Lesson 3: Natural Selection

Question 1

Microevolution

Answer 1

-the change in the gene frequencies within a population over time
-evolution within a species

Question 2

Natural Selection

Answer 2

-The process by which the characteristics of population of organisms change because idvs w/ certain heritable traits survive specific local environmental conditions
-operates on the variation that is already present in a species

Question 3

Adaptation

Answer 3

is necessary for natural selection. Species that are well adapted to their environment survive and reproduce

Question 4

Natural selection CANNOT

Answer 4

create new structures or processes

Question 5

Natural selection DOES NOT

Answer 5

result in new improved species

Question 6

Natural selection DOES

Answer 6

produce better suited species for an environment

Question 7

Variation pt 1: definition

Answer 7

Natural selection can only occur if there is a variation amongst member of the same species

Question 8

Variation pt 2: sources

Answer 8

mutation- the original source of the variation, new alleles are produced by random mutation
meiosis- every gametes produced by meiosis is likely to carry a different combination of alleles due to crossing over and random assortment.
sexual reproduction-the offspring are a combination of the alleles of two individuals.

Question 9

Variations in populations

Answer 9

The expression of a trait should follow a normal distribution pattern (bell curve)

Question 10

Adaptations

Answer 10

–>traits that enable a idv to fit into their surroundings and way of life.
–these include of physiological, behavioral, and structural adaptations; some variants are more environment-suited, leading to differential survival and reproduction. Some organisms will be able to produce, while others may not

Question 11

Differential Reproduction

Answer 11

Not every individual will be able to obtain enough resources to survive and reproduce because most species produce more offspring than the environment can support. idvs that are better adapted to their environment will be better able to pass on their alleles to the next generation. a shift in allele frequencies within a population over time.

Question 12

Stabililizing selection

Answer 12

-favours individuals with the “average” expression of the trait
-> selects against individuals w/ extreme expressions of the trait

ex. Human birth weight: until recent medical advancements, infants that were born too small tended not to survive while larger infants died during child birth (7lbs)

Question 13

Direction Selection

Answer 13

-favours individuals with one extreme of the trait.
-selects against individuals with average expressions as well as the other extreme

Ex. Camouflage in walking stick insects: born in an array of colours that blend into their surroundings are selected for, while all other colours are selected against

Question 14

Disruptive selection

Answer 14

-favours individuals at both extremes of the trait
-selects against individuals with the average expression of the trait

Question 15

Disruptive selection: limpets (marine organism)

Answer 15

-have shell colours that range from white to very dark brown
-darks limpets attach to dark rocks and are less visible to predators
-light limpets attach to light rocks and are less visible to predators
-intermediate colours are all visible and are consumed by predators (selected against)