3.1 Ecology & Biodiversity
In brief:Ecology is the study of the interactions between organisms and their environment. Biodiversity refers to the variety of life in a given area.
Ecology is the study of how organisms interact with each other and their environment.
Hierarchy of ecological organisation:
Biosphere → Ecosystem → Habitat → Community → Population → Individual Organism
Biodiversity is the variety of living organisms in an area. It can be measured using Simpson's Diversity Index:
Ds = 1 − Σn(n−1) / N(N−1)
Where n = number of individuals of each species, N = total number of all individuals
Result closer to 1.0 = high diversity, closer to 0 = low diversity
Factors affecting ecosystems:
• Abiotic (non-living): temperature, light, water, soil pH, oxygen, space
• Biotic (living): competition, predation, disease, food availability, parasitism
Population curves:
• S-curve (sigmoid): population grows, then levels off at carrying capacity (limited resources)
• J-curve: population grows exponentially with unlimited resources (unsustainable)
Carrying capacity is the maximum population size that an environment can sustain indefinitely, determined by limiting factors.
A simple food chain showing energy flow
Wikimedia Commons (CC)
Pyramid of numbers / energy across trophic levels
Wikimedia Commons (CC)
Simpson's Diversity Index
n = individuals per species | N = total individuals | Closer to 1.0 = more diverse
Ecological Hierarchy
Key Points
- 1Biosphere > Ecosystem > Habitat > Community > Population > Organism.
- 2Biodiversity loss has environmental, economic, social, and cultural impacts.
- 3Simpson's Diversity Index: Ds = 1 − Σn(n−1) / N(N−1). Higher = more diverse.
- 4Abiotic factors: water, oxygen, space, temperature, soil.
- 5Biotic factors: food, disease, competition, predation.
- 6Carrying capacity: maximum population an environment can sustain.
- 7S-curve: population in resource-limited environment. J-curve: unlimited resources.
- 8Niche: the role and position of an organism within its ecosystem.
Learning Outcomes
- Outline what is meant by the biosphere, ecosystems, habitats, biodiversity
- Discuss the impact of biodiversity loss in local ecosystems and the important role conservation plays in limiting biodiversity loss
- Evaluate primary or secondary data relating to the effects of human activity on species diversity
- Model species diversity in ecosystems using the Simpson's Diversity Index equation
- Illustrate how limiting factors determine the carrying capacity for species in Irish ecosystems