This unit dwells on behavioural changes

Behaviour can be defined as a set of activities that orient an animal to its external environment or

Behaviour is what an animal does and how it does it.

The short come of this definition is that the definition includes non-motor components of behaviour (components not related to nervous system).

Includes animal observation action.

Behaviour is apparent interms of observable movement. But may also include internal responses of adaptive nature for example.

A young bird that hears an adult song may show no obvious muscle related activities but the memory of the song is stored in the brain and it is used later.

All behavioural pattern centres around;

  1. Acquiring food.
  2. Seeking a male
  • Caring for the young
  1. Guarding against danger.
  2. And also other tasks vital to life of an individual.

Integral system, muscular, skeletal, endocrine system.

Simple orientation

  1. Taxes (Taxis); a simple kind of behaviour elicited by even unicellular organisms like the protozoa. These will orient an organism to condition in its environment e.g. euglena will normally swim towards light. (Phototactic).
  1. This is closely related to taxis, this involves change in activity rate in response to a stimuli e.g. there can be changes in rate of movement brought about by environmental stimuli; e.g. woodlice in the choice chamber will show active movement in dry areas than wet areas.

The behaviour tends to help these animals to remain in moist environment and it is randomly directed (in other wards; animals will not move towards or a way from specific condition). They will show random movement but slow down in favourable condition

Conclusion. The environment cues will guide the animal’s movement.

The study of behaviour is a new science but it is an old aspect of Biology which was practiced by early man to ensure his survival, e.g. man needed to learn habitats of animals around him to ensure his survivals, e.g. man needed to learn habits of animals around him giving him more chance of securing more food and decreased chances of themselves becoming a meal for animals.

The above chance what is called Darwinian fitness.

The study of behaviour is still more descriptive and less analytical however the trend is changing.

  • Animal will behave in a way that maximizes its fitness.
  • Feeding behaviour maximizes energy gain; choice of a male will maximize number of fertile offsprings.

This is so if genes influence behaviour and genes do exact a strong influence in many behaviour.

Learned behaviour depends on genes that creates a neural system receptive to learning; based on Darwinian fitness. This is sometimes called behaviorual ecology.

Formulating testable hypothesis


  1. Male birds learn more song types as they grow so that repertoire size is a reliable indicator of age.
  2. Females prefer to males with males having large repertoire.

Testing 2nd prediction determines whether females are more sexually stimulated by a large song repertoire than a small song.

Conclusion; may be evolutionary explanation being “Bird song repertoire result in famale’s mating more often with experienced males who will give their offsprings a better chance to survive.

Testable hypothesis helps us explain behaviour of fitness or it can helps find out that repertoire has nothing to do with fitness.

Ultimate and proximate factors (cause of behaviour)

When observing certain behaviour, 2 questions can be asked;

  1. Why the animal has the behaviour i.e. why u think something exists. This refers to ultimate causation and this can be evdutionary questions. The hypothesis proposing that the behaviour maximizes fitness are ultimate.
  2. How the animal carries about the immediate cause of something proximate causation. Your are trying to understand mechanism underlying that particular behaviour.


Proximate causes include the following;

  1. Environmental stimuli, these are responsible for triggering internal process of animal’s internal neuromuscular, enocrine and other physical system to bring about particular behaviour.

Two, ultimate and proximate causation are related. Examples, the blue-gills fish breed in spring and early summer. This is when breeding is more productive and adaptive. During this period, the water are warm so allow growth of the young ones and there is abundant supply of food. Breeding at other times would be a selective disadvantage. In terms of proximative causation, the possible hypothesis is that breeding is triggered by the effect of increased day length on the fish photoreceptions. The blue gill fish can be stimulated to begin breeding by experimentally lengthening their daily exposure to light. The stimulus of light leads to neuro and hormonal changes that will induce nest building and other reproductive behaviour.

Other examples are the pressure derived by some people when some people when they taste sweet foods. Increased likelihood of eating sweet high energy food is a approximate mechanism. The fitness associated with the consumption of the sweet food is ultimate factor for natural selection, because you are a selective advantage.

The digger’s wasp nest locating behaviour, in this case, it uses land marks to locate the position of different nests. The wasp can also other visual cucs which it will use to locate the nest, the proximate cause of wasp’s nest locating behaviour id the environmental sues of the landmarks arrangement the response it elicits in the animal.

The ultimate causation; is that this behaviour enhances the wasps fitness by targeting food to her offspring.

Conclusion; the how and why question about animal behaviour are related to evolutionary basis. Proximate mechanism produce behaviour that ultimately …..because of increased fitness.

Components of behaviour

There are 2 forms of behaviour;

Internal behaviour

  1. Learned behaviour Difference between 2 are not clear out down cut down, because behaviourral response in higher animals contain both.

Innate behaviour, there is a genetic basis for the behaviour. But behaviour also changes as a result of experience.

Interaction with the environment may modify and even elicit specific type of behaviour.

Natural (internal genetical programme) vensus nature (Environmental influence. It suggests as follows:

Behaviour is a result of both innate features of organism and interaction with environment that accumulates during lifetime.

Innate behaviour (Fixed Action Pattern (FAP)

At the start of study of behaviour, Ethiologits concentrated on looking at stimulus that triggers behaviour and the work was pioneered by Konard Lorene and Tinbergen, Karl on Frisch.

One of their major findings was that animals can carry out many behaviours without ever seeing performed.

Conclusion, many behaviours are innately programmed- responses are predetermined by inheritance of specific nerves or cytoplasmic pathways in an organism. Therefore these built in pathways for a given stimulus will always produce the same response. This is Fixed Action Pattern.

Fixed Action Pattern can be defined as a constant response to an eliciting stimulus called a sign stimulus coming from another member of the same species is reffered to as releaser. FAP is innate ability for an animal for detects certain stimulus associated with the animal’s survival.


It has an intensity of inner push, whatever its nature is can be referred to as a drive.

Drive is actually motivation. This motivation springs from a a disturbance in the internal equilibira of an animal. The drive can be modified by factors that can either be internal or environmental.

Sometimes motivation or drive may be referred to as instinct.

Example, an animal which as not eaten for a long period will show a shift in its internal equilibria which will be expressed in the behaviour of food foraging.

The internal equilibria is characterized by decrease in blood sugar. The lowering of blood sugar is the body trigger, the hunger, the drive complex hormonal pathways are involved. If the animal is ill or weak, the drive is less intense. Previous experience may also modulate the intensity of the drive eg a heavy rainstorm may deter us completely from living our homes even though there is a need to look for food.

Female mammals are receptive to mating at certain coincides with the optimum time for fertilization. So that the offsprings are produced at the mat favourable time of the year. These are behavioural responses associated with reproductive and they tend to have motivational elements.

The degree of motivation has to be synchronized in both males and females. In this case, sign stimuli or releasers are very important e.g. the swelling and the changes in colour in the genital area of the female primate is the sign of the onset of estrus and this is usually displayed to the male.

Sign stimuli can be classified as releasers or terminating stimuli or s motivational stimuli.

Examples of motivational stimuli.

  • Day length increase in likely to increase territorial and courtship behaviour in birds.
  • Decrease in the stoned food in the body of hibernating animals e.g. the polar bear can lead to awakening and food seeking. In this case, motivational stimuli provide the drive or goal.
  • The releaser stimuli e.g. the young herring gulls begging response intensity will depend on the contrasting colour on the beaks of their parents.
  • Adult herring gulls have a red spot on the yellow lower mandible of the beak.
  • Terminating stimuli, this one completes the behavioural response and can be external or internal e.g. external visual stimuli of a successful built nest will terminate nest building in birds.

The physiologically and physiological pressure derived by a man on

ejaculation terminates copulation.

  1. Full stomach will terminate feeding.

Innate factors are involved and this helps in filtering out irrelevant stimuli. In this case, when the irrelevant stimuli are filtered out, only correct stimuli should be responded. The CNS is involved eg

Chemoreceptions on the male moth antennae are only sensitive to the attracting chemicals produced by the females of that species and not those of other species. These sex attracting chemicals are called pheromones.

Biological rhythm (Biorhythms)

These are behavioural activities occurring at regular interevals eg courtship displays; resting behaviour of birds, migration of certain birds.

Rhythms that are controlled by internal factors are referred to as endogenous rhythms and those controlled by external factors are called exogenous rhythms.

Mat biological rhythms are a blend of both, but the major factor is the photoperiod; i.e. length of day and night. This one sets the clock which include both various and endocrine systems.

Photoperiod is important in preparing animals for hibernation, aestivation, migration and in insects e.g.

  1. The lunar rhythm; the palolo worms of the samoa islands in the pacific. These mate on only one day in a year, 2nd November whereby the adults die immediately to give way for the new generation.
  2. Some terrestrial insects have their behaviour controlled endogenously and this is related to light and dark for example, drosophila will emerge from the pupa at down and cockroaches in the dark, they become active.

Sexual behaviour (courtship mating in animals)

Courtship behaviour are species-specific; all elaborate and complex till these courtship behaviours are all aimed at making sexual apparatus ready. In some organism sexual activities are restricted to a relatively short season so that mating will be turned off at some point.

Sexual behaviour involves periodic changes, internal characteristics for instance endocrine activity, central nervous status and tone of reproductive tract. It could also be modified by the environment factors such as amount of light available; amount of food present the building up food reserves and presence of males etc.

Presence of these trigger courtship behaviour enhanced by secondary sexual characteristics, companied by behavioural activities like……….24 hour period between regular occurring biological rhythms known as circadian or diurnal rhythms.

Example the red belly of the molesticle back fish, increase in body size eg increase in bird plumage, mating calls, postoral display.


  • Use of chemicals, use of chemical sex attractions e.g. in butterflies (phenomones).
  • Motivation stimuli used to attract opposite; most common are sight, smell, sound and play for example fidder crats uses enlarged chela in bowing movement which is similar to someone playing a violin; (violinist). These movements became vigorous as female is attracted to the male.
  • Visual attraction, insects, amphibian, birds and mammals use auditory signals in courtship for exaple grass hpphers, crickets and locusts stridulate.


Learning is adaptive in behaviour resulting from past experience learned behaviour are acquired during the life time of an individual as a result of experience. Some learning are species-specific and they do not change; for example innate learning, however, some learning is still evolved for we know that most fixed action pattern improve with performance  so that animals can learn to carry them out efficiently.


Animals subjected to repeated stimulation may gradually stop to respond to the important stimuli or to a stimuli that does not provide appropriate feedback for example hydra will stop contracting if disturbed too often by water current. Grey savirrels and other animals learn to ignore alarms made by co-specifics threatened by predators, if not followed by immediate attack. Animals soon come to ignore unffective scarecrows, anima habituates to the scarce crow.

Habituation prevents an animal repeatedly to release that leads to nowhere.

Look at;

  1. Associative learning (conditioned reflex)
  2. Operant conditioning (Trial/error)
  • Exploration learninf (Latent learning)
  1. Imprinting
  2. Observational learning
  3. Play

Relationship between evaporative heat, loss, skin and hypothalamus temperatures in humans following experiment ice meals.

Three changes occurred immediately after taking the ice.

  1. Temperature of hypothalamus dropped due to withdraw of the heat from the blood by the ice in the gut.
  2. Heat loss from the sun dropped because of decreased sweating; evaporative heat loss.
  • Skin temperature rose owing to reduced heat loss from it.


  1. Decreased temperature of blood is detected by the thermal regulatory centre which then causes a decrease in the rate of sweating.
  2. The skin temperature rising during this period indicates that the skin receptors play little or no part in the response and their only function is to detect changes in the external environment temperature.

Effects of lowering and raising environmental temperature.

Body temperature is regulated by physical (insulatory) and chemical (metabolic) means but the extent to which an animal depends on each of these processes in its life differs.

Effect of lowering environmental temperature.

If the environment temperature of a naked man is gradually lowered from a pleasant 290C to freezing point, the following occurs

  1. At first the subject relies on physical mechanisms only to maintain a constant temperature, his metabolic rate remaining unchanged until the lower critical temperature.


Lower critical temperature is the environmental temperature at which the physical mechanisms alone can no longer maintain a constant body temperature; hence the metabolic rate starts to go up as the environmental temperature is lowered.

There its only metabolic processes which can regulate the body temperature.

The metabolic rate continues to increase as the outside temperature is further lowered until the chemical mechanisms break down at a temperature called the lower lethal temperature.


The lower lethal temperature is the environmental temperature lower than the critical temperature, at which the increase in metabolic rate can no longer generate enough heat to maintain the body’s temperature.

At this temperature both metabolic rate and temperature fall and the organism is liabic to death due to hypothermia.


Hypothermia is the condition in which the body temperature falls dangerously below normal and happens when heat energy is lost from the body more rapidly that it can b produced.  Its results in death because a low temperature impairs brain function and heartbeat.

The following are more at risk,

  1. Mountain climbers due to the lowering of temperature altitude.
  2. The elderly because their thermal regulatory mechanisms may have deteriated due to old age.
  • Babies because of the small size their SA to volume ratio is high and heat loss occurs very readily also the thermal regulatory mechanisms are poorly developed, e.g. there is thin so blood flows close to the surface, the skin is also extremely porous so water evaporates freely from it causing cooling of the blood.


) Effect of increasing environmental temperature

At the start, the various mechanisms promoting heat loss can keep the body’s temperature up to the higher or upper critical temperature.



This is the environmental temperature above which the thermal regulating mechanisms such as sweating cannot keep the body temperature constant and the metabolic rate gives up as the body’s rxns double their rate for every 100C rise in temperature thus the effect of enzymes (positive feedback).


As the body temperature continues to rise, heat exhaustion characterized by impairment of the brain cramps and dizziness sets in. this is followed by death at a body temperature of about 420. This is the upper lethal temperature for most human beings; during which enzymes controlling cell rxns are denatured.


The upper lethal temperature is the environmental temperature above the higher critical temperature at which the organism dies as a result of a very high body temperature which it can no longer control, even metabolic mechanisms.




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