12th Class Biology Chapter 3 Coordination and Control Short Question Answers

All the aspects such as organization regulation integration and control in the Constitution and work of the complex multicellular animals come under the fold of the term coordination.

Chlorosis usually arises from short supplies of mineral nutrients in the soil.

It is brought about in higher animals by nervous coordination and chemical coordination.

Photoreceptors are electromagnetic receptors.These respond to stimuli of light for example in eyes rods and cones.

The chief structural and functional unit of the nervous system are neurons but there are other cells in higher animals and in humans called neuroglia which make up as much as half of the nervous system.

In human there are 12 pairs of nerves which arise from the brain or lead to the brain these are called cerebral or cranial nerves.

Nicotine affects postsynaptic membrane in CNS and PNS.It minimizes the action of acetylchoine on nicotine receptors so it is stimulant of nerve impulse.It increases the heart beat rate blood pressure and digestive tract mobility.Nicotine may induce vomiting and diarrhoea and even may cause water retention relation by kidneys.

The early ethologists thought that animals sometimes respond instinctively to specific though often complex stimuli.Such stimuli came to be called sign stimuli.

Thrope defined learning as the process which manifests itself by adaptive changes in individual behaviour as a result of experience.

This type of learning has been demonstrated and studied by thorndike and B.F. Skinner a Harvard psychologist.

The neuron fibres and cell bodies can be excited by small electric shocks mechanical chemical light and temperature stimuli.

Plants respond by: Regulating their growth and development in appropriate ways. Controlling their body functions through plant hormones or growth hormones.

If plants are grown without light they become extremely long and they fail to form chlorophyll.They are said be etiolated.

Many plants take on a yellowish hue when they fail to form chlorophyll in sufficient amounts.This condition is known as chlorosis.

If plants are wounded they often develop masses of amorphous material with very poor differentiation known as calluses.

Galls are growths on a plant that are induced by parasites and usually highly organized growth galls are tumors induced by bacteria.They are usually less differentiated then other types of galls.

In living things the behavioural activities occur at regular intervals which are called biorhythms or biological rhythms.

Biorhythms may occur showing periodicity of about 24-hours.These are called circadian which means about one day so they are also called diurnal rhythms.

If the biorhythms are less than or about 365 days.these rhythms in activity are called circaannual.

The special substances produced by the plants which influence the growth and plant responses to various stimuli are called plant hormones.

Auxins giberrellins cytokinins abscisic acid and ethane.

Promote cell enlargement in presence of auxiuns. Promote leaf growth and fruit growth.

GA₃ is used in the brewing industry to stimulate a-amylase production in barley and this promotes malting.

Promote stem growth by cell division in apical meristem and cambium. Promote bud initiation.

Cytokinins delay the aging of fresh leaf crops such as cabbage and lettuce as well as keeping flowers fresh.They can also be used to break dormancy of some seeds.

Inhibits stem growth notably during physiological stress e.g.drought water-logging. Promotes bud dormancy.

Abscisic acid can be sprayed on tree crops to regulate fruit drop at the end of the season.This removes the need for picking over a large time-span.

Ethene induces flowering in pineapple.It stimulates ripening of tomatoes and citrus fruits.It stimulates flow of latex in rubber plants.

This type of co-ordination involves specialised cells or neurons linked together directly or via the central nervous system to form network that connect the cell or organs which receive stimuli and those which carry out actions or responses(effectors).

The elements of nervous system which help in co-ordination are: i) Receptors. ii) Neurons. iii) Effectors.

Receptors detect changes in the external and internal environment of the animal.The receptor may be a cell or neuron ending or a receptor organ.

The receptors which are stimulated by the chemicals are called chemoreceptors.These are for smell taste and for blood CO2 oxygen blood glucose amino acids and fatty acids.

The receptors which detect stimuli of touch pressure and hearing and equilibrium are called-mechanoreceptors.

The receptors which respond to cold and warmth are called thermoreceptors.

These are undifferentiated nerve endings which produce the sensation of pain.

Each type of the principal type of sensation that we can experience e,g.pain touch sight sound and so forth is called a modality of sensation.

These are encapsulated nerve endings which lie in papillae which extend into the ridges of the fingertips.The corpuscle consists of spiral and much twisted endings each of which ends in a knob.These are touch receptors.

Pacinian corpuscles are situated quite deep in the body.These are encapsulated neuron endings and receive deep pressure stimulus.Those located in the limbs probably form a basis for vibration sense.

The cytoplasmic process which carries impulse towards cell body is called dendron.if it is a single fibre but if smaller fibres- they are called dendrites.

The processes conducting impulses away from cell body are termed axons.These may be more than a meter long in some neurons.

Nissl’s granules are groups of ribosomes associated with rough endoplasmic reticulum and protein synthesis and golgi apparatus and are present in the cell body.

The cell body or soma is the main nutritional part of the nerve cell and is concerned with the biosynthesis of materials necessary for the growth and maintenance of the neuron.

There are three functional types of neurons in mammals i.e.the sensory associative and motor neurons.

These are the neurons which carry nerve impulses from receptors to brain or spinal cord.They have a single elongated dendron and shorter axon.

These are the neurons which carry nerve impulses from brain and spinal cord to the effectors in all parts of the body.They have a long axon and a number of small dendrites.

These are the neurons which occur exclusively in the spinal cord and brain.They serve as intermediate links between numerous sensory and motor neurons.

These are the structures which respond when they are stimulated by impulse coming via motor neuron.The principle effectors are glands which respond by secreting and muscles which respond by contracting.

Reflex arc is the path way of passage of impulse during a reflex action.Reflex action is a type of involuntary action.The direction of stimulus is from receptors to sensory neuron to associative neuron and then through motor neuron to the effectors.

Nerve impulse is a wave of electrochemical changes which travel along the length of the neuuron involving chemical reactions and movement of ions across the cell-membrane.

Electrical potential is a measure of the capacity to do electrical work.The electrical potential that across a cell membrane is known as membrane potential.

In unicellular organisms, coordination occurs between various cellular processes.

No. They are unable to detect and respond to many stimuli in their environment as, for example, they are unable to detect and respond to the presence of bacteria on the surface of our body.

Etiolation is the condition of the plants when they grow in the absence of light. In this condition, plants look pale due to lack of chlorophyll and have extremely long internodes.

Chlorosis is a condition of green plants in which they turn unhealthy and yellowish in colour due to failure to form chlorophyll. This pathological condition is caused on account of deficiency of iron magnesium or copper.

The gall is an abnormal localized swelling or outgrowth produced by a plant as a result of attack by a parasite like bacterium.

The circadian rhythm is an endogenous biological rhythm in which behavior activities occur at 24-hourly intervals.

In living beings, the occurrence of behavioral activities at regular intervals is called biorhythm.

The endogenous rhythm in which physiological responses occur after 365 (or lesser) days in called circannual rhythm.

The plant hormone (growth substance) is a special substance produced by the plant that has a marked and specific effect on plant growth and plant response to the stimulus. It produces its effect when present in very low concentration.

It is the in dole acetic acid (IAA).

The natural auxin promotes cell division in the cambium and cell enlargement in the region behind the stem apex.

Naphthalene acetic acid (NAA) and in dole propionic acid stimulate fruiting, sometimes even without pollination (parthenoearpy); 2, 4 – diehlorophenoxy acetic acid kills weed without harming the crop, prevents spouting of potatoes in stores ad checks premature fruit drop.

The development of the ovary into the fruit without fertilization is called parthenocarpy. Such fruits are called parthenocarpic fruits which lack seeds.

Gibberellins are commercially produced from fungal cultures.

The gibberellins promote fruiting in tangerines and pears, and are used for growing seedless grapes by parthenocarpy. Gibberellin acid (GAa, the first, isolated gibberellin) is used in breweries to stimulate a-amylase production in barely so as to prepare wine, Gibberellins also delay ripening and thus improve storage life of bananas and grape fruits.

Cytokinins delay the life of fresh leaf crops such as cabbage and lettuce as well as keep flowers fresh. They can also be used to break dormancy of some seeds.

Ethene induces flowering in pineapple and stimulates ripening of tomatoes and citrus fruits.

The names of the plant hormones are auxins, gibberellins, cytokinins, abscises acid ad ethane etc.

The working of different organs of the body of an organism in close cooperation with one another is called coordination.

The stimulus may be defined as a change in the external or internal environment that elicits a response in the organism.

The receptors are the neuron endings or the cells or organs that are specialized for detecting stimuli.

It is the neuron (nerve cell).

The receptors of the stomach wall are concerned with the arousal of hunger; the stretch receptors in the carotid and aortic arteries of tetrapods have important roles in the regulation of blood pressure.

The receptors that are sensitive to the chemical stimuli are called chemoreceptors such as those for smell; taste, concentration of oxygen, carbon dioxide, glucose, amino acids and fatty acids in the blood. The receptors which are sensitive to mechanical stimuli are known as mechanoreceptors such as these for touch, pressure, hearing and equilibrium.

These are called nociceptors.

The thermo receptors to cold and warmth.

Meissner’s corpuscles are encapsulated nerve endings forming corpuscles (papillae) and extending into the fingertips. These are touch receptors.

These are encapsulated neuron endings located quite deep in the body. These are touch receptors which receive deep pressure stimuli.

The terrestrial vertebrates detect vibrations of the ground probably by the receptors at the joints.

These are touch, pressure, heat, cold and pain.