WHAT IS AN ECOSYSTEM? We often hear the word “ecosystem” used when people are talking about the environment. An ecosystem is a geographical area like a forest, desert, swamp, coral reef, lake, lagoon, mountain, wetland, marsh, and many other different forms of landscapes. A backyard can be an ecosystem. Tide pools (as the tide goes out it leaves little ponds of water where you can sometimes find things like seaweed, algae, clams, mussels, sea stars, abalone, crabs, small fish) can be complete ecosystems. In these different geographical areas, the different plants, birds, animals, other organisms, weather, and landscape, all work together to form a system of life. Fungi and bacteria are examples of “other organisms.” There are both biotic and abiotic factors in an ecosystem. Biotic factors are the living parts which include plants, birds, animals, and the other organisms, while abiotic factors include things like rocks, soil, air, water, temperature, humidity, rain, which is essentially the physical environment.
Ecosystems can be very large, very small, or anything in between, and earth’s entire surface is a series of connected ecosystems. Every factor in an ecosystem is either directly or indirectly dependent upon every other factor, so that changes in the ecosystem can affect which types of living things are able to survive. For example, changes in temperature, water, sunlight, or soil quality can affect what plants will grow. If the plants that different types of animals eat or use for shelter disappear, those animals must adapt to the changes in that ecosystem, move to another ecosystem, or they will die.
WHAT IS A FOOD CHAIN? Let’s refresh our memories about food chains. In an ecosystem plants and animals depend on each other to live by eating each other. A simple way to think of a food chain is to imagine a real chain where plants are at the bottom end of the chain, the top animal predators of that ecosystem are at the top end of the chain, and other animals are at different places on the chain between both ends. The plants at the base of the food chain (i.e. grass) are the producers for the ecosystem because they convert sunlight into energy through photosynthesis. All the energy in the food chain comes from the producers. The rest of the food chain uses this energy, and going up the food chain there is less and less energy available. In a food chain, nutrients and energy pass as one organism eats another. The further along in the food chain, the fewer organisms there are at the higher levels. In the single food chain below, there should be more grass than grasshoppers and more frogs than eagles, and all along the food chain each animal is using more energy. The eagle uses the most energy growing into adults, flying, fishing, hunting, fighting, mating, feeding their young, and guarding the nest. There are many different food chains in an ecosystem, and all those food chains together make up a food web, which is a more realistic representation of an ecosystem. Below, the grasshopper may eat other plants besides grass, the frog may eat other animals besides grasshoppers, and the same for snakes and eagles.
The grasshopper is a primary consumer which eats the grass (the producer). The organisms that eat the primary producers are called primary consumers. Primary consumers are usually planteaters (“herbivores”), but they can also be algae eaters or bacteria eaters. The frog eating the grasshopper is a secondary consumer which are usually meat-eaters (“carnivores”). The snake eating the frog (a carnivore eating a carnivore) is a tertiary consumer. Animals at the very top of the food chain are apex consumers, which in this example might be the eagle if there aren’t any animals in the ecosystem eating the eagle. The following is an example of a food web containing different food chains:
References:
https://education.nationalgeographic.org/resource/ecosystem/
https://education.nationalgeographic.org/resource/marine-ecosystems/
https://www.britannica.com/science/ecosystem
https://images.search.yahoo.com/search/images?p=ecosystems&fr=mcafee&type=E211US714G0&imgurl=https%3A%2F%2Fimages.saymedia-content.com%2F.image%2Ft_share%2FMTc0NTEwMTc3MTcxNTQ4MTUw%2F3-different-kinds-of-ecosystems.png#id=2&iurl=https%3A%2F%2Fimages.saymedia-content.com%2F.image%2Ft_share%2FMTc0NTEwMTc3MTcxNTQ4MTUw%2F3-different-kinds-of-ecosystems.png&action=click
https://www.ducksters.com/science/ecosystems/food_chain_and_web.php
https://www.khanacademy.org/science/ap-biology/ecology-ap/energy-flow-through-ecosystems/a/food-chains-food-webs
