SSC CGL Biology · Ecology and Environment
Ecosystems, Adaptations and Environment
Kinds of ecosystem and the terms for energy and mass in them, the nitrogen-cycle microbes, named adaptations and the ecologists behind them, and greenhouse gases and threatened species.
Why this matters
Seventeen questions in the bank: four from the 2023 shifts, 12 from the 2024 shifts and one from the 2025 shifts, three of them HARD. The hard ones ask a scientist and a year, so learn the short list of names with their dates.
Concept 1 of 3: Ecosystems and their terms
Definition
Kinds:
- The ecosystem is the functional unit of nature.
- Two basic kinds: terrestrial (forest, grassland, desert) and aquatic (fresh water and sea).
- Freshwater habitats: rivers, creeks, lakes, ponds, streams. Sea water is salt water.
- Man-made ecosystems: an aquarium, a crop field, a garden.
Terms:
- Standing crop: the living material at a trophic level at one time, measured as biomass.
- Ecological efficiency: the ratio of energy flows at two points in a food chain, about 10% from one level to the next.
Nitrogen cycle: Rhizobium fixes nitrogen in legume roots; Nitrosomonas and Nitrobacter turn ammonia into nitrite and then nitrate.
Practise this conceptself-check · 3 quick reps
The same idea in a real exam question:
Example 1 · Ecology and Environment · Ecosystems, Adaptations and Environment
Standing crop is not productivity
Concept 2 of 3: Adaptations, interactions and ecologists
Definition
Adaptations and interactions:
- Allen's rule: mammals from cold climates have shorter ears and limbs, to lose less heat.
- Brood parasitism: a parasite gets another animal to raise its young, as the cuckoo does with a crow.
- Calotropis defends itself chemically with poisonous glycosides, so cattle do not eat it.
Branches and people:
- Paleoecology: ancient environments and the organisms of the past.
- Henry Chandler Cowles: plant succession in the Indiana Dunes, from 1896.
- Pierre François Verhulst: the logistic growth equation, 1838.
Practise this conceptself-check · 3 quick reps
The same idea in a real exam question:
Example 2 · Ecology and Environment · Ecosystems, Adaptations and Environment
Kleptoparasitism is stealing food
Concept 3 of 3: Greenhouse gases and threatened species
Definition
The facts:
- Greenhouse gases (Kyoto list): carbon dioxide, methane, nitrous oxide (N2O). Nitric oxide (NO) is a smog pollutant, not a greenhouse gas.
- Hubbardia heptaneuron is a grass of the Western Ghats, first found in the spray of Jog Falls; a dam cut the falls' flow, and it is now critically endangered.
- In the Western Ghats, beyond habitat loss, invasive alien species such as Lantana threaten native plants.
| Item | Fact |
|---|---|
| Nitrous oxide | Greenhouse gas |
| Nitric oxide | Not a greenhouse gas |
| Hubbardia heptaneuron | Endangered grassQ |
Practise this conceptself-check · 3 quick reps
The same idea in a real exam question:
Example 3 · Ecology and Environment · Ecosystems, Adaptations and Environment
Nitric and nitrous differ
Summary — formulas & gotchas at a glance
A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.
Reference tables (3)
Greenhouse gases and threatened species3 rows
| Item | Fact |
|---|---|
| Nitrous oxide | Greenhouse gas |
| Nitric oxide | Not a greenhouse gas |
| Hubbardia heptaneuron | Endangered grassQ |
Watch out for (3)
- Standing crop is not productivity→ Ecosystems and their terms
- Kleptoparasitism is stealing food→ Adaptations, interactions and ecologists
- Nitric and nitrous differ→ Greenhouse gases and threatened species
Test yourself on a real paper
Sit a past SSC CGL paper, timed and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.