Question

15 multiple choice 6.25 points
why do pesticides designed to kill insect species become less effective after multiple applications?
some insects are resistant to the pesticide and pass on this favorable trait to offspring.
some insects are larger and shield other pest organisms from the pesticide.
pesticides contain strong odors, and insects learn to detect and avoid them.
pesticides quickly break down in the environment, and they no longer harm the insects.
16 multiple choice 6.25 points
a scientist studied how the populations of two different insect species changed on a farm after the farmer started using an insecticide on the crops. the diagram shows the sizes of both populations before and after two applications of the insecticide.
based on the data, which conclusion can be made about the insects?
the population of insect a became more resistant after the first application.
some insects passed a beneficial mutation to their offspring.
the population of insect b was resistant to the insecticide.
some insects survived because they were not sprayed with insecticide.

Explanation:

• Question 15:
• Option 1: This is in line with the concept of natural selection. Insects with resistance traits survive, reproduce, and pass on the resistance trait to their offspring. Over multiple applications, the proportion of resistant insects in the population increases, making the pesticide less effective.
• Option 2: There is no scientific basis that larger - sized insects shield other pests from pesticides. Insect size is not directly related to shielding behavior in this context.
• Option 3: Insects do not "learn" to detect and avoid pesticide odors in a way that would cause the pesticide to be less effective after multiple applications. Pesticide resistance is mainly a genetic and evolutionary phenomenon, not a learned behavior.
• Option 4: While pesticides do break down in the environment, this is not the main reason for their reduced effectiveness after multiple applications. The key is the development of resistance in the insect population.
• Question 16:
• Option 1: For Insect A, after the first application, its population decreased significantly. If it became more resistant after the first application, we would expect a less - drastic population decline or even an increase in the next application. But from the graph, after the second application, its population is still very low.
• Option 2: The change in the population of Insect B (its population remains relatively stable after two applications) can be explained by the fact that some insects had a beneficial mutation (resistance to the insecticide) and passed it on to their offspring. This is in line with the principles of evolution and natural selection.
• Option 3: If the population of Insect B was completely resistant, its population before application would not be as low as shown in the graph. Resistance is usually due to a subset of the population having the trait initially.
• Option 4: The problem states that the farmer used the insecticide on the crops. There is no indication that some insects were not sprayed. The change in population is due to the presence of resistant traits in the insect population.

Answer:

1. Some insects are resistant to the pesticide and pass on this favorable trait to offspring.
2. Some insects passed a beneficial mutation to their offspring.