Ecology Basics — Set 4

Correct Answer: A. Organism and Environment

• **Organism and Environment** = ecology is defined as the scientific study of interactions between organisms and their physical and biological environment. • **Levels of ecological study** — ecology operates at four levels: individual, population, community, and ecosystem, all focused on organism-environment interactions. • 💡 Wrong-option analysis: Plants and Sunlight: photosynthesis only, far too narrow; Soil and Water: pedology/hydrology, not ecology; Humans and Cities: urban studies, not ecology in the biological sense.

Correct Answer: A. Crop field

• **Crop field** = an artificial/man-made ecosystem created and maintained by human intervention, with very low species diversity and dependence on external inputs like fertilisers. • **Low self-sustainability** — unlike natural ecosystems, crop fields require constant human inputs (irrigation, pesticides, fertilisers) and have simplified food chains. • 💡 Wrong-option analysis: Pond: a natural freshwater ecosystem; Forest: a natural terrestrial ecosystem; Lake: a natural freshwater body, not man-made.

Correct Answer: D. Recycle nutrients

• **Decomposers** = recycle nutrients by breaking down dead plants and animals into simple inorganic compounds, releasing them back into soil and atmosphere for producers. • **Without decomposers** — waste would accumulate indefinitely and nutrients would remain locked in dead biomass, eventually halting all life processes. • 💡 Wrong-option analysis: Capture sunlight: role of producers/autotrophs; Eat primary consumers: role of secondary consumers/carnivores; Produce oxygen: byproduct of photosynthesis by producers.

Correct Answer: A. Habitat

• **Habitat** = the specific natural environment (the 'address') where an organism lives, providing food, water, shelter, and space to meet its biological needs. • **Habitat vs Niche** — habitat is WHERE an organism lives (address); niche is HOW it lives (functional role or 'profession') in that habitat. • 💡 Wrong-option analysis: Ecosystem: includes all organisms and their abiotic environment, much broader than a habitat; Biome: large climate-defined geographic region; Niche: the functional role of an organism, not its physical location.

Correct Answer: A. Food Web

• **Food Web** = a network of interconnected food chains representing the complex feeding relationships in an ecological community. • **Greater stability** — food webs are more stable than single food chains because multiple energy pathways mean the loss of one species does not collapse the whole system. • 💡 Wrong-option analysis: Food Spiral: not an ecological term; Energy Pyramid: shows energy distribution across trophic levels, not feeding relationships; Trophic Level: a single feeding position in a food chain, not the network.

Correct Answer: A. Oxygen

• **Oxygen** = released as a byproduct of photosynthesis when plants split water molecules (photolysis) to obtain electrons for the light reaction. • **CO2 absorbed, O2 released** — plants simultaneously absorb CO2 and release O2 during photosynthesis, maintaining the atmospheric balance of these two gases. • 💡 Wrong-option analysis: Nitrogen: not produced by photosynthesis; released/absorbed through the nitrogen cycle; Methane: produced by anaerobic decomposition, not photosynthesis; Carbon dioxide: absorbed during photosynthesis, not released (released only during respiration).

Correct Answer: A. Omnivores

• **Omnivores** = animals with a diet consisting of both plant-based and animal-based food, such as humans, bears, and crows. • **Multiple trophic levels** — omnivores can occupy more than one trophic level simultaneously, making food webs more complex and resilient. • 💡 Wrong-option analysis: Herbivores: eat only plants, strictly primary consumers; Carnivores: eat only other animals, secondary or higher consumers; Decomposers: feed on dead organic matter, not living plants or animals.

Correct Answer: C. Autecology

• **Autecology** = focuses on the study of a single species or individual organism in relation to its environment, including its adaptations and survival strategies. • **Autecology vs Synecology** — autecology studies one species (single); synecology studies entire communities (group) of organisms in their environment. • 💡 Wrong-option analysis: Paleoecology: study of past ecosystems through fossils; Synecology: study of communities and groups of species together; Global ecology: study of ecosystems at the global biosphere level.

Correct Answer: C. Primary Productivity

• **Primary Productivity** = the rate at which producers convert solar energy into organic compounds (biomass), measured in grams per square metre per year. • **Net Primary Productivity (NPP)** — the biomass remaining after deducting the producer's own respiratory losses, the actual energy available to consumers. • 💡 Wrong-option analysis: Ecological Balance: general equilibrium state, not a productivity measure; Biodiversity: variety of life forms, not biomass production; Respiration: process of energy release from food, reduces rather than measures productivity.

Correct Answer: D. A.G. Tansley

• **A.G. Tansley** = proposed the term 'Ecosystem' in 1935, describing it as an integrated system of living beings and their physical environment. • **1935** — the year Tansley introduced 'Ecosystem' as a concept, which became central to modern ecological studies and conservation planning. • 💡 Wrong-option analysis: Charles Elton: developed food chain and niche concepts, not 'ecosystem'; Raymond Lindeman: formulated the 10% energy law in 1942; Ernst Haeckel: coined 'Ecology' in 1866, not 'Ecosystem'.