Question

farmers spray pesticides on their plants to protect the plants from being eaten by insects.
some individual insects have a genetic mutation that makes them resistant to the toxins in
the pesticides.
which statement best describes how only a few resistant individuals resulted in the pesticide
becoming ineffective?
f the resistant insects change the toxin on the plants, making it safe for others.
g the resistant insects grow larger and eat less of the plants.
h the resistant insects eat the contaminated surface and leave the rest for others.
j the resistant insects are able to survive to reproduce and create a population that is also
resistant.
male guppies found in areas without predators are more colorful than the ones found in
locations with large predator populations. a population of adult guppies originating from an
area with a large number of predators is transferred to a nearby area with few predators.
which of these is most likely to happen over a few generations?
a the mortality rate of the guppies will increase.
b offspring will stop competing for resources.
c there will be an increase in mutations in the offspring.
d there will be an increase in the number of colorful guppies.
the bar graph shows the average beak depth (distance from the top of the beak to the bottom) of a population of
finches. the data were collected in 1976 and in 1978, after a drought occurred in 1977 in the area.
finch beak depth
source: grant, rosemary and peter,
bioscience, 2003
which factor best describes the change in this population of finches?
a an increase in resource availability
b a change in the reproductive success of one individual bird
c a decrease in fitness that increased survival rates
d a change in phenotype distribution because of an environmental factor

Explanation:

First Question (Insect Pesticide Resistance)

To determine the correct statement about pesticide - resistant insects, we analyze each option:

• Option F: Insects can't change the toxin on plants to make it safe for others. This is not a valid mechanism for pesticide ineffectiveness.
• Option G: The size of insects and their plant - eating amount have no relation to the development of pesticide resistance in the population.
• Option H: Eating the contaminated surface and leaving the rest for others does not lead to the spread of resistance in the insect population.
• Option J: Resistant insects survive, reproduce, and pass on the resistance trait. Over time, the population becomes resistant, making the pesticide ineffective. This is in line with the principle of natural selection.

We consider the effect of the new environment (few predators) on the guppy population:

• Option A: In an area with few predators, the mortality rate of guppies is likely to decrease, not increase.
• Option B: Offspring will always compete for resources as long as resources are limited, and the change in predator population does not make them stop competing.
• Option C: A change in predator population does not directly cause an increase in mutations in the offspring. Mutations are random events.
• Option D: In areas with few predators, colorful male guppies are more likely to reproduce successfully (as there is less predation pressure on them). So, over generations, the number of colorful guppies will increase.

We analyze the change in finch beak depth after the drought:

• Option A: A drought usually decreases resource availability, not increase it.
• Option B: The change in beak depth is a population - level change, not due to the reproductive success of one individual bird.
• Option C: A decrease in fitness would not increase survival rates. Fitness is related to an organism's ability to survive and reproduce.
• Option D: The drought (an environmental factor) caused a change in the available food sources. Finches with beaks better adapted to the new food sources (deeper beaks, maybe to crack harder seeds) survived and reproduced more. This led to a change in the phenotype (beak depth) distribution of the finch population.

Answer:

J. The resistant insects are able to survive to reproduce and create a population that is also resistant.

Second Question (Guppy Coloration and Predators)