How do energy and nutrients flow through an ecosystem? Give an example of a food chain and food web.

Energy enters an ecosystem from the outside(sun). Energy is converted to chemical energy and is passed from organism to organism through the ecosystem. Energy is lost to the surrounding through heat as it flows through the ecosystem and the heat energy cannot be recycled. Hence, energy has to be constantly supplied to the ecosystem. Living organisms in any ecosystem are made up of producers, consumers and decomposers. Energy and nutrients are transferred from producers to consumers to decomposers through feeding. The feeding relationships between organisms in an ecosystem is food chains. It is the transfer of energy from organism to organism through the form of food.

Example:

An example of a food web:
Copyright by www.absc.usgs.gov

What comprises ecology?

The ecology comprises of habitat, community, population and ecosystem. It is the study of interaction between the organisms with one and other and with their surroundings.

A habitat is a place where organism lives in. A population is a group of species living in a particular habitat together. A community consist of many population of different species living together. Lastly, an ecosystem is a community and its physical environment together.

Why is there a need for conservation?

Conservation is necessary for the maintenance of the Earth’s biodiversity. Conservation is the protection and preservation of natural resources in the environment.
Reasons for conservation:

• Prevent the extinction of plants and animal species.
• Maintain a stable and balanced ecosystem, this prevents disruption of natural cycles such as water and carbon cycles, and also prevents global warming.
• Maintain a large gene pool. Many wild plants and animals posses favourable genes. By cross-breeding the different varieties of wild plants and animals, we can improve agriculture produce.
• Ensure the conservation of marine life, as they are a major source of human food.
  Conservation is of scientific value. The study of wildlife provides useful information to humans.
• Conservation preserves natural scenery and wildlife for many people to appreciate. It also maintains natural resources for outdoor recreational activities such as fishing, hiking and skiing.
• To maintain biodiversity(raw materials, medicinal drugs,food and natural insecticides)

Discuss the impact of human activities on our ecosystem, highlighting issues on deforestation, over-fishing, eutrophication(increase in chemical nutrients) and biomagnifications(increase in concentration of a substance, such as pesticides).

Humans beings are continually using and depleting the world’s natural resources, upsetting the balance of nature in many places. Some of the ways humans destroy the environment is:

Deforestation. It is the clearing of forest, to increase the amount of land for agriculture, industries or settlement. However, deforestation may lead to soil erosion, flooding, desertification(desert-like conditions) and climate change.
Uncontrolled fishing practice. As the population of humans increases, so does the demand of fishes. Some fishes are over-fished due to the demand of large quantity. Also, most of the modern fishing gear lead to the destruction of marine life, such as turtles and corals. Some use Trawling, where they trap many unwanted species in the process and Dredging, scraping the seabed, destroying corals, in search for scallops. If fishing practices are not controlled, the number of fishes will decline and the number of fishes lost will not be replaced as quickly. Also, other marine organisms that are unintentionally caught often dies, causing the some species to be endangered or extinct.
Pollution. It is a process where harmful substances are released to the environment, damaging it. Sewage is waste matter from home or industries. Untreated sewage may contain disease-causing bacteria that may cause diseases if they are released to rivers or lakes for human consumption. It may cause an outbreak of diseases(epidemic). Eutrophication is caused when fertilizers(contain nitrates and phosphates) are washed away into the rivers, causing a profuse growth and multiplication of algae and water plants in the river or lakes. Its effects are lack of oxygen, severe reductions in water quality, fish and other animal population. Inorganic waste are thrown dump in large amount in rivers and lakes. They may include poisonous metals such as mercury, lead, zinc, arsenic, cadmium. Insecticides are used to kill insects, however, it may be washed out to a river or lake and in high concentration may poison fish or animals that take in the polluted water or contaminated fish. Insecticides like DDT(dichlorodiphenyltrichloroethane) is insoluble in water. Organisms cannot break down DDT. Hence, DDT accululate in the bodies of consumers. This results in the insecticide being passed along food chains, increasing in concentration in the bodies of organisms along the trophic levels. This process is called bioamplification.

What happens to most of the energy in the ecosystem?

In any ecosystem, the Sun is the energy source. Light energy absorbed by the chlorophyll in producers(or plant) is converted to chemical energy during photosynthesis. Energy in the producers is then passed to the next trophic level by feeding. The flow of energy through the ecosystem is non-cyclic(linear)Energy is released as heat to the surrounding as it flows through the ecosystem. This heat energy does not return to the same system or organism that produced it. Hence, the energy cannot be recycled in the ecosystem. Dead organisms and egested and excreted materials contain trapped chemical energy. This energy is released by the activity of decomposers. Decomposers use some of these trapped chemical energy for their needs. The rest is lost as heat energy.

Why are short food chains better?

Energy is lost at every trophic level to the surroundings. By going to the next trophic level, more and more energy is lost. Therefore, it is better that food chains are short. A shorter food chain means more energy available to the final consumer because less energy is lost to the surroundings. Therefore, a shorter food chain is more efficient than a longer food chain.

What are ecological pyramids? Describe the different types of ecological pyramids.

We can compare the trophic levels(describing an organisms position in the food chain) in the food chain with the help of ecological pyramids. There is the pyramid of numbers which allow us to compare the number of organisms present in each trophic level at a particular time. There is also the pyramid of biomass which allow us to compare the mass organisms present in each trophic level at any one time. It is called the standing mass of organisms. Lastly, there is the pyramid of energy. It can represent the total energy in the various trophic levels of a food chain. Unlike the pyramid of biomass, we need to determine the total energy content over a period of time.