Chapter 4, Problem 5STP

Summary Introduction

Introduction:

The ecosystem constantly changes due to various factors. Environmental catastrophes like hurricanes, drought, and forest fires alter the communities existing in the ecosystem.

Forest fires becomes necessary in some ecosystems which helps the soil to replenish nutrients and allows to get rid of debris built up. A forest fire helps to grow new species to thrive in charred conditions.

Answer to Problem 5STP

Correct answer :

The correct answer is option (D) Pioneer species are established.

Explanation of Solution

Explanation/justification for the correct answer:

Option (D). Pioneer species are established. After any environmental disruptions, predictable changes occurs after old community organisms have been removed. New species of plants and animals will thrive in these new conditions because the soil remains intact.

Plants that are able to grow in the disturbed area are the first species or pioneer species. Thus, the pioneer species are first to be established in such ecosystem disturbed by forest fires. So, the correct answer is option (D).

Explanation for incorrect answer

Option (A). A climax community is established. When in an ecosystem, there occurs little or no changes in the composition of species resulting in stable, mature community, it is known as a climax community. In a climax community, little or no changes occur. So, this is an incorrect answer.

Option (B) New plants grow from seeds that the wind carries to the area. In a barren rock or unused area where no such soil for optimum growth of mature plants, the wind carries seeds, plant pollen grains etc. from mature communities. These seeds may grow on the new surroundings and eventually help to establish a stable complex community. So, this is an incorrect answer

Option (C). New soil forms. In an undeveloped or barren rock or area, the soil or substratum is not developed for establishment of any species. Few fungi, lichens grow in these extreme conditions. After completing their life cycle, they die and contribute to form the soil which is now suitable for the growth of more complex communities. So, this is an incorrect answer.