14. Irritability and sensitivity in (a) plants (b) animals Questions And Answers

14. Irritability and sensitivity in (a) plants (b) animals Questions

1.  Give two functions of the exoskeleton in arthropods.

2.  When shoots of young plants are exposed to unidirectional light they bend towards light;

 a) Name the type of response exhibited by the young shoots  

 b) Explain the cause of the observation above  

3.  Study the drawing below and use it to answer the questions that follow :-

a) Name the part labeled X.

 b) Describe the changes that occur in the structure X in dim light.  

 c) What is meant by the term accommodation with reference to the eye?

4.  (a) State two differences between taxes and tropisms

 (b) Give two survival values of tactic movements to organisms  

5.  The diagram below represents a type of neurone.

 (a) (i) identify the neuron above.

  (ii) Give a reason for your answer in a (i) above.

 (b) With an arrow, indicate on the diagram the direction of an impulse through the neurone.

 (c) Name the chemical substance that brings about transmission of impulse across a synapse

6.  A student was traveling from Nairobi to Mombasa. As the bus descended down hill he felt an

unpleasant sensation in the ear.

(a) How did the sensation come about?  *

(b) How can the unpleasant sensation be relieved?

7.  An experiment was carried out to investigate a growth response in maize seedling as shown

 in the diagram below:

 (a) State the type of response that is being investigated ………..

 (b) Explain the response exhibited by the shoot  

8.  State three genetic disorders caused by gene mutations

9. The diagram below shows the position of an image formed in a defective eye:-

(a) Name the defect  

(b)Explain how the defect named in (a) above can be corrected  

10.  (a) State three structural differences between arteries and veins in mammals  

 (b) Name a disease that causes thickening and hardening of arteries  

11.  (a) Name the part of the eye in which the light sensitive cells are located

 (b) List the two types of sensory cells found in the part named in (a) above  

12.  The diagram below illustrates a certain eye defect

 (a) State the defect  

  (b) On the diagram illustrate how the defect can be corrected

 (c) State one advantage of having two eyes in human beings

13.  Briefly explain the role of the following part of skin

 a) Cornified layer  

 b) Malpighian layer  

14.  State the functions of the following structures of the mammalian ear

 a) Eustachian tube  

 b) Essicles  

15.  a) Distinguish between conditioned and simple reflexes

 b) State how the nerve cell structure is suited to its function of impulse transmission

16.  (a) Name the part of the mammalian eye that:

  (i) Transmits impulses to the brain  

  (ii) Regulates the amount of light entering the eye  (b) State the changes that occur in the part of the eye named in (a) (ii) above when one moved

from bright light to dim light conditions

16.  Name the type of response exhibited by the following:

 (a) A pollen tube growing towards the embryo sac

 (b) Maggots moving from lit side of a box to the dark side  

17.  A response exhibited by a certain plant tendril is illustrated below:  

(i) Name the type of response

(ii) Explain how the response named in (i) above occurs  

18.  A response exhibited by a certain plant tendril is illustrated below:-  

 Name the type of response

19.  Removal of the apical bud from a shrub is a practice that results in the development of many

 lateral buds which later form branches  

 (a) Give reasons for the development of lateral branches after the removal of the apical bud

 (b) Suggest one application of this practice?  

20.  In an accident a victim suffered brain injury. Consequently he had loss of memory which

 part of the brain was damaged?

21.  A person was able to read a book clearly at arm’s length but not at normal reading distance  (a) State the eye defect the person suffered from  

 (b) Why was he unable to read the book clearly at normal distance?  

 (c) How can the defect be corrected?  

22.  The diagram below represents a simple reflex arc;

 (a) Name the parts labeled A and B

 (b) Explain how an impulse is transmitted across the gap labeled C  

23.  (a) State two functions of a mammalian ear

  (b) How is the cochlea suited to its function  

24.  State one function of potassium ions in the human body.

25.  State two functions of vitamin B₅ (pantothenic acid).

26.  (a) What is the biological importance of tactic responses?

  (b) A person had an accident and had problems with his vision, hearing and memory.  

Identify the part of the brain that was affected

27.   Identify the following responses shown by plants:-  (a) Shoots grow towards light

(b) Roots grow towards gravity

(c) Tendril intertwine around an object

28.  Name the type of responses exhibited by:-

 (a) (i) Marine crabs burrowing into the sand to avoid dilution of their body fluids

  (ii) Chlamy domonas plant moving towards a region of high light intensity

 (b) (i)What type of neuron is drawn above?  

  (ii) Using an arrow, show the direction of the nerve impulse  

  (iii) Name the part labelled X  

  (iv) State the function of part labelled Y  .  

 (c) Give two differences between reflex action and conditioned reflex action

29.  In an experiment to investigate the effect of heat on germination of seeds, 12bags each  

Containing 60 pea seeds were placed in a water bath maintained at 85^oC .

 After every two minutes a bag was removed and seeds contained in it planted. The number that

 germinated was recorded. The procedure used for pea seeds was repeated for wattle seeds. The

results were as shown in the table below:-

 (a) Using a suitable scale and same axes, draw graphs of number of seeds that germinated against

time in hot water for each plant

 (b) (i) At what time would number of seeds that germinated for each plant be same?  

  (ii) How many wattle seeds would have germinated if the 13^th bag was available and was

removed and seeds contained in it planted at 24minutes?

 (c) Explain why the ability of pea seeds that germinated declined with time of exposure to heat

 (d) Explain why the ability of the wattle seeds to germinate improved with time of exposure

  to heat

 (e) Account for the shape of the graph for the wattle seeds which germinated between 20-24

minutes  (f) Some of the pea seeds were allowed to germinate and placed in a large air tight flask

and left for four days:-

  (i) Suggest the expected changes in the composition of gases in the flask on the fifth day  

  (ii) Give reasons for your answer in (f)(i) above

 (g) Name three factors other than those investigated in (a) above which would affect dormancy

30.  How is the mammalian skin adapted to its functions?

31.  Explain how the mammalian skin is adapted to it’s functions  

32.  Explain the structure and functions of the human eye.

33.  The diagram below shows the position of an image in a defective eye.

 (a) (i) Name the defect

(ii) State the causes of the defect

 (b) Explain how the defect in a(i) above can be corrected.  

 (c) State the functions of cones

 (d) How are nocturnal animals adapted to seeing?

 14. Irritability and sensitivity in (a) plants (b) animals Answers

1.  – To prevent excessive water loss/desiccation;

 – Provide surface area for muscle attachment;

 – Support and protect inner delicate tissues;

2.  a) Phototropism;  

 b) Auxins migrate from the side of the shoot that is exposed to light towards the darker side;

The higher concentration of auxins on the darker side stimulates rapid growth hence the

shoot bends towards the light source;

3.  a) Iris;

 b) Circular muscles relax; radial muscles contract widening the pupil;

c) Adjustment of the eye structure to bring an image from a near or far object into sharp focus on the retina;

4.  a)

(b) – Escape from harmful conditions/stimuli;

  – Move in search of food/nutrients;

5.  (a) (i) Motor neurone;

 (ii) Cell body located in the central nervous system;

 (b) Arrow head towards terminal dendrites

 (c) C- Protection/insulate axon;

D- Speeds up transmission of an impulse

6.  (a) Due to the difference in atmospheric pressure and the pressure inside the ear;  

 (b) Swallowing; yawning;

7.  (a) Photosynthesis;  

(b) Night on the list side makes the auxin to move/migrate/Diffuse to the dancer side;

there auxin cases faster elongation/growth I the dark side; Hence curvature/bending;

8.  – Colour blindness;

– Haemophilia;

– Sickle cell anemia;

– Albinism  

9.  a) short-sightedness/myopia;

b) This defect can be corrected by wearing glasses with concave (diverging) lenses; these bend light rays outwards before they reach the eyes enabling them to be focused ion the retina;

10.  a)

b) Arteriosclerosis; reject Artheroma

11.  a) Retina;

 b) Cones and rods;

12.  a) Long sightedness / hyper metropia..  

 b)

 c) Stereoscopic vision/ binocular vision/ improved visual acuity; gives a wider angle of vision; if

one is damaged man is not blinded;

13.  Water proof – Prevent water from reaching the inner cells

 Has Karatin – For protection against mechanical injury

14.  i) Equalizes the pressure between the outer ear and the middle ear;

 ii) Transmits and amplifies vibrations from the ear drum to the oval window;

15.  a) – Conditioned reflex requires repeated stimulus to bring about response while simple

reflex requires single stimulus to bring about response;

  – Conditioned reflex requires behaviour modification hence experience while simple

reflex involves direct action and is independent of experience;

 b) It has a long axon to transmit nerve impulse myelin sheath and rod of ranvier for faster

impulse transmission;

16.  a)  i) Iris;  

ii) Optic name;

 b) Circular muscles of the iris;

Radial muscles contract;

  The size of the pupil enlarge to allow more light to enter;

17.  Chemotropism; Reject chemotrophism

Negative photo taxis; Reject photo taxis alone

18.  i) Thigmotropism / 1-laptotropism

ii) High concentration of auxin on side away from contact surface; promotes faster growth of this

side; causing tendril to curl round the object.

19.  Thigmotropism / haptotropism;  

20.  a)Hormone/growth substance /IAA; which inhibits the development/growth of lateral

shoots/buds/causes apical dominance; /removal of the terminal buds cause the  

growth/development and sprouting of lateral buds 2mks

 b)The pruning of coffee /tea/ledge; etc Rej. Pruning alone/trimming

21.   cerebrum/cerebral hemisphere/cerebral cortex;

22.  a)long sightedness/hyper netropia;  

 b)the eye ball too short/eye lenses are unable to focus because they are flat//thin/weak;

hence unable to focus the image on the retina OR the eye are unable to commodate/change

their focal length; 2

  c)by wearing convex/biconvex lens/converging lenses; 1mk

23.  a)A-relay/intermediate /associates;  

  B-motor neurone/efferent neurone;

 b) Impulse initiates release of acetyl choline /transmitter substance (at the end of the

sensory neurone);acetyl choline which diffuses across the gap; generate an impulse

in the next neurone; (Rj. Message for impulse)

24. (a) -Hearing;

-Body balance (and posture);

(b) Coiled to accommodate many sensory cells:

– Filled with endolymph to transmit (sound) vibrations.

– Has sensory hairs/cells to generate nerve impulses when stimulated:

25.  Used in the transmission of nerve impulse.  

 – For respiration;  

26.  – Proper functioning of the nervous system and alimentary canal; 

27.  (a) Enables the organism to escape from injurious stimuli/seek favourable habitats;

 (b) Cerebrum

28.  The conified layer of the epidermis consist of dead cells which form a tough outer coat;

that protects the skin against mechanical damage/bacterial infection/ water loss;

Sebaceous glands produce an oily secretion sebum which give hair its water repelling property; that keeps the epidermis sapple and prevents it from dyring/sebum too prevents bacterial attack due to its antiseptic property;

Has blood vessels; that dilate and contract;

In hot conditions, they dilate; increasing blood flow near the skin surface enhancing blood flow near the skin surface; minimizing heat loss;

Has hairs; stand during cold weather thus trapping a layer of air which prevents heat loss; In hot weather they i.e close to the skin surface; to enhance heat loss to the atmosphere.

Hair follicle; has many sensory neurons which respond to movements of the hair; increasing sensitivity of the skins. Has subcutenous layer; contains fat whihch acts as a heat-insulating layer and a fuel storage;

Has malpighian layer; consists of actively dividing cells tht contain fine granules of melanin; that prevents the skin against ultraviolet light rays from the sun;

29.  a) i) Myopia/ short sightedness  

  ii) Long eyeball/ too long eye ball

 b) Use of concave/ diverging lens; to diverge the rays from image to focus onto retina

 c) For colour reception/ vision

For vision in bright light/ day

 d) Retina has many rods; to perceive / enable organism see in dim light/ darkness

30.  Water proof – Prevent water from reaching the inner cells

 Has Karatin – For protection against mechanical injury

31.  i) Equalizes the pressure between the outer ear and the middle ear;

 ii) Transmits and amplifies vibrations from the ear drum to the oval window;

32.  a) – Conditioned reflex requires repeated stimulus to bring about response while simple

reflex requires single stimulus to bring about response;

  – Conditioned reflex requires behaviour modification hence experience while simple

reflex involves direct action and is independent of experience;

 b) It has a long axon to transmit nerve impulse myelin sheath and rod of ranvier for faster

impulse transmission;

33.  a)  i) Iris; ii) Optic name;

 b) Circular muscles of the iris; Radial muscles contract;

  The size of the pupil enlarge to allow more light to enter;

34.  Chemotropism; Reject chemotrophism

Negative photo taxis; Reject photo taxis alone

35.  i) Thigmotropism / 1-laptotropism

ii) High concentration of auxin on side away from contact surface; promotes faster growth of this

side; causing tendril to curl round the object.

36.  Thigmotropism / haptotropism;  

37.  a)Hormone/growth substance /IAA; which inhibits the development/growth of lateral

shoots/buds/causes apical dominance; /removal of the terminal buds cause the  

growth/development and sprouting of lateral buds 2mks

 b)The pruning of coffee /tea/ledge; etc Rej. Pruning alone/trimming

38.  cerebrum/cerebral hemisphere/cerebral cortex;

39.  a)long sightedness/hyper netropia;  

 b)the eye ball too short/eye lenses are unable to focus because they are flat//thin/weak;

hence unable to focus the image on the retina OR the eye are unable to commodate/change

their focal length; 2

  c)by wearing convex/biconvex lens/converging lenses; 1mk

40.  a)A-relay/intermediate /associates;  

  B-motor neurone/efferent neurone;

 b) Impulse initiates release of acetyl choline /transmitter substance (at the end of the

sensory neurone);acetyl choline which diffuses across the gap; generate an impulse

in the next neurone; (Rj. Message for impulse)

41. (a) -Hearing;

-Body balance (and posture);

(b) Coiled to accommodate many sensory cells:

– Filled with endolymph to transmit (sound) vibrations.

– Has sensory hairs/cells to generate nerve impulses when stimulated:

42.  Used in the transmission of nerve impulse.  

43.  – Proper functioning of the nervous system and alimentary canal; 

 – For respiration;  

44.  (a) Enables the organism to escape from injurious stimuli/seek favourable habitats;

 (b) Cerebrum

45.  (a) Positive phototropism; reject phototropism only

  (b) Positive geotropism; reject geotropism only

  (c) Thigmotropism  

46.  – comified layer made of dead cells to protect from mechanical damage, also protect *KKE*

from desiccation/dehydration.

• Granular with living cells to replace the worn out layer.

• Malphigian layer – cells divide to form new epidermis.
• Malphigian cells with melanin pigment which protect from c ultra violet rays from the sun.
• Blood vessels to supply oxygen and nutrients. Remove CO₂ and nitrogenous wastes.
• Superficial blood vessels/arterioles dilate. When it is hotg. So that more blood flows near the skin surface for more heat loss.
• Superficial blood vessels consmet/vasoconstriction. When it si cold. So that less blood flows near the skin surface to reduce heat loss.
• Erector pili muscle contract when it is cold to raise hair/hair stands upright. To trap more a ir to reduce heat loss/insulate.
• Erctor pili muscles relax when it is hot to make hair lie flat. On the skin to trap less air hence reduce insulation/increase heat loss.
• Sweat glands excrete excess water, mineral salts traces of live and lactin acid.
• The water in sweat evaporates carrying away latent heat of vaporization to lower the body temperature.
• Subcutaneous layer/dispose tissue insulation the bod y/ reduce heat loss.
• Sensory nerve ending which are sensitive to touch/pain/heat cold.

47.  Conjuctiva – protects eyeball from mechanical injury

 Cornea – Allows light to pass through

 Iris – Controls amount of light passing through

 Retina – Where image is formed

 Forea – Where image is formed

 Sctera – Protect the eye ball; give it shape

 Choroid – Absorbs stray lights

Provide nourishment to the eye

 Aqueous/ vitreous humour – refract light into the eye towards retina maintain shape of eye ball

 Ciliary body – Controls curvature of the lens

 Rods – Perceive light of low intensity

 Cones – Perceive light of high intensity