Question

//there is no "more knowledge needed" as this was already given as the homework itself

HOMEWORK #4

Succession

Background: The evolution of a body of water from a lake to marsh can last for thousands of years. The process cannot be observed directly. Instead, a method can be used to find the links between stages, and then put them together to develop a complete story. Read the passage to answer the following questions.

Water levels of a large lake fluctuate due to a major drought. As water levels fall, land is exposed, and many small lakes or ponds are left behind where there were depressions in the land once covered by the large lake. Over time, these small lakes or ponds begin to fill with water and enough organic matter that they become marshes or meadows. Below are descriptions of four ponds as they exist today.

Pond A: Cattails, bulrushes, and water lilies grow in the pond, especially near the edges. These plants have their roots in the bottom of the pond, but they can reach above the surface of the water. This pond is an ideal habitat for animals that must climb to the surface for oxygen, such as turtles & frogs. Aquatic insect larvae are abundant. They serve as food for larger insects, which in turn are food for crayfish, frogs, salamanders, and turtles.

Pond B: Plankton growth is rich enough to support animals that entered when the pond was connected to the lake, but there are no aquatic plants or large algae. Fish make nests on the sandy bottom. Mussels crawl over the bottom. This pond is the most similar to the original lake.

Pond C: Decayed bodies of plants and animals form a layer called humus over the bottom of the pond, covering most of the sand. Chara, a type of branching green algae, covers the humus. Fish that build nests on the bare bottom are rare, but those that lay their eggs on Chara are common.

Pond D: The pond is so filled with vegetation that there are no large areas of open water. Instead, the pond is filled with grasses, and a few shrubs that tolerate wet soil are found near the margins of the pond. There are no fish in the pond, but frogs, salamanders, turtles, and many different species of insects are common. The water dries up during the summer months.

1. What was the disturbance that occurred in this area?

2. What type of succession would you categorize this scenario?

3. What is the logical progression of the ponds? Rank the ponds from youngest to oldest.

***Hint: the youngest pond is most similar to the original lake, while the oldest pond would be the most different***

Answer 1

The disturbance that occurred in the area was because of drought. As in the above lines of question it is already mentioned that 'Water levels of a large lake fluctuate due to a major drought'.

It is a type of Hydrach succession, in which a water body is converted into different kind of woodland such as swamp and marshes.

Logical progression of pond are:

Planktonic stage: This stage inclue mainly phytoplanktons like Blue Green Algae, Diatoms, green algae etc. They make their own food and die after some time resulting in increase of organic matter in the pond.

Rooted Submerged stage: Due to increase in organic content, rooted submerged plant like Hydrilla and Ceratophyllum etc start growing. Death of these plant make the condition more favourable for other plant to colonize.

Rooted Floating Stage: In this stage the number of rooted floating plant like Nelumbo, Nymphaea start growing. The leaves of these plant float on the surface of water but their roots are atteched to the ground. when these plant die there is huge accumulation of organic matter at the bottom of the pond and makes the favourable condition for next stage plant to colonize.

Reed Swamp Stage: This stage include the plants whose root remains at the base of pond while the upper part of plant remains exposed in the air.

Forest stage: this stage include climax (final stage of succession) community whis are rapidly colonized by large trees and remains in equillibrium with the environment for a longer period of time.

(Youngest) B>C>A>D (Oldest) Order of these ponds can be explained by logical progression stages.