Biology GCSE key questions and answers

Acid Rain:

How do humans affect the environment?

More waste is being produced which unless properly handled may pollute air with smoke and gases, such as sulfur dioxide, which contribute to acid rain. 

Steps for the investigation:

1. A simple method would involve the use of seeds such as cress. These should be germinated in Petri dishes on filter paper dampened with weak acidic buffered solutions.
2. Determine how many seeds have germinated after a suitable time interval.  
3. Investigate at least three pH values of acidic solutions, along with a solution at pH7.
4. Measure measure the pH of each solution they use. 
5. Before carrying out the investigation determine a suitable range of buffers to use along with a suitable time interval between setting up the dishes and collecting results.

Osmosis:

How do dissolved substances get into and out of cells?

Water often moves across boundaries by osmosis. Osmosis is the diffusion of water from a dilute to a more concentrated solution through a partially permeable membrane that allows the passage of water molecules. Differences in the concentrations of the solutions inside and outside a cell cause water to move into or out of the cell by osmosis.

Steps to carry out an investigation concerning the effect on the mass of pieces of plant material when the concentration of sucrose solution in which they are immersed is changed.  

1. Immerse weighed pieces of potato tuber in sucrose solutions of varying concentration, including pure water.
2. After a minimum of half an hour carefully remove and surface-dry the potato pieces before reweighing.
3. Use at least three different sucrose solution concentrations, along with pure water. It is not necessary to calculate percentage change of mass. Determine a suitable range of concentrations to use before you carry out their investigation. 
   

    Fatique:

How does exercise affect the exchanges taking place within the body?

 If muscles are subjected to long periods of vigorous activity they become fatigued, ie they stop contracting efficiently.

A simple method of investigation

Use clasping and unclasping the hand at the rate of two times per second until: it begins to hurt a little or a lot or the rate falls or it becomes too painful to continue.

Collect data from at least six different people and might, for example, compare left
and right hands, gender or athletic build.
 
Alternatively, measure the time for which different people can hold the same
masses at arm’s length: in which case, collect results from a minimum of six people to allow comparison of left and right hand, gender or athletic build.
 
Or, measure the time for which different masses can be held at arm’s length by the
same person: in which case, use a minimum of four different masses.