chapter 21 and 22

Question 1

microevolution

Answer 1

change in allele frequencies over generations– 3 mechanisms ; natural selection, genetic drift, gene flow

Question 2

genetic variation

Answer 2

individuals differ in inherited traits - selection acts on differences– mendel= mode of inheritance. - phenotypic variations reflects genetic variation.
-heritable variations occur on either or basis– single gene locus with multiple alleles that have distinct phenotypes or other phenotypic differences created from different alleles acting together (hair colour in humans)
genetic differences measured- in average percent of loci that are heterozygous
- nucleotide variability- doesn’t change phenotype if it occurs in introns

Question 3

sources of genetic variation

Answer 3

mutation or gene duplication can create new allele and genes- if reproduction is fast variation an change rapidly
**sexual reproduction

Question 4

new alleles

Answer 4

• can arise through mutations in gametes which are passed to offspring -most mutations in animals are in somatic cells
  point mutation- one nucleotide and it can impact the phenotype (usually don’t do anything
  -since phenotypes tend to match environment it is unlikely that a new mutation will improve

Question 5

altering gene # or position

Answer 5

CHROMOSOME CHANGES-usually harmful but can rarely be good= mutations can accumulate and expand the genome -and give new functions

Question 6

rapid reproduction

Answer 6

mutation rate is low but many mutations accumulate after many generations such as viruses

Question 7

sexual reproduction

Answer 7

genetic variation from unique combination of alleles from each parent shuffles allies through meiosis and crossing over

Question 8

population

Answer 8

group of individuals of same species - same area that interbreed and produce fertile offspring

Question 9

gene pool

Answer 9

all copies of every type of alley at every locus in all members of population

Question 10

fixed allele

Answer 10

only one allele that exists for a locus - all individuals homozygous

Question 11

hardy weinberg equation

Answer 11

each allele has a frequency (proportion in population) hardy weinberg can determine genetic population if evolution is not occurring at a specific locus and compare it with the data observed - no difference between the two- the population is not evolving
principle- frequency of alleles / genotype in population will remain constant from gen to gen if only mendelian segregation and recombination of alleles are at work
equation pxp + 2pq +qxq = 1 and p + q = 1

Question 12

conditions for hardy weinberg equilibrium

Answer 12

1 no mutations
2random mating
3no natural selection
4extremely large population
5no gene flow 
if these conditions are not met evolutionary change will occur and it is possible that specific genes can be in the hardy weinberg equilibrium

Question 13

natural selection

Answer 13

different success in mating/ survival is due to better traits that are suited to the particular environment
genetic terms-alleles passed to next gene in proportions that differ from those present in the first one- allele frequency can rise if allele is beneficial
- certain alleles are favoured– ADAPTIVE EVOLUTION- evolution that results in batter match between organisms and their environment

Question 14

genetic drift

Answer 14

chance events cause allele frequencies to fluctuate *** especially in small populations – founder effect and bottle neck effect
founder effect- individuals become isolated from a larger population and the new population has a differing gene pool this can account for high frequency of inherited diseases amongst isolated human populations
bottleneck effect- drop in population size due to sudden environmental changes- even if population can recover the frequency of alleles can still be altered. humans can cause severe bottlenecks
** can cause harmful alleles to become fixed

Question 15

case study genetic drift and prairie chicken

Answer 15

praire to farmland which resulted in population drop of the prairie chicken the few that survived had little genetic variety , this was known as a bottleneck there was a loss of variation and increase in harmful alleles. when compared the prairie chickens lost 9 alleles.

Question 16

gene flow

Answer 16

transfer of alleles into and out of the population due to movement of fertile individuals or gametes - this reduces genetic differences amongst populations ( two populations could even combine)
- alleles transferred by gene flow can affect how well populations adapt to local environmental conditions – gene flow is mating with other populations.

Question 17

natural selection in depth

Answer 17

natural selection not random and favours some alleles over others adaptive evolution.
-relative fitness- certain traits in populations lead to greater relative fitness which is the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals - selection acts more on phenotype then genotype– the whole organism is up to selection

Question 18

types of selection

Answer 18

( depends on phenotypes favoured)

• direction selection-codntions favour individuals at ONE extreme end of a phenotypic range shifting the populations frequency curve in one direction and it is common in environmental changes or migration
• disruptive selection-conditions favour individuals at both extremes of the phenotypic range
• stabilizing selection-acts against both extremes favours intermediate variants and it reduces variation

Question 19

role of natural selection

Answer 19

adaptive evolution is a continuous dynamic process- natural selection is the only evolutionary mechanism that constantly leads to adaptive evolution

Question 20

sexual selection

Answer 20

form of natural selection - individuals with certain inherited characteristics are more likely than other individuals to obtain mates and this sometimes results in *dimorphism- differences in secondary sexual characteristics between males and females of the same species.
intrasexual selection- selection within the same sex-compete for mates of the opposite sex, this is known as mate choice. one sex is choosy in selecting mates

Question 21

preservation of genetic variation

Answer 21

neutral variation- differences in DNA that do not confer a selective advantage or disadvantage - directional and stabilizing selection reduce allele variation and diploidy and balancing selection restores it

• diploidy- genetic variation hid- recessive alleles if they are less favourable they survive within heterozygotes - if environment changes they may become more common.
• balancing selection- natural selection maintains two or more forms in a population and may preserve variations at some loci– heterozygous advantage and frequency dependant selection ?

Question 22

heterozygous advantage

Answer 22

heterozygous at locus have greater fitness- in this case natural selection maintains two or more alleles at one locus in this case its genotype over phenotype- it could be any type of selection just depends on relationship between genotype and phenotype- ex of this is sickle cell in africa.

Question 23

frequency dependant selection

Answer 23

fitness of phenotype depends on how common it is in a population ex two different alleles can oscillate depending on environmental conditions such as prey

Question 24

why can’t natural selection make perfect organisms

Answer 24

1 selection can only act on existing variations- only favours traits actually in population
2evolution is limited by historical constraints it can only work on existing structures
3 adaptations are often compromises- colour attracts mates and predators
4chance, natural selection and environment interact
natural selection works on a better than basis ( not perfect)

Question 25

microevolution

Answer 25

change in allele frequency of a population over many generations and these are caused by natural selection, genetic drift and gene flow LOOK AT HARDY WEINGBERG PRINCIPLE WORK SHEETS

Question 26

macroevolution

Answer 26

broad scale evolution

Question 27

biological species concept

Answer 27

species group of organisms who have potential to interbreed and produce fertile viable offspring

Question 28

reproductive isolation

Answer 28

existence of biological berries that don’t allow members of a species to interbreed barriers bock gene flow r
**reproductive berries -habitat isolation-temporal isolation - bread at different times-behavioural isolation- mating and behavioural rituals– mate can’t recognize its mate mechanical isolation- morphological differences precent mating -gametic isolation-sperm can’t fertilize egg

Question 29

pre zygotic barriers

Answer 29

block fertilization 1 members can’t meet
2attempted mate not completed hindering fertilization
3. development error?

Question 30

post zygotic barriers

Answer 30

reduced hybrid viability- the development of the hybrid are impaired
reduced hybrid fertility- hybrids are sterile
hybrid breakdown- first hybrid get good but the second is impaired or sterile

Question 31

limitations of biological species concept

Answer 31

its good because it shows speciation from reproductive isolation
its and because theres no way to evaluate reproductive isolate from fossils and it does not apply to organisms that do not reproduce sexually
species morphologically and ecologically disntict gene flow still occurs – ex grizzly and polar bear
increase in gene flow decrease in natural selection

Question 32

morphological species concept

Answer 32

characterizes species according to body and structure - asexual and sexual organisms included. useful when gene flow unknown, bad- subjective criteria disagree on what features distinguish a species

Question 33

phylogenetic species concept

Answer 33

smaller group of individuals that shares common ancestor (one branch ) compare morphology and DNA the bad part is how much can DNA differ of a species before you consider them different species.

Question 34

ecological species concept

Answer 34

species in terms of ecological niche(interaction with environment)

Question 35

allopatric speciation + process of allopatric speciation + evidence

Answer 35

-gene flow interrupted when population divided into geographically isolated subpopulations
-size of barrier to cause specetion depends on the species
if geographic separation occurs then gene pools may diverge and different mutations may arise in the gene pools an d natural selection causes genetic dat that alter allele frequencies ending up resulting in reproductive isolation (the two species can no longer mate)
-regions that are isolated or highly subdivide by berries typically have more species than do the similar regions that lack such features. ex galapagos islands with all the finches

Question 36

sympatric speciation

Answer 36

occurs in populations that live in the same area– gene flow reduced by polyploidy, habitat differentiation, and sexual selection (LESS COMMON THAN ALLOPATRIC SPECIATION)

• polyploidy-extra chromosomes- common in plants
• autoploidy-individual has more than two chromosome sets that are all derived from a single species in plants a failure of chromosomal division 2n turns to 4n (tetraploid)- these are reproductively isolated from the parent cell and they can fertilize themselves and mutations can occur and so on resulting in a 4n plant.
• habitat differentiation- genetic factors enable sub population to split a habitat or a resource not used by the parent population– new food source and natural selection can occur
• sexual selection- mate choice based on male breeding- such as colouration can be the main reproductive barrier that keep gene pool separate

Question 37

hybrid zone

Answer 37

region in which members of different species meet and mate producing offspring with mixed ancestry
PATTERNS- some form as narrow bands that usually occur where the two species habitats meet
ALLELE FREQUENCY PATTERN-gene flow does not occur- hybrid species usually are impaired and have a low chance of successful reproduction and natural selection can limit gene flow – if hybrid zones do not become their own species there are three possibilities 1. reinforcement- reproductive barriers reinforced when hybrids are less fit then their parents and natural selection reinforces the pre zygotic barriers.2 fusion- barriers are weak gene flow may occur and the gene pools may become increasingly similar and this can reverse speculation the two hybrids may fuse into a single species 3.stability the hybrids continue to be produced and the hybrids sure and reproduce better offspring than parent species in certain habitats or years

Question 38

time of speciation

Answer 38

how long it takes a new species to form- broad patterns from fossil record morphological data or DNA sequences
patterns of fossil record- appears that new species appear suddenly and some disappear
–punctuated equilibrium- periods of apparent stasis functioned by sudden change

Question 39

speciation rates

Answer 39

punctuated pattern- speciation begins and can be completed rapidly and natural selection can produce extensive genetic changes in hybrid populations over a short period of time– divergence must occur first but a new species can be produced fast
time- divergence of a species to the time when speciation is complete carries a lot and can range from thousands to millions of years the average is 6.5 million– speciation begins only after gene flow between populations interrupted and the population must diverge genetically so they become reproductively isolated.