CSIR NET Life Sciences Ecological Principles Syllabus

Classify interspecific interactions by their effect on each species (+, −, 0).

Mutualism (+/+), Competition (−/−), Predation/Parasitism/Herbivory (+/−), Commensalism (+/0), Amensalism (−/0), Neutralism (0/0).

What is interspecific competition and its two main mechanisms?

Competition between individuals of different species for a shared limiting resource. Mechanisms: exploitation (resource) competition — indirect, via depleting a common resource; and interference competition — direct, via aggression, territoriality, or allelopathy.

Define herbivory and one common plant defense against it.

Herbivory is consumption of plant tissue by animals (a +/− interaction). Plant defenses include chemical defenses (toxins/secondary metabolites like alkaloids, tannins) and morphological defenses (thorns, spines, tough cuticle).

What is the difference between a predator and a parasite as consumers?

A predator (carnivore) typically kills and consumes multiple prey and is usually larger than its prey; a parasite lives on/in a single host, usually does not kill it immediately, and is smaller than the host.

What is pollination and name a typical mutualistic reward offered to pollinators?

Pollination is transfer of pollen from anther to stigma, often mediated by animals (entomophily, ornithophily). Plants reward pollinators with nectar and/or pollen; it is a classic mutualism.

Define symbiosis and give its three principal types.

Symbiosis is a close, long-term living-together of two species. Types: mutualism (+/+, both benefit, e.g. mycorrhizae, lichens), commensalism (+/0, one benefits, other unaffected), and parasitism (+/−, parasite benefits at host's cost).

What is a biological community (biocoenosis)?

An assemblage of populations of different species living together and interacting in a common environment/area, forming the biotic part of an ecosystem.

List major attributes used to describe community structure.

Species richness and diversity, dominance, relative abundance, growth/life forms and stratification (vertical layering), trophic structure, frequency, and the pattern of interactions/food web.

Differentiate alpha, beta, and gamma diversity.

Alpha (α) = species diversity within a single community/habitat; Beta (β) = the change/turnover in species composition between habitats along a gradient; Gamma (γ) = total diversity over a large landscape/geographic region.

What does the Shannon-Wiener diversity index (H') measure and its formula?

It measures species diversity combining richness and evenness. H' = −Σ(pi·ln pi), where pi is the proportion of individuals belonging to species i. Higher H' = greater diversity.

What does the Simpson's diversity index measure and its formula?

Simpson's index measures dominance/the probability two randomly picked individuals are the same species: D = Σ(pi²). Diversity is expressed as 1 − D or 1/D; higher values mean greater diversity.

What is species evenness?

Evenness measures how equally individuals are distributed among the species present; high evenness = abundances are similar across species, low evenness = one or few species dominate.

Define an ecotone and the edge effect.

An ecotone is the transition zone between two adjacent ecosystems/communities (e.g. forest–grassland boundary). The edge effect is the tendency for ecotones to have greater species richness and density of some species than either bordering community.

What is ecological succession?

The gradual, directional, and predictable change in species composition and community structure of an area over time, until a relatively stable climax community is reached.

Differentiate primary and secondary succession.

Primary succession starts on a bare lifeless substrate with no pre-existing soil (e.g. bare rock, lava, new sand dune) and is slow. Secondary succession occurs where a community was removed but soil remains (e.g. abandoned field, after fire), and is faster.

Name the pioneer community in primary succession on bare rock (xerarch) and in water (hydrarch).

On bare rock (lithosere/xerosere) the pioneers are crustose lichens; in water (hydrosere) the pioneers are phytoplankton.

What is a sere and a seral community?

A sere is the whole sequence of communities that successively replace one another in a given area during succession; each transitional community in the sequence is a seral (stage) community.

Distinguish autogenic from allogenic succession.

In autogenic succession, the organisms themselves modify the environment and drive the change (internal cause). In allogenic succession, change is driven by external environmental factors (e.g. climate change, sedimentation).

What is the climax community, and name two theories of climax.

The climax is the final, relatively stable, self-perpetuating community in equilibrium with the regional climate. Theories: monoclimax (Clements) — one climax determined by climate per region; polyclimax — many climaxes set by various factors (soil, fire); and climax-pattern (Whittaker).

Define an ecosystem and its two structural components.

An ecosystem is a functional unit of biotic community plus abiotic environment interacting via energy flow and nutrient cycling. Structural components: abiotic (climate, inorganic and organic substances) and biotic (producers, consumers, decomposers).

What are the main functions of an ecosystem?

Energy flow (one-way, through trophic levels), nutrient/biogeochemical cycling (cyclic), productivity, decomposition, and maintenance of trophic structure and homeostasis.

State the 10% law (Lindeman) of energy transfer.

On average only about 10% of the energy at one trophic level is transferred to and stored at the next higher trophic level; the rest (~90%) is lost mainly as metabolic heat (respiration). This limits food chains to ~4–5 trophic levels.

Why is energy flow in an ecosystem described as unidirectional?

Energy enters as sunlight, is fixed by producers, and flows producer→consumer→decomposer, being progressively lost as heat at each step (per the 2nd law of thermodynamics); it cannot be recycled, unlike nutrients.

Define Gross Primary Productivity (GPP) and Net Primary Productivity (NPP).

GPP is the total rate of organic matter (energy) fixed by producers via photosynthesis. NPP = GPP − respiration (R) by producers; it is the biomass actually available to consumers.

What is the role of decomposers (decomposition) in an ecosystem?

Decomposers (bacteria, fungi) break down dead organic matter and detritus through fragmentation, leaching, catabolism, humification, and mineralization, releasing inorganic nutrients back to the abiotic pool for reuse by producers.

Contrast gaseous and sedimentary biogeochemical cycles with examples.

Gaseous cycles have their main reservoir in the atmosphere/hydrosphere and are relatively fast (carbon, nitrogen, oxygen). Sedimentary cycles have their main reservoir in the Earth's crust/rocks and are slow (phosphorus, sulfur). The phosphorus cycle has no significant gaseous phase.

Name the key steps of the nitrogen cycle.

Nitrogen fixation (N2→NH3, by bacteria like Rhizobium, Azotobacter, cyanobacteria, or lightning), ammonification (organic N→NH4+), nitrification (NH4+→NO2−→NO3−, by Nitrosomonas and Nitrobacter), assimilation, and denitrification (NO3−→N2, by Pseudomonas, returning N to atmosphere).

Name two characteristic Indian ecosystems and a defining feature of each.

Examples: the Sundarbans mangrove ecosystem (largest mangrove forest, halophytic, pneumatophores, Bengal tiger); coral reefs (Gulf of Mannar, Lakshadweep); the Western Ghats wet evergreen forests (megadiverse); and Chilika Lake (brackish lagoon, migratory birds).

According to MacArthur and Wilson's theory of island biogeography, what determines the number of species on an island?

Species number is a dynamic equilibrium between immigration rate and extinction rate. Immigration is higher on islands nearer the mainland; extinction is higher on smaller islands. Thus large, near islands hold more species than small, distant ones (the species–area relationship).

Name the major terrestrial biomes along a gradient of decreasing latitude/increasing temperature.

Tundra → boreal forest (taiga) → temperate deciduous forest → temperate grassland → desert → tropical savanna/grassland → tropical rainforest. (Distribution governed mainly by temperature and precipitation.)

How many biogeographic zones is India divided into, and name a few.

India is divided into 10 biogeographic zones: Trans-Himalaya, Himalaya, Indian Desert, Semi-Arid, Western Ghats, Deccan Peninsula, Gangetic Plain, North-East India, Islands, and Coasts.

What are the major direct drivers of biodiversity loss (the 'Evil Quartet'/HIPPO)?

Habitat loss and fragmentation, Invasive (alien) species, Pollution, Population growth (human)/overexploitation, and Overharvesting — plus climate change. (Habitat loss is the single greatest cause.)

Differentiate in-situ and ex-situ conservation with examples.

In-situ conservation protects species in their natural habitat (national parks, wildlife sanctuaries, biosphere reserves, sacred groves). Ex-situ conservation protects them outside natural habitats (zoos, botanical gardens, seed/gene banks, cryopreservation, captive breeding).

Name two notable Indian species-specific conservation projects.

Project Tiger (1973, conserving tigers via tiger reserves) and Project Elephant (1992); also crocodile conservation and the Gir lion (Asiatic lion) conservation programme.

What is a biodiversity hotspot, and how many lie (wholly/partly) in India?

A biodiversity hotspot is a region with exceptional endemism (≥1,500 endemic vascular plants) that has lost ≥70% of its original habitat. Four hotspots extend into India: the Himalaya, Western Ghats–Sri Lanka, Indo-Burma, and Sundaland (Nicobar Islands).