Biology Edexcel B3 Topics 2 and 3 Notes

B3.11 -- Courtship and parenting:

• "Behaviour" is defined simply as the various ways in which animals respond to external or internal stimuli (without and within their bodies respectively).
• It is essential, for those organisms who reproduce sexually, that whatever mate is chosen is of good reproductive quality; i.e., it is healthy and well-adapted to its environment. Courtship behaviour thus often involves the male putting on elaborate displays in order to display his high quality as a mate to a female. This is why, for example, male birds often tend to be far more brightly coloured than their female counterparts: for a male bird, the bright colouring helps in courtship displays, whereas for a female a less conspicious colour scheme is more advantageous as this makes it easier for her to care for any young without attracting a predator.
• Some animals such as swans mate for life with a singly partner, until they or their partner dies, whilst others, such as robins, pair up with a mate during a "breeding season". Animals in these relationships tend to raise offspring together. On the other hand, in some species (such as deer), groups of females date with one, dominant male: these groups can come together during breeding seasons or can be more permenant in nature. Males in such relationships generally do not play a role in bringing up offspring.
• Many animals look after young until they are sufficently developed to fend for themselves: this is why many birds keep their chicks in a nest, for example. By doing this, the chances that the offspring will survive are increased, and thus the chances that the parents' genes will be passed on is also increased as, if the offspring in question survive to breed, they will pass some of their parent's genes (as they have inherited their own genes from their parents) onto their own offspring.
• An "evolutionary strategy" is a strategy used by animals which affects how a species changes and spreads over time: caring for offspring is an example of such a strategy as, the more offspring survive, the more likely it is that there will be offspring who are healthy and well-adapted to changes in their environment, thus increaseing the probability that the species as a whole will survive and evolve.

B3.12 -- Innate behavior and imprinting:

• Innate behavior is that behavior which is present from birth and which thus does not need to be learnt in any way. Examples of such behaviour include the "startle reflex" in human babies (a baby whose head is let go of will curl its fingers and throw out its arms). A reflex is simply an automatic response to a stimulus. The presence of such innate reflexes increases the chance of an animal surviving, and such reflexes are controlled by genes. Innate behavior pattens by no means have to be as simple as this: the dragonfly nymph, for example, can innately undergo a complicated procedure of crawling out of the water, shedding its skin and then…