2008-01-11 / Columnists

Drawing On Science For Kids

When Competition Is Not A Sport
Commentary By Stephen S. Yaeger

Any sport or game is a competition. Only one person or team can be a winner. In nature plants and animals are always in competition. But if there's a winner then the loser may become extinct or pushed out of its environment. By studying nature we know that plants and animals need certain things to survive. This study of natural history is known as ecology (from the Greek: oikos=house + logia=study). So ecology means the "study of the house." Ecology shows us how members of the same species get along with each other, with different species, and with their environment.

The environment is made up of biotic factors, which includes all living things and abiotic factors or non-living things (temperature, water, rocks, etc.). All living things need shelter; food; water; and, within the same species, reproductive rights to survive.

A population consists of only one type of organism (plant or animal). You can have a population of porgy fish, mud snails, honey bees, or garden spiders. Populations that live and interact with each other in the same environment make up a community. An ecosystem is composed of the community and its surrounding abiotic factors. An ecosystem must have a constant source of energy; living things able to take in, use, and pass on that energy; and a recycling system. Jamaica Bay is an example of an ecosystem. Finally all ecosystems on Earth make up the biosphere.

Different populations are able to survive in a given environment because they don't compete with each other. The special place where a plant or animal lives out its life is called its habitat. A gray squirrel's habitat is a tree. An earthworm's habitat is the soil. And an alligator lives in a swamp. If many organisms live in the same habitat, how do they compete for food and things? Simple, they each occupy a different

niche (=neesh). Think of a niche as the role an actor plays. The stage on which he performs is the habitat. There are many actors playing a different part on one stage. For example let's look at a centipede, millipede and a mushroom as actors (occupying different niches). The soil on which they live is their stage (habitat). The centipede's role is that of a predator. It dines on beetles, ants and other goodies. The millipede is a scavenger looking for and feeding on decaying material. The mushroom breaks down decaying material acting as a decomposer. So you see there's no competition among them.

Living things can also be placed into feeding groups. Amaple tree, being able to use the sun's energy to produce its own food, is an autotroph (auto=self+troph=feeder) or producer. A caterpillar feeding on the leaves of the tree is an herbivore (from Latin: herba=grass+vorare=to devour) or plant eater. A cardinal feeding on the caterpillar is a carnivore (caro=flesh) or meat eater. An omnivore feeds on both plants and animals. When a living thing dies bacteria act as

decomposers converting its remains into recyclable material. This material is used by plants and the cycle keeps going on and on. Herbivores and carnivores are grouped as heterotrophs (hetero=other) or consumers.

Living things depend on food

chains. All food chains begin with producers. Producers are the most abundant of living things. Next are the herbivores and finally the carnivores. Energy in the form of food is passed up the line in a food pyramid (Diagram A). Producers are fed upon by herbivores and herbivores are fed upon by carnivores. Atypical food chain is this: grass ? grasshopper ? English sparrow ? Sparrow hawk ? bacteria of decomposition. Many food chains make up a food web (Diagram B), which interact with each other.

Nature provides for all living things to exist on our planet because there's a balance between biotic and abiotic factors. Any disturbance of that balance will result in the loss of life and habitat over the long run.

To do: You can study your backyard as an ecosystem or set up an aquarium or terrarium in your home.

Test yourself: Look at the diagram of the pyramid of energy and food web. 1) How many food chains can you find? 2) List the carnivores, herbivores, producers. 3) What's missing from the pyramid and food web? 4) How would the loss of the grasshopper population affect the web? 5) How many omnivores can you find? 6) In the pyramid the locust is a primary consumer, the sparrow is a secondary consumer, and the owl is the top consumer. a) Why must the number of consumers be less as we move up the pyramid or food chain (think balance of nature)? b) Name the top consumers in the food web. Questions/comments? E-mail Steve: Drawingonscience@aol.com

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