d4.1 (natural selection)

Question 1

reasons for natural selection x2

Answer 1

Not all offspring that are produced will survive and reproduce because of a struggle for resources

Some individuals are more likely to survive and reproduce than others because of their heritable traits

Question 2

what 3 levels can see variation across a species?

Answer 2

physical, physiological, and behavioral levels

Question 3

4 ways variation within a species can occur

Answer 3

Mutation: is the original source of variation, with new alleles produced by changes in the DNA

Gene flow: the movement of genes between different groups of organisms

Meiosis: crossing over and independent assortment during the formation of egg and sperm which leads to the creation of new combinations of alleles

Sexual reproduction: random fertilization between egg and sperm of different parents

Question 4

what type of cells see the most mutations?

Answer 4

highest in bacteria and viruses

Question 5

rates of mutation largely depend on what?

Answer 5

on reproductive rate

Question 6

how does processes of meiosis and fertilization cause genetic variation?

Answer 6

shuffles alleles from past mutations into new combinations

Question 7

however there is an overall trend for more offspring to be produced than can be supported by what?

Answer 7

the resources available in the habitat

Question 8

2 evolutionary benefits to overproduction of offspring

Answer 8

increases the odds that at least some of the offspring will survive to adulthood, required for continuity of the species.

ensures there is ample genetic variation in the population should the species need to adapt to changing environmental conditions

Question 9

overproduction of offspring leads to the potential for what type of growth? what does it mean?

Answer 9

exponential growth of a population in which it increases in size each year

Question 10

why can’t exponential growth of a natural population grow infinitely?

Answer 10

resources in the environment (such as adequate food, shelter, water, and mates) are limited

Question 11

define logistic growth

Answer 11

in which there is rapid growth at first when the population is small and resources are plentiful, but the growth rate slows as the population size increases and resources begin to be in short supply

Question 12

competition is the result of what 2 key reasons?

Answer 12

overproduction of offspring and limited resources

Question 13

definition and example of direct competition (elk)

Answer 13

when one individual directly affects another’s ability to obtain resources

for example, a male elk will use aggression demonstrate dominance and to prevent other males from mating with a female

Question 14

definition and example of indirect competition (grizzly)

Answer 14

when individuals indirectly compete for resources, such as territory, light, or prey

for example, an individual may deplete a shared resource, such as a grizzly bear catching a salmon so that the salmon can no longer be eaten by bears at different points along the river

Question 15

impact of a negative selection pressures

Answer 15

decreases the frequency of a trait

Question 16

impact of a positve selection pressures

Answer 16

increases the frequency of a trait

Question 17

biotic selection pressures x5

Answer 17

predation
competition
disease
finding and attracting mates
availability of food

Question 18

abiotic selection pressures x7

Answer 18

temperature
water availability
light availability
oxygen and carbon dioxide concentrations
natural disasters (floods, fires, storms)
pollutants
wind

Question 19

abiotic selection pressures are often what? what does this mean

Answer 19

density independent, meaning they act the same no matter the population density

Question 20

define biological fitness, what makes an individual more or less ‘fit’?

Answer 20

a measure of an organism’s ability to survive to reproductive age, find a mate, and produce offspring

individuals are more or less “fit” which means they are more or less likely to survive and reproduce as a result of a selective pressure and their heritable traits

Question 21

how can the pace of evolutionary change in a population vary from selection pressure?

Answer 21

rapid evolution will occur if the selection pressure is higher
gradual evolution will occur if the selection pressure is lower

Question 22

state and explain the two major forms of sexual selection as a selection pressure

Answer 22

intersexual selection (one biological sex chooses which individual of the other sex to mate with): females are usually choosier while selecting their partners based on structural and behavioural traits, therefore individuals with the most appealing characteristics are likelier to mate and reproduce successfully, ↑ frequency of the trait in the population over time

intrasexual selection (competition between members of the same sex for access to members of the opposite sex): can be physical combat, displaying strength, and vocalization, responsible for the evolution of secondary sexual characteristics in males (i.e. deer antlers, beetle horns, and large body sizes). individuals with the advantage when fighting off potential competitor are likelier to mate and reproduce successfully, ↑ frequency of the trait in the population over time

Question 23

sexual selection can result in the development of physical and behavioural traits which do not provide what?

Answer 23

any survival benefits but do help to maximize an individual’s reproductive success

Question 24

watch a video on models of endler’s investigation of selection in guppy fish. ensure you can answer the following questions:

what is the impact of predators on the number of spots on male guppies? use natural selection to explain the results.

what is the impact of female preference on the number of spots on male guppies? use sexual selection to explain the results.

use the link to the simulator as well https://leosiiman.neocities.org/lab-guppy/guppy-lab

Answer 24

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Question 25

what did endler’s investigation on selection in guppy fish prove? x3

Answer 25

females prefer to mate with ‘flashier’ males (more orange spots on their tails)

flashier males may also be more visible to predators and be more likely to be eaten

Question 26

what are the two guppy predators? in what parts of the river do they live? which one is more agressive (how does their diet reflect this)?

Answer 26

rivulus “killifish” = higher elevation (begging of guppy streams), less vicious as they only eat young guppies

pike cichlids = lower elevations (larger deeper stretches of guppy streams), more vicious as they eat 4-5 guppies daily

Question 27

how did guppies differ in high vs low predation habitats? x3 ways

Answer 27

larger in low predation, smaller in high predation

more colourful in low predation, less colourful in high predation

less babies in low predation, more babies in high predation

Question 28

why are models used in science? x3

Answer 28

can simplify complex processes/concepts

change the scale of objects/processes that are too big/small to be seen

change the rate of a phenomenon (slow down/speed up)

Question 29

define allele

Answer 29

different versions of the same gene

Question 30

define gene pool

Answer 30

the collection of all the genes and the various alleles of those genes within a population

Question 31

define gene flow

Answer 31

any movement of individuals, and/or the genetic material they carry, from one population to another

Question 32

what effect does gene flow have within a population?

Answer 32

can introduce new alleles to a population, increasing the genetic variation of that population

Question 33

what effect does gene flow have across populations?

Answer 33

can make distant populations genetically similar to one another, hence reducing the chance of speciation

Question 34

define allele frequency

Answer 34

prevalence of a specific allele out of all alleles for a gene in a gene pool

Question 35

the frequency of the alleles of a gene must equal what?

Answer 35

1

Question 36

how to calculate allele frequency

Answer 36

dividing the number of times a specific allele is observed in the population by the total number of all alleles for that gene in the population

(see slide 73)

Question 37

define genetic shift as a change in allele frequency

Answer 37

when a population is altered due to random events, such as natural disasters. the surviving individuals are a sample of the original population and their allele frequencies may be very different than other populations

Question 38

define founder effect as a change in allele frequency

Answer 38

a type of genetic drift (chance event) that occurs when a small group of migrants—not genetically representative of the population from which they came—establish in a new area. the new population will have different allele frequencies than the original population

Question 39

define natural selection as a change in allele frequency

Answer 39

different populations may have different selection pressures acting on the alleles within the gene pool, maintaining alleles that provide an advantage and selecting out alleles that negatively impact survival and/or reproduction

Question 40

define new mutations as a change in allele frequency

Answer 40

new alleles produced by changes in the DNA. any new allele in the gene pool causes a change in the frequency alleles in a population relative to a population in which the mutation did not occur

Question 41

define neo darwinism

Answer 41

a cohesive theory of evolution that integrates darwin’s idea of natural selection with understandings of genetics and gene pools of populations

Question 42

what does neo darwinism include x4 elements

Answer 42

the molecular variation in DNA between individuals
with how those variations are inherited through cells
with the differential survival and reproduction of organisms
with the ultimate change a population over time.

Question 43

visible indicator that a gene is NOT evolving

Answer 43

if allele frequency of a specific gene in a population remains stable over time

Question 44

what are the 5 processes that can alter allele frequencies

Answer 44

mutation
gene flow
nonrandom mating
genetic drift
selection

Question 45

the long term effect of a mutation on allele frequencies depends on what?

Answer 45

the allele’s fitness

Question 46

is gene flow is more likely to have a strong effect on allele frequencies on smaller or larger populations?

Answer 46

smaller

Question 47

examples of nonrandom mating x3

Answer 47

sexual selection (chosen by genetic traits)
mating with closer neighbours than distant members of population
choosing mates that are most like themselves

Question 48

what can genetic drift cause in terms of alleles in a population? x2

Answer 48

rare alleles to become more common in a population
some alleles to disappear entirely

Question 49

what are three patterns of evolutionary change that result from natural selection?

Answer 49

stabilizing selection
disruptive selection
directional selection
(see slides 93 to 96 for visuals)

Question 50

how does stabilizing selection curve change with natural selection?

Answer 50

reduces phenotypic variation in the population by selecting against the extreme varieties at each end of the phenotypic range (makes the bell curve narrower (reduced phenotypic range))

Question 51

how does directional selection curve change with natural selection?

Answer 51

favours individuals with phenotypes at one extreme of the phenotypic range. common during periods of environmental change (bell curve shifts in the direction of the selected phenotype)

Question 52

how does disruptive selection curve change with natural selection?

Answer 52

favours individuals with phenotypes at both extremes of a phenotypic range while removing those with intermediate varieties. (starting bell curve shapes results in what looks like two bell curves side by side and merged in the middle)

Question 53

6 steps to using the hardy-weinberg equation

Answer 53

find q² (dd/total number)

take the square root of q² to find q.

determine p by subtracting q from 1 (p= 1 - q)

determine p² by multiplying p by itself

determine 2pq by multiplying p time q times 2 (2pq = 2 x p x q)

check that your calculations are correct by checking the values for p and q in the hardy-weinberg equations

Question 54

in order for a population to be in hardy-weinberg equilibrium, what conditions must be met? x5

Answer 54

the population is large to minimize impact of changes due to chance (genetic drift)

there is random mating between organisms

natural selection is not favouring one phenotype over another

there are no new mutations, so new alleles are not generated

there is no gene flow (emigration or immigration)

Question 55

how many generations of allele frequencies of a gene are compared to determine if a population is either in hardy-weinberg equilibrium OR is evolving?

Answer 55

at least 2