Animal Behaviour
- explain the advantages to organisms of innate behaviour
Behaviour – the responses of an organism to its environment, which increase its chances of survival. An organism must be able to detect changes in the environment, which form stimuli, then carry out an appropriate response through the operation of effectors.
Innate Behaviour – animal responses, which does not involve learning. It is an inherited response, similar in all members of the same species and is always performed in the same way in response to the same stimulus.
Advantages of Innate Behaviour:
- describe escape reflexes, taxes and kineses as examples of genetically-determined innate behaviours
- describe, using one example, the advantages of social behaviour in primates
Social Behaviour – behaviour that is learnt from those in the rest of the group with relatively defined roles for each member of the group.
Hierarchy – where individuals have a place in the order of importance within the group.
Mountain gorillas live in stable groups (called a troop) of around 10 individuals. It consists of:
- One dominant silverback male:
- Protects the other members of the group.
- Leads them in search of food.
- Is the only male that mates with the mature females.
- Females:
- Care of the young offspring – during the first 5 months the infant remains in constant contact with the mother, suckling at hourly intervals. By the age of 12 months, infants will venture as far as 5m from the mother.
- Teaches the young the social and other skills necessary to live independently.
- Offspring:
- Play
- Imitate adult behaviour of foraging for food.
- As younger males reach sexual maturity they leave the group to live alone until they are mature enough to attract females.
- As younger females mature they either stay with the same group or leave to join another group.
As with all primates, grooming for gorillas is an important social activity – one individual picks the parasites from the fur of another – reinforcing relationships between individuals. A variety of calls, displays and grants are used to signal danger to other members of the group, to issue threats to predators or other groups, and in play fighting displays as juveniles learn how to behave as adults. Facial expressions are also important in gorillas and other large primates, especially in terms of recognition of other members of the group.
Advantages of Social Behaviour:
- Maternal care and group protection enhances survival rate of the young.
- Learned behaviour increases survival.
- Group security allows the slow maturation of the brain to not impede survival.
- Knowledge and protection of food sources is shared with the group.
- Group works deters predators
- discuss how the links between a range of human behaviours and the dopamine receptor DRD4 may contribute to the understanding of human behaviour
Dopamine – acts as a neurotransmitter and a hormone. It is produced all over the body and controls the ‘pleasure and reward’ centre of our brain. It is a precursor molecule in the production of adrenaline and noradrenaline. Dopamine increases general arousal and decreases inhibition, leading to an increase in creativity in conjunction with cerebral activity.
Low brain levels of dopamine are associated with Parkinson’s disease, the treatment of which involves clinical administration of the dopamine precursor L-dopa, as dopamine cannot cross the blood-brain barrier (capillaries in the brain are ‘less leaky’). However, L-dopa can lead to changes in behaviour including addition, anxiety, hallucinations and sleepiness. High brain levels of dopamine has been linked to the development of mental health conditions such as schizophrenia.
There are five different dopamine receptors referred to as DRD1 to DRD5. Each of these is coded for by a separate gene. The range and variations within number of receptors means that dopamine has different effects on different people. Binding of dopamine to its receptor is involved in a number of processes, including the control of motivation and learning, and is linked to regulatory effects on other neurotransmitter release. A number of antipsychotic drugs work by blocking dopamine receptors.
The DRD4 Receptor Gene:
DRD4 – one of the five genes that code for dopamine receptor molecules.
There are currently over 50 known variants of the DRD4 gene. The variants differ in a specific sequence known as a variable number tandem repeat. This means there are numerous combinations of the genetics controlling the production of the receptor. It is thought that the inheritance of particular variants of the DRD4 gene affects the levels and action of dopamine in the brain, implicating in human behaviour.
Attention-deficit Hyperactivity Disorder (ADHD):
For example, people some combinations of alleles are shown to have a higher risk of becoming ADHD. Drugs such as methylphenidate (Ritalin) used to treat ADHD affect dopamine levels in the brain. In a number of studies, a particular dopamine receptor variant of DRD4, has been shown to be more frequent in individuals suffering from ADHD.
Addictive and Risk Behaviours:
Also, a number of studies have suggested that particular variants of DRD4 receptor gene are implicated in increased likelihood of addictive behaviours, including smoking and gambling. A study into the effects of administering L-dopa to one group of individuals and haloperidol (drug that blocks dopamine receptors) to another group showed not only a difference in general arousal, but also a significant difference in the risk-taking levels of the individuals.
Obsessive-compulsive Disorder (OCD):
OCD is thought to result from a deficiency in the levels of the neurotransmitter serotonin. In 2007, a genome-wide scan for DNA sequences related to OCD was carried out when the DNA from 1008 people from 219 families were analysed. Eight genetic markers that appear to be linked to OCD were found.