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Biology II (115) > EXAM 2 Part 2 > Flashcards

EXAM 2 Part 2 Flashcards

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0
Q

EVOLUTION

A

Change in the allele frequency of a population over generations.

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1
Q

What is the NEW SYNTHESIS

A

The combination of the theories of Mendel and Darwin. Mendel reveled the mechanism of inheritance and Darwin

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2
Q

HARDY WEINBERG EQUILIBRIUM

A

Genotype frequencies and gene frequencies of a large randomly mating population remain constant provided that immigration , mutation and selection do not take place.

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3
Q

A population is fixed when

A

All the individuals are homozygous for one allele. Fixed at “a” allele for example

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4
Q

A population with GENETIC VARIATION

A

Is one where there is multiple type alleles in the population. Population is not fixed at a gene locus.

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5
Q

The assumptions of the H-W equilibrium model. That allele frequencies can predict the genes type frequencies in the next population in if:

A
  1. Large population size
  2. No mutation
  3. No Migration
  4. No selection
  5. Mating is random ( non assortive mating)
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6
Q

As long as the H-w assumptions are not violated what happens to the frequency of the alleles and tthe frequency of genotype

A
  1. The frequency of alleles is the same in each generation

2. The number of individual with each genotype is the same each generation

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7
Q

Why do we use h-w equil

A

To test if a population is evolving

can occur with more that 2 sets of alleles

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8
Q

If a population is not in H-w equilibrium

A

Then one of the requirements have been violated and the population is evolving.

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9
Q

Violation of the “ large population” assumption

A

Small population

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10
Q

How can a small population affect HW

A

GENETIC DRIFT
. BOTTLENECK EFFECT
. FOUNDERS EFFECT

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11
Q

GENETIC DRIFT IS

A

The frequency of alleles in a population fluctuate due to random events ( by chance)
. A violation of HW “ small population
. When a percentage who are selected to mate are chosen by chance in a small population, it does not reflect the true genotype of the population as it would in a large population.

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12
Q

BOTTLENECK EFFECT

A

Is a type of GENETIC DRIFT
. VIOLTION OF LARGE POPULATION ASSUMPTION OF HW
.It is when a population has a major shrinking event ( population drops rapidly over a short period) causing the loss of many alleles that were present in the original population and the surviving population( allele frequency) is not representative of the original population.
. There is a loss in genetic diversity- a single change in the environment might doom them all.

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13
Q

Eg of bottleneck effect

A

red wolves that are highly endangered whose population allele variety is greatly reduced from the original population

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14
Q

FOUNDERS EFFECT

A

Genetic drift that occurs when a few individuals become isolated from a larger population and form a new population whose gene pool composition is not reflective of that of the original population.
by chance the founding population have different allele frequency from the original. A

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15
Q

Eg of FOUNDERS EFFECT

A

In North America the Pennsylvania Amish settled away from their original population, and by chance one of the founding population carried an allele for short limb dwarfism and extra fingers which is recessive in the original population and extremely rare. In the isolated Amish population intermarriage has kept the disease incidence high in the small population.

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16
Q

Violation of “ no mutation”

A

Mutation of introduces new alleles in the population would change the overall allele frequency.
Mutations are rare events in population

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17
Q

Violation to “ no migration “ assumption of H W

A

. Gene flow

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18
Q

GENE FLOW

A

results from migration. Movement of alleles into or out of a population.

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19
Q

Eg of GENE FLOW

A

Grass have developed a hightolerance to the polluted soil of mine tailings while grass grown off the mine tailings have low tolerance, however there is not a 100 % tolerance. Wind has blown pollen/ from grass off the mine tailing to area of grass on the mine tailing. Gene flow from low tolerance seed has constrained perfect tolerance of high tolerance France on the polluted soil.

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20
Q

Violation of “ random mating “ of H-W

A

ASSORTATIVE MATING

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21
Q

ASSORTATIVE MATING

A

Individuals choosing mates that a similar phenotype or genotype to their own. ( POSITIVE ASSORTATIVE MATING)

NEGATIVE ASSORTATIVE MATING choosing the opposite phenotype or genotype in a mate

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22
Q

Eg. Of ASSORTATIVE MATING

A

A population that is original homozygous and all it’s individuals mate by ASSORTATIVE mating the future population will remain constant. An over abundance of homozygotes

. In diaprepes weevils found in the Caribbean large females tend to mate with large males and small females are left to mate with small males.

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23
Q

EG. NEGATIVE ASSORTMENT

A

negative ASSORTATIVE mating tend to result in more allele diversity in the population - an over abundance of heterozygotes.
. Preference based on MHC in mammals ( immune function) MHC are genes that help the immune system detect foreign substance. Certain mice tend to mate with individuals with a different MHC than their own.

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24
Q

Violation “ no selection “ for H-W

A

NATURAL SELECTION

25
Q

NATURAL SELECTION

A

It is the only one that results in adaption. It it’s the only mechanism of evolution.
. Other violations of HW do not each to organisms being better adapted to their environment.

. A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits.

26
Q

ADAPTION

A

Inherited characteristic of an organism that enhances its survival and reproduction in a specific environment.

27
Q

selection is divided into 3 ways that fitness can be affected

A

There is selection on the following
. SURVIVAL ( the ability to capture food eg.)
. FECUNDITY ( how many offspring one can produce) ( in fish and frog it is related to go ad size)
. The ability to attract MATES ( SEXUAL SELECTION)

28
Q

SEXUAL SELECTION

A

The ability to compete and attract mates.

29
Q

Two types of SEXUAL SELECTION

A

. INTRASEXUAL SELECTION

. INTERSEXUAL SELECTION

30
Q

INTRASEXUAL SELECTION

A

Type of sexual selection where individuals of the same gender compete against each other for mates. ( access to mating territory, or directly to mates)

Often more intense in males ( so often called male - male competition)

why? Because mating is skewed. The ratio of female whoa are available for mating is far less than male. female May be available only once per mating season or once per year while males are always available. So females do not have to compete as much. So males compete for the few available females.

31
Q

INTERSEXUAL SELECTION

A

Usually referred to as FEMALE MATE CHOICE. It is sexual selection based on the mate choice of the opposite sex.
. When the ratio of male available is higher than female. Females can be more selective in mate choice. There is a greater incentive to getting the best possible male because she is only capable to breed once per mating season and so must make a large investment in the genes of the male.

32
Q

When would a male be out of the mating pool

A

When they have made a large investment in parental care

Eg. Sunfish, penguins,

33
Q

SEXUAL DIMORPHISM

A

SECONDARY SEXUAL CHARACTERISTICS

Where males look significantly different from the female.
.
Females use these differences as fitness cues in determining mAte choice ( brightness of color, sound, size, symmetry)

Males use them in mate attraction or competition

34
Q

Eg of SEXUAL SELECTION

A

. Grey tree frog ( there is a variation in the call they produce short call vs long call. Female prefer long call frogs. Through experiments it was shown that the tadpoles of long call males had a higher fitness. So long call as it relate to fitness was the basis of female preference.

35
Q

FITNESS

A

The contribution of a group of like individuals ( eg lc males) to the gene pool of the next generation over some time span( lifetime )

This incorporates the means of natural selection
.growth and survival
. Mate attraction
. Fecundity
.
36
Q

Fitness has a measurement ( RELATIVE FITNESS)

A

It is a way to compare the success of different phenotypes in a population in terms of their contribution to the next generation

We measure fitness by quantifying the reproductive success of individuals ( over a lifetime) but ascribe to phenotype or genotype.
.
It is used as a measurement of a trait

RELATIVE FITNESS
fitness put on a scale “ w= 1 “ a trait of high fitness . 1-s indicates the reduction in fitness relative to most fit phenotype or genotype

37
Q

Eg of how relative fitness may change over time

A

Insecticide resistance in red scale insects.

Limited use of insecticide or limited use in medication which allows resistance pathogen to compete with non resistant so the population would be more susceptible the next time medication or insecticide is used. Resistance is cyclical. If this trait is rare it is probably be that it lessens fitness in the absence of spray, but increases when spray or medication is reintroduced. ( relative fitness increasing during spraying decrease when not.

38
Q

what is referred to by MODE OF SELECTION

A

How a trait shows distribution in a population before selection, and the selection acts on that trait, then after selection there is a different distribution of that trait in that population

39
Q

What are the 3 MODES OF SELECTION

A

. DIRECTIONAL
. STABILIZATION SELECTION
. DISRUPTIVE SELECTION

40
Q

DIRECTIONAL SELECTION

A

The response to selection is in one direction

41
Q

Example of DIRECTIONAL SELECTION

A

Trichomes and thorns reduce herbivory in plants. There is directional selection on trichome production which lead higher production of these successful deterrent. ( there’re is a correlation between trichome density and and survivorship and fitness.

42
Q

STABILIZING SELECTION

A

Fitness is higher at the intermediate phenotype. It is lowering variation in traits selecting for the average.
After a round of selection the new phenotypic distribution is narrower.
Some of the variation is lost ( there are fewer high value phenotype and low value phenotype.

43
Q

Eg. Of stabilizing selection

A

Human babies see lower fitness/ higher mortality at higher and lower birth weights and higher fitness at the intermediate birth weights

Starlings have stabilizing selection on having 3 eggs having more would lessen the survivorship of all the eggs.

44
Q

DISRUPTIVE SELECTION

A

Favors extreme variants of a population and select against the intermediate.

45
Q

Egs of DISRUPTIVE VARIATION

A

Male lazuli buntings the disruptive selection selects for low plumage brightness in male who are able to avoid direct competition with among brightly plumage males for mates by looking like a female; and high plumage brightness male are more preferred by female as mates. Intermediates they are unable to defend territory or compete for mates.

46
Q

Rate of evolution depends on what ( how quickly and how fast the population is evolving)

A

1.The strength of the selection: ( the steepness of the gradient)
( how important it is to fitness fitness : the steeper fitness the more rapid the evolutionary change. How far the distribution goes depends on the steepness of the gradient

  1. The amount variation in a trait: a narrow curve indicates a limited variation which would result in a small distribution change
    , but a wider curve indicates more variation in a trait and will result in a larger distribution change.
47
Q

What is meant by the PARADOX OF SELECTION

A
  1. How is genetic variation maintained in light of strong selection? Won’t selection ultimately favour one phenotype over another
  2. Continued directional and stabilizing selection could reduce diversity and cause the population to be fixed at at one trait and stop evolving.
48
Q

How is variation maintain for natural selection to be continually acting upon. ( natural selection acts on phenotypic variation, but both phenotypic and genotypic variation is needed)

Different mechanism is needed to maintain each.

A
  1. Mutations
  2. Dominance and Codominance
  3. Migration/ Geneflow ( coupled with)
  4. Geographic variation
  5. Independent assortment
  6. Variation in selection
49
Q

MUTATIONS ( genetic and phenotypic)

A

Rare occurrence when entirely new allele arises. It is a spontaneous change in the genetic sequence of an allele which may happen to errors in replication, meiosis.

50
Q

Eg of MUTATION

A

DeVries primroses

51
Q

DOMINANCE AND CODOMINANCE maintains variation ( new phenotypic variation from existing variation - no new alleles )

A
  1. Rare deleterious alleles remain hidden when dominant phenotype is favored
    Eg. Sickle cell as a recessive trait that is hidden. When the normal blood type is dominant over the recessive one, the damaging allele can remain in the population even though selection is favoring that
    dominant phenotype.
  2. HETEROZYGOTE ADVANTAGE in incomplete and codominance
    ( where both of your alleles are being express and are affecting your fitness, when heterozygosity is favored that will maintain that phenotype and it will be maintain along with its variation.

Eg. MHC ALLELES: women favour men with a higher variety of MHC alleles because they would have. More immune defenses to a wider variety of diseases

52
Q

GENE FLOW/ MIGRATION maintains Variation along with GEOGRAPHIC VARIATION.
( genetic variation because there is new genes being brought into the population and phenotypic variation because new alleles can result in different phenotypes. )

A 
Geneflow occurs when individual migrate in or out of a population. However variation only is maintained if the area migrated from has a different alleles from the new area( GEOGRAPHIC VARIATION allele frequencies).. 
Eg. Of geographic variation causes: bottleneck effect, local adaptation)
53
Q

Eg of LOCAL ADAPTATION that occurs along with Geneflow

A

Beach mouse of the south east. There is a relationship between fur color and sand color: at the southern end the mice match well with the light color sand but get darker as the sand does. But there is not a perfect Match because there is some Geneflow between the two population

54
Q

INDEPENDENT ASSORTMENT maintains variation

( polygenic variation because now new alleles but different combinations of alleles.

A

Through POLYGENIC INHERITANCE: ( additive or EPISTATIC)additive inheritance in human skin color and EPISTATIC IN MICE AND LAB COLOR) can exhibit new variation if previously isolated alleles are brought into contact with each other.

. No new alleles but new combinations resulting in new phenotypes because multiple genes( and different loci that will be assorted independently causing new combinations) are interacting with one another.

55
Q

VARIATION IN SELECTION maintains variation ( based on phenotypic variation)

A

Variation in selection over time prevents loss of alleles
1. NEW ENVIRONMENT may favor rare alleles.

  1. Selection may be FREQUENCY DEPENDENT
    ( selection and fitness depends on its frequency in the population.

Eg. Negative frequency dependence in orchids: Two varieties of orchids do not provide nectar, however still needs to be pollinated.
The rare the variety less likely pollinators will learn that their is no reward. When rare flowers are favored to be pollinated they soon become abundant causing the alternate phenotype to become rare. Overtime the pollinators now wise to lack of nectar in the first variety will switch to the rarer form.

56
Q

ADAPTATION

A

Inherited characteristic of an organism that enhances its survival and reproduction in a specific environment.

57
Q

What are the constraints to adaptation

A
  1. Standing variation in traits
  2. Evolutionary trade offs
  3. Evolution is not only drive by natural selection.
58
Q

standing variation as a constraint on adaptation

A

If there is no variation present for selection to act upon there will be no adaptation.

Eg. WINGS
Groups evolved different wing anatomy because existing variations present in ancestor’s limb structure differed ( insect, bird, bat wings)

Eg. 2 the number of digits a mammal has
- Variation in digit growth occurs late in development.
all tetrapods develop from a 5 digit embryo. SO NO VARIATION PRESENT IN EARLY DEVELOPMENT OF THE EMBRYO ONLY LATE. SO THE CHANGE FROM 5 to less could only happen later.

59
Q

Evolutionary trade off as a constraints to adaptation

A

Eg. Horn beetles either have big horns or large gonads
( produce more sperm) never both.
Both are advantageous for competition. Sperm and territorial competition. They energy constrained from making both, so if the cells that produce horns are cauterized the beetles develop larger testes ( energy trade off).

60
Q

” evolution isn’t driven by natural selection alone” as a constraints

A

Adaptation scan be slowed by
GENETIC DRIFT: in small population
. GENEFLOW when population are interconnected

Egs. Grasses on mine tailings: pollen from intolerant grasses mix with the tolerant ones preventing perfect adaptation to the environment.

Eg. Geneflow of beach mice : alleles for brown or white alleles become mixed preventing individuals from being completely white or completely brown.

61
Q

No

A

Yes

Biology II (115) (13 decks)

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