Unit 2: Chapter 2 - Organisms in the Environment

Question 1

Photosynthesis

Answer 1

CO2 + H2O -> GLUCOSE + O2

Chlorophyll within chloroplast absorb light for photosynthesis. The CO2 is then converted to soluble glucose and oxygen.

Some glucose is used up by the plant but some of it is also stored as insoluble starch.

Iodine turns dark blue when reacted with starch.

Question 2

Limiting Factors

Answer 2

Plants have a supply which inhibits growth is called a LIMITING FACTOR. These limiting factors are:

• Light (brighter the light, the faster the rate of photosynthesis)
• Temperature (There has to be a suitable temperature for enzymes to work in. Too high and it will denature. Too low and it doesn’t work efficiently.
• Carbon dioxide (A plant needs a good supply of CO2 but it can only take in so much. It should also be noted that CO2 levels in the atmosphere increase at night as no CO2 is taken in).

Question 3

How Plants use Glucose

Answer 3

Some glucose produced by plants are absorbed straight away. It is transported through the PHLOEM as it is dissolved in water.

Other glucose is stored as insoluble starch. This can be used to make CELLULOSE to strengthen cell walls. They will have no affect on the water balance unlike glucose.

Plants can make AMINO ACIDS by combining sugars with NITRATE ions other MINERAL ions.

Glucose can also be used to make FATS and OILS. This is also an energy store and can be used to strengthen cell walls.

Question 4

Making the Most of Photosynthesis

Answer 4

Perspex greenhouse called ‘polytunnels’ are used for growing a variety of crops. The plastic structure allows the environment to be much more controllable than outside.

Science labs can control factors and change factors one at a time.

Commercial greenhouses control temperature and CO2 as well as light levels to produce the optimum photosynthesis. Nothing slows the growth - this type of system is called HYDROPONICS.

• A bigger yield for the company will produce bigger profits .
• There is also no ploughing or preparing land for these crops.
• These systems can be built where land is poor.

Question 5

Organisms in Their Environment

Answer 5

Factors that affect living organisms are:

• Temperature (Arctic plants will be smaller and so the number of herbivores will decrease)
• Light (Affects distribution of plants and animals. Some plants are adapted to live in low light levels, however most plants need light to survive.

Animals only breed where day length and light intensity suits them).

• Water (All living organisms need water and so this affects the distribution of plants and animals. No water, no life).
• Availability of oxygen and carbon dioxide (This has a major impact of water-living organisms. Plants are more vulnerable to insect attacks where carbon dioxide levels are high. This applies to animal blood too).
• Nutrients (Plants particularly struggle because they need this for protein synthesis.)

Question 6

Measuring the distribution of Organisms

Answer 6

Quadrats is a simple way to sample an area to see the distribution of a particular living organism.

CONTROL VARIABLES

• Same Quadrat
• Random samples of areas (random number generator)

This is a technique known as QUANTITATIVE SAMPLING and can be used to compare living organisms in different habitats.

COUNTING ALONG A TRANSECT LINE

A line transect is most commonly used to see the distribution of living organisms.

Transects are NOT RANDOM but can also be used to measure other physical factors such as pH and light levels.