- Population: All the organisms of a particular species found in an ecosystem at any one time.
- Community: Populations of all species found in a particular ecosystem at any one time.
- Ecosystem: A distinct, self-supporting system of organisms interacting with each other and with the physical environment.
Quadrats 🔲
In I/GCSE Biology, quadrats are squares that count species a small part of a habitat and use it to estimate the population size of the species in the habitat, as it would be annoying to count them all. The smaller part of the population in the quadrat, which will then represent its population in that habitat, is called a sample. Quadrats are scattered randomly around the habitat to avoid bias (favour).
Feeding Relationships 🐯🐶🐹
Food chains show the feeding relationships within an ecosystem. Arrows show the flow of energy as well as who eats what. 10% of total energy is passed down each food chain. The other 90% is used for waste, respiration, kinetic, chemical (poo), and heat energy.
In I/GCSE Biology, there are stages in a food chain, called trophic levels.
- Producers can convert inorganic elements into complex molecules (i.e. photosynthesize) and uses cellular respiration to release energy. They produce the food with the energy from the Sun. Consumers cannot make their own energy.
- Primary consumers are herbivores. They eat the producer.
- Secondary consumers eat the primary consumer and are also carnivores or herbivores, predators or scavengers.
- Tertiary consumers eat secondary consumers. These can be carnivores, herbivores or omnivores, predators or scavengers.
- Decomposers can be in all three levels of consumers. These are bacteria, fungi or detrivores (worms…etc).
Food webs show how food chains relate to each other and are basically a combination of many food chains. In other words, food webs show the feeding relationships and energy flow between food chains.
- Pyramids of numbers represent the numbers of organisms in each trophic level in the food chain.
- Pyramids of biomass show the total mass of the organisms in each trophic level.
- Energy pyramids show the transfer of energy in an ecosystem. The amount of energy available decreases down the food chain, reducing by 90%. Lots of producers are needed to support a small number of primary consumers and so on…
Note: In I/GCSE Biology, sometimes you may be asked to fill in a Sankey diagram. Just remember that energy can never be created or destroyed, so make sure the useful/waste energy is equal to the total energy input.
That's the end of the topic!
Drafted by Joey (Biology)
Reference:
https://www.teachoo.com/11170/3197/Trophic-Level/category/Concepts/
https://indomoraltales.com/difference-between-food-chain-and-food-web/