Organisms in the environment Flashcards
Photosynthesis can only be carried out by which two organisms?
Green plants and algae
What structure in chloroplasts absorb light energy?
Chlorophyll
Give the word equation for photosynthesis.
Carbon dioxide + water +(light energy) => glucose + oxygen
Give the three main steps in the process of photosynthesis.
1) Carbon dioxide is taken in by the leaves and water up by the roots.
2) The chlorophyll traps the light energy needed for photosynthesis.
3) The light energy is used to convert the carbon dioxide and water into glucose, a sugar.
What is the by-product of photosynthesis?
What is some of the glucose converted to?
Oxygen
Some of the glucose is converted to insoluble starch for storage.
How can we identify starch in a leaf and what does this show?
What is the difference between white and green patches on a variegated leaf?
We can identify starch in a leaf by testing it with iodine solution and this shows that photosynthesis has occurred.
The green patches have chlorophyll and the white patches are without chlorophyll, only green patches will turn the iodine a blue-black colour to show starch is present.
What is a limiting factor?
What are the limiting factors of the process of photosynthesis and explain how they would affect a plant.
Anything which puts a cap on rate of photosynthesis.
1) Light - a lack of light would slow down the rate of photosynthesis as light provides the energy for the process.
2) Temperature - if it is too cold enzymes do not work effectively and this will slow down the rate of photosynthesis.
3) Carbon dioxide - if there is too little carbon dioxide then the rate of photosynthesis would slow down, it may be limited in enclosed spaces such as greenhouses.
What is the independent variable?
What is the dependent variable?
The independent variable is the variable being tested, i.e the one that you change.
The dependent variable is the one you measure.
Give the five main uses of glucose produced by photosynthesis.
1) Converted to insoluble starch for storage.
2) Used for respiration.
3) Converted into fats and oils for storage.
4) Used to produce cellulose which strengthens cell walls.
5) Used to produce proteins.
Why do plant and algal cells need a supply of mineral ions such as nitrate ions?
Where do they obtain nitrate ions from?
In order to produce proteins
Plants absorb nitrate ions from the soil and algae absorb nitrate ions from they water they live in.
What six factors affect the distribution of organisms in their environment? Explain the affect.
1) Temperature - many plants struggle to grow in extreme temperatures.
2) Availability of nutrients - many plants struggle to grow in areas where mineral ions are in short supply, few animals will survive in that area.
3) Availability of light - few plants live in areas with little light such as the forest floor.
4) Availability of water - Water animals can be affected by oxygen levels, fish need high levels of dissolved oxygen.
5) Availability of carbon dioxide - lack of carbon dioxide will affect plant growth and consequently food available for animals.
How can quantitive data about how physical factors affect the distribution of organisms be obtained? (2)
1) Random quantitive sampling using a quadrat.
2) Sampling along a transect.
Why is sample size important?
How are estimates of the number of organisms in a certain area usually quoted?
A big enough sample must be taken to ensure the sample is representative of the whole area being investigated.
As a mean per metre.
How is a transect used? Give the two main steps.
What else could also be measured at each quadrat point?
What is the benefit of this method of sampling?
1) A transect is not random, a line is marked between two points, e.g. from the top of a rocky shore down to the sea.
2) A quadrat can be placed every five metres along the line and the organisms counted.
Physical factors could also be measured at each quadrat point.
It provides a lot of information about the habitat and the organisms in it.
How can a quadrat be used in random sampling?
1) If several quadrats are placed randomly in a field, the number of organisms in each quadrat can be counted.
2) This can then be used to estimate the number of organisms in the whole area.
