Ch 9

Question 1

when does natural selection occur

Answer 1

when selection pressures in the environment confer a selective advantage on a specific phenotype to enhance its survival and reproduction; this results in changes in allele frequency in the gene pool of a population

Question 2

what can contribute to changes in allele frequency

Answer 2

environmental selection pressures, sexual selection, mutation, gene flow, selective breeding and genetic drift

Question 3

what needs to be considered to conserve viable gene pools

Answer 3

biogeography
reproductive behaviour
population dynamics

Question 4

what percentage of our gene are ‘fixed’

Answer 4

80-85%

Question 5

gene pool is…

Answer 5

the total collection of alleles within a population

Question 6

what 6 factors can effect allele frequency

Answer 6

mutation of an allele
immigration & emigration of individuals
reproduction rate of various individuals in the population
genetic drift
the bottleneck effect
the founder effect

Question 7

bottle neck effect

Answer 7

when the size of a population is drastically reduced & certain alleles may be lost through chance

Question 8

founder effect

Answer 8

when a few individuals move to a new area & become isolated from a larger population e.g. the amish community
deleterious recessive alleles may have a higher chance of coming together

Question 9

what are the principles of natural selection

Answer 9

individuals show variation from one another, within a population
many variations are caused by mutations in alleles & are inheritable
more offspring are born than can survive to maturity & reproduce; there is a struggle for existence & only some organisms can reproduce
some individuals have traits that make them more suited to their environment than others, making them more likely to reproduce & pass on their alleles

Question 10

what’s artificial selection

Answer 10

parental stock with certain desirable traits are selected and mated; over time, new traits can be established in later populations

Question 11

list 5 Selection pressures

Answer 11

competition between species for food & territories
predator-prey relationships
competition within species for food or water
competition within species for territories/nesting places
sexual selection

Question 12

what’s sexual dimorphism

Answer 12

when males and females have different appearances

Question 13

microevolution

Answer 13

the outcome of natural selection pressure shows a change in the frequency of various alleles within a population; any change in the gene pool of a population.

Question 14

macroevolution

Answer 14

major evolutionary changes above the species level

Question 15

true or false; speciation and macro-evolutionary changes result from an accumulation of micro-evolutionary changes over time

Answer 15

true

Question 16

speciation

Answer 16

when a species disappears only to be replaced by a new organism

Question 17

what are 4 pre-reproductive isolation mechanisms

Answer 17

geographic
temporal (time)
behavioural
morphological (can no longer mate)

Question 18

what are 3 post-reproductive isolation mechanisms

Answer 18

gamete mortality – the gametes don’t survive
zygote mortality – zygote forms, but doesn’t survive
hybrid sterility – an infertile offspring survives e.g. mule

Question 19

what’s allopatric speciation

Answer 19

when gene flow is disrupted as populations become physically separated through geographical isolation (populations diverge)

Question 20

What may cause sympatric speciation

Answer 20

may feed on different things
choose mates based on different characteristics
mate at different times
pre & post zygotic factors

Question 21

Why are larger populations more resistant to change

Answer 21

large populations hold a greater reserve of different alleles to draw on as selection pressures change

Question 22

stabilising selection

Answer 22

when an environment is unchanging, then selection pressures act against deleterious alleles

Question 23

direction selection

Answer 23

Changes in the environment lead to selection pressures to favour new traits, changing the gene pool over time

Question 24

disruptive selection

Answer 24

when both extreme traits are favored in an environment. Disruptive selection increases genetic and phenotypic diversity in a population, since more than one phenotype, or physical trait, is favored.
results in divergence