Synopsis:

• Habitat = physical place where an organism lives.
• Niche = functional role and position of a species.
• Ecotone = transitional zone between two ecosystems/communities.
• Prelims trap: Habitat ≠ niche.

Synopsis:
A keystone species has a disproportionately large influence on ecosystem structure relative to its population size. Its removal may cause major ecological changes.
Example: Sea otter → controls sea urchins → helps maintain kelp forests.

Synopsis:

• Flagship species = public awareness/conservation symbol.
• Umbrella species = protecting it protects its wider habitat and other species.
• Flagship ≠ necessarily keystone.

Synopsis:
Edge effect occurs in an ecotone, where species from adjoining ecosystems may coexist and environmental conditions change. It can result in higher species diversity.
Ecotone → Edge effect.

Synopsis:
Indicator species reflect environmental conditions because their presence, absence or abundance changes with ecological disturbances.
Example: Lichens are commonly used as indicators of air pollution.

Synopsis:
Abiotic = non-living components such as temperature, light, water, soil, minerals and pH. Bacteria are biotic components.

Synopsis:
Producers are autotrophs. Most use photosynthesis, but some organisms such as certain bacteria use chemosynthesis. Therefore, all producers are not necessarily green plants.

Synopsis:
A grazing food chain begins with living green plants.
Example: Grass → Grasshopper → Frog → Snake → Eagle.

Synopsis:
Standing crop = biomass of living organisms present in an ecosystem at a particular time. Usually expressed as biomass per unit area.

Synopsis:

• Standing crop = amount of living biomass.
• Standing state = amount of inorganic nutrients available in an ecosystem.
  Mnemonic: Crop → Organisms; State → Nutrients.

Synopsis:

• Grazing food chain: Plant → Herbivore → Carnivore.
• Detritus food chain: Dead organic matter → Detritivores/decomposers → Consumers.
  Forest ecosystems have an important detritus pathway.

Synopsis:
A food web contains interconnected food chains. If one food source declines, organisms may sometimes use alternative food sources. More interconnections → greater ecological resilience.

Synopsis:

• Energy pyramid = always upright due to energy loss at each trophic level.
• Biomass pyramid = can be inverted, especially in aquatic ecosystems.
• Numbers pyramid = may be upright, inverted or spindle-shaped.
  Very important UPSC concept.

Synopsis:
According to Lindeman’s trophic-dynamic concept, only a small fraction—traditionally approximated as 10%—of energy at one trophic level is transferred to the next. Energy decreases sharply towards higher trophic levels.

Synopsis:
Producers = 10,000; primary consumers ≈ 1,000; secondary consumers ≈ 100.
Sequence: 10,000 → 1,000 → 100 → 10.

Synopsis:
Bioaccumulation = pollutant builds up within an individual organism because intake exceeds elimination.
Biomagnification = concentration increases as pollutant moves through successive trophic levels.

Synopsis:
Persistent and fat-soluble pollutants are particularly prone to biomagnification.
Classic examples: DDT, PCBs, methylmercury

Synopsis:
This demonstrates biomagnification. Persistent pollutants become increasingly concentrated at higher trophic levels.
Highest trophic level → generally highest pollutant concentration.

Synopsis:
GPP = total photosynthetic production by producers before accounting for their own respiration. It represents the total rate at which producers capture energy.

Synopsis:
NPP = GPP − Respiration.
NPP is the energy/organic matter remaining after producers use part of the captured energy for respiration. It is available to herbivores and higher trophic levels.

Synopsis:
Primary succession starts on a relatively barren surface with little/no developed soil. It is generally slower, not faster, than secondary succession.
No soil → Primary succession.

Synopsis:
Bare rock has little/no developed soil. Lichens can act as pioneer organisms and contribute to soil formation.
Bare rock → Lichens → Soil formation → Grasses → Shrubs → Trees.

Synopsis:
Secondary succession occurs after disturbance where soil and some biological components remain.
Examples: forest fire, abandoned agricultural land, flood-disturbed area.

Synopsis:
Pioneer species → Grasses/herbs → Shrubs → Mature community.
The community becomes progressively more complex, with increasing biomass and soil development.

Synopsis:
Succession involves directional changes in community composition. Primary succession is usually slower because ecosystem development starts from a very early stage. A climax community is not necessarily identical everywhere, because local conditions also influence succession.