2008-12-26T01:39:00.000-08:00

--Ecology Homework--

1) What comprises ecology? [Habitat, population, community and ecosystem, how are they linked?]

A habitat is a place where an organism lives in. A population is a group of organisms of the same species living in a particular habitat. All the population of organisms living and interacting with one another in a particular habitat make up a community. A community and its physical or abiotic environment together make up an ecosystem.

2) How do the physical features of the surroundings affect organisms? What are these physical factors? Give examples of how organisms adapt to these physical factors.

The type of plant found in a region is affected by the physical features of the surroundings. Animal has to rely directly or indirectly on plants for food, this is becuase plants are the food producers. Hence animal living the region are also affected by the type of plant and indirectly affected by the physical features of the surroundings.

These physical factors are the light intensity, temperature, availability of water, oxygen content, salinity and the pH of water and soil.

An example of how organisms adapt to the physical factors is fishes in saltwater have a waterproof coat consisting of closely-fitting scales covered by a slimy mucous material, reducing the rate of water loss.

Bears have thick fur coating to trap heat, keeping themselves warm from the extreme cold temperature

Source : http://www.mediabistro.com/fishbowlny/original/3-lazy-polar-bears.jpg

3) Are organisms interdependent? Why?

Yes, organisms are interdependent. Organisms in any habitat are never completely independent because the life of each organism depends on, and is influenced by, other organisms around it. Organisms are hence interdependent.

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

In terms of energy flow through ecosystems, organisms can be either producers or consumers. Producers are the only organisms that can manufacture or produce complex organic food from inorganic raw materials. They convert energy from the environment into the chemical energy stored in carbon bonds, such as those found in the sugar glucose. Green plants are the most obvious examples of producers, because green plants are self nourished and do not depend on other species of animals for food. Green plants use energy from sunlight to convert carbon dioxide and water into glucose (or other sugars) through the process known as photosynthesis. Algae and bacteria that photosynthesize are examples of producers too.
Consumers obtain their energy by feeding on other organisms. All animals are therefore consumers. Herbivores feed directly on plant are known as primary consumers. Carnivores that feed on herbivores are known as secondary consumers. Carnivores that feed on carnivores are known as tertiary consumers. Dead animals, faeces and unwanted material that is produced by the consumers as the end product of their digestion, are being decomposed and broken down by bacteria or organisms known as decomposers. Breaking down of unwanted material releases chemical energy to soil for plants to use.

An example of a food chain: Green plant --> Aphid --> Spider --> Bird

An example of a food web:

Source : http://usr-lazio.artov.rm.cnr.it/darwin2007/presentazioni/Modulo14_file/slide0242_image272.jpg

5) What is the relationship between a predator and a prey? Two predators with the same prey?

A predator is an organism that kills and feeds on other organism. The organisms that are eaten are called the prey. An increase in the population size of the prey means there are more food available for the predator, the population of the predator hence increases. Once the number of predator increases, the population of the prey decreases, which in turn results in the decrease in the predator population. The population of the prey thus increases again. This process is constantly repeated.

When two predators feeds on the same prey, the population of the prey is lower than that of the predators, therefore less food is available. The population of the two predators will decrease as result.

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

An ecological pyramid is a graphical representation designed to show the biomass or productivity at each trophic level in a given ecosystem.

There are three different types of ecological pyramids. The pyramid of numbers, pyramid of biomass, pyramid of energy.
The pyramid of numbers shows the relative number of individual organisms at each trophic level of a particular ecosystem. The width of each block is proportional to the
number of organisms in each trophic level.

The pyramid of number

Source :

http://www.bbc.co.uk/schools/gcsebitesize/science/images/bi01010.gif

The pyramid of biomass represents the biomass in each trophic level in an ecosystem; the width of each block is proportional to the biomass in each trophic level. This pyramid usually expresses as grams of organic matter per cubic unit area. Dry mass of the organism is used.

The pyramid of biomass

Source :
http://earth.rice.edu/MTPE/bio/biosphere/topics/energy/40_biomass.html

Pyramid of energy represents the energy in each trophic level in an ecosystem, the width of each block in proportional to the energy in each trophic level, usually measured in KJ m.

The pyramid of energy

Source : http://kingfish.coastal.edu/biology/sgilman/770trophicpyramid.gif

7) Why are short food chains better?

Since energy is lost as each trophic level, less and less energy is available for the organism at the next level as we go down the food chain. Only 10% of the energy is used for life processes and the rest is lost as heat. Hence food chains are generally short. A shorter food chain means more energy is available to the final consumer because less energy is lost to the environment. It is said that shorter food chains are more efficient than long food chains.

8) What happens to most of the energy in the ecosystem?

90% of the energy is lost when it is transferred from one trophic level to the next. Most energy are lost as heat through respiration of organism to the environment and cannot be recycled.

9) Describe the carbon cycle.

During photosynthesis, green plants takes in carbon dioxide from the atmosphere and use it to manufacture carbohydrates, for example, glucose. Glucose maybe changed to other organic compounds such as fats, amino acids and proteins.

When animals feed on green plants, the carbon compound found in the plant would become part of these consumers. The carbon compounds may also be preserved in fossil fuels such as coal ,natural gas and oil.

Carbon dioxide is released into air by respiration, combustion and decaying. The carbon compounds found in fossil fuels that are burnt or undergo combustion, are broken down into carbon dioxide and released into air.

Decomposers breaks down a dead organism and respires, they too releases carbon dioxide to the environment during the process.

Source : http://www.kidsgeo.com/images/carbon-cycle.gif

10)Deforestation causes soil erosion. The loss of trees, which anchor the soil with their roots, causes widespread of erosion.

Topsoil, which is the most fertile layer, gets washed away during heavy rain. Eroded soil may be deposited in rivers and streams, causing a rise in height of the river bed and the water level, thus causing floods.

Desertification is the degradation of land into a desert-like condition.When sunlight falls directly onto the soil, water will be evaporated quickly from the soil and causing it to harden. Since the topsoil had been eroded away, plants can no longer grow using the soil. Organisms which depend directly or indirectly on plants for food would eventually die due to lack of food.

Over-fishing cause species of fish to become endangered or extinct.

Eutrophication is the increase in chemical nutrients in an ecosystem. When an ecosystem experiences an increase in nutrients, primary producers reap the benefits first. In aquatic ecosystems, species such as algae experience a population increase (called the algal bloom). Algal blooms limit the sunlight available to marine organisms and cause wide swings in the amount of dissolved oxygen in the water. As a result, creatures such as fish, shrimp, and especially immobile bottom dwellers dies.

Biomagnification is the increase in concentration of a substance, such as the pesticide Dichloro-Diphenyl-Trichloroethane (DDT). Organisms feeding at higher level of a food chain would accumulate huge amounts of DDT from eating their prey. This might cause food poisoning to people when they consume the organisms at the higher level of the food chain.

11) Why is there a need for conservation?

By conserving, it will prevent the extinction of plant and animal species, preserving the natural scenery and wildlife for scientific value. Conservation also allow us to maintain a stable and balanced ecosystem, a large gene pool and the biodiversity.

Ecosystem