ecology (to be refined!)

Producers

Organisms that make their own food by photosynthesis and start energy flow in ecosystems.

Primary consumers

Herbivores that feed directly on producers.

Secondary consumers

Carnivores that feed on primary consumers.

Tertiary consumers

Carnivores that feed on secondary consumers; often top predators.

Decomposers

Organisms that break down dead matter and release nutrients back to the environment.

Trophic level

A step in a food chain representing how many times energy has been transferred.

Food chain

A linear sequence showing one pathway of energy flow.

Food web

A network of interconnected food chains showing multiple feeding relationships.

Pyramid of energy

Diagram that shows energy transfer at each trophic level; always upright because energy decreases upward.

Pyramid of biomass

Diagram of total mass at each trophic level; can be inverted when producers turn over rapidly.

Abiotic factors

Non‑living components of an ecosystem (temperature, water, light, pH, etc.).

Biotic factors

Living components of an ecosystem (plants, animals, microbes).

Energy loss between trophic levels

~10 % of energy is transferred; the rest is lost as heat, movement, respiration, excretion.

Carbon cycle

Movement of carbon through photosynthesis, respiration, decomposition, and combustion.

Photosynthesis (carbon cycle)

Plants absorb CO₂ to make glucose, locking carbon into biomass.

Respiration (carbon cycle)

Organisms release CO₂ back into the atmosphere when breaking down glucose for energy.

Combustion (carbon cycle)

Burning of fossil fuels or biomass releases stored carbon as CO₂.

Decomposition (carbon cycle)

Breakdown of dead organisms releases carbon compounds to soil and atmosphere.

Nitrogen fixation

Conversion of atmospheric N₂ into ammonia or nitrates by bacteria, making nitrogen available to plants.

Nitrifying bacteria

Soil microbes that convert ammonia → nitrites → nitrates.

Denitrifying bacteria

Bacteria that convert nitrates back to atmospheric N₂, lowering soil fertility.

Leaching

Loss of soluble nutrients (e.g., nitrates) from soil as water drains through.

Eutrophication

Nutrient runoff causes algal blooms, oxygen depletion, and death of aquatic life.

Persistent pollutant

Chemical that does not break down easily and remains in the environment for long periods.

Bioaccumulation

Build‑up of a toxic substance in the tissues of one organism over time.

Biomagnification

Increase in toxin concentration at each successive trophic level of a food chain.

DDT

Persistent, fat‑soluble pesticide that bioaccumulates and biomagnifies, causing eggshell thinning in birds.

Toxins in fat tissue

Fat‑soluble pollutants stored in body fat, making excretion difficult.

Entry of toxins into food chain

Pollutants absorbed by producers, then passed to consumers and magnified upward.

Top predators and toxins r/s

Apex consumers have the highest toxin concentrations due to biomagnification.

Properties favouring bioaccumulation

Fat‑soluble, chemically stable, not metabolised or excreted.

Human health risk from fish

Eating contaminated seafood can lead to nerve damage, hormonal disruption, and reproductive issues.

Why does energy flow only one way in food chains?

Energy is lost as heat at each transfer and cannot be recycled, unlike matter.

Why are food chains usually ≤5 links long?

Energy falls to unusable levels after several transfers, limiting higher trophic levels.

Why are top predators most affected by biomagnification?

They consume many contaminated organisms, so toxins concentrate the most in their bodies.

Difference between bioaccumulation and biomagnification?

Accumulation in one organism over time vs. increasing concentration along a food chain.

Why are fat‑soluble toxins dangerous?

They lodge in body fat, persist for years, and magnify through diets.

Effect of DDT on birds

Causes thin eggshells and reduced reproductive success.

How do humans introduce pesticides into aquatic food chains?

Run‑off carries sprayed chemicals into rivers and lakes where producers absorb them.

Why does toxin concentration rise while energy falls up a food chain?

Toxins are conserved and ingested repeatedly, whereas energy is lost as heat.

How can reducing pollution at producer level help?

Prevents toxins from entering the base of the food web, stopping magnification entirely.

Why are aquatic ecosystems vulnerable to biomagnification?

Pollutants disperse easily in water and aquatic chains can be long, magnifying toxins.

Why are polar bears prone to high toxin loads?

They are apex predators with large fat reserves that store persistent pollutants.

How do persistent pollutants disrupt ecosystems?

They accumulate, magnify, and interfere with growth, reproduction, and survival of organisms.

Why is nitrogen fixation essential for life?

It makes inert N₂ usable for protein synthesis in plants and, ultimately, all consumers.

How does leaching harm plant growth?

It removes soil nitrates, depriving plants of essential nitrogen.

Why is a pyramid of energy always upright but a biomass pyramid might not be?

Energy inevitably decreases up trophic levels, while instantaneous biomass can be lower in fast‑growing producers.

What role do decomposers play in matter vs. energy flow?

They recycle nutrients (matter) but still lose energy as heat, so energy cannot be recycled.

How does eutrophication connect to human activity?

Excess fertiliser runoff elevates nutrient levels, triggering algal blooms and oxygen depletion in water.