Ecosystem, Food Chains, Carbon Cycle, Trophic Level

Ecosystem

A community and the habitat in which it lives

Food Chain

A food chain shows what eats what in a particular habitat. It shows the flow of energy and materials from one organism to the next, beginning with a producer.

Food Web

A food web is a network of interconnected food chains. It shows the energy flow through part of an ecosystem.

Environment

All the conditions that surround a living organism

Population

All the members of a single species that live in a habitat

Community

All the populations of different organisms that live together in a habitat

Biodiversity

Biodiversity is a measure of the variety of different species living in a habitat. The greater the number of different species in a habitat, the greater its biodiversity.

Pyramids of biomass

Biomass is the total dry mass of one animal or plant species in a food chain/food web. A pyramid of biomass shows the biomass at each trophic level, rather than the population. The biomass goes down from one trophic level to the next, just like the amount of energy, so the bars always get narrower towards the top. It can be difficult to get valid data for a pyramid of biomass because: measuring dry biomass means that all the water has to be removed from the organisms an organism may belong to more than one trophic level, so it cannot easily be represented by one bar

Returning carbon dioxide to the atmosphere

Carbon dioxide is released to the atmosphere through respiration by animals, plants and microorganisms. It is also released by the combustion of wood and fossil fuels (such as coal, oil and natural gas). The use of fossil fuels is gradually increasing the carbon dioxide levels in the atmosphere, which can lead to global warming. Decomposition or decay also releases carbon dioxide. This process happens faster in warm, moist conditions with plenty of oxygen because it involves microorganisms. Decay can be very slow in cold, dry conditions, and when there is a shortage of oxygen.

Carbon Cycle

Carbon is passed from the atmosphere, as carbon dioxide, to living things. It is then passed from one organism to the next in complex molecules, and returned to the atmosphere as carbon dioxide again. This is known as the carbon cycle. Stage 1: Carbon enters the atmosphere as carbon dioxide from respiration and combustion. Stage 2: Carbon dioxide is absorbed by producers to make carbohydrates in photosynthesis. Stage 3: Animals feed on plants, passing the carbon compounds along the food chain. Most carbon they consume is exhaled as carbon dioxide during respiration. The animals and plants eventually die. Stage 4: Dead organisms are eaten by decomposers and carbon in their bodies is returned to the atmosphere as carbon dioxide.

Organisms and how they get their energy

Consumer: Feeding on other organisms Primary consumer: Eating plants Secondary consumer: Eating primary consumers Tertiary consumer: Eating secondary consumers Herbivore: Eating plants Carnivore: Eating other animals Decomposer: Feeding on dead and decaying organisms, and on the undigested parts of plant and animal matter in faeces

Energy Transfer

Energy is transferred along food chains from one trophic level to the next. However, the amount of available energy decreases from one trophic level to the next. In a food chain only around 10% of the energy is passed on to the next trophic level. The rest of the energy passes out of the food chain in a number of ways: - it is used as heat energy - it is used for life processes (ex. movement) - faeces and remains are passed to decomposers Less energy is transferred at each level of the food chain so the biomass gets smaller. As a result, there are usually fewer than five trophic levels in food chains.

Information from a food web

Examples of a food web: oak tree → squirrel → fox oak tree → earthworm → wood mouse → fox oak tree → earthworm → wood mouse → owl The oak trees are the producers. Squirrels and earthworms are primary consumers, and the wood mice are secondary consumers. The foxes and owls are tertiary consumers (the foxes are also secondary consumers). Foxes and owls eat the wood mice, and foxes eat wood mice and squirrels. The fungi and earthworms are decomposers in this food web. Question: Let's say there are slugs, insects and rabbits. What would happen if the slugs were to go extinct? Answer: 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 available, the populations of rabbits and insects would increase.

Competition

Habitats have limited supplies of the resources needed by plants and animals. Therefore, plants and animals may need to compete with one another for food, water, space and mates in order to survive. Plants make their own food using photosynthesis, so they do not compete for food. However, plants do compete for resources like water, space and mineral salts.

Interdependance

In a food web, changes in the population of one organism have an effect on the populations of other organisms. This is called interdependence.

Removing carbon dioxide from the atmosphere

Plants use carbon dioxide from the atmosphere for photosynthesis. The carbon becomes part of complex molecules in the plants, such as proteins, fats and carbohydrates.

Producers

Producers are organisms that make their own organic nutrients (food) - usually using energy from sunlight. Green plants make their food by photosynthesis. The other organisms in a food chain are consumers, because they all get their energy by consuming other organisms.

Pyramids of Numbers

Shows the population at each stage in a food chain. It is drawn as a bar chart with the bars stacked on top of each other. Wider the bar = the more organisms it represents. The producer always goes at the bottom of the pyramid. ex. https://bam.files.bbci.co.uk/bam/live/content/z7wngk7/large Often a pyramid of numbers does not look like a pyramid at all. This could happen if the producer is a large plant, such as a tree, or if one of the animals is very small. Here is an example: https://bam.files.bbci.co.uk/bam/live/content/z2jsr82/large

What is the ultimate source of energy?

The Sun is the ultimate source of energy for most communities of living things. Green plants are usually the producers in a food chain.

Habitat

The place where an organism lives

Trophic Levels

The position of an organism in a food chain, food web or pyramid is its trophic level.

Passing carbon from one organism to the next

When an animal eats a plant, carbon from the plant becomes part of the fats and proteins in the animal. Microorganisms and some animals feed on waste material from animals, and the remains of dead animals and plants. The carbon then becomes part of these organisms.

Percentage efficiency of energy transfer equation

energy transferred to next level ÷ total energy in × 100