it passes copies of its genes to its offspring
what happens each time an organism reproduces?
evolutionary fitness
an organisms success in passing genes to the next generation
evolutionary adaptation
any genetically controlled physiological, anatomical, or behavioral trait that increases an individuals ability to pass along its gnees
True
natural selection never acts directly on genes... T or F?
because it's an entire organism (not a single gene) that either survives and reproduced or dies without any reproducing. So, natural selection can only affect which individuals survive and reproduce and which don't.
why does natural selection ever act direction genes?
evolutoonb
any change over time in the relative frequencies of alleles in a population
changes in allele frequencies and thus to evolution
what can natural selection on single gene traits lead to?
directional selection, stabilizing selection, or disruptive selection
which three ways can natural selection affect the distributions of phenotypes?
directional selection
form of natural selection in which the entire curve moves; occurs when individuals at one end of the distribution curve have higher fitness than individuals in he middle of at the other end of the curve
they shift as some individuals fail to survive and reproduce while others succeed
what happens to the range of phenotype in directional selection?
limited resources
lack of necessities
stabilizing selection
form of natural selection by which the center of the curve remains in its current position; occurs when individuals near the center of a distribution curve have higher fitness than individuals at either end
disruptive selection
form of natural selection in which a single curve splits into two; occurs when individuals at the upper and lower ends of a distribution curve have higher fitness than individuals near the middle
acts most strongly against individuals of an intermediate type
in disruptive selection, how does selection act?
this situation can cause the single curve to split into two
what happened if the pressure of natural selection is strong and long enough? (disruptive selection)
two distinct phenotypes
what does selection create? (disruptive selection)
genetic drift
a random change in allele frequency
in small populations, individuals that carry a particular allele may leave more descendants than other individuals, just by chance. over time, A series of chance occurrences of this type can cause an allele to become common in a population
how for genetic drift take place?
founder effect
change in allele frequencies as a result of the migration of a small subgroup of a population
Hardy-Weinberg principke
states that allele frequencies in a population will remain constant unless one or more factors cause those frequencies to change
genetic equilibrium
the situation in which allele frequencies remain constant
1) there must be random mating2) the population must be very large3) there can be no movement into or out of the population 4) no mutations 5) no natural selection
what are the five conditions required to maintain genetic equilibrium from generation to generation?
401
401