I thought the essay was really good but as someone said earlier the paragraphing could have been more clear. I've done an improved version if anyone would like to use it for revision purposes:The biological approach attempts to explain all behaviour through biology, particularly focusing on genetics, neurochemistry and hormonal changes as well as how evolution may have shaped human behaviour. Firstly genes carry the instructions for the development of characteristics like intelligence, temperament and height. One key assumption is everything psychological is at first biological, this means it focuses on how genetics has influenced our behaviour by looking specifically at the genotype and phenotype. Genotype is a person’s genetic make-up, where as Phenotype is the way our genes are expressed through physical, behavioural and psychological characteristics. However the difference is that the expression of genotype (phenotype) is influenced by environmental factors. For example PKU is a rare genetic disorder that can be prevented by a restricted diet, suggesting that human behaviour depends on the interaction of nature and nurture. Another key assumption is that behaviour has a genetic and neurochemical basis. The genetic basis of behaviour has focused on trying to identify how much behaviour is influenced by genes and how much is influenced by the environment, the use of twin studies helped further investigation in this. Identical and non-identical twins have been used in research to clarify heritability and variation of traits within a population. For example, MZ twins (monozygotic) have exactly the same DNA (100%) and so have a higher likelihood of sharing behaviours and disorders. Whereas, with DZ twins (dizygotic), there is a lower likelihood of sharing behaviour and disorders because they don’t share the same DNA (approx only 50%). Moreover, Nestadt et al in 2010 compared that 68% of MZ twins both have OCD compared with only 31% of DZ twins. The biological structures of the brain consist of the CNS and PNS, both of which influence behaviour. The CNS comprises of the brain and spinal cord and these send messages to and from the environment. The PNS consists of the somatic and autonomic nervous system and sends and receives information to and from the CNS. Neurochemistry and its behaviour focus on hormones and neurotransmitters. Hormones are chemicals which are produced by the endocrine systems like the pituitary gland. Hormones stimulate receptors on the surface or inside cells. Their presence causes physiological reactions. Neurotransmitters are chemicals which are released when nerve impulses reach the end of a neuron. Dopamine and Serotonin are two neurotransmitters psychologists have focused on as they are believed to affect behaviour. For example, low levels of serotonin can lead to increased aggression. Also, high amounts of Dopamine have also been linked to Schizophrenia. Charles Darwin’s natural selection theory is used to explain behaviour from an evolutionary perspective. A random mutation in the genes of an animal due to environmental pressures will lead to a physical characteristic change or behavioural change. This will either increase or decrease their likelihood of survival. Psychologists believe many psychological characteristics like aggression can be explained through evolution. Aggression may have served the purpose of increasing survival and protecting territory. One Strength of the biological approach is that it uses the scientific method like the experimental method as its main form of investigation which gives this approach validity. Studies using this approach take place in highly controlled lab settings which are reliable as they make replication of the same experimental conditions for the verification of results possible. The results gained are also more objective as they are based on biology compared to subjective reporting or observations which also give the biological approach more validity. Another strength of the biological approach is that it can make clearer predictions regarding behaviour and possible links it has to biology. For example, predicting the effects of neurotransmitters on behaviour become easier when looking at those who are genetically related. This has contributed to the development of drug treatments and real world applications. For example, high concordance rates between family members for depression have led to identifying common neurochemical imbalances and then creating drug therapies.This is a strength of the approach because it means that sufferers are able to live a relatively normal life, rather than in a hospital.On the other hand a major weakness of the biological approach is that it’s reductionist. This is because it attempts to break down complicated human behaviour and explain though the smallest part of genetics, neurotransmitters and hormone imbalances. This stops us considering other possible explanations for behaviour which may be contributing such as cognitive and emotional factors. Lastly the approach is also deterministic as human free will is over looked with biological an explanation which is another weakness. This is suggested as it sees human behaviour governed by internal, biological causes over which we have no control. Implying it’s a strong supporter of the nature debate.However the fact that family members are often exposed to similar environmental conditions is an important confounding variable. This can be seen as a problem for the biological approach because findings could be just as easily interpreted assuppporting nurture rather than nature. Implying a methodological problem is the difficulty of sepa