Ecology

An ecosystem includes both living (biotic) organisms and non-living (abiotic) physical conditions like soil, water, and climate. The interaction between these components defines an ecosystem.

Oxygen is an abiotic factor in aquatic ecosystems. While oxygen levels can be influenced by plants and algae, oxygen itself is a dissolved gas - a non-living chemical component. Plants, fish, and algae are all biotic (living) factors.

The biosphere is the term for the global ecosystem - it encompasses all living organisms and their relationships with each other and with the physical environment across the entire Earth.

A biome is a large geographical region characterized by its distinctive climate (temperature, precipitation) and the specific plant and animal communities (biota) that have adapted to those conditions.

A niche describes the specific role and position of a species within its ecosystem - including what it eats, where it lives, how it reproduces, and how it interacts with other organisms. A habitat is just the physical location, while a niche is the species' ecological 'profession'.

The logical order begins with the abiotic environment (non-living foundation), followed by producers that create energy from it, then consumers that eat producers, and finally decomposers that break down all organisms to recycle nutrients back to the abiotic environment.

Statement A is incorrect because the environment includes BOTH physical (abiotic) factors AND living (biotic) organisms. Options B, C, and D correctly identify physical factors and acknowledge that environment provides habitat for animals.

Lions are carnivores because they primarily eat meat. Deer, goats, and cows are herbivores that eat only plant material.

Herbivores are primary consumers because they eat plants (producers). They are not producers themselves - they cannot photosynthesize.

Humans are omnivores because we eat both plant and animal products. We are not specialized herbivores, carnivores, or parasites.

Omnivores consume both plant and animal matter. Herbivores eat only plants, carnivores eat only meat, and piscivores specifically eat fish.

The trophic levels represent the steps in a food chain.

Plants are always at the first trophic level because they are producers that make their own food through photosynthesis. All other levels depend on them.

The correct order follows energy flow: Algae (producer) → Fish (primary consumer) → Duck (secondary consumer) → Human (tertiary consumer). Energy moves up through each trophic level.

Herbivores occupy the second trophic level because they eat plants from the first trophic level (producers). They are primary consumers in the food chain.

An ecosystem includes all living organisms (biotic factors) interacting with non-living components (abiotic factors) like water, soil, and air in a specific area. A biome is a larger geographic region, trophic level is a feeding position, and biotic factor refers only to living things.

Each trophic level has limited total biomass because energy is lost at each transfer (10% rule). This means higher trophic levels can support less total biomass. Deer are herbivores, lions are heterotrophs not autotrophs, and predators typically have fewer numbers than prey (not greater).