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B5.3 - Ecosystems
Ecosystems & Sustainability - OCR A2 Biology
| Question | Answer |
|---|---|
| Define Ecosystem: | A group of living and non-living things occurring together, and the relationships between them. |
| Define Habitat: | The place where an organism lives. |
| Define Population: | All of the organisms of one species that live in the same place at the same time, and that can interbreed. |
| Define Community: | All of the populations of different species that live in the same place at the same time, and can interact. |
| What is a Biotic factor? | A living factor. Examples being food supply, predation and disease. |
| What is an Abiotic factor? | A non-living factor. Examples being pH, temperature and soil type. |
| Why are ecosystems dynamic? | Living things within an ecosystem interact with each other, causing population sizes to rise and fall. Small changes in one can affect another. |
| Define Producer: | An organism that produces organic molecules via photosynthesis. |
| Define Consumer: | An organism that feeds on other organisms. |
| Define Decomposer: | An organism that breaks down dead or un-digested material, releasing molecules that they then absorb or can be used by other living organisms. |
| Define Trophic Level: | The level at which an organism feeds in a food chain. |
| How is energy lost at each trophic level in a food chain? | The organism needs to carry out life processes such as respiration, these may release heat. Energy remains in dead organisms or waste material. |
| What is a pyramid of biomass? | This measures the dry mass of all the organisms at that trophic level. |
| What is a pyramid of energy? | How much heat energy an organism releases per unit gram, when they are burnt. |
| What is the gross Primary Productivity? | The rate at which plants convert light energy into chemical energy. |
| What is the Net Primary Productivity? | The amount of energy that is left available to the primary consumer. |
| Define succession: | A directional change in a community of organisms over time. |
| How does succession occur? | A pioneer community begin to live on the land. These organisms die and provide enough soil for large plants to grow. This repeats until a final stable community is reached. Known as a CLIMAX COMMUNITY. |
| A Quadrat: | Record the abundance. Record the percentage cover. |
| A Belt Transect: | A quadrat is placed next to the line at regular intervals, and either the abundance or the percentage cover recorded. |
| A Line Transect: | At regular intervals, make a note of what organisms are touching the tape. |
| What type of organisms are bacteria and fungi? (in respect to decomposition) | Saprotrophs. They feed saprotrophically. |
| How does a saprotroph feed? | It secretes enzymes onto dead and waste material. These enzymes digest the material into small molecules, which are then absorbed. Once absorbed they are stored and respired. |
| What is Nitrogen-Fixation? | Converting Nitrogen Gas in the atmosphere into Ammonium ions or Nitrates. |
| Give an example of nitrogen-fixing bacteria and where it may be found. | Rhizobium. Found in the root nodules of Legumes. Converts Nitrogen Gas in the air into Ammonium ions. |
| What is Nitrification? | The conversion of Ammonium ions into Nitrates. |
| What does Nitrosomonas do? | Converts Ammonium ions into Nitrites. |
| What does Nitrobacter do? | Converts Nitrites into Nitrates. |
| What is Denitrification? | The conversion of Nitrates back into Nitrogen Gas. This is done by bacteria when they are growing in anaerobic conditions, as they use Nitrates as a source of oxygen, and release Nitrogen Gas in the process. |
| Define Carrying Capacity: | The maximum population size that can be maintained over a period of time for a particular habitat. |
| Define Competition: | When resources are not present in adequate amounts to satisfy the needs of all the individuals who depend on them. |
| What is the difference between Interspecific and Intraspecific competition? | Interspecific is between individuals of different species. Intraspecific is between individuals of the same species. |
| What is Coppicing? | Cutting the trunk of a tree near to the ground, so that several new shoots grow from the cut surface. |
| What is Pollarding? | This is similar to Coppicing, but the trunk is cut higher up. This is so that animals such as deer can not feed on the exposed shoots. |
| What is Rotational Coppicing? | This is where different sections of a large woodland are cut each year until they have all been cut. Once they start the cycle the next year, the initial section will have grown back. |
| Why does clear-felling trees affect the soil? | Trees remove water from the soil, stopping it being washed away. Trees maintain soil nutrient levels through recycling. |
| Describe modern sustainable forestry (Large-Scale): | Any tree that is harvested is replaced. Forest as a whole must maintain it's ecological function. Local people should benefit from the forest. |
| Define Conservation: | The maintenance of biodiversity. |
| Define Preservation: | Protecting areas of land as yet unused by humans. |
| Ethical reasons for conservation: | Every species has value in it's own right. |
| Economic & Social Reasons for conservation: | Provide a valuable food source. Potentially a source for beneficial resources such as medicines. Natural predators can control pest populations. |
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Sparksy
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