evolution Flashcards
(34 cards)
evolution
the process where organisms develop and diversify
population
all the inhabitants in a certain area
species
a population of organisms that can produce fertile offspring but cannot breed with other groups
problematic for asexually reproductive animals, extinct species, and not all organisms can be observed in their natural environment (deep sea etc.)
adaptation
where organisms develop or inherit traits to help them survive and reproduce in their environment
sexual selection / non random mating
occurs when certain traits increase mating success
females are choosy about their mates because their investment in offspring is higher
competition between males, winner gets to mate
drives evolution by enhancing an individuals mating success
reproductive isolation
prezygotic barriers- prevents the formation of a zygote
postzygotic barriers- if a zygote is formed, these prevent it from becoming a fertile adult
zygote
the first cell that results from the union of an egg and sperm cell
types of reproductive isolation
temporal (timing), ecological (location), behavioral (ignoring reproductive cues), mechanical (physical incompatibility), gamete incompatibility (no fertilization),
speciation
evolutionary process in which new species arise
occurs when a part of a species is isolated from the rest of the population
extinct
having no living members, no longer in existence
coevolution
the influence of closely associated species on each other in their evolution
EX: predator and pray, polinators and plants
natural selection
organisms better adapt to their environment so they are more likely to survive and reproduce, passing down the traits that allow them to survive
allele frequency
how often a particular version of a gene appears in a population
gene pool
the stock of different genes in an interbreeding population
genetic equilibrium
where there are NO changes in allele frequencies in a population over time
EVOLUTION WILL NOT OCCUR IF: population is large, random mating, no migration, no mutations, no natural selection
disruptive selection
a process that splits a population into two groups; removes individuals with average traits
FAVORS THE TWO EXTREMES
EX: On an island there are large seeds and small seeds. Birds with large beaks are very good at eating the big seeds and birds with small beaks are very good at eating small seeds, but birds with medium size beaks are not as good at either
directional selection
increases the expression of an extreme version of a trait in a population
EX: Most of the moths had light-colored wings, but dark moths started to appear. Because moths lived against dark tree barks, years later, most of the moths were dark. Thus, more dark moths survived, adding more genes for dark color to the population.
stabilizing selection
eliminates extreme expression of a trait when the AVERAGE expression leads to higher fitness
EX: Human babies born with below-normal and above-normal birth weights have lower chances of survival than babies born with average weights. Therefore, birth weight varies little in human populations.
homologous structures
a physical feature shared by different organisms because they derived from a common ancestor
EX: limbs of some vertebrates like wings of birds and forelimbs of primates
analogous structures
features in different species that have similar functions, different structures, and are not derived from a common ancestor
EX: wings of birds and wings of butterflys
vestigial structures
body parts that are reduced or impaired from their past needed condition and no longer serve a functional purpose
EX: appendix, wisdom teeth
allopatric speciation
a physical barrier arrives and separates two populations, ending gene flow between them
ex: Galapagos finches when they landed on seperate islands
sympatric speciation
populations inhabiting the same geographic region separate in the absence of a physical barrier
genetic drift
when an allele becomes more or less common by CHANCE (not natural selection) and allele frequencies show a dramatic change
often results in a loss of genetic variation
changes are more apparent in SMALLER populations
If an allele disappears completely and variation is reduced so much - extinction is likely
