biology - topic 4: community level systems

What is material cycling?

The breakdown of biological molecules.

What do microorganisms do?

Decompose, take part in nitrification and denitrification. Typically bacteria or fungi.

Why is the water cycle important?

All life on Earth depends on water for survival, e.g. photosynthesis.

Why do we recycle carbon and nitrogen?

The resources are finite.

How is carbon taken out of the atmosphere?

In the form of carbon dioxide.

How is carbon passed on to animals?

Via feeding.

How is carbon returned to the atmosphere?

Respiration from plants and animals.

The carbon cycle allows the movement of carbon through what four reservoirs?

Biomass, atmosphere, soil, and oceans.

Why is the carbon cycle important?

What is a global example of the disruption of the balancing of carbon?

Global warming.

Define decomposition.

The breaking down and digestion of biological material by decomposers.

What are the three factors affecting rate of decay?

Temperature: Enzymes work faster at warmer temps, but if it’s too high they can denature.

Water: Decomposers require water to survive, so decreased water availability will decrease rate.

Oxygen: Some decomposers need this for aerobic respiration, so the rate for these decomposers will decrease if less oxygen is available.

Define population.

A group of the same species living in the same place at the same time.

Define community.

All of the populations living in the same area at the same time.

Define ecosystem.

All the biotic factors (living) and all the abiotic factors (non-living) that interact within an area at one time

What are four main abiotic factors and how are they measured?

Light intensity (lux), temperature (degrees), moisture levels (percentage), and soil pH (no units).

What is the concept of interdependence?

Organisms in an ecosystem relying on one another.

What are the three ecological relationships and what do they involve?

Predation: Relationship between a prey and a predator.

Mutualism: Both organisms benefit, e.g. fish that clean shark teeth.

Parasitism: Only one organism benefits, e.g. humans and mosquitoes.

What do we use to display the feeding relationships between the organisms?

Trophic levels.

How do producers get their energy?

From the sun.

Why are food webs a more accurate representation of connections between organisms?

Because most organisms rely on more than one food source.

How could the removal of an apex predator affect a population?

Organisms on the trophic level below would thrive, meaning the organisms on the trophic level below them would suffer from an increased amount of predation.

What is a pyramid of numbers?

Shows how many animals are at each trophic level of a food chain

What is a pyramid of biomass?

Shows how much mass the organisms at each level would have.

Define biomass.

Organic material from an organism used as an energy source.

Why is a pyramid of biomass always triangular?

Because the mass always decreases as you go up the trophic levels.

Note: This is why food chains are not more than five trophic levels long.

Where is the lost biomass transferred to?

The atmosphere.

How do animals release biomass?

Excretion (urine and faeces).

What is the calculation for efficiency of biomass?

(Biomass in higher trophic level / biomass in lower trophic level) × 100