population (migration)

Allopatric speciation

a mode of speciation that occurs when biological populations become geographically isolated from each other to an extent that prevents or interferes with gene flow

Sympatric speciation

evolution of a new species from a surviving ancestral species while both continue to inhabit the same geographic region.

Balanced Polymorphism

a situation in which two different versions of a gene are maintained in a population of organisms because individuals carrying both versions are better able to survive than those who have two copies of either version alone (think malaria and sickle cell)

Stasis

Relative lack of evolutionary change in a species over a long period of time.

Exaptations

When a trait evolves for one purpose but then gets used for an additional purpose later on ie feathers evolving to control body temperature then becoming used for flight

Phylogeny

evolutionary history of a species

Phylogenetic tree

a diagram used to predict evolutionary relationships among groups of organisms (branch points show a new species diverging from the common ancestor, hypothesis are based upon ana;yzing shared morphology, genes, and behaviors)

Patterns of evolution

speciations (reproductive isolation), adaptive radiation/divergent evolution, extinction, convergent evolution, coevolution

Extinction

elimination of a species, background extinctions (slow and steady extinctions that would be expected to occur over time due to non

Convergent evolution

Similar environments select for similar traits so organisms that are not related/not closely related evolve to have similarities

Divergent evolution

Different species evolve from one common ancestor, evidence for this is homologous structures

Endemic species

species that exist only in one geographic region (galapagos tortoises)