Fix the mistake: Ecosystems and the Environment

Ecosystems and Food Chains

A system consisting of organisms and the environment surrounding them, such as a forest or lake, is called an ecosystem. Organisms are connected through relationships of “eating and being eaten.”

Basic Knowledge

Ecosystem: A view of the organisms and abiotic environment(light, air, water, and soil) in a certain place as one system.
Food chain: The way organisms are connected in a single chain through relationships of “eating and being eaten.” Examples:
Plants → grasshoppers → frogs → snakes → eagles
Phytoplankton → zooplankton → small fish → large fish → birds
In reality, organisms form a food web in which many species are complexly interconnected rather than a single chain.
Classification by ecological role:
① Producers: Organisms that make their own nutrients through photosynthesis(plants and phytoplankton).
② Consumers: Organisms that obtain nutrients by eating other organisms(animals).
　・Primary consumers(herbivores), secondary consumers(carnivores), tertiary consumers...
③ Decomposers: Organisms that decompose the remains and waste products of plants and animals(fungi and bacteria). More details next time.
Pyramid of population: The higher the trophic level in a food chain, the fewer individuals there are(many plants→moderate herbivores→few carnivores).

Important Terms
Ecosystem(A system consisting of organisms and the environment surrounding them)
Food chain(A linear relationship in which organisms eat and are eaten)
Food web(A network of food chains that are intricately interconnected)
Producer(An organism that makes organic matter through photosynthesis. Plants and algae)
Consumer(An organism that obtains nutrients by eating other organisms. Animals)
Ecological pyramid(A diagram that stacks the number or amount of organisms at each level of a food chain)

Further Exploration (Background and Significance)

When a food chain is stable, the populations of each organism maintain a balance within a certain range.
For example, when herbivores increase, plants decrease, causing a shortage of food for the herbivores and reducing their numbers. Then the plants recover. This kind of negative feedback maintains the balance.
However, this balance can be disrupted by the introduction of invasive species or environmental changes. For example, native fish have sharply decreased because largemouth bass were released in Japan, and mongooses in Amami attacked the Amami rabbit.
The phenomenon in which animals at higher levels of a food chain are more likely to accumulate harmful substances in their bodies is called biological magnification. Marine plastic, the pesticide DDT, and mercury may become concentrated in higher-level fish and birds and eventually in humans, causing health problems.

Key Points
  • Ecosystem = organisms + abiotic environment
  • Food chain = eating and being eaten, food web = network
  • Producer(plants)→primary consumer(herbivores)→secondary consumer(carnivores)
  • Higher levels have fewer individuals(pyramid shape)
  • Balance is maintained by negative feedback
  • Invasive species disrupt the balance
  • Biological magnification = harmful substances accumulate more at higher levels

Points to Note (Often Confused)

① Distinguish between a food chain(linear) and a food web(network). In reality, food webs exist. ② Producers are not only plants but all organisms that carry out photosynthesis. Animals are consumers. ③ A food chain begins with plants(the arrows for food relationships are often written from “the organism being eaten→the organism that eats it,” not “the eater→the organism eaten”). ④ Biological magnification and “balance of populations” are different concepts.

Practice

  1. State two components that make up an ecosystem.
  2. What is the role of organisms such as plants that carry out photosynthesis in a food chain?
  3. What is the phenomenon in which animals at higher levels of a food chain are more likely to accumulate harmful substances in their bodies?

Biology (Junior High): related lessons