Topic 1: Ecology Fundamentals
Study notes
Ecology is the scientific study of interactions among organisms and between organisms and their physical environment.
Levels of ecological organization
Organism: An individual living entity.
Population: Individuals of the same species living in a particular area.
Community: Populations of different species interacting in an area.
Ecosystem: Living organisms interacting with their non-living environment.
Biome: A large ecological region characterized by climate and dominant vegetation.
Biosphere: The global zone of life on Earth.
Important ecological terms
Habitat: The place where an organism lives.
Niche: The functional role of an organism in an ecosystem.
Biotic factors: Living components, such as plants, animals and microorganisms.
Abiotic factors: Non-living components, such as sunlight, water, temperature and soil.
Ecotone: A transition zone between two ecosystems.
Carrying capacity: The population an environment can sustain over time under given conditions.
Autecology: Study of an individual species in relation to its environment.
Synecology: Study of ecological communities and their relationships with the environment.
Species interactions
Interaction | Effect | Example |
|---|---|---|
Mutualism | Both benefit | Mycorrhiza |
Commensalism | One benefits; other largely unaffected | Epiphytic orchid on a tree |
Parasitism | Parasite benefits; host is harmed | Tapeworm in humans |
Predation | Predator benefits; prey is harmed | Tiger hunting deer |
Competition | Both experience a cost | Plants competing for sunlight |
Key pointers for UPSC Prelims
Habitat refers to the living place; niche refers to the functional role.
A population contains individuals of one species, whereas a community contains populations of different species.
An ecosystem includes both biotic and abiotic components.
The edge effect describes changes in ecological conditions and species composition near ecosystem boundaries.
Carrying capacity changes with resource availability and environmental conditions.
Mutualism benefits both species; commensalism benefits one without a significant effect on the other.
MCQs with answers and explanations
Q1. Which ecological level includes both living organisms and their non-living environment?
1) Population
2) Community
3) Ecosystem *
4) Species
Explanation: An ecosystem consists of interacting organisms and abiotic components such as water, soil, light and temperature.
Q2. The functional role of a species in its environment is known as its:
1) Habitat
2) Niche *
3) Biome
4) Biosphere
Explanation: A niche describes how a species uses resources, interacts with other organisms and functions within its environment.
Q3. Which of the following is an example of mutualism?
1) Tiger and deer
2) Tapeworm and human
3) Fungus and plant roots in mycorrhiza *
4) Two plants competing for sunlight
Explanation: In mycorrhiza, the fungus helps plant roots absorb water and minerals, while receiving carbohydrates from the plant.
Q4. The maximum population that an environment can sustain over time is called:
1) Population density
2) Carrying capacity *
3) Ecological succession
4) Species richness
Explanation: Carrying capacity depends on available resources and environmental conditions.