Natural Selection Flashcards
(34 cards)
natural selection explains …
- every adaptation
- adaptation is step-by-step
examples of natural selection
- the human eye
- immune system
- how fish evolved limbs and whale flippers
who came up with natural selection?
Darwin, with the help of Wallace
artificial selection
an evolutionary process in which humans consciously select for or against particular features
natural selection is not a ______, its a _____________
force, multi-step process
natural selection
a difference between the survival & reproduction of individuals with certain phenotypes compared to individuals with other phenotypes
natural selection main points
- individuals vary in phenotype
- some of this phenotype variation is heritable
- the variable, heritable traits affect an individuals probability of leaving offspring
equation: individuals vary in phenotype
- coefficient of variation
CV = standard deviation / mean
example of phenotypic variation being heritable
you look like your parents, not random people
struggle for existence
- not all individuals survive to reproduce or reproduce maximally
- there is a leading struggle for existence, leading to variability in reproductive output
outcome of natural selection
genetic composition of the population changes across generations
what do traits under natural selection impact?
the probability of survival and reproduction
what does natural selection operate on?
the phenotypes of individuals within a population, while populations evolve across generations
natural selection can operate even if …
the characters under selection are not heritable
natural selection is …
a process composed of testable components
why do individuals vary in phenotype?
variation could be due to genetic factors, environmental factors, or their interaction
struggle for existence in finches
- average rainfall dropped dramatically
- no reproduction during drought year
- 84% of finches died
example of how direction of selection depends on ecology
- droughts in 1977 & 2004
- by 2004, Large Ground Finches had colonized Daphne Major & dominated access to large seeds
- thus, there was selection for smaller beak sizes during the drought
natural selection cannot predict …
the future
in natural selection, every generation reflects …
the impacts of natural selection on the previous generations
natural selection is not _________, & does not lead to __________
progressive, perfection
what does natural selection filter?
it can only filter variation according to fitness in the current population
how can new traits evolve?
natural selection
how does an adaptation evolve?
by increasing the reproductive success of its possessor
