Ecosystems (1)

What are the levels of organisation in an ecosystem?

-Individual

-Population

-Community

-Ecosystem

Define population

All organisms of the same species living together in a habitat

Define community

All of the populations of different species living together in a habitat

Define ecosystem

The community of organisms and non-living components of an area and their interactions

What does 'interdependent' mean?

-Organisms are dependent upon each other

-A change in the population of one species can affect other populations within a community

Give examples of interdependence in a community

-Plants depend on pollinators (e.g. bees)

-Herbivores depend on plants

-Animals depend on mates

Describe mutualism

Interaction between two organisms where both benefit

Describe parasitism

Interaction between two organisms where only the parasite benefits, the host does not

What are abiotic factors? Give examples

-Non-living aspects of an ecosystem

-e.g. temperature, water availability, light intensity, pollutants

How are communities affected by environmental conditions?

-Environmental conditions affect abundance and distribution of organisms

-e.g. light intensity affects rate of photosynthesis in producers, which provide food and shelter for other organisms

How are communities affected by pollutants?

-Toxic chemicals (e.g. pesticides) bioaccumulate in food chains, killing tertiary and quaternary consumers

-Fertilisers contaminating water cause eutrophication, killing multiple populations -Air pollution affects the ability of some plant species to survive

What are biotic factors? Give examples

-Living components of an ecosystem

-e.g. competition, predation

How does competition affect communities?

-Competitors affect population distribution and size

-If one species is better adapted, it outcompetes others, causing their populations to decline

How does predation affect communities?

-Predation affects prey populations

-e.g. if predators decrease, prey increase as fewer are killed

-Populations of all other organisms in the food chain are also affected

What apparatus measures abundance and distribution of organisms?

Quadrat

What apparatus studies distribution of organisms across a gradient?

Belt transect

What does a food chain show? (biology only)

It describes feeding relationships between organisms and the resultant stages of biomass transfer

Define biomass (biology only)

The total mass of living material

What are trophic levels? (biology only)

The stages in a food chain

What do arrows in a food chain represent? (biology only)

The direction of biomass transfer

Describe a simple food chain (biology only)

Producer → primary consumer → secondary consumer → tertiary consumer

Why are producers the first trophic level? (biology only)

-Producers provide all biomass for the food chain (via photosynthesis) -The rest of the food chain involves the transfer of this biomass

What does a pyramid of biomass represent? (biology only)

The dry mass of living material at each trophic level of a food chain

Why is a pyramid of biomass almost always pyramid-shaped? (biology only)

-Producers have the greatest biomass so have the longest bar

-As you move up the pyramid, biomass is lost so the bars decrease in length

Why is biomass lost between each trophic level? (biology only)

-Glucose is used for respiration in plants

-Respiration generates heat energy, energy for movement etc.

-Some parts of organisms are indigestible -Egestion, excretion

Why are there rarely more than four or five trophic levels? (biology only)

Above this, there is insufficient energy to support another breeding population

What is the equation for calculating the efficiency of biomass transfer between trophic levels? (biology only)

Efficiency = (biomass transferred to next level ÷ biomass available at previous level) × 100