Key Idea 2: Ecosystems Ecosystems An ecosystem is a living community of plants and animals sharing an environment with non-living elements such as climate and soil. An example of a small scale ecosystem is a pond. A medium scale ecosystem could be a forest. The tropical rainforest is an example of a very large ecosystem (biome ). What makes up an ecosystem? All elements of an ecosystem interact. If one element is disturbed, the ecosystem does not function properly. Biotic (Living) Elements Plants Bacteria Insects Mammals Birds Abiotic (Non-Living) Elements Climate Soils Rocks 2.1 What physical processes connect living and non-living elements of ecosystems? The Link between Biome Location and Climate: Similar vegetation types are found in parts of the world that have a similar climate. This is because the main control on what grows / lives in an area if the climate (temperatures and amount of rainfall). Biome The largest scale ecosystem eg tropical rainforest, desert, temperate forest
Relationship between climate zones and biomes: Arctic: Features of an Arctic Ecosystem: - The Arctic climate is found in Northern Scandinavia and Iceland - Cold winters and short, mild summers. - Plants grow slowly because of the freezing temperatures, strong winds and snowfall in winter and the short growing season during summer. - South of the Arctic Circle the ecosystem is taiga which is a forest ecosystem of conifer trees and birch. - The further north you go the smaller the trees become until it is too cold and the treeless arctic tundra takes over. Vegetation Features: - Temperatures are only above 10 C (the temperature at which most plants grow) for two months or three months so plants have a short growing season. - Precipitation in the winter months falls as snow so plants have small leaves and so don t lose any moisture. - Rocks weather (break down) slowly in the cold conditions which means soils have few nutrients so plants are extremely slow growing. - With few trees around there is little shelter from wind so plants grow close to the ground where they are less likely to be damaged. Nutrient Cycles in the taiga: Nutrient cycling is essential for plant growth. In the taiga it happens slowly because of the cold temperatures. Leaf litter and other matter are broken down by decomposers like fungi and beetles. Dead leaves and branches fall from trees forming a litter layer on the soil Roots are shallow so they can take in nutrients near the surface Decomposers such as beetles and fungi grow in the litter Plants use nutrients from the soil to help growth Leaf litter breaks down slowly in the cold conditions Nutrients from leaf litter return to the soil
Tropical Rainforest Ecosystem: Features / Nutrient Cycles of a Tropical Ecosystem: - The winter months are warm and sunny so plants are able to photosynthesise all through the year. - Bacteria in the soil reproduce very quickly in the hot weather so decomposition of dead plant matter is very rapid. This means nutrients are transferred from the leaf litter into the soil very quickly. - The chemical reactions that release nutrients from rocks into the soil are rapid because of the heat. - This process is known as weathering. If trees are cut down, heavy rainfall can wash nutrients out of the soil. This process is known as leaching. - In equatorial regions the temperature is constantly above 25 c so plants can grow all year and grow quickly. - There is plenty of water, sunshine and nutrients so there are a large variety of plants. This means that there is also a wide variety of animals, insects and birds. - There is plenty of sunlight overhead so plants and trees grow straight and tall. - The intense rain that falls in the rainforest is the result of the heating from the tropical sun and so is convectional rainfall. 2.2 How do ecosystem processes benefit people? Key Services Provided By Ecosystems Globally: - Provide a safe environment for fish to spawn and juvenile fish to mature, so helping to maintain fish stocks eg tropical coral reefs - Provide people with the opportunity to develop recreation or tourism businesses eg tropical coral reefs, coniferous forests - Support thousands of plants and wild animals that contain chemicals that may be useful to agriculture or medicine eg tropical rainforests - Inspire a sense of awe and wonder in human beings eg all / any ecosystem (tropical rainforest, tropical coral reefs etc) - Act as a natural coastal defence against storm surges, string winds and coastal floods eg mangrove forests, sand dunes - Soak up rainwater and release it slowly, therefore reducing the risk of flooding downstream eg peat bogs / moors, forests - Act as a huge stores of carbon dioxide, so helping to regulate the greenhouse effect eg peat bogs / moors, tropical rainforests
Food chains: A food chain shows the different organisms that live in a habitat, and what eats what. Producers and s A food chain always starts with a producer, which is an organism that makes food. This is usually a green plant, because plants can make their own food by photosynthesis. A food chain ends with a, which is an animal that eats a plant or another animal. Here is an example of a simple food chain: grass cow human Take care - the arrow points to the organism that is doing the eating. If you get the arrows the wrong way round, instead of showing that humans eat cows, you are showing that cows eat humans, and that grass eats cows. Other words in a food chain There are several words used to describe the organisms in a food chain. Study this food chain: Grass Grasshopper Frog Hawk Producer Consumer Consumer Consumer Primary Secondary Tertiary The plant is the producer and the animals are s. Herbivore Carnivore Carnivore Notice that the first in the chain is also called the primary, the next one is the secondary and the one after that is the tertiary. A that eats plants is called a herbivore, and a that eats other animals is called a carnivore. An omnivore is an animal that eats both plants and animals. Predators and prey A predator is an animal that eats other animals, and the prey is the animal that gets eaten by the predator. In the food chain above: - The frog is a predator and the grasshopper is its prey. - The hawk is a predator and the frog is its prey.
Food Webs: When all the food chains in a habitat are joined up together they form a food web. Although it looks complex, it is just several food chains joined together. Here are some of the food chains in this food web: grass insect vole hawk grass insect frog fox grass insect vole fox one predator, but the rabbits and slugs have just one predator. Notice that the frogs, voles and insects have more than This leads to some interesting effects if the population of a particular organism in the food web decreases. Some animals can just eat more of another organism if food is in short supply, while others may starve and die. This in turn can affect the populations of other organisms in the food web. What would happen if the grass died? The grass is the producer, so if it died the s that feed on it - rabbits, insects and slugs - would have no food. They would starve and die unless they could move to another habitat. All the other animals in the food web would die too, because their food supplies would have died out. The populations of the s would fall as the population of the producer fell. What would happen if the population of slugs decreased? Slugs, rabbits and insects all eat grass. If there were fewer slugs there would be more grass for the rabbits and insects. With more food the populations of rabbits and insects would increase. However, the thrushes would have to eat more insects to maintain their population, so it is also possible that the population of insects could decrease. This is turn may reduce the populations of voles and frogs. What would happen if the population of insects decreased? There would be more food for the rabbits and slugs, so their populations would increase. However, there would be less food for the frogs and voles, so their populations would decrease. This means less food for the foxes and hawks. However, there are likely to be more rabbits and thrushes for them to eat, so their populations are likely to stay the same. 2.3 How does human activity affect physical processes within ecosystems? 2.4 How can ecosystems be managed sustainably? SEE CASE STUDY 8: TROPICAL RAINFOREST ECOSYSTEM AMAZON RAINFOREST