6. Chapter 5: The Evolution of Populations (9-53)

Question 1

What is the only evolutionary change of adaption?

Answer 1

Natural selection

Question 2

What is a mutation?

What are they the source of?

Answer 2

A mutation is the changes in the DNA sequence of an organism and can be chromosomal on large segment of DNA include DNA segment loss, repetition of DNA segments, addition or loss of
chromosomes

Question 3

What is the source of genetic variability?

Answer 3

Mutations

Question 4

What are characteristics of mutations?

Answer 4

Mutations are:

1. Random
2. Transmissible only in the gametes
3. Frequent throughout the gene pool, but rare at each locus.
4. Will influence allele frequencies but is a weak evolutionary force from generation to generation, especially in large population.
5. Source of genetic variability

Question 5

What is a type of mutation (and their various effects)?

Answer 5

1. Point mutation: is an addition, deletion, or substitution of a base (ie. a-c instead of a-t):
   a. Negative effect ie. elhers-danlos syndrome
   b. Lethal effect will cause death
   c. Neutral effect when mutation falls on non-coding protein of DNA or synonymy of codons for the formation of amino acids
   d. Positive effect when the effect enables the individual to be better adapted to their environment

Question 6

Explain the effect a point mutation may have on hemoglobin?

Answer 6

Changes in DNA sequence can alter normal hemoglobin into sickle cell hemoglobin. Changes in primary, secondary, tertiary, and quaternary structures’ shapes and base. Changes in function and shape will occur. Normal hemoglobin functions by not associating with one another and each carries oxygen. Sickle-cell hemoglobin functions through hydrophobic interactions with one another leading to their aggregation into a fibre and their capacity to carry oxygen is greatly reduced. Red blood cell shape differs in that normal is disk shaped and mutation causes crescent shape.

Question 7

What do mutations provide in the long-term?

Answer 7

A small portion of mutations is considered advantageous as it offers a good genetic basis for evolution over millions of years.

Question 8

What is the unit of measure for mutations?

Answer 8

Pair of bases per generation (pbg)

Question 9

What is the rate of mutations in humans? How many base pairs are in the human genome? How many new mutations are in babies?

Answer 9

The human genome contains approx. 6.4x10^9 base pairs. The rate is approx. 2.5x10^-8 mutations by pbg. Babies will approx. have 175 new mutations in their genome.

Question 10

What are the two type of mating in relation to the Hardy-Weinberg Equilibrium?

Answer 10

1. Random mating: maintains Hardy-Weinberg equilibrium ie. American eel mate in a sprawling ground somewhere in the Saragossa Sea
2. Assortative mating: modifies Hardy-Weinberg equilibrium by choosing partners in relation to the phenotype, does not change allele frequencies but it changes genotypic frequencies

Question 11

What are the types of assortative mating? Examples?

Answer 11

When paired with natural selection…
1. Positive assortative mating: more frequent mating between similar individuals than expected chance which INCREASES HOMOZYGOSITY but loses genetic variability.
Ex. Self-fertilization of plants, geographical proximity of individuals, or in humans mating according to height and skin colour
2. Negative assortative mating: more frequent mating between individuals that do not look alike than expected by chance which INCREASES HETEROZYGOSITY
Ex. Staminate and carpellate flowers (male/female), thrum and pin flower (different shape of sexual organ)

Question 12

What is the negative effect of (positive) assortative mating? Provide example.

Answer 12

A loss of genetic variability due to:
1. Phenomena of endogamic depression since the harmful alleles will express themselves
2. Natural selection will purge the population of a portion of its harmful alleles
Ex. Positive assortative of mating occurred to guppies based on colour, they had no genetic variability as they were just clones of one another and the first (fungus) disease wiped them all out

Question 13

What is endogamic depression?

Answer 13

Selection will act on it and will eliminate a portion of the gene

Question 14

How does gene flow occur? And how can it be manipulated by protection officials?

Answer 14

Migration where an exchange of genes between populations not species. Migration has a tendency to standardize the genetic pool of the
populations involved and it can play a similar role as mutations by introducing new genes in one of the populations.
Officials will introduce new alleles (bears) into a (bear) population because although its a healthy population there is a direction towards positive assortment

Question 15

What is genetic drift?

Answer 15

Genetic drift is the result of chance which is especial important in small populations. As chance will have increasingly more impact on a population as the size of the population gets smaller. In small populations, genetic drift will trigger a decrease in genetic variability and a decrease in heterozygosity. In a large population genetic drift will cause little changes to the allelic or genotypic frequency of a population. If there are no other processes (mutation, migration,
or selection) that will affect allelic frequencies at a particular locus, genetic drift will eventually result in the fixation of an allele and the elimination of all others for this locus. If no other evolutionary processes are acting on
allelic of genotypic frequencies, then the probability that an allele will become fixed is equal to its frequency.

Question 16

What is the relationship between the size of a sample and sampling errors?

Answer 16

We expect to see in a biological population that the larger the sample, the smaller the differences will be between expected frequencies and observed frequencies.

Question 17

What are cases of the effects of genetic drift?

Answer 17

1. The population bottleneck: In small populations, genetic drift
   can lead to the fixation of deleterious alleles and a loss of genetic variability. Thus, increasing the risk of extinction. Ex. Genetic drift doesn’t impact cheetahs as much since very little genetic variability, greater prairie chicken lost genetic variability which is why they now hatch less eggs and are a smaller population as they were negatively impacted by adaptability with homozygosity
2. Founder effect: is the prevalence of an allele that should be rare when a few individuals from a large population create a new colony, the genetic make-
   up of the colony differs from the source population
   Ex. Polydactyl in Amish communities, Myotonic dystrophy in Charlevoix/Lake St-Jean regions of Quebec occur due to inbreeding (limited genetic pool Amish originated from 100 Germans)

Question 18

What is natural selection in terms of the evolution of populations?

Answer 18

A process by which the individuals with certain hereditary particularities survive and reproduce in larger numbers than other individuals. The alleles favoured by selection are more abundant in offspring than in the parental generation. The action of natural selection on the frequency of an allele can be cancelled by the action of mutation, genetic drift, and migration. The only evolutionary mechanism that aids the survival and the reproduction of organisms in their environment.

Question 19

Is the colour of map butterflies linked to natural selection?

Answer 19

No, because only hereditary variations constitute the basis of natural selection. Map butterflies have non-hereditary variability. Their colours have no genetic basis only based on different feedings of plants during different seasons giving a different colour.

Question 20

How can someone know if a characteristic in a species is a genetic difference or environmental effect (environmental or genetic basis)?
Give example of yarrow

Answer 20

Variability in yarrow height is due to altitude differences. This can be confirmed through testing using controlled variables, and if the yarrow is the same length with same conditions than its environmental but if the yarrow differs in length within same conditions then it would be considered genetic.

Question 21

How was the Hardy-Weinberg discovered?

Answer 21

Weinberg, a German biologist, and Hardy, an English mathematician, both made the same discovery, demonstrating that, under certain conditions, allele frequencies in a population stay constant from one generation to the next. Thus, no evolution will occur.

Question 22

When is a population under Hardy-Weinberg’s equilibrium?

Answer 22

The frequencies of alleles and genotypes within a
population will remain constant (according to the equation p2 + 2pq + q2 = 1) from generation to generation as long as the following conditions are respected:
1. There are no mutations.
2. Mating is done randomly.
3. The size of the population is extremely large.
4. There is no genetic (gene) flow (no migration of alleles between
populations).
5. There is no natural selection.

Question 23

What does Hardy-Weinberg’s principle describes?

Answer 23

Hardy-Weinberg’s principle describes a hypothetical population that does not evolve.

Question 24

What is an adaptive value?

Also known as…

Answer 24

fitness, the selective value, or the adaptive value of a genotype corresponds to the contribution of an individual to the genetic pool of the next generation when compared with the contribution of other individuals.

Question 25

What are the types of hereditary traits?

Examples?

Answer 25

– Qualitative a discrete variation like colour

– Quantitative a continuous variation like height or weight

Question 26

Polymorphe populations show..

Answer 26

.. distinct morphological types of genetic variability.

Question 27

How are continuously variable traits selected for?

Remember graphs + examples

Answer 27

1. Directional selection (ie. so evolution towards darker or lighter colour) beaks of medium ground finch
2. Disruptive selection: (ie. evolution towards both extreme version so both lightest and darkest colours) longest and shortest width of lower jaws of P. Ostrinus bird
3. Stabilizing selection (ie. an evolution towards the intermediate (blended) trait) ie. mortality of babies, seven cervical vertebrae from mammals

Question 28

How is genetic variability maintained in nature?

Answer 28

1. Diploid and genetic load
2. Advantage of heterozygotes
3. Frequency-dependent selection
4. Neutral genetic variability
5. Other mechanisms