Ecological Concepts
What is the natural place where an organism lives called?
Habitat
What does a food chain show?
A single feeding pathway through which energy is transferred.
Which organisms capture sunlight to make food?
Producers, such as green plants.
Name the three biological pyramids.
Pyramids of numbers, biomass and energy.
Give one limitation of a pyramid of numbers.
It ignores the size of organisms
It can be misleading
Difficult to count organisms accurately
Define an ecosystem
A community of organisms interacting with one another and their non-living environment.
What is a food web?
A network of interconnected food chains.
In which direction does energy flow through trophic levels?
From producers to consumers.
What does a pyramid of numbers measure?
The number of individual organisms at each trophic level.
Why might counting organisms produce an inaccurate pyramid?
Organisms may hide, move, be missed or be counted twice.
What is an ecological niche?
The role and position of an organism in its environment.
What do the arrows in a food chain represent?
The direction of energy transfer, from food to consumer.
Give two reasons why energy transfer is inefficient.
Energy is released as heat during respiration, and some energy remains in waste or uneaten material.
What does a pyramid of biomass measure?
The total dry mass of living material at each trophic level.
Why can a pyramid of numbers have an inverted base?
One large producer, such as a tree, may support many insects.
Name two non-living components of an ecosystem.
For example, sunlight and water.
State two advantages of food webs.
They provide alternative food sources and can increase ecosystem stability.
What percentage of energy is transferred if 1,000 kJ reaches grasshoppers from 10,000 kJ in grass?
10%: (1,000 ÷ 10,000) × 100.
Which pyramid is always upright, and why?
Pyramid of energy, because energy decreases at successive trophic levels.
Why can an aquatic pyramid of biomass be inverted?
Phytoplankton reproduce and are consumed rapidly, so their standing biomass can be less than that of zooplankton.
Explain the difference between habitat and ecological niche using a bee.
The habitat is where the bee lives; its niche includes feeding on nectar and pollinating flowers.
Why might a food web be more stable than a single food chain?
Organisms may have alternative food sources if one food source becomes scarce.
Why is energy transfer efficiency not always exactly 10%?
Respiration, feeding, digestion and waste vary among organisms and ecosystems.
Construct an energy pyramid using grass = 10,000, grasshopper = 1,000, frog = 100, snake = 10 kJ m⁻² yr⁻¹.
Base to top: grass (10,000), grasshopper (1,000), frog (100), snake (10), with bars proportional to the values.
State two limitations of a pyramid of energy.
It requires extensive data and is difficult to construct; energy flow also varies with time, location and species.