Biology AS Level is made up from the following 3 Units:

Unit 3.1

The digestive and gas exchange systems are examples of systems in which humans and other mammals exchange substances with their environment. Substances are transported from one part of the body to another by the blood system. An appreciation of the physiology of these systems requires candidates to understand basic principles including the role of enzymes as biological catalysts, and passive and active transport of substances across biological membranes.

The systems described in this unit, as well as others in the body, may be affected by disease. Some of these diseases, such as cholera and tuberculosis, may be caused by microorganisms. Other noncommunicable diseases such as many of those affecting heart and lung function also have a significant impact on human health. Knowledge of basic physiology allows us not only to explain symptoms but also to interpret data relating to risk factors.

The blood has a number of defensive functions which, together with drugs such as antibiotics, help to limit the spread and effects of disease.

It is anticipated that the smaller size of this unit will allow opportunity for the development of the skills of application and analysis as well as for the acquisition of the investigatory skills associated with Investigative and practical skills detailed in Unit 3.

Unit 3.2

Unit 2 builds on concepts developed in Unit 1.

Although a species may be defined in terms of similarity, there is frequently considerable intraspecific variation and this is influenced by genetic and environmental factors. DNA is an informationcarrying molecule, and similarities and differences in the sequence of bases in DNA result in genetic diversity.

The variety of life is extensive and is reflected in similarities and differences in its biochemical basis and cellular organisation. Factors such as size and metabolic rate affect the requirements of organisms and this gives rise to adaptations such as specialised exchange surfaces and mass transport systems. Classification is a means of organising the variety of life based on relationships between organisms and is built round the concept of a species. Originally, classification systems were based on observable features but more recent approaches draw on a wider range of evidence to clarify relationships between organisms. Variation that exists at the interspecific level contributes to the biodiversity of communities and ecosystems.

It is anticipated that this unit will allow opportunity for further development of the skills of application and analysis as well as for the acquisition of additional investigatory skills associated with Investigative and practical skills, detailed in Unit 3.

Unit 3.3

This unit will address the following aspects of the AS subject criteria. The ability to

• Demonstrate and describe ethical, safe and skilful practical techniques, selecting appropriate qualitative and quantitative methods
• Make, record and communicate reliable and valid observations and measurements with appropriate precision and accuracy
• Analyse, interpret, explain and evaluate the methodology, results and impact of their own and others’ experimental and investigatory activities in a variety of ways.

Candidates will be assessed on their understanding of investigative and practical skills in this unit and in Units 1 and 2. Guidance on Internal Assessment can be found in Section 3.8. Opportunities to carry out practical work are provided in the context of material contained in Units 1 and 2.

The Biology A2 level is made up from the following units:

Unit 3.4

Living organisms form structured communities within dynamic but essentially stable ecosystems through which energy is transferred and chemical elements are cycled. Humans are part of the ecological balance and their activities affect it both directly and indirectly. Consideration of these effects underpins the content of this unit and should lead to an understanding that sustainability of resources depends on effective management of the conflict between human needs and conservation.

It is expected that candidates will carry out fieldwork involving the collection of quantitative data from at least one habitat and will apply elementary statistical analysis to the results.

Unit 3.5

Multicellular organisms are able to control the activities of different tissues and organs within their bodies. They do this by detecting stimuli and stimulating appropriate effectors: plants use specific growth factors; animals use hormones, nerve impulses or a combination of both. By responding to internal and external stimuli, animals increase their chances of survival by avoiding harmful environments and by maintaining optimal conditions for their metabolism.

Cells are also able to control their metabolic activities by regulating the transcription and translation of their genome. Although the cells within an organism carry the same genetic code, they translate only part of it. In multicellular organisms, this control of translation enables cells to have specialised functions, forming tissues and organs. The sequencing and manipulation of DNA has many medical and technological applications.

Consideration of control mechanisms underpins the content of this unit. Students who have studied it should develop an understanding of the ways in which organisms and cells control their activities. This should lead to an appreciation of common ailments resulting from a breakdown of these control mechanisms and the use of DNA technology in the diagnosis and treatment of human diseases.

Unit 3.6

This unit will address the following aspects of the A2 subject criteria. The ability to

• Demonstrate and describe ethical, safe and skilful practical techniques, selecting appropriate
• qualitative and quantitative methods Make, record and communicate reliable and valid observations and measurements with appropriate precision and accuracy
• Analyse, interpret, explain and evaluate the methodology, results and impact of their own and others’ experimental and investigatory activities in a variety of ways.

Candidates will be assessed on their understanding of investigative and practical skills in this unit and in Units 4 and 5. Guidance on Internal Assessment can be found in Section 3.8. Opportunities to carry out practical work are provided in the context of material contained in Units 4 and 5.