Evolution Flashcards
What is a population?
The same species in an area
What are the mechanisms for evolution?
- Natural selection
- Gene flow
- Genetic drift
- Artificial selection
What mechanisms of evolution lead a population to adapt?
- Natural selection
- Artificial selection
What mechanisms of evolution do not lead a population to adapt?
- Gene flow
- Genetic drift
What is natural selection?
When phenotypes are more likely to be passed on depending on their ability to help an individual survive in an environment
What are the causes of natural selection?
- Competition
- Predation
- Sexual selection
What are the two types of sexual selection?
Intersexual selection
- Choosiness of sexual partners
Intrasexual selection
- Competition between individuals of the same sex for mates
What is gene flow?
Genes leaving and entering the gene pool due to movement
What is genetic drift?
A change in the gene pool strictly by random chance
What is artificial selection?
Selective breeding is controlled by humans to produce the desired trait
What is stabilizing selection?
When the frequency of the extreme phenotype is reduced because predators don’t eat the intermediate phenotypes since they are easiest to see if they are inedible, so the population is skewed in the direction of the intermediate phenotype and the extremes start to decrease in population
What is directional selection?
The inedible species of one extreme phenotype disappears so predators eat the species that mimics it,
this causes a skew in the phenotypes away from the one that disappeared
What is disruptive selection?
When the extreme phenotypes are not eaten by predators so the population of phenotypes that mimic the extreme inedible organisms remains unharmed, the population is skewed in either extreme direction and there are two peaks on either side of the graph
What are homologous structures?
Structures that share similarities because of a common ancestor
What are analogous structures?
Structures that are different b/c they come from different ancestors
What are bottleneck events?
A random event that drastically reduces the size of the population
- A variation of genetic drift
What is the founder effect?
When a small group of a population is separated and isolated from the original population
- Creates a difference in allele frequency from the original population, which can result in speciation
What type of evidence can be used for evolution?
- Geographical (habitats)
- Geological (fossils/isotopes)
- Physical (observable phenotypes)
- Biochemical (DNA/proteins)
- Mathematical (models/simulations)
What are morphological traits?
Traits that have been modified but shared among different species from a common ancestor
What are vestigial structures?
Reduced/obsolete structures that serve little to no function
- Human tail bone
What are some examples of evidence for common ancestry in eukaryotes?
- Linear DNA
- Chromosomes made of condensed DNA with histones
- DNA in a nucleus
- Genome is large
- Genome contains introns (prokaryotes don’t)
- Chromosomes capped with telomeres (repetitive no coding DNA)
What are telomeres?
Repetitive non-coding DNA at the end of a chromosome
What are some examples of evidence of common ancestry in prokaryotes?
- Small genome
- Found in cytoplasm
- Circular Double stranded DNA
What is reproductive isolation?
When a portion of a population is separated from the original and evolves on its own to develop a new species
- Necessary for speciation
What is a species?
A group capable of interbreeding and exchanging gametes to produce viable, fertile offspring
What are the prezygotic barriers during reproductive isolation?
- Habitat isolation
- Behavioral isolation
- Temporal isolation
- Mechanical isolation
- Gamete isolation
What is habitat isolation as a prezygotic barrier to reproductive isolation?
When the population that is isolated lives in a different habitat
What is behavioral isolation as a prezygotic barrier to reproductive isolation?
Breeding preferences dependent on rituals or courtship,
- e.g. singing/ dancing
What is temporal isolation as a prezygotic barrier to reproductive isolation?
A difference in breeding times/seasons
What is mechanical isolation as a prezygotic barrier to reproductive isolation?
When there is a sexual structural difference between the organisms preventing reproduction
What is gamete isolation as a prezygotic barrier to reproductive isolation?
When the gametes cannot fuse to create a fertilized egg
What are the postzygotic barriers during reproductive isolation?
- Hybrid sterility
- Hybrid breakdown
- Reduced hybrid viability
- Reduced hybrid fitness
What is hybrid sterility as a postzygotic barrier to reproductive isolation?
When the offspring cannot produce any fertile gametes for mating
What is hybrid breakdown as a postzygotic barrier to reproductive isolation?
When the first generation is viable and fertile but continuing generations are not
What is reduced hybrid fitness as a postzygotic barrier to reproductive isolation?
When the offspring have a low chance of survival and reproduction,
- Could be due to the offspring not being a desirable mate b/c they are in between two species, for example a hybrid peacock could be too ugly to mate with normal peacocks b/c they may not have as beautiful feathers
What is reduced hybrid viability as a postzygotic barrier to reproductive isolation?
If the zygote terminates at some point in its development
What is allopatric speciation?
Evolution of a new species due to geographical barriers
What is sympatric speciation?
Evolution of a new species without a geographical barrier,
- Can be sexual selection
- Habitat differentiation (same location but varying habitat like too cold or hot)
- Mutations
What is punctuated equilibrium?
when evolution in a population was static for a very long time, then due to an environmental stimulus, evolution happens rapidly
What is gradualism?
When evolution happens gradually over a very long period of time
What is adaptive raditation?
The availability for a species to fill a gap/niche in an ecosystem due to extinction
- leads to rapid speciation
What is extinction?
When a species disappears and no population of it can naturally occur on Earth
What is an affect of extinction on biodiveristy?
Decreases
What are some causes of extinction?
- Catastrophic changes to an ecosystem
- Rising sea levels
- Natural disasters
- Human activity
- Climate change
- Habitat degradation
- Pollution
- Poaching
- Invasive species
What is the relationship between levels of speciation and extinction in an ecosystem with high biodiversity?
- High levels of speciation
- Low levels of extinction
What is the relationship between levels of speciation and extinction in an ecosystem with low biodiversity?
- Low levels of speciation
- High levels of extinction
