Make a list of all the different animals, birds, and insects you see in your school or home community. Can you tell what each animal eats and how it might be connected to other animals, plants, and humans?
We all live amidst many other living and non-living things, whether or not we're aware of the environmental diversity around us. Have you seen sparrows feeding on seeds, squirrels nibbling berries, frogs eating small insects, and bees circling around flowers? They are all participating in the same environment. Some animals depend on each other for survival.
In this lesson, we will learn about the following:
An ecosystem consists of a community of plants and animals interacting with each other in a given area, and also the environment that they live in. The living parts of an ecosystem are called biotic factors while the environmental factors that they interact with are called abiotic factors. The abiotic factors include weather, earth, sun, soil, climate, and atmosphere. As living things respond to and are influenced by their environment, it is important to study both biotic and abiotic factors together to get a full picture.
Below is a picture of the pond ecosystem.
The term 'ecosystem' is slightly different from 'community'. An ecosystem includes both the living things and the physical environment of an area; a community includes only the biotic or living component and does not include the physical environment.
In an ecosystem, each organism has its own niche or role to play.
Ecosystems can be of any size. It can be small or large. An ecosystem may be as small as a puddle on the ground where tadpoles interact with water, food, predators, and the weather or as big as the Great Barrier Reef, Amazon Rainforest, and Himalayan mountain range.
An entire mountain chain with interacting plants, animals, forest soils, rocky mountaintops, mild foothills, and ancient bedrock can be called an ecosystem, too.
There are no rigid lines that separate the boundaries of ecosystems. They are often separated by geographical barriers such as deserts, mountains, oceans, lakes, and rivers. As these borders are never rigid, ecosystems tend to blend into each other. Therefore, the whole Earth can be seen as a single ecosystem, and a lake can be considered as a combination of several different ecosystems. Scientists call this blending or steep transition between two ecosystems an “ecotone”.
Ecotones are considered areas of great environmental importance. Apart from providing an area for a large number of species, ecotones often experience an influx of animals looking to nest or searching for food.
There are two main categories of ecosystems - aquatic and terrestrial. Terrestrial ecosystems are land-based, and aquatic ecosystems are water-based.
Forests, deserts, grasslands, tundra, freshwater, and marine are the major types of ecosystems. Terrestrial ecosystems extending across a large geographic area are also known as "biomes". Specific features vary widely within an ecosystem - for instance, an ocean ecosystem in the Mediterranean Sea contains vastly different species than an oceanic ecosystem in the Gulf of Mexico.
Have you ever recycled an old plastic bottle? When you drop off a plastic bottle in a trash can, it is taken to a recycling center where it is melted down and reused in new products like picnic tables, planters, shopping bags, and many other items. But it is still the same plastic that made up the original bottle.
This process is similar to the movement of matter through an ecosystem. The matter is recycled through different ecosystems of Earth.
The matters like water, carbon, and nitrogen are taken up by the plants from soil, air and water bodies. This is made into food, which is then passed on to the animals like herbivores and carnivores in a food chain.
After the death and decay of plants and animals, the materials like water, carbon, and nitrogen present in their bodies are returned to the soil, air, and water, from where they were taken originally. These materials can then be reused for the growth of new plants.
In this way, the same materials are used, again and again, the materials are not lost from the environment. So, the flow of materials like water, carbon, and nitrogen, etc., in the ecosystem is said to be cyclic.
The recycling systems of an ecosystem are called biogeochemical cycles.
All living things require energy to live. The flow of energy is vital for the survival of living organisms. Nearly all the energy in Earth's ecosystems originates from the Sun. Once this solar energy reaches Earth, it is distributed among ecosystems in an extremely complex manner. A simple way to analyze this distribution is through a food chain or food web. A food chain consists of varying levels, known as trophic levels, all starting at the producers which originally absorb the sunlight. The energy then moves up to the organisms that eat or decompose it, which continues all the way to the apex predators which can only decompose at a later point.
The flow of energy in the ecosystem is unidirectional (or one-directional). The energy enters the plants from the sun through photosynthesis during the making of food. This energy is then passed on from one trophic level to another in a food chain. During the transfer of energy through successive trophic levels in an ecosystem, there is a loss of energy all along the path. No transfer of energy is 100 percent.
The main reason for this loss is the second law of thermodynamics, which states that whenever energy is converted from one form to another, there is a tendency toward disorder (entropy) in the system. In biological systems, this means a great deal of energy is lost as metabolic heat when the organisms from one trophic level consume the next level. At each step up the food chain, on average 10 percent of the energy is passed on to the next level, while approximately 90 percent of the energy is lost as heat. The more levels in the food chain, the more energy is lost as it gets to the top.
An energy pyramid (sometimes called a trophic pyramid or an ecological pyramid) is a graphical representation, showing the flow of energy at each trophic level in an ecosystem. The energy in an energy pyramid is measured in units of kilocalories (kcal). Energy pyramids are always upright, that is, narrower at each successive level—unless organisms enter the ecosystem from elsewhere.
The number of organisms at each level decreases relative to the level below because there is less energy available to support those organisms. The top level of an energy pyramid has the fewest organisms because it has the least amount of energy. Eventually, there is not enough energy left to support another trophic level; thus most ecosystems only have four trophic levels.
Apart from Energy Pyramid, there are also the Pyramid of Biomass and the Pyramid of Numbers.
