Evolution Flashcards
Evolution: changes in _____, _____, and groups of _____; changes in _____ __________ in populations.
populations, species, and groups of species; allele frequency.
Microevolution
evolutionary changes in a species over a short period of time.
Macroevolution
evolutionary changes in a species over a longer period of time.
Phylogeny
evolutionary relationship among species and groups of species.
Genetics incorporated into evolutionary thinking is variously called:
- neo-Darwinism
- synthetic theory of evolution
- modern synthesis
5 evidences of evolution
- Paleontology
- Biogeography
- Embryology
- Comparative anatomy
- Molecular biology
Paleontology
fossils are evidence of evolution and no longer existing species.
Biogeography
similar conditions in different geographic locations give rise to species of similar traits, suggesting evolution due to condition. ex. placental rabbit in USA and marsupial wallaby in Australia.
Embryology
similarities in embryo and developmental stages (ontogeny) suggest evolution and phylogeny. ex. vertebrates have embryos with gill slits and tails.
Comparative anatomy
a) Homologous structures
b) Analogous structures
similarities in body parts.
a) similar body parts between species with common ancestor
b) similar body parts between species without common ancestor but rather similar living environments. ex. fins of sharks, penguins, and porpoises.
Molecular Biology
closely related species have similar genetic code.
Natural selection
survival of the fittest.
Adaptation
superior inherited traits
5 types of selection
- stabilizing selection
- directional selection
- disruptive/diversifying selection
- sexual selection
- artificial selection
Stabilizing selection
trait that is more middle-ground is adaptive while extreme ends of a trait are maladaptive and selected against.
Directional selection
one extreme end of a trait is adaptive. ex) insecticide resistance, industrial melanism of peppered moths.
Disruptive/diversifying selection
extreme ends of a trait are adaptive. ex) tall weeds and short weeds are selectively favored over average-height weeds. tall weeds receive more sunlight and have efficient growth; short weeds escape destruction by mows.
Sexual selection
a) male competition
b) female choice
* sexual dimorphism
males who can reproduce more and better are adaptive.
a) males who are stronger and fitter survive and reproduce
b) males who are attractive to the females reproduce
* disruptive/diversifying selection between males and females as a result of sexual selection.
Artificial selection
directional selection as a result of human tempering of organisms. ex) humans breeding dogs led to different breeds.
5 Sources of Variation
- Mutations
- Sexual reproduction
- Diploidy
- Outbreeding
- Balanced polymorphism
Mutations
changes in genetic code
Sexual reproduction
genetic recombination results in various combinations of alleles; random joining of gametes (fertilization), crossing over (prophase I meiosis), and independent assortment (metaphase I meiosis) are sources of this variation.
Diploidy
presence of two copies of each chromosome that results in a heterozygous condition through dominant and recessive alleles, storing the recessive allele for future generations.
Outbreeding
mating with unrelated partners to create more diverse combinations of alleles.
Balanced polymorphism
a) Heterozygote advantage
b) Hybrid Vigor/Heterosis
c) Frequency-dependent selection (minority advantage)
more than one variant of a phenotype is adaptive.
a) when heterozygous phenotype is favored over homozygous phenotypes (ex. heterozygous condition for sickle cell disease is favorable)
b) offspring has greater fitness than parents (due to reduction in loci with deleterious homozygous recessive conditions and increase in loci with heterozygous advantage)
c) least common phenotypes have selective advantage and increase in frequency overtime to become common phenotype (ex. a few individuals in a population of prey share a trait which allows them to escape from predators, but overtime this small group grows in size and becomes the majority).
5 Causes of Changes in Allele Frequency
- Natural Selection
- Mutations
- Gene flow
- Genetic Drift
- Nonrandom Mating
Natural Selection (cause of change in allele frequency)
increases or decreases allele frequencies due to impact of the environment
Mutations
provide new alleles; most are random and/or deleterious.
Gene flow
introduction or removal of allele frequency as a result of immigration or emigration of a population (ex. Swedes move to Southeast Asia and reproduce offsprings with blue eyes and blond hair)
Genetic Drift
a) founder effect
b) bottleneck
random increase/decrease of alleles
a) a migrating group of a population has unique allele frequency by chance and create a new species.
b) population undergoes dramatic change in size and remaining individuals have unique allele frequency by chance.
Nonrandom mating
a) inbreeding
b) sexual selection
when reproduction is not random and causes changes in frequency
a) mating between siblings who share allele frequencies and/or cause mutations during reproduction
b) female choice
Genetic Equilibrium/Hardy-Weinberg Equilibrium
when evolution does not occur and there is stability in allele frequency.
3 Types of Speciation
- Allopatric speciation
- Sympatric speciation
- Adaptive radiation
Allopatric speciation
geographic divide prevents mating within a species and differing environments create two new species as a result.
Sympatric speciation
a) Balanced polymorphism
b) Polyploidy
c) Hybridization
speciation without geographic divide.
a) individuals possess more than one variant of a trait that is convergently adaptive, creating a divide in the population.
b) more than the normal two sets of chromosomes result from nondisjunction, causing new species that cannot mate with original species.
c) when two species mate to produce hybrid species that can sometimes have hybrid vigor/heterosis.
Adaptive radiation
rapid evolution when species is introduced to an environment rich with resources that small groups within the species form in preference to different resource, causing speciation.
Maintaining Reproductive Isolation
Prevention of speciation
5 Prezygotic Isolating Mechanisms
- Habitat isolation
- Temporal isolation
- Behavioral isolation
- Mechanical isolation
- Gamete isolation
Habitat isolation
species do not encounter one another
Temporal isolation
species’ mating times differ
Behavioral isolation
mating rituals are different
Mechanical isolation
mating parts are structurally incompatible
Gamete isolation
male gamete is inhospitable in female gamete.
3 Postzygotic Isolating Mechanism
- Hybrid inviability
- Hybrid sterility
- Hybrid breakdown
Hybrid inviability
hybrids cannot survive
Hybrid sterility
hybrids cannot reproduce
Hybrid breakdown
hybrid offsprings cannot reproduce
4 Patterns of Evolution
- Divergent evolution
- Convergent evolution
- Parallel evolution
- Coevolution
Divergent evolution
common ancestor
Convergent evolution
different ancestor, similar environment (ex. sharks and penguins’ fins and torpedo bodies)
Parallel evolution
similar environment and lineage (ex. Wallaby and Rabbits)
Coevolution
evolution of two different species dependent on one another (ex. predator and prey)
Macroevolution (2)
1) Phyletic evolution - gradual accumulation of small changes
2) Punctuated evolution - pointed changes in short periods of rapid evolution.
Origin of Life
Chemical Evolution and Heterotroph theory: first cells were heterotrophs (can’t make own food)
9 Steps of the Origin of Life
- Earth and atmosphere with elements
- Primordial seas
- Complex molecules synthesized
- Polymers and self-replicating molecules synthesized
- Organic molecules concentrated and imbedded into protobionts. Protobionts are precursors of cells and carry out chemical reactions; microspheres/coacervates
- Primitive heterotrophic prokaryotes
- Primitive autotrophic prokaryotes from mutated heterotrophic prokaryotes
- Oxygen and ozone
- Eukaryotes (endosymbiotic theory: eukaryotes formed from mutually beneficial symbiosis among various prokaryotes)
