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Essay On Producers Consumers And Decomposers 3rd

According to the manner in which they obtain their food from the environment, all the organisms can be divided into three groups: producers, consumers and decomposers.

1. Producers:

Those organisms which produce food are called producers. Producers are the organisms which can prepare their own food from simple inorganic substances like carbon dioxide and water by using sunlight energy in the presence of chlorophyll.

The examples of producers are green plants and certain blue-green, algae. The green plants synthesize their food during photosynthesis by taking raw materials from the earth and energy from the sun maize (makkd) as food.

The green plants produce carbohydrates by photosynthesis and also synthesize proteins and fats. Thus, the green plants are called producers in the living world. Producers are the autotrophic organisms (self- feeder organisms) in the ecosystem upon which other organisms depend for food. Thus, producers (like green plants) are autotrophs.

2. Consumers:

Those organisms which consume food (eat food) prepared by producers are called consumers. The consumers depend on producers for food, directly or indirectly. The consumers get their food by eating other organisms or their products. In most simple words, consumers .are the organisms that eat other organisms.

All the animals are consumers. Even the microscopic animal lives of the water called protozoa are consumer organisms. The examples of common consumer organisms are man, goat, deer, fish, lion, cow and buffalo, etc. The cow and buffalo eat green grass and other green fodder because green grass and other green plants are producers of food.

The bio-mass of grass and plants supplies food and energy to these animals like cow and buffalo. It should be noted that the consumer organisms like animals cannot prepare food from simple inorganic substances through photosynthesis.

The consumers need ready-made food for their survival which they get from producers (green plants), either directly or indirectly. If an animal eats grass or other green plants or their products itself we say that it gets the food from producers directly.

For example, a goat gets the food from producers directly when it eats grass. On the other hand, if an animal eats the meat of another animal (which eats grass), then we say that it gets the food from producer indirectly. For example, a lion gets food by eating goat which in turn eats grass. So, in this case the lion gets its food indirectly from producer grass (through the goat). Consumer organisms are also called heterotrophs. Consumers can be further divided into three groups: herbivores, carnivores and omnivores.

(i)Herbivores:

Some animals eat only plants (or their products). Those animals which eat only plants are called herbivores. The herbivores may eat grasses, leaves, grains, fruits or the bark of trees. Some of the examples of herbivores are: Cow, Buffalo, Goat, Sheep, Horse, Deer, Camel, Ass, Ox, Elephant, Monkey, Squirrel, Rabbit and Hippopotamus. Cow is called an herbivore because it eats only plants (or plant products) as food. Herbivores are also known as herbivorous animals.

The animals which get their food by eating the producers (plants) directly are called primary consumers. Since herbivores obtain their food directly from plants (or producers), therefore, herbivores (like cattle, deer, goat, etc.) are primary consumers.

(ii)Carnivores:

Some animals eat only other animals. They do not eat plant food at all. Those animals which eat only other animals as food are called carnivores. The carnivores eat the meat (or flesh) of other animals.

So, we can also say that those animals which eat only the meat (or flesh) of other animals are called carnivores. Some of the examples of the carnivores are: Lion, Tiger, Frog, Vulture, Kingfisher, Lizard, Wolf, Snake and Hawk. Lion is called a carnivore because it eats only the meat (or flesh) of other animals like deer, rabbit and goat, etc. Carnivores are also known as carnivorous animals.

The carnivores are usually of two types: small carnivores and large carnivores. The small carnivores which feed on herbivores (primary consumers) are called secondary consumers.

For example, a frog, lizard, bird and fox, etc., are secondary consumers. The large carnivores (or top carnivores) which feed upon the small carnivores (secondary consumers) are called tertiary consumers. For example, lion, tiger and birds of prey (such as hawk) are some of the tertiary consumers. Please note that humans (man) can be primary, secondary or tertiary consumers depending on the food which they eat.

(iii)Omnivores:

Some animals eat both, plants as well as other animals. Those animals which eat both, plants and animals are called omnivores. In other words, the omnivores eat plant food as well as the meat (or flesh) of other animals. Some of the examples of omnivores are: Man (human beings), Dog, Crow, Sparrow, Bear, Mynah and Ant. Man is called an omnivore because he eats both, plant food (such as grains, pulses, fruits and vegetables) as well as meat of animals (such as goat, chicken and fish). Omnivores are also called omnivorous animals.

We will now describe another type of producers and consumers which are extremely small. These are called planktons. Planktons are very minute or microscopic organisms freely floating on the surface of water in a pond, lake, river or ocean. Planktons are of two types: Phytoplanktons and Zooplanktons.

The microscopic aquatic plants freely floating on the surface of water are called phytoplanktons. The free-floating algae are an example of phytoplankton. Phytoplanktons are capable of producing food by the process of photosynthesis. The microscopic aquatic animals freely floating on water are called zooplanktons.

The freely-floating protozoa are an example of zooplankton. A very, very small fish is also a zooplankton. Planktons float near the surface of water and provide food for many fish and other aquatic animals.

3. Decomposers:

The non-green micro-organisms like some bacteria and fungi, which are incapable of producing their food, live on the dead and decaying (rotting) plants and animal bodies and are consumers of a special type called decomposers.

We can now say that: The micro-organisms which break down the complex organic compounds present in dead organisms like dead plants and animals and their products like faeces, urine, etc., into simpler substances are called decomposers. The examples of decomposers are certain bacteria and fungi.

The bacteria which act as decomposers are called putrefying bacteria. The bacteria and fungi act as decomposers by the secretions of their body surfaces which decompose the organic matter present in dead plants and animals into simpler substances and liberate ammonia, carbon dioxide, etc.

They absorb some of these simpler substances for their own maintenance and release the remaining into the soil, water and air to be used by the producers again In this way, decomposers help in the recycling of materials in ecosystem. The decomposers are also known as micro-consumers or saprotrophs.

Importance of Decomposers:

The decomposers help in decomposing the dead bodies of plants and animals, and hence act as cleansing agents of environment. The decomposers also help in putting back the various elements of which the dead plants and animals are made, back into the soil, air and water for re-use by the producers like crop-plants.

This maintains the fertility of soil and the soil would continue to support crops again and again. For example, the decomposers like putrefying bacteria and fungi decompose the dead plants and animal bodies into ammonia (and other simpler substances).

This ammonia is converted into nitrates by the nitrifying bacteria present in soil. These nitrates act as fertilizer in the soil and are again absorbed by the plants for their growth. Thus, it is only due to the presence of decomposers that the various nutrient elements which were initially taken by plants from the soil, air and water are returned to the soil, air and water, after the death of plants and animals.

If, however, there were no decomposers, then the dead bodies of plants and animals would keep lying as such and the elements of which plant and animal bodies are made, would never be returned to their original pools like soil, air and water. In that case, the cyclic process of life and death would be disrupted.

This is because in the absence of decomposers the soil, air and water would not be replenished by elements from the bodies of dead organisms. All the nutrients present in soil, air and water would soon be exhausted and evolution of life would come to an end. Thus, the decomposer organism's help in recycling the materials in the ecosystem so that the process of life may go on and on like an unending chain.


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Food web and food chain



Photo by: cappi thompson

The terms food chain and food web both refer to groups of organisms that are dependent on each other for food. A food chain is a single series of organisms in which each plant or animal depends on the organism above or below it. As an example, a food chain might consist of garden plants, such as lettuce and carrots, fed upon by rabbits which, in turn, are fed upon by owls which, in turn, are fed upon by hawks.

A food chain is largely a theoretical idea and probably seldom, if ever, exists in the real world. It is a useful concept, however, as it helps ecologists understand how specific plants and animals are dependent upon one another.

The feeding relationships of organisms in the real world is almost always more complex than suggested by a food chain. For that reason, the term food web is more accurate than is food chain. A food web differs from a food chain in that it includes all the organisms whose feeding habits are related in some way or another to those of other organisms. In the example above, small animals other than rabbits feed on lettuce and carrots and, in turn, those animals are fed upon by a variety of larger animals.

Structure of food webs

Food webs are organized into three main categories, depending on the kinds of organisms they contain. These three categories are known as trophic levels. The three primary trophic levels are those that consist of (1) producers, (2) consumers, and (3) decomposers. Producers are organisms that can make their own organic compounds or food using energy and simple inorganic compounds. Producers are sometimes called autotrophs, meaning "self-feeders." For example, green plants are autotrophs because they manufacture the compounds they need through photosynthesis.

The next trophic level above the producers consists of consumers. Consumers are organisms that cannot make their own foods and so have to eat other organisms to obtain the nutrients they use. The consumer trophic level can be subdivided depending on the kind of organisms included. Immediately above the producers are the herbivores, organisms that eat plants only. Some common examples of the herbivores include squirrels, rabbits, mice, deer, cows, horses, sheep, and seed-eating birds. The herbivores are sometimes called first-order consumers or primary consumers because they occupy the first level above the producer trophic level.

Above the primary consumers, the food web fans out to include two other kinds of consumers. The carnivores are animals that eat other animals, and the omnivores are animals that eat both plants and animals. Within the food web, carnivores and omnivores can be on any higher trophic levels. Some are secondary consumers or second-order consumers, meaning that they eat primary consumers. Snakes that eat mice (primary consumers) are secondary consumers. Other higher-level consumers are tertiary consumers or third-order consumers, and eat further up on the food web or perhaps on many levels. Examples of third-order consumers are mountain lions and hawks, both of whom eat second-order consumers such as snakes and owls.

Words to Know

Biomagnification: The increasing concentration of compounds at higher trophic levels.

Food chain: A sequence of organisms directly dependent on one another for food.

Food web: An interconnection of many food chains.

Photosynthesis: The conversion of solar energy into chemical energy that is stored in the tissues of primary producers (for example, green plants).

Primary consumer: An organism that eats primary producers.

Primary producer: An organism that makes its own food.

Trophic level: A feeding level in a food web.

The third trophic level consists of decomposers or detritivores (pronounced de-TRY-tuh-vorz). Organisms in this trophic level survive by eating dead organisms. Some decomposers, such as earthworms, feed directly on dead plants and animals. These organisms convert dead organisms to simpler substances that are then digested even further by other decomposers, such as bacteria and fungi.

Unlike organisms in the consumer/producer part of the food web, decomposers are extremely efficient feeders. They can rework the remains of dead organisms, progressively extracting more and more energy. Eventually the waste materials are broken down into simple inorganic chemicals such as water, carbon dioxide, and simple nutrients. The nutrients may then be reused by the primary producers in the lowest part of the food web. The decomposer food web is very active inside of compost piles where kitchen wastes are converted into a soil conditioner. Decomposers are active in all natural ecosystems.

Ecological pyramids

Food webs are, of course, collections of organisms. However, they also can be thought of as accumulations of energy. Think, for example, of the energy changes involved in the food chain described at the beginning of this essay. Lettuce and carrots, like other green plants, have the ability to capture solar energy from sunlight and convert it into the stored chemical energy of starches and other chemical compounds. When rabbits eat lettuce and carrots, they take in that stored energy. At the next level, owls that eat rabbits take in the energy stored in the bodies of their prey.

No organism ever collects 100 percent of the energy stored in the plant or animal it eats, however. In fact, studies have shown that only about 10

An ecological or energy pyramid. The lowest level consists of producers, the next higher level of first-order consumers, the next higer level of second-order consumers, and so on. Note that the total number of organisms found in any one level decreases as one goes up the pyramid. (Reproduced by permission of

The Gale Group

.)

percent of the energy stored in an organism gets transferred from one trophic level to the next: the rabbit gets only 10 percent of the energy stored in a carrot, the owl 10 percent of the energy stored in the rabbit, and so on.

One way to illustrate this fact is by means of an ecological pyramid or energy pyramid. The lowest level of an ecological pyramid consists of producers, the next higher level of first-order consumers, the next higher level of second-order consumers, and so on.

An ecological pyramid makes clear two important facts about food webs. First, as pointed out previously, the total amount of energy at any one level decreases as one goes up the pyramid. That is, the producer level contains the greatest amount of energy, the first-order-consumer level the next largest amount, the second-order-consumer level the next largest amount, and so on. Second, the total number of organisms found in any one level also decreases in going up the pyramid. An ecosystem that contains 10,000 lettuce plants may be able to support no more than 100 rabbits, 10 owls, and 1 hawk, as an example.

Biomagnification

One interesting phenomenon associated with food webs is biomagnification. The term biomagnification refers to the accumulation of

Manatees have an enormous capacity to eat aquatic plants. (Reproduced by permission of the

U.S. Fish and Wildlife Service

.)

certain substances as one moves up the food web. Biomagnification has become an important issue in ecology because of the presence in the environment of certain human-made substances that can have harmful effects on animals.

For example, suppose that a farmer sprays his or her fields with a pesticide designed to control insects that destroy his or her crops. A small amount of that pesticide will be washed off into rivers, streams, and lakes near the field. The pesticide will be ingested by fish living in those bodies of water. Those fish, in turn, may be eaten by larger fish, by birds, by bears, by humans, and by higher-level carnivores.

At each stage of the food web, however, the amount of pesticide stored in an organism's body increases. A single bass, for example, might eat a dozen perch in a month. A single hawk or bear or human might eat a dozen bass in a month. The amount of pesticide stored in one perch gets multiplied many times over in the body of other animals that feed on perch. In one study of a food web in Lake Ontario, scientists found a concentration of pesticide 630 times greater in herring gulls than in primary consumers, such as zooplankton found in the lake.

Biomagnification has serious consequences for all species. It is particularly dangerous for predator species at the top of long food webs. Those predators are at risk because the degree of biomagnification is high by the time it reaches their trophic level. Also, top predators usually consume large quantities of meat, which has lots of fatty tissue and contaminants. Polar bears, humans, eagles, and dolphins are examples of top predators, and all of these organisms are vulnerable to the effects of biomagnification.

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