19.1 - Populations & Ecosystems
- 1Defining key ecology terms
- 2Exploring how abiotic factors influence ecosystems
Key definitions in ecology
Ecology is the study of the inter-relationships between organisms and their environment, including both non-living (abiotic) and living (biotic) factors.
Here are some essential terms in ecology you should know:
| Term | Definition |
|---|---|
| Ecosystem | A community of living organisms interacting with each other and their physical environment in a defined area. |
| Biotic factor | A living component of an ecosystem, such as competition. |
| Abiotic factor | A non-living component of an ecosystem, for example, temperature. |
| Population | Organisms of the same species living together in one habitat at the same time. |
| Community | All the different species' populations within an ecosystem. |
| Habitat | The physical location where an organism lives. |
| Microhabitat | A smaller habitat with its own microclimate within a larger habitat. |
| Niche | The role of an organism in its ecosystem, including all the biotic and abiotic conditions to which an organism is adapted to survive, reproduce, and maintain a viable population. |
| Competitive exclusion | A principle stating that two species cannot occupy the same niche in the same environment simultaneously. |
The size of ecosystems can range widely, from small microbial communities to the entire biosphere encompassing the planet. The scope of an ecosystem studied by scientists is determined by their research focus, which might be an isolated environment like a tidepool or a broader area such as a meadow.
How abiotic factors influence ecosystems
Abiotic factors play a crucial role in determining the population size of species within ecosystems, affecting the entire biological community. If the conditions of an ecosystem change so drastically that a species cannot adapt and survive, it risks extinction.
Temperature:
- Influences enzyme activity and metabolic rates.
- At low temperatures, enzymes work more slowly, and at high temperatures enzymes may denature.
- For plants and ectotherms (cold-blooded animals), their metabolic rate is entirely dependent on the surroundings so temperatures outside their preferred range can reduce survival, reproductive success, and population size.
- Endotherms (warm-blooded animals) use more energy to maintain their body temperature when it is outside their optimal temperature range, which can decrease their reproductive success and population size.
Light:
- Increased light intensity boosts photosynthesis rates, inputting more energy into ecosystems.
- This leads to faster plant growth and higher reproduction rates, which can increase their population size.
- This provides more food for animals, potentially increasing their population sizes as well.
pH:
- This directly affects enzyme activity, and populations are larger when pH levels are optimal for an organism's enzymes.
- Deviations from the optimal pH can lead to smaller population sizes.
Water availability:
- Populations are generally smaller under conditions of low water availability, as only drought-resistant species can thrive.
- Low humidity increases transpiration in plants and water evaporation from animals, leading to decreased population sizes due to water stress.