Ecosystem

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•Communities are well ordered and integrated in an ecosystem.
•There is intense competition b/w living organisms for the available resources.
•Every organisms has a role in the functioning of the ecosystem (niche)
•It is an important rule of nature ,that communities should be made of species that have different needs for resources,so that each can have different positions.
•Hence ensuring that natural resouces available

Vegetative succession

•When a new surface is created due to landslide or volcanic eruption.
•Sequence of events results in an area covered by vegetation.
•The change in vegetation is called plant succession.
•The 1rst organism to colonize the area is the pioneer community-on rocky surface,its usually the lichens and mosses,that do not need soil to survive.
•Lichens and mosses gradually break the rock into particles of sand, silt and clay, when they die, they adds humus to soil.
•Hence deeper and richer soil is made.
•Eventually grasses and herbs grows,
•Wind ,birds and animals bring seeds.
•Eventually trees grows.
•Dominant trees and species forms the climax

PHOTOSYNTHESIS

•Green leaves use light energy to combine carbon dioxide and water together to make glucose and oxygen.
•This process is called photosynthesis and takes place in the leaves of green plants.
•Chlorophyll is a green chemical found in plant cells which is essential for photosynthesis because it captures light energy from the sun and converts it into chemical energy.

STOMATA

•The carbon dioxide which a plant uses diffuses into the leaf through the stomata.
•If the stomata are closed ,then photosynthesis cannot take place.
•Stomata often close if the weather is very hot and sunny ,to prevent too much water being lost.
•This means that really hot day photosynthesis may slow down.

What is trophic levels?

The trophic level of an organism is the level it holds in a food pyramid. The sun is the source of all the energy in food chains. Green plants, usually the first level of any food chain.

Energy flow in food chains

•The amount of energy at each trophic level decreases as it moves through an ecosystem.
• As little as 10 percent of the energy at any trophic level is transferred to the next level; the rest is lost largely through metabolic processes as heat.
• If a grassland ecosystem has 10,000 kilocalories (kcal) of energy concentrated in vegetation, only about 1,000 kcal will be transferred to primary consumers, and very little (only 10 kcal) will make it to the tertiary level.

• Energy pyramids such as this help to
explain the trophic structure of an
ecosystem: the number of consumer
trophic levels that can be supported is
dependent on the size and energy richness
of the producer level.

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