SimUText

Question 1

state the difference between ecologists and evolutionary biologists

Answer 1

• ecologists study processes that relate to how organisms interact with each other and their environment
• evolutionary biologists study the processes that lead to change in the genetic composition of populations over generations

Question 2

give examples of processes that ecologists study

Answer 2

population growth, nutrient cycling, competition, herbivory, and predation

Question 3

examples of processes that evolutionary biologists study

Answer 3

speciation, extinction, adaptation

Question 4

describe Pink bollworms and the issues associated with them

Answer 4

• adults are not problematic
• larvae (caterpillars) are pests of cotton: eat the flowers and seeds of cotton plants, reducing their fibre production and staining fibres

Question 5

what makes the pink bollworm such a serious pest?

Answer 5

its capacity for explosive population growth. a single female can lay between 100 and 200 eggs.

Question 6

a pink bollworm population can go through as many as —- generations during a single growing season

Answer 6

five

Question 7

drawbacks of chemical insecticides

Answer 7

• toxic to humans and other animals
• expensive
• kill beneficial arthropods, including bollworm predators
• resistance can form

Question 8

describe Bollgard

Answer 8

• cotton variety genetically engineered to produce its own biological insecticide
• gene from bacterium Bacillus thuringiensis (Bt) inserted into cotton plant’s genome
• encodes protein called Bt toxin Cry1Ac
• poisonous to the larvae of butterflies and moths

Question 9

how does Bt toxin Cry1Ac harm caterpillars?

Answer 9

• when swallowed by a caterpillar, the toxin binds to molecules of cadherin (protein) in the membranes of the caterpillar’s midgut cells
• triggers series of events that disrupt the caterpillar’s digestion and kill it

Question 10

what is the risk with usage of Bollgard?

Answer 10

there is a risk that species of moths may evolve resistance to Bt toxins

Question 11

how are evolution and ecology intertwined?

Answer 11

evolution is often facilitated by ecological processes, and the resulting impacts can often be ecologically important

Question 12

what are the four mechanisms of evolution?

Answer 12

mutation, natural selection, migration, and genetic drift.

Question 13

are the four mechanisms of evolution exclusive of each other?

Answer 13

The four mechanisms of evolution (natural selection, genetic drift, migration, and mutation) do not act exclusively of each other. In natural populations, evolution can occur via any combination of mechanisms acting simultaneously.

Question 14

when does evolution by natural selection happen?

Answer 14

when individuals with certain traits survive and reproduce at higher rates than others

Question 15

the theory of evolution by natural selection consists of a set of 3 requirements for populations of organisms:

Answer 15

1. there is variation among individuals
2. at least some of this variation is passed genetically from parents to offspring
3. some variants survive and reproduce at higher rates than others

Question 16

what is the automatic consequence of all requirements for evolution by natural selection being met?

Answer 16

the composition of the population changes from one generation to the next. Traits associated with survival and reproduction become common; traits associated with early death and reproductive failure become rare.

Question 17

when do alleles automatically change?

Answer 17

When there are differences in phenotype that are at least partly due to differences in genotype and some phenotypes have higher fitness than others. Alleles associated with high fitness become common; alleles associated with low fitness disappear. This is evolution by natural selection.

Question 18

evolution by genetic drift.

Answer 18

Allele frequencies may also change across generations due to purely random events that result in sampling error

Question 19

define the founder effect

Answer 19

a form of genetic drift that occurs when a few individuals from a source population establish a new population. Usually, the allele frequencies will be different in the new population than they are in the source population.

Question 20

when does migration lead to evolution?

Answer 20

if it alters allele frequencies in one or the other populations

Question 21

how does understanding the mechanism of descent with modification help researchers and farmers?

Answer 21

it helps them devise ways to control crop pests like the pink bollworm without encouraging rapid evolution of resistance

Question 22

why do pink bollworm populations evolve resistance to Bt toxins?

Answer 22

because normally rare resistant genotypes enjoy much higher fitness than susceptible genotypes on Bollard cotton

Question 23

how is the high-dose/refuge strategy effective in limiting the generation of resistance?

Answer 23

uses fields planted with patches of Bollgard and patches of normal cotton. The Bollgard cotton is well-protected against bollworms. The normal cotton allows susceptible bollworms to survive, reducing the fitness advantage associated with resistance.

Question 24

describe fish present in Lake Washington

Answer 24

home to a population of threespine sticklebacks. These small fish are prey to cutthroat trout.

Question 25

how do sticklebacks protect themselves against cutthroat trout?

Answer 25

• have bony plates in their skin that serve as armor.
• some sticklebacks wear a complete set of armor plating, some wear a partial set, and some wear a minimal set.

Question 26

what is the benefit/cost of more armour plating?

Answer 26

• gives better protection against cutthroat trout, but this protection comes at a cost compared to lightly armored sticklebacks, completely armored individuals grow more slowly, survive
  the winter at lower rates, and breed later.
• in addition, because heavily armored sticklebacks grow more slowly, they are more vulnerable to predatory insects that eat juvenile fish.

Question 27

where do sticklebacks tend to be more heavily armored

Answer 27

in lakes and streams where they are more vulnerable to attack by predatory fish, and less heavily armored where they are less vulnerable.