Life On Earth Flashcards
What is biodiversity?
Total variety of all living things on Earth.
What is a habitat?
The place where a organism lives.
What is a population?
All the members of one species living in a habitat.
What is a community?
All the different organisms living in a habitat.
What is an ecosystem?
All the living organisms in a habitat + the non-living components with which they interact.
What is a producer?
Green plant that makes its own food by photosynthesis.
What is a consumer?
Organism that eats a producer / another consumer for energy.
What is a herbivore?
Organism that eats only plant material.
What is a carnivore?
Organism who only eats animal material.
What is a niche?
The role an organism plays within a community.
What is an omnivore?
Organism that eats both plant and animal material.
What is a predator?
Organism that hunts other animals for its food.
What is a prey?
Organisms hunted by a predator.
What is a species?
A group of organisms that can interbreed to produce fertile offspring.
What is a food chain?
A diagram which shows how energy is passed on from one organism to another in an ecosystem, when they are eaten.
What does a food chain always start with?
Producer
What do the arrows in a food chain represent?
Direction of energy flow
Organise these organisms into a food chain: lion, grass, zebra.
grass → zebra → lion.
What are the three ways that energy is lost from a food chain?
Heat, movement, undigested material.
Refer to this food chain:
zoo plankton → animal plankton → clownfish → shark.
What will happen to the number of clownfish and zooplankton if the shark becomes vegetarian?
Clownfish: Increase because they are not being eaten by sharks anymore.
Zooplankton: decrease because they are eaten by sharks.
What is a pyramid of numbers?
Diagram that represents the number of organisms at each stage.
What is a pyramid of energy?
Represents the energy available at each stage of a food chain. As energy is lost at each stage, it is always a pyramid shape.
When will competition between organisms occur?
When they require the same resources but they are in short supply.
What might animals compete for?
Food, water, shelter, mates
What might plants compete for?
Light, water, soil nutrients, root space.
What are the two types of competition?
Intraspecific and interspecific
Give an example of intraspecific competition?
Polar bears fighting for one prey animal.
Give an example of Interspecific competition.
Rabbits and cats fighting for shelter.
What type of competition is more intense?
Intraspecific, because it is for all resources required.
What are the two types of factors that affect biodiversity?
Abiotic, biotic
What are abiotic factors?
Non-living factors
What are biotic factors?
Factors directly related to living organisms.
Describe how soil pH can be measured
Insert the probe of a pH meter into the soil and take a reading
What are examples of biotic factors?
Predation, competition, food availability, disease, grazing
Describe how light intensity can be measured
Direct the solar panel of a light meter towards the light source being measured and take a reading
What are examples of abiotic factors?
Temperature, pH, moisture, light intensity.
Describe how temperature can be measured
Insert a thermometer into the soil and take a reading
How can predation affect biodiversity?
Affects the numbers of population of prey and predators. The two will have a delicate balance.
Describe how the moisture level can be measured
Insert the probe of a moisture meter into the soil and take a reading
How can disease affect biodiversity?
Could remove whole species from food webs.
What are quadrats?
Quadrats mark off an exact area of ground so that the organisms in that area can be identified and counted.
What sources of error occur when measuring soil pH and how can they be minimised?
- Reading may be contaminated from a previous measurement
- Wipe the probe clean between each use
What sources of error occur when measuring light intensity and how can they be minimised?
- Sensor could be blocked
- Stand to the side of the meter when taking a reading
What are some sources of error regarding quadrats and how can you minimise them?
Sources of error:
- Non-random sampling
- Sample size too small
How to minimise:
- Throw quadrat at random
- Throw many quadrats
What are transects?
A line across a habitat or part of it. It can be a string or a rope placed on the ground. The number of organisms can be observed and recorded along the transect.
What sources of error occur when measuring soil moisture and how can they be minimised?
- Reading may be contaminated from a previous measurement
- Wipe the probe clean and dry between each use
What sources of error occur when measuring temperature and how can they be minimised?
- Reading may be inaccurate
- Leave it for some time to adjust before taking a reading
- Or you insert the probe to the same depth each time
What is the word equation for photosynthesis?
carbon dioxide + water (light energy + chlorophyll) → oxygen + glucose
Where does photosynthesis take place?
Chloroplasts
What is chlorophyll?
A chemical found in the chloroplasts of plant cells.
What method can be used to represent the population of organisms in an ecosystem?
A sample
What is the function of chlorophyll?
To absorb light energy and convert it to chemical energy in ATP.
What are the two stages of photosynthesis?
Light reactions and carbon fixation
What would you use to sample small, invertebrate animals?
Pitfall traps
What happens in the light reactions stage?
The light energy absorbed by chlorophyll is converted into chemical energy. Some of this energy used to split water into hydrogen and oxygen. Some of the chemical energy is used to make ATP from ADP + Pi. The oxygen is a by product which is released from the leaf by diffusion. The hydrogen is carried forward to carbon fixation.
What is carbon fixation controlled by?
Enzymes.
Give some sources of error of pitfall traps, its problems associated with them and how to fix them.
- Trap not level with soil surface, organisms don’t fall in**, make sure trap is level with soil so insects fall in
- Too many fall into the trap because it was left for too long, organisms eat each other, don’t leave trap for too long
- Trap not camouflaged, predation occurs, camouflage the trap
- No drainage holes, trap floods and organisms lost, make drainage holes small enough but not too big so organisms don’t fall out
What happens in carbon fixation?
The ATP and hydrogen produced during the light reactions are used. The energy from ATP allows hydrogen to join with the gas carbon dioxide to form sugar.
What are the 3 limiting factors of photosynthesis
- Light intensity
- Temperature
- Carbon dioxide concentration
The sugar produced contains chemical energy. What is the sugar used for?
Respiration, converted to starch for storage, converted to cellulose to build up the cell wall.
Why is temperature a limiting factor?
Because photosynthesis is an enzyme-controlled reaction
How can you measure the rate of photosynthesis?
Measure the number of oxygen bubbles per minute
How can you determine limiting factors on a graph?
- When the line is diagonal, then the limiting factor is the one on the x-axis.
- When the line is horizontal, then the limiting factor one that’s not the one being measured.
What are some farming techniques that have been used to increase food production?
Fertilisers and pesticides.
How do plants obtain nitrogen?
In the form of nitrates which are dissolved in soil water and absorbed by roots
What are nitrates used to produce?
Amino acids, which are synthesised into proteins.
What is biological control?
Biological control involves using animals that are natural predators to keep numbers of pests down
Where is biological control useful?
In areas where pests have been introduced to a habitat where there are no natural predators
What are genetically modified crops?
This involves taking a useful gene from one organism and inserting it into another.
What is the benefit of using genetically modified crops?
GM crops can metabolise nitrogen more effectively, reducing the need for fertilisers and increasing yields
What is an indicator species?
Species whose presence/absence can show the conditions of an environment
What is a mutation?
A mutation is a random change to genetic material. Mutations are spontaneous and the only source of new alleles
What are types of mutations?
- Neutral
- Advantageous
- Disadvantageous
Describe how an algal bloom forms and its effects.
Fertilisers that are sprayed onto crops can leach into freshwater, adding unwanted nitrates.
Fertiliser greatly increases growth of algae, causing algal bloom after which, the algae die.
Algal blooms reduce light levels, meaning that plants can’t photosynthesise and die.
Dead plants and dead algae become food for bacteria which greatly increase in number.
Bacteria use large quantities of oxygen, so there is less oxygen for other organisms in freshwater, causing them to die.
What are pesticides used for?
Killing a range of pests that reduce crop yield.
What is an unintended effect of pesticides?
Pesticides aren’t biodegradable so they have to be broken down by the organism that ingests them.
The toxicity levels of this increase as you go up the food chain because organisms become larger and eat more from the level below.
What is bioaccumulation?
The build up of toxic substances in living organisms.
What do new alleles produced by mutation allow plants and animals to do?
Adapt to changing environmental conditions
What is an adaptation?
An inherited characteristic that makes an organism well suited to be able to survive its environment
What is natural selection?
A process where organisms are better adapted to their environment survive and reproduce, passing on their favourable alleles.
Those organisms less well-adapted die before they reproduce
How does natural selection occur?
When there are selection pressures such as:
- Temperature: some might be better adapted to colder temperatures
- Predators: some organisms might be better adapted to camouflage and avoid predators
Describe the process of natural selection.
Species produce more offspring than the environment can sustain.
Variation then exists between members of a species.
The best adapted survive
Those who survive reproduce passing on their favourable alleles that give a selective advantage
This happens over many generations and these alleles increase in frequency within the population.
Define speciation.
The evolution of new species from a pre existing one.
Under what condition will speciation occur?
When sub-populations become isolated from each other and so can’t interbreed.
What are some example of isolating barriers between sub-populations?
- Geographical: mountains, rivers, forests.
- Ecological: temperature, pH
- Behavioural: courtship mechanisms, breeding times.
Describe each stage of speciation.
New sub-populations are created by creating an isolation barrier.
New mutations occur through each sub-population breeding with their own, causing new variation.
Natural selection occurs, choosing favourable alleles that are advantageous to each sub-population.
Each sub-population continues to breed until they become so genetically different that they can’t interbreed to create fertile offspring.
You now have two separate species.
