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(a) Which figure shows the correct position taken by the parts A and B of the plant ?
(b) What type of phenomenon is exhibited by the figure chosen in (a) above ?
Name the plant hormones which are responsible for the following effects :
(a) falling of leaves
(b) opening of stomata
(c) bending of stem towards light (d) closing of stomata
(a) Abscisic Acid
(d) Abscisic Acid
Name the plant organs which are :
(a) positively phototropic (b) positively geotropic
(c) negatively geotropic (d) positively hydrotropic
Why is the folding up of the leaves of a sensitive plant on touching with a finger not a tropism ?
The folding of leaves of a sensitive plant is not a case of tropism (like thigmotropism) because in this case the direction of movement of leaves does not depend on the direction of stimulus (touch).
Why is the closing of a dandelion flower at dusk (when it gets dark) not a tropism ?
The closing of a dandelion flower at dusk (when it gets dark) is not a tropism because the direction of movement of petals of dandelion flower does not depend on the direction of stimulus (light).
(a) What is meant by ‘tropisms’ (or tropic movements) ? Explain with an example.
(b) What are the different types of tropisms ? Define each type of tropism. Write the name of stimulus in each case.
(c) How do tropisms differ from nasties (or nastic movements) ?
(a) A growth movement ofa plant part in response to an external stimulus in which the direction of stimulus determines the direction of response is called tropism. Example – The bending of plant stem towards light is an example of positive phototropism.
(b) Different types of tropisms are:
(i) Phototropism – The movement of a plant part in response to light is called phototropism. Its stimulus is light.
(ii) Geotropism – The movement of a plant part in response to gravity is called geotropism. Its stimulus is gravity.
(iii) Chemotropism – The movement of a plant part in response to a chemical stimulus is called chemotropism. Its stimulus is chemical.
(iv) Hydrotropism – The movement of a plant part in response to a water stimulus is called hydrotropism. Its stimulus is water.
(v) Thigmotropism – The movement of a plant part in response to a touch stimulus is called thigmotropism. Its stimulus is touch.
1. These movements are always in the direction of the stimulus.
2. These movements are slow.
3. These movements are exhibited by all parts of a plant.
For example, movement of shoot towards the light and not towards
1. These movements are neither away nor towards the stimulus.
2. These movements are fast.
3. These movements are exhibited by the flat organs (like leaves and petals of flowers) of a plant.
For example, the bending and dropping of leaves in ‘Touch-me-not’ plant.
(a) Define phototropism. Give one example of phototropism.
(b) How does phototropism occur in a plant stem (or shoot) ? Explain with the help of labelled diagrams.
(c) What is meant by positive phototropism and negative phototropism ? Give one example of each type.
(a) Phototropism – The movement of a plant part in response to light is called phototropism. Example -Stem bends towards the light is positive phototropism.
(b) Phototropism in a plant stem – The bending of a plant stem towards light is an example of phototropism. The plant stem responds to light and bends towards it due to the action of auxin hormone. The auxin hormone is present at the tip of the stem of the growing plant. Auxin prefers to stay in shade away from light so when sunlight falls on the stem from one side, it gets concentrated on the opposite side. Due to more auxin, the shady side of the stem grows to be longer than the side of stem which is facing light, and makes the stem bend towards light.
Diagram to explain the bending of a plant stem (or shoot) toward light by the action of 'auxin' hormone
(c) The movement of a plant part towards light is called positive phototropism. Example ? the stem of the growing bends towards light. The movement of a plant part away from light is called negative phototropism. Example ? The roots of a plant move away from light.
(a) Define geotropism. Give one example of geotropism.
(b) What is meant by ‘positive geotropism’ and ‘negative geotropism ? Give one example of each type. Draw a labelled diagram to illustrate your answer indicating the plant part which shows positive geotropism and the plant part which shows negative geotropism.
(c) Name one plant part which exhibits positive thigmotropism.
(a) The movement of plant part in response to gravity is called geotropism. Example – Roots grow towards gravity.
(b) If the plant part moves towards the direction of gravity, it is called positive geotropism. Example – Roots. If the plant part moves against the direction of the gravity it is negative geotropism. Example – Stem
Experiment to show the response of a plant to gravity (Geotropism)
(a) How does control and coordination take place in plants ? How does it differ from that in animals ?
(b) Name five stimuli which act on plants. Name the type of tropism produced by each one of these stimuli.
(c) Define hydrotropism. Give one example of hydrotropism. State whether this example is of positive hydrotropism or negative hydrotropism. Illustrate your answer with the help of labelled diagram.
(a) The plants do not have a nervous system but they can sense things in the presence of stimuli such as light, touch, water etc. and respond to them by the action of hormones. Thus, the plants coordinate their behavior against environmental behavior by using organic chemicals called hormones. This is called chemical coordination. The hormones in plants coordinate their behavior by affecting the growth of a part of the plant resulting in the movement of that plant part in response to a stimulus. The control and coordination in animals takes place by both nervous system and hormones.
(i) Light – Phototropism.
(ii) Gravity – Geotropism.
(iii) Chemical – Chemotropism.
(iv) Water – Hydrotropism.
(v) Touch – Thigmotropism.
(c) The movement of a plant part in response to water is called hydrotropism. Example: The roots of a plant always go towards water, this is positive hydrotropism.
Experiment to show the response of a plant to water (hydrotropism)
(a) What is meant by positive tropism and negative tropism ? Explain with examples.
(b) Define thigmotropism. Give one example of thigmotropism.
(c) What is the difference between thigmotropism and thigmonasty ? Name one plant which exhibits thigmotropism and one plant which exhibits thigmonasty. What behaviour (or responses) of these plants make you think that they exhibit thigmotropism and thigmonasty respectively ?
(a) The growth of a plant part in response to a stimulus is called positive tropism and if the growth of a plant part is away from the stimulus, then it is called negative tropism.Example: The roots of a plant go towards earth in response to gravity is an example of positive geotropism whereas stem grows away from earth against gravity is an example of negative geotropism.
(b) The directional growth movement of a plant part in response to the touch of an object is called thigmotropism.Example: Tendrils grow towards any support which they happen to touch and wind around it.
The directional growth movement of a plant part in response to the touch of an object is called thigmotropism
Example : Tendrils
the non- directional movement of a plant part in response to touch of an object called thigmonasty
Example : mimosa pudica
Tendrils grow towards a stimulus hence it is a directional movement which shows that it is a case of thigmotropism whereas, the folding of leaves in mimosa plant does not depend on the direction of stimulus (touch) which shows that it is an example of thigmonasty.
Page No - 115
Name the two systems of control and coordination in higher animals.
Nervous system and Endocrine system.
What are the two parts of the vertebrate nervous system ?
Central nervous system and Peripheral nervous system.
If we happen to touch a hot object unknowingly, we immediately pull back our hand. What is this type of action known as ?
Name the three components of a neuron (or nerve cell).
Cell body, dendrites and axon.
(a) What are the short fibres of a neuron known as ?
What is the long fibre of a neuron known as ?
Name the most important part of the human brain.
Which part of the brain maintains posture and balance of the body ?
State one function each of cerebellum and pons.
(a) Cerebellum ? It helps in maintaining posture and balance of the body.
(b) Pons ? It regulates the respiration process.
Name one hormone secreted by the pituitary gland.
Where are hormones made in the human body ?
What is the name of the system of glands which produces hormones ?
Which gland secretes the growth hormone ?
Name the hormones secreted by (a) testes, and (b) ovaries
(b) Progesterone and oestrogen.
What are the scientific names for the following receptors in animals ?
(a) receptors for light
(b) receptors for heat
(c) receptors for sound
(e) receptors for smell
(e) receptors for taste
(d) Olfactory receptors.
(e) Gustatory receptors.
Name the disease caused by the deficiency of insulin hormone in the body.
Name, the disease caused by the deficiency of thyroxine hormone in the body.
Which halogen element is necessary for the making of thyroxine hormone by the thyroid gland ?
Why are some patients of diabetes treated by giving injections of insulin ?
The people having severe diabetes are treated by giving injections of insulin.
What is the name of in-built ‘arrangement’ in our body which controls the timing and amount of hormones released by various endocrine glands in the body ?
Name one gland each :
(a) which acts only as an endocrine gland.
(b) which acts only as an exocrine gland.
(c) which acts both as an endocrine gland as well as an gxocrine gland.
(a) Thyroid gland.
(b) Salivary glands.
What part does the diet play in helping us to have a healthy thyroid gland ?
Diet provides iodine for making thyroxine hormone which keeps the thyroid gland healthy.
If sugar is detected in the urine of a person, name the disease he is suffering from.
Name two parts of the body which contain receptors of chemical stimuli.
Nose and Tongue.
Which part of the eye contains cells which are sensitive to light ?
What are the two main communications systems in an animal’s body ?
Nervous system and endocrine system.
Which one term in each of the following includes the other three ?
(a) thyroid, ductless gland, thymus, pituitary, ovary
(b) adrenalin, insulin, hormone, thyroxine, estrogen
(a) Ductless gland.
Which parts of the body form the central nervous system ?
Brain and spinal cord.
Give three examples of reflex actions.
(i) Knee jerk reflex.
Why do you need iodine in your diet ?
Because iodine is necessary for making thyroxine hormone.
State whether coughing is a voluntary action or reflex action.
Fill in the following blanks with suitable words :
(a) The two examples of effectors are…………. and………………
(b) Our…………. system allows Us to react to our surroundings. Information from receptors passes along…………. neurons to our brain. Our brain sends impulses along………… neurons to our muscles.
(c) A neuron which carries an impulse to the brain is called a……………….
(d) The neuron which carries a message for action to a muscle or gland is known as a……………….
(a) Muscle; glands.
(b) Nervous; sensory; motor.