Question

1. How do ecosystems change over time? What causes those changes to occur? Include a specific example in your answer.
   
2. Identify three critical factors (abiotic or biotic) required for primary succession to occur.
   
3. Give two reasons why ecological succession progresses from populations with low diversity to populations with high diversity?
   
4. Highly diverse ecosystems are often regarded as more “healthy.” Explain why.
   
5. How does ecological succession demonstrate the evolutionary process of “survival of the fittest”?

Answer 1

The ecosystems are consistently changing. This process is known as succession. There are two types of succession- primary and secondary.

1. Primary succession is the series of community changes which occur on an entirely new habitat which has never been colonized before. E.g. area of cooled down lava.
2. Secondary succession is the changes over a previously colonized habitat, which is disturbed or distracted as a result of natural events for human activity. E.g. deforestation

If the succession continued,it will end in a climaxc which is stabilized, with a small community of prominent species. Introduction of a new species can cause distraction for this stabilization. This change in stabilization of ecosystem is called disturbance. The disturbance brings a positive effect on ecosystem making it more diverse. But the human activities have a negative effect on ecosystem. For example if human introduces an invasive species into the environment, they may hunt and prey the native species of that ecosystem.

Succession of the ecosystem occurs through different stages:

• Pioneer
• Establishing
• Sustaining
• Producing

The pioneer stage is usually in primary succession. This is a starting of an ecosystem were the animals and plants of the native place start growing.

The establishing stage is when the animals and plants find things that sustain their lives and allows them to live in that particular area.

The sustaining stage is usually in the climax succession. It is when the area can sustain the lives and allows life to continue in that area.The animals do not have to leave that environment in search of food.

The final stage producing stage is in secondary succession.hear the population of animals increases and they might have to migrate to another ecosystem in search for food.

This type of succession, stages and disturbances causes the changes over the ecosystem through the years. An example for the change is given below:

• The change of a desert into a dense forest occurs in the following steps:

1. Stage 1 : bare rocks with lichens
2. Stage 2.: Ferns mosses and grasses
3. Stage 3 : Pioneer trees dominate
4. Stage 4 : deciduous trees become dominant
5. stage5 : all one species climax forest