Question

use the text below to answer the question.

a healthy environment can become unbalanced in many ways. changes are often, but not always, gradual. in some environments one species may slowly replace others over time, a change called ecological succession. a marsh or swampland may gradually fill in with sediments; water plants may be succeeded by grasses, reeds and soon by bushes and pine trees. in time, oak and maple trees may push out the pines. this natural ecological succession of a marsh becoming a hardwood forest may take hundreds of years, but it happens. there is hope for our planet, however. the actual health of our atmosphere has improved in our cities and towns. many american rivers that had become totally dead can once again support fish and healthy wildlife populations.

which of the following is an example of ecological succession?
choose one option

a new trees are now providing constant shade, and plants around them that needed sun to survive are being overgrown by shade - dependent shrubbery.

b marigolds and sunflowers are planted every year in a flower bed. both flourish for a few months and then die off at the end of the season.

c every spring buds appear on the trees, then they turn into leaves. in the fall, these leaves change colors and die and eventually fall off the trees.

d tomato plants growing in a pot are replanted into the ground next to basil and other herbs. all of the plants flourish.

Explanation:

To determine the example of ecological succession, we refer to the definition from the text: one species slowly replaces others over time.

• Option A: New trees (a species) provide shade, and sun - dependent plants are replaced by shade - dependent shrubbery (other species) over time. This fits the definition of ecological succession.
• Option B: Marigolds and sunflowers are planted annually and die at the end of the season. There's no long - term replacement of species, just a seasonal cycle.
• Option C: This describes the annual cycle of tree leaves (buds to leaves to falling), not the replacement of one species by another.
• Option D: Tomato plants are replanted with basil and herbs, and all flourish. There's no species replacement; it's just different plants growing together.

Answer:

A. New trees are now providing constant shade, and plants around them that needed sun to survive are being overgrown by shade - dependent shrubbery.