What is an ecological community?
Rivers and lakes are two of many ecological communities. A community consists of organisms living in the same habitat. Swamps, forests, meadows, and the sea are also ecological communities that we will get to know in the future. Species living in a community are connected to each other, and each species has a smaller or larger role in the community.
Although phytoplankton are organisms almost invisible to the eye, without them, neither lake nor river communities could function. Uni- and multicellular small animals called zooplankton, as well as fish hatchlings, feed on phytoplankton. Then, fish feed on zooplankton. After that, predatory fish, as well as some mammals and birds feed on fish. After each death, all organisms are broken down in digestion, by invertebrates, bacteria, or fungi. Organisms that feed off of one another make up the food chain.
- Organisms living in the same habitat form a community.
- Organisms living in different habitats form a community.
- Some species are not important at all in the community.
- Each species has a smaller or larger role in the community.
Plants produce living matter and oxygen
To live, you need to eat. All organisms need substances to build their bodies, and need energy for various activities. Plants produce organic matter from the simple compounds that they obtain from their environment. That is why plants are called producers.
- They produce organic matter from carbon dioxide and water.
- They produce oxygen.
- They are producers.
Consumers consume existing organic matter
Animals need to eat existing organic matter to get energy. That is why they have to eat other organisms. Herbivores eat plants and, in turn, are eaten by omnivores or carnivores. All animals are called consumers. All the organic matter that animals are made of has originally come from plants. In animals, these substances change somewhat. From substances derived from plants, animals also acquire all the energy they need for life.
- Animals are able to produce organic matter from inorganic substances.
- All animals need to eat organic matter.
- All animals are consumers.
- All the energy needed for animal life comes from plants.
Decomposers
Decomposers feed on all dead creatures, as well as animal faeces. The group of decomposers is much more diverse than that of producers and consumers. Crustaceans (including amphipods), snails, small insects, and worms begin to eat the remains of dead plants and animals in aquatic communities. However, bacteria and fungi play a much more important role in the breakdown of living matter– they complete the breakdown. Sludge deposited on the bottom of water bodies is formed from the decomposing residues of living organisms.
Decomposers are very important because, without them, dead organisms wouldn't go away. The decomposed substances can become nutrients for the plants and other creatures. As a result of the activities of decomposers, death becomes new life.
This organism receives the substances necessary for life by eating other living things –
This organism feeds on dead creatures and animal feces –
This organism produces organic matter from inorganic substances –
Food chain and food web
Let's look at a food chain and a food web in a body of water. Unicellular algae are food for the wheel animal. The roach often eats the wheel animal, the pike eats the roach, and the otter eats the pike. Together, they form a food chain.
Most animal species eat a variety of foods, so food chains are interconnected. Therefore, the feeding relationships in the communities are better characterised by a food web rather than a food chain.
- algae → wheel animal → roach → black-headed gull → otter
- algae → water weed → perch → otter
- otter → perch → water flea → algae
- water weed → perch → pike → black-headed gull → otter
- water weed → water flea → perch → otter
I now know that…
Plants are producers. They use solar energy to make organic matter from carbon dioxide and water. Animals eat plants and other animals and are therefore called consumers. Organisms that feed on dead organisms are called decomposers. The main decomposers in nature are fungi and bacteria. In ecological communities, species are interconnected by food chains. Food chains form a food web.
