evolution Flashcards
Allele frequency equation
number of copies of an allele
______
Total #of alleles for the same gene in the population
Evolution
The change in allele frequencies and genetics in a population over time
Allele
A version of a gene that produces a specific trait (B vs. b)
Do individuals evolve?
No, since an individual’s alleles don’t change
Population
Group of organisms of the same species
Natural Selection
Features best suited to an environment are able to survive and reproduce better than others
Habitat
The type of natural environment that a species lives, made up of both physical and biological features
What are some abiotic factors?
Temperature, rainfall, humidity, heat
Fitness
reproductive success
Niche
The role the species takes in that habitat including the precise location and resources used
What does “variation among individuals in a population” mean?
Variation in a trait that impacts an individual’s ability to acquire resources and/or survive in an environment
What does “variation must be heritable” mean?
Variation is passed from parent to offspring
What does “over-production” in natural selection mean?
Each generation, more offspring are produced than can be supported by local resources
What does “differential survival and reproduction” mean?
Individuals possessing traits that increase their success will contribute more offspring to the next generation
What happens when two or more species occupy the same niche?
Competition, forcing the other species to adapt or risk extinction
Explain how natural selection determines who survives to reproduce and who does not
As environmental conditions change, the phenotypes that
natural selection favors will also change
Genetic variation
Within a species, no 2 individuals are exactly alike
Over production of off spring
More individuals are born than survive to reproduce
Unequal reproductive success
The inherited characteristics of some individuals make them more likely to obtain resources, survive, and reproduce
Descent with modification
a population’s characteristics can change by natural selection, even giving rise to new species
Modern evolutionary synthesis
Genetic variation is the raw material on which evolution acts
Adaptation
A genetically-based trait that increases an individuals ability to produce off spring in a particular environment
Mutations
Changes in a DNA nucleotide sequence
Variation
A trait that impacts an individuals ability to acquire resources and for survive in an environment
Directional Selection
The median variation for a trait moves toward one of
the extremes
Stabilizing Selection
Selection against the extreme phenotypes of a
particular trait
Disruptive Selection
Selection for the two extreme phenotypes of a
particular trait
Sexual Selection
selection for an enhanced ability to attract mates
Genetic drift
a change in allele frequencies due to chance alone
-> causes evolution to occur
What does it mean to “fix” or “lose” an allele in a population?
In populations in which an allele has become either fixed or lost, the process of random genetic drift stops at that locus
The Founder Effect
Phenomena that occurs when a small group of individuals becomes isolated from a larger population
The Bottleneck Effect
An extreme example of genetic drift that happens when the size of a population is severely reduced
-> hurricanes
Gene flow
the movement of alleles from one population to another
Example of the Biological Species Concept
Western meadowlarks and Eastern meadowlarks
Reproductive isolation
prevents individuals from producing viable and fertile offspring
Prezygotic barriers and 2 examples
prevent members of different species from mating to produce a zygote
Example: Geographical Isolation and temporal Isolation
Postzygotic barriers and 2 examples
blocks reproduction after fertilization and zygote formation
Example: Hybrid viability and hybrid sterility
How does evolution lead to speciation?
Microevolution and Macroevolution
Speciation
the formation of new and distinct species in the course of evolution
Allopatric speciation
speciation driven by physical (geographical) isolation of populations
Sympatric speciation
speciation occurring within the same geographic region
habitat differentiation
mutations within a population cause individuals to exploit different conditions within the same environment
Disruptive selection
Selection for the two extreme phenotypes of a particular trait
Examples of how adaptations can change the physical body, behavior, biochemistry of an organism
webbed feet for ducks
migration
trout acclimating to warm and cold temperatures
What’s the difference between acclimation and adaptation
Adaptation - a long-term permanent adjustment
Acclimatization - a short-term rapid temporary adjustment
Ecological niche
the range of resources and conditions allowing the species to maintain a manageable population
How do populations change over time?
Access to resources
Immigration
Emigration
Carrying capacity
The maximum abundance of a species population that a habitat or ecosystem has the resources to support
How does carrying capacity limit population growth?
limited supply of resources
Example of a tradeoff
Developing colored feathers helps attract a mate, but colorful birds tend to be more easily spotted by predators
Competitive Exclusion Principle
Two species that occupy the same ecological niche cannot stably coexist
Intraspecific competition
competition between individuals of the same species
interspecific competition
competition between individuals of different species
Co-evolution
Evolutionary change in two closely interacting species
Example of morphological defense
turtle going into its shell
Cryptic coloration
makes prey difficult to spot
Aposematic coloration
bright warning coloration, often exhibited by animals with effective chemical defenses
Batesian mimicry
when a harmless species mimics the appearance of an unpalatable or harmful model
How do plants respond to herbivory?
Resistance
Tolerance
Mutualism
interspecific interaction in which both species benefit
Commensalism
one species benefits and the other species is neither helped nor harmed
-> clownfish hiding in coral
Amensalism
one species is harmed and the other species is neither helped nor harmed
-> pine needles killing grass
Altruism
refers to an interaction in which one organism decreases their own fitness to increase the fitness of another
