Ecosystems
What is meant by a species?
A species is a group of organisms whose members can interbreed with one another to produce fertile offspring.
Give two examples of biotic factors.
State the word equation for photosynthesis.
Carbon dioxide + water -> glucose + oxygen
Where are producers found in the pyramid of energy?
Producers are found at the bottom of the pyramid.
Why is increased food production needed worldwide?
An increasing human population requires increased food yeild.
What is meant by biodiversity?
Biodiversity is the variety of life in an area (or across the world), including animals, plants, fungi and micro-organisms.
Name two abiotic factors that can affect organism distribution
Light intensity, temperature, moisture, pH
State two stages of photosynthesis.
Light reactive (light dependent stage) and carbon fixation.
What happens to most energy when it is transferred between trophic levels?
Most energy is lost as heat, movement or undigested material.
What are fertilisers used for in food production?
Fertilisers provide chemicals such as nitrates and increase crop yield.
Explain the difference between a population and a community.
A population is a group of organisms of the same species in the same habitat, while a community consists of all the different populations in an area.
Which sampling technique would be used to study ground invertebrates and why?
Pitfall traps are used because they collect ground-dwelling invertebrates effectively.
Describe what happens during the light reactions of photosynthesis.
Light energy is trapped by chlorophyll; water is split to form hydrogen and oxygen; ATP is produced; oxygen diffuses out of the cell.
Explain why only a small amount of energy is available to the next level of a food chain.
Only a small amount of energy is used for growth; most is lost through heat, movement and waste.
Explain how nitrates from fertilisers enter plants.
Nitrates dissolve in soil water and are absorbed into plants through their roots.
Describe the difference between interspecific and infraspecific competition.
Interspecific competition occurs between different species for one or a few resources. Whilst intraspecific competition occurs within the same species for all required resources.
Describe one source of error when using a quadrant and how it affects results.
Plants growing in clumps may give unrepresentative results because the sample may not reflect the whole area.
Explain what happens during carbon fixation.
Enzyme-controlled reactions use hydrogen and ATP with carbon dioxide to produce glucose.
Explain why pyramids of energy are always a true pyramid.
They state how the energy available at each level, and because energy is lost at each transdermal, less energy is available higher up.
State how plants and animals use nitrates and amino acids differently.
Plants use nitrates to make amino acids and proteins; animals obtain amino acids by eating plants or other animals to make their own proteins.
Describe the effects of removing one organism from a food web.
Removing one organism can cause other populations to increase or decrease, because predators may loose food and prey may increase due to reduced predation, changing energy flow and biodiversity.
Explain why repeated sampling and replication are needed when collecting ecological data.
Repeated sampling increases reliability and ensures results are representative of the area studied.
Explain why increasing light intensity will not increase the rate of photosynthesis if temperature is low.
Photosynthesis is controlled by enzyme-controlled reactions, and at Lowe temperatures, enzymes work more slowly; limiting the rate regardless of light intensity.
Explain why pyramids of numbers can be irregular in shape.
They can be irregular in shape because organisms at different trophic levels can have very different body sizes, so fewer organisms may support many smaller ones (or vice versa).
Explain how fertiliser runoff can reduce biodiversity in aquatic ecosystems.
Extra nitrates cause algal blooms; light levels drop and aquatic plants die; bacteria decompose dead material and use oxygen; oxygen levels fall and biodiversity decreases (eutrophication).