3.1Unit 3 — Life on Earth
Ecosystems and Biomes — SQA National 5 Biology — SQA National 5 Biology Revision Notes & Topical Questions
5 min read 2 parts Lesson 1 of 6
Section 1 of 2Ecological terminology
- SpeciesA group of organisms that can interbreed with each other to produce fertile offspring.
- BiodiversityThe variety and abundance of different species present in a biological ecosystem.
- PopulationThe total number of individuals of one single species living in a particular area at the same time.
- CommunityAll the populations of living organisms (plants, animals, fungi, microbes) co-existing in an ecosystem.
- HabitatThe physical place or geographical environment where an organism lives.
- EcosystemAll the living organisms (community) interacting with the non-living physical components of their environment.
- NicheThe specific ecological role an organism plays within its community, including its resource use (light, temperature, moisture), food interactions, and environmental tolerances.
Section 2 of 2Biotic and abiotic factors
| Category | Definition | Examples | Measuring Instruments & Source of Error |
|---|---|---|---|
| Abiotic Factors | Non-living physical and chemical components of the environment | Light intensity, soil moisture, pH, ambient temperature | Light meter (casting shadows over sensor), Moisture meter / pH meter (failing to wipe probe between samples) |
| Biotic Factors | Living interactions between organisms | Competition (intraspecific and interspecific), predation, disease/pathogens, grazing | Observational surveys, mark-release-recapture |
- Competition:
- Occurs when required resources are in short supply.
- Interspecific competition: Between individuals of different species competing for one or a few shared resources (e.g. red and grey squirrels competing for food).
- Intraspecific competition: Between individuals of the same species competing for all the exact same resources (food, territory, mates). Intraspecific competition is significantly more intense because individuals have identical requirements.
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