B 2.2 Organisms in the enviorment

• Carbon dioxide is taken in by the leaves, and water is taken up by the roots 
• the chlotophyll traps the light energy needed for photosynthesis. 
• this energy is used to convert the carbon dioxide and water into glucose  (a sugar)
• oxygen is released as a by peoduct of photosynthesis.
• Some of the glucose is converted into soluble starch for storage
• Testing leaves for iodine we can test for starch on a leaf and show that photosynthesis has occured.

A lack of light would slow down thr tate of photosunthesos as light provides the energy for the process.

If it is cold, then enzymes do not work effectively and this will slow down the rate of photosynthesis.

If there is too little Carbon dioxide, then the rate of photosynthesis will slow down. Carbon dioxide may be limited in an enclosed space e.g. in a green house on a sunny day where there is plenty of light energy availible but the plants run out of carbon dioxide.

The uses of soluble glucose

the glucose produced by photosynthesis may be:

• converted into insoluble starch for storage
• used for respiration
• converted into fats and oils for storage 
• used to prosuce cellulose which strengthens cell walls
• used to produce proteins

plant and algal cells also heed a supply of mineral ions such as nitrate ions in nitrate ions from thr water they live in

Living organisms form communities. ot is important to umderstand thr relationships within anf between these communities. these relationships can be influenced by external factors. physical factors that may affect the distribution of organisms are:

• temperature - for example, arctic plants are small which limits the number of plant eaters which can survive in the area.
• availability of nutrients -  most plants struggle to grow when mineral uons are in short supply and again few animals will survive in that area
• amount of light - few plants live on a forest floor because the light is blocked out by the trees. shaded plants often have broader leaves or more chlotophyll.
• availability of water - water is important for all organisms so few will live in a deser. if it rains in the desert then plants grow, produce flowers and seeds very quickly then there will be food for animlas
• Availibility of oxygen - water animlas can be affected by lack of oxygen. Some invertebrates can live on low levels of oxygen, but most fish need high levels of oxygen disolved in water.
• Availability of carbon dioxide -  lack of carbon dioxide will affect the plant growth and consequently the food available for animals