What is an Ecosystem?
Ecosystems are dynamic interactions between plants, animals, and micro organisms and their environment working together as a functional unit. There are consumers and producers and ecosystems will fail if they do not remain in balance. Plant forms provide food for animals, but when animals die and decompose, they provide nutrients for the plants as well. Ecosystems include both biotic (living organisms) and abiotic (non-living features, such as rocks, soil, climate, and water). No community can carry more organisms than its food, water, and shelter can accommodate. Food and territory are often balanced by natural phenomena such as fire, disease, and the number of predators. Each organism has its own niche, or role, to play. There is a “chain of being” in an ecosystem. This means that any factor that affects one organism in the ecosystem, ultimately affects all other aspects of that ecosystem because they are all dependent on one another.
How have humans affected the ecosystems?
We have affected ecosystems in almost every way imaginable! Every time we walk out in the wilderness or bulldoze land for a new parking lot we are drastically altering an ecosystem. We have disrupted the food chain, the carbon cycle, the nitrogen cycle, and the water cycle. Mining minerals also takes its toll on an ecosystem. We need to do our best to not interfere in these ecosystems and let nature take its toll.
What is the difference between the 'Food Chain' and 'Food Web?'
A popular misnomer, the 'food chain' is not actually a linear chain but a complex web. Energy is passed from one organism to another in a complex network like a spider's web. The flow of energy from one type of organism to the next is called a trophic pattern, and the new level of energy is call a trophic level.
Food Web: Food Chain:
The food chain consists of four main parts:
The Sun: which provides the energy for everything on the planet.
Producers: these include all green plants. These are also known as autotrophs, since they make their own food. Producers are able to harness the energy of the sun to make food. Ultimately, every (aerobic) organism is dependent on plants for oxygen (which is the waste product from photosynthesis) and food (which is produced in the form of glucose through photosynthesis). They make up the bulk of the food chain or web.
Consumers: In short, consumers are every organism that eats something else. They include herbivores (animals that eat plants), carnivores (animals that eat other animals), parasites (animals that live off of other organisms by harming it), and scavengers (animals that eat dead animal carcasses). Primary consumers are the herbivores, and are the second largest biomass in an ecosystem. The animals that eat the herbivores (carnivores) make up the third largest biomass, and are also known as secondary consumers. This continues with tertiary consumers, etc.
Decomposers: These are mainly bacteria and fungi that convert dead matter into gases such as carbon and nitrogen to be released back into the air, soil, or water. Fungi, and other organisms that break down dead organic matter are known as saprophytes. Even though most of us hate those mushrooms or molds, they actually play a very important role. Without decomposers, the earth would be covered in trash. Decomposers are necessary since they recycle the nutrients to be used again by producers.
How have humans affected the food chain?
When we spray pesticides, we put the food chain in danger. By breaking one link on the chain means all of the organisms above that link are in threat of extinction (like the domino effect). By hunting animals nearly to extinction, everything above the animal in the food chain is put in danger. A 'chain reaction' in the food chain can be perilous! Since the food chain provides energy that all living things must have in order to survive, it is imperative that we protect it.
What is a food pyramid?
It is a pyramid that shows the hierarchy of the food chain:
· There are fewer organisms at each increasing trophic level
· Less energy available at each increasing level
· Fewer organisms can obtain energy to live
· There is a high degree of energy loss at each trophic level
· Each consumer level loses energy for several reasons:
§ much of the energy is lost as heat
§ most of the energy is used to carry out life functions. ie. We burn many calories of energy each day by performing daily activities such as eating, breathing, walking, talking, etc.
§ If an organism dies without being eaten the energy goes to the decomposers and not up the trophic levels.
§ Consequently only about 10-15% of the energy is stored as usable food energy at each level
Food Pyramid:
http://www.evh.k12.nf.ca/dantle/World_Geography/
http://library.thinkquest.org/
Questions
1. In your own words describe an ecosystem.
2. What are the major components of an ecosystem? And how do they depend on each other?
3. What does “chain of being” mean?
4. Describe the difference between a food web and a food chain.
5. Draw your own food pyramid, with humans at the top.
6. How are ecosystems destroyed? Give an example of how you think we destroy certain ecosystems. Do not use the example of the bulldozer and the parking lot.