biology4alevel600

19.1 Principles of genetic technology 19.2 Genetic technology applied to medicine 19.3 Genetically modified organisms in agriculture The discovery of the structure of DNA by Watson and Crick in the early 1950s and discoveries since have led to many applications of gene technology in areas of medicine, agriculture and forensic science. This section relies heavily on prior knowledge of DNA structure and protein synthesis studied in the section on Nucleic acids and protein synthesis. Where possible, candidates should carry out practical work using electrophoresis, either with DNA or specially prepared dyes used to represent DNA or proteins.  Candidates will be expected to use the knowledge gained in this section to solve problems in familiar and unfamiliar contexts. Learning outcomes  Candidates should be able to: 19.1 Principles of genetic technology  Genetic engineering involves the manipulation of naturally occurring processes and enzymes.  Genome sequencing gives in...

18.1 Biodiversity 18.2 Classification 18.3 Conservation The biodiversity of the Earth is threatened by human activities and climate change. Classification systems attempt to put order on the chaos of all the organisms that exist on Earth. Field work is an important part of a biological education to appreciate this diversity and find out how to analyse it. There are opportunities in this section for candidates to observe different species in their locality and assess species distribution and abundance. Conserving biodiversity is a difficult task but is achieved by individuals, local groups, national and international organisations. Candidates should appreciate the threats to biodiversity and consider the steps taken in conservation, both locally and globally.  Candidates will be expected to use the knowledge gained in this section to solve problems in familiar and unfamiliar contexts. Learning outcomes  Candidates should be able to: 18.1 Biodiversity Biodiversity is much more t...

17.1 Variation 17.2 Natural and artificial selection 17.3 Evolution Charles Darwin and Alfred Russel Wallace proposed a theory of natural selection to account for the evolution of species in 1858. A year later, Darwin published On the Origin of Species providing evidence for the way in which aspects of the environment act as agents of selection and determine which variants survive and which do not. The individuals best adapted to the prevailing conditions succeed in the ‘struggle for existence’.  Candidates will be expected to use the knowledge gained in this section to solve problems in familiar and unfamiliar contexts. Learning outcomes  Candidates should be able to: 17.1 Variation The variation that exists within a species is categorised as continuous and discontinuous. The environment has considerable influence on the expression of features that show continuous (or quantitative) variation. a) describe the differences between continuous and discontinuous variation and expla...

15.1  Control and co-ordination in mammals 15.2  Control and co-ordination in plants All the activities  of multicellular organisms require  co-ordinating, some very rapidly and some more slowly. The nervous system and the endocrine system provide co-ordination in mammals. Similar co-ordination systems exist in plants. Candidates will be expected to use  the knowledge gained  in this section to solve problems in familiar and unfamiliar contexts. Learning outcomes Candidates should  be able to: 15.1  Control and co-ordination in mammals The nervous system provides fast communication between receptors and effectors. Transmission between neurones takes place at synapses. a)   compare the nervous and endocrine systems as communication systems that  co-ordinate responses to changes in the internal and external environment (see  14.1a and 14.1b) b)   describe the structure of a sensory neurone and a motor neurone c)   outline ...

14.1  Homeostasis in mammals 14.2  Homeostasis in plants Cells function  most efficiently if they  are kept  in near  constant conditions. Cells in multicellular animals are surrounded by tissue fluid. The composition, pH and temperature of tissue fluid are kept  constant by exchanges with the blood as discussed in the section on Transport in mammals. In mammals, core  temperature, blood glucose concentration and blood water potential are maintained within narrow  limits to ensure the efficient  operation of cells. Prior knowledge for this section includes an understanding  that  waste products are excreted from the body – a role that  is fulfilled by the kidneys  – and an outline of the structure and function  of the nervous and endocrine systems. In plants,  guard cells respond to fluctuations in environmental conditions and open  and close  stomata as appropriate for photosynthesis and conservin...

13.1   Photosynthesis as an energy transfer process 13.2  Investigation of limiting factors 13.3  Adaptations for photosynthesis Photosynthesis is the energy transfer process that  is the basis  of much  of life on Earth. It provides the basis  of most food chains  providing energy directly or indirectly for all other  organisms. In eukaryotes, the process occurs within chloroplasts. Candidates use  their knowledge of plant cells and leaf structure from the section on Cell structure while studying photosynthesis. Various environmental factors influence the rate  at which photosynthesis occurs. Candidates will be expected to use  the knowledge gained  in this section to solve problems in familiar and unfamiliar contexts. Learning outcomes Candidates should  be able to: 13.1  Photosynthesis as an energy transfer process Light energy absorbed by chloroplast pigments in the light dependent stage of photosynthesis is ...

12.1  Energy 12.2  Respiration Energy is a fundamental concept in biology. All living things  require  a source of cellular energy to drive their various activities. ATP is the universal  energy currency as its molecules are small, soluble  and easily hydrolysed to release energy for cellular activities. All organisms respire to release energy from energy- rich molecules such  as glucose and fatty acids  and transfer that  energy to ATP. Respiration is a series  of enzyme-catalysed reactions that  release energy in small ‘packets’. In eukaryotes, aerobic  respiration occurs in mitochondria. Learning outcomes Candidates should  be able to: 12.1  Energy ATP is the universal  energy currency as it provides the immediate source of energy for cellular processes. a)   outline  the need for energy in living organisms, as illustrated by anabolic reactions, such  as DNA replication  and protein synthes...

• Levels of ecological organisation • Energy flow through ecosystems • Recycling of nitrogen Learning Outcomes Candidates should be able to: (a) define the terms habitat, niche, population, community and ecosystem and be able to recognise examples of each ; (b) explain the terms autotroph, heterotroph, producer, consumer and trophic level in the context of food chains and food webs ; (c) explain how energy losses occur along food chains and discuss the efficiency of energy transfer between trophic levels; (d) describe how nitrogen is cycled within an ecosystem, including the roles of nitrogen-fixing bacteria (e.g. Rhizobium) and nitrifying bacteria (Nitrosomonas and Nitrobacter); (e) use the knowledge gained in this section in new situations or to solve related problems. Note: An ecosystem should be studied in relation to an area familiar to the candidates.

11.1  The immune system 11.2  Antibodies and vaccination An understanding of the immune system shows how cells and molecules function  together to protect the body against infectious diseases and how the body is protected from further  infection  by the same pathogen. Phagocytosis is a more  immediate non-specific part of the immune system, while the actions of lymphocytes provide effective defence against specific  pathogens. Learning outcomes Candidates should  be able to: 11.1  The immune system The immune system has non-specific and specific responses to pathogens. Auto-immune diseases are the result  of failures in the system to distinguish between self and non-self. a)   state that  phagocytes (macrophages and neutrophils) have their origin in bone  marrow and describe their mode of action b)   describe the modes of action of B-lymphocytes and  T-lymphocytes c)   describe and explain the significance o...

• The immune system • Vaccination Candidates should be able to: (a) [PA] recognise phagocytes and lymphocytes under the light microscope; (b) state the origin and describe the mode of action of phagocytes (macrophages and neutrophils); (c) describe the modes of action of B-lymphocytes and T-lymphocytes; (d) explain the meaning of the term immune response, making reference to the terms antigen, self and  non-self; (e) explain the role of memory cells in long-term immunity; (f) relate the molecular structure of antibodies to their functions; (g) distinguish between active and passive, natural and artificial immunity and explain how vaccination can  control disease ; (h) discuss the reasons why vaccination programmes have eradicated smallpox but not measles, tuberculosis (TB), malaria or cholera;

10.1  Infectious diseases 10.2  Antibiotics The infectious diseases studied in this section are caused by pathogens that  are transmitted from one human host  to another. Some, like Plasmodium that  causes malaria, are transmitted by vectors; others are transmitted through water and food or during sexual  activity. An understanding of the biology of  the pathogen and its mode of transmission is essential if the disease is to be controlled and ultimately prevented. Learning outcomes Candidates should  be able to: 10.1  Infectious diseases While many  infectious diseases have been successfully controlled in  some parts  of the world, many people worldwide are still at risk of these diseases. a)   define  the term  disease and explain the difference between an infectious disease and a non-infectious disease (limited to sickle cell anaemia and lung cancer) b)   state the name and type  of causative organism...

• Cholera, malaria, tuberculosis (TB), HIV/AIDS, smallpox and measles • Antibiotics Learning Outcomes Candidates should be able to: (a) define the term disease and explain the difference between an infectious disease and non-infectious diseases; (b) state names and types of causative organism of each of the following diseases: cholera, malaria, TB, HIV/AIDS, smallpox and measles (detailed knowledge of structure is not required. For smallpox (Variola) and measles (Morbillivirus) names of genus only is needed); (c) explain how cholera, measles, malaria, TB and HIV/AIDS are transmitted; (d) discuss the factors that need to be considered in the prevention and control of cholera, measles, malaria, TB and HIV/AIDS (a detailed study of the life cycle of the malarial parasite is not required) (an appreciation of social and biological factors and how economic factors can affect these should be included); (e) discuss the factors that influence the global patterns of distribution of malaria, TB a...

9.1    The gas exchange system 9.2    Smoking The gas exchange system is responsible for the uptake of oxygen  into the blood and excreting carbon dioxide. An understanding of this system shows how cells, tissues and organs function  together to exchange these gases between the blood and the environment. The health  of this system and of the cardiovascular system is put at risk by smoking. Learning outcomes Candidates should  be able to: 9.1    The gas exchange system The gas exchange surface in the lungs is extensive, very thin, well supplied with blood and well ventilated. The trachea and bronchi  provide little resistance to the movement of air to and from the alveoli. a)   describe the gross structure of the human gas exchange system b)   observe and draw plan diagrams of the structure of the walls of the trachea, bronchi,  bronchioles and alveoli indicating  the distribution of cartilage,  ciliated epit...

• The gas exchange system • Smoking and smoking-related diseases Learning Outcomes Candidates should be able to: (a) [PA] describe the structure of the human gas exchange system, including the microscopic structure of  the walls of the trachea, bronchioles and alveoli with their associated blood vessels; (b) [PA] describe the distribution of cartilage, ciliated epithelium, goblet cells and smooth muscle in the  trachea, bronchi and bronchioles; (c) describe the functions of cartilage, cilia, goblet cells, mucous glands, smooth muscle and elastic fibres in  the gas exchange system; (d) describe the process of gas exchange between air in the alveoli and the blood; (e) describe the effects of tar and carcinogens in tobacco smoke on the gas exchange system; (f) describe the signs and symptoms that enable diagnosis of lung cancer and chronic obstructive pulmonary disease (COPD) (emphysema and chronic bronchitis); (g) describe the effects of nicotine and carbon monoxide on the ...

8.1    The circulatory system 8.2    The heart As animals  become larger, more  complex and more  active,  transport systems become essential to supply nutrients to, and remove waste from, individual cells. Mammals are far more  active than  plants  and  require  much  greater supplies of oxygen.  This is transported by haemoglobin inside red blood cells. Candidates will be expected to use  the knowledge gained  in this section to solve problems in familiar and  unfamiliar contexts. Learning outcomes Candidates should  be able to: 8.1    The circulatory system The mammalian circulatory system consists of a pump, many  blood vessels and blood, which is a suspension of red blood cells and white  blood cells in plasma. a)   state that  the mammalian circulatory system is a closed double circulation consisting of a heart,  blood vessels and blood b)   observ...

• The need for, and functioning of, a transport system in mammals • Structure and functioning of the mammalian heart Learning Outcomes Candidates should be able to: (m) [PA] describe the structures of arteries, veins and capillaries and be able to recognise these vessels  using the light microscope; (n) explain the relationship between the structure and function of arteries, veins and capillaries; (o) [PA] describe the structure of red blood cells, phagocytes (macrophages and neutrophils) and lymphocytes; (p) state and explain the differences between blood, tissue fluid and lymph; (q) describe the role of haemoglobin in carrying oxygen and carbon dioxide (including the role of carbonic  anhydrase, the formation of haemoglobinic acid and carbaminohaemoglobin); (r) describe and explain the significance of the oxygen dissociation curves of adult oxyhaemoglobin at  different carbon dioxide concentrations (the Bohr effect); (s) describe and explain the significance of the incr...

7.1    Structure of transport tissues 7.2    Transport mechanisms Flowering  plants do not have compact bodies like those of animals. Leaves and extensive root systems spread out to obtain  the light energy, water, mineral ions and carbon  dioxide that  plants gain from their environment to make organic molecules, such as sugars and amino  acids. Transport systems in plants move  substances from where they  are absorbed or produced to where they  are stored or used. Plants  do not have systems for transporting oxygen  and carbon  dioxide; instead these gases diffuse  through air spaces within stems, roots  and leaves. Learning Outcomes Candidates should  be able to: 7.1    Structure of transport tissues Plants  have two transport tissues: xylem and phloem. a)   draw and label from prepared slides  plan diagrams of transverse sections of stems, roots  and leaves of herb...

• The need for, and functioning of, a transport system in multicellular plants Learning Outcomes Candidates should be able to: (a) explain the need for transport systems in multicellular plants and animals in terms of size and surface  area to volume ratios; (b) define the term transpiration (see section 5) and explain that it is an inevitable consequence of gas exchange in plants; (c) [PA] describe how to investigate experimentally the factors that affect transpiration rate; (d) [PA] describe the distribution of xylem and phloem tissue in roots, stems and leaves of dicotyledonous  plants; (e) [PA] describe the structure of xylem vessel elements, phloem sieve tube elements and companion cells  and be able to recognise these using the light microscope; (f) relate the structure of xylem vessel elements, phloem sieve tube elements and companion cells to their  functions; (g) explain the movement of water between plant cells, and between them and their environment, in te...

6.1 Structure and replication of  DNA 6.2 Protein synthesis  Nucleic acids have roles in the storage and retrieval of genetic information and in the use of this information to synthesise polypeptides. DNA is an extremely stable molecule that cells replicate with extreme accuracy. The genetic code is used by cells for assembling amino acids in correct sequences to  make polypeptides. In eukaryotes this involves the processes of transcription in the nucleus to produce  short-lived molecules of messenger RNA followed by translation in the cytoplasm. Learning Outcomes Candidates should  be able to: 6.1 Structure and replication of  DNA Understanding the structure  of nucleic acids allows an  understanding of their role  in the storage of genetic  information and how that  information is used in the  synthesis of proteins. a) describe the structure of nucleotides, including the  phosphorylated nucleotide ATP (structural formula...

• Structure and replication of DNA • Role of DNA in protein synthesis Learning Outcomes Candidates should be able to: (a) describe the structure of RNA and DNA and explain the importance of base pairing and the different  hydrogen bonding between bases (includes reference to adenine and guanine as purines and to  cytosine, thymine and uracil as pyrimidines. Structural formulae for bases is not required but the recognition that purines have a double ring structure and pyrimidines have a single ring structure should  be included); (b) explain how DNA replicates semi-conservatively during interphase; (c) state that a polypeptide is coded for by a gene and that a gene is a sequence of nucleotides that forms  part of a DNA molecue and state that a mutation is a change in the sequence that may result in an  altered polypeptide; (d) describe the way in which the nucleotide sequence codes for the amino acid sequence in a polypeptide  with reference to the nucleotid...