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Check the answers after the questions

1.     The diagrams below repents a nerve cell

  1. Identify the nerve cell.                                                              (1mark)

(b)  (i)   Give a reason for your answer in (a) above                                     (1mark)

                (ii) Show by use of an arrow the direction of flow of the nerve impulses.          (1mark) 2.     Below is a diagram showing parts of a synapse observe and other the questions that follow

  • Name the parts labeled: A, B.                                                       (2mks)
    • What is the role of part labeled C.                                                                        (1mk)

3.         A student set up an experiment as shown in the diagram below.

The set up was left for 4 days.

a) What was the aim of the experiment.                                                                    ( 1mk)

b)  i)  State the expected results after 4 days.                                                                   ( 1mk)

        ii)  Account for the results you have stated in ( b) (i) above.                               ( 4mks)

c) In another experiment, a student placed a seedling horizontally on moist cotton wool. Later the shoot grew upwards while the Radicle grew downwards. Explain why the radicle showed a downward curvature.                                                                                 ( 2mks )

4.     Describe how different types of tropisms adapt plants for survival in their habitats.    (20mks)

5.     Diagram below shows the structure of motor neuron. 

a)  State the functions of the ear.                                                    (2mks)

        b)  Give the names of the structure labelled C,G and F.                        (3mks)

c)  (i)  What is the function of the structure labeled H?                         (1mk)

 (ii)  Name the structure in the ear that detects sound waves.                        (1mk)

d)  In which structure of the ear is the velocity of the sound waves fastest?            (1mk)

P  

7.     The diagram below represents a nerve cell.  Study it and answer the questions that follow.

a)  (i)  Identify the cell                                                            (1mk)

 (ii)  Give a reason for your answer in a (i) above                                  (1mk)

b)  Name the parts labelled N, P, Q and R.                                            (4mks)

c)  State the functions of the parts labelled N and Q.                                     (2mks)

8.     Use the diagram below to answer the questions that follow

        a) (i) Name the eye defect represented above                                        (1 mk)

        (ii) What is the cause of this defect                                                (1 mk)

        (iii)How can the defect you have named (a) (i) be corrected?                       (1 mk)

9      The diagram below shows three different types of neurones along a reflex   arc

a) Identify the neuron labelled 1 ,2 and 3                                               (3 mks)

b) Using arrows show the direction of impulse transmission on the diagram   (1 mk)

c) Name the part of the spinal cord where the cell bodies of neurone 2 and 3 are located (1mk)

d) Describe the transmission impulse across the  part labelled P                   (3 mks)

10    A response exhibited by a certain plant tendril is illustrated below

  • Name the type of response                                          (1mk)
    • Explain how the response named in (i) above occurs.                  (3mks)
    • What is the importance of tactic responses to microscopic plants?       (1mk)

11    Describe how the mammalian ear is adapted to perform its functions.               (20mks)      

12.   a)     Describe how the structure of the eye is adapted to its function.                (16mks)

    b)     Identify two defects of the eye and how they can be rectified.            (4mks)

13    Differentiate between nervous and endocrine communication in animals           (3mks)

14.   The diagram below represents a section through the mammalian ear. Study it and answer the questions that follow.

(a)    Name the structures labeled H and J                                              (2mks)

        (b)   State how the structures labeled H, M and N are adapted to their functions (3mks)

        (c)    State what would happen if the structure labeled K was completely damage (1mk)

        (d)   Name the fluid contained in structure N                                 (1mk)

        (e)    Apart from hearing, state the other role performed by the human ear       (1mk)

15    The following experiment was set up in a chamber made from two connected Petri dishes. Housefly maggots were introduced at the centre of the chamber, so the maggots could move to either Petri dish A or B as shown below.

(a) Name the type of response being investigated in the set up.                            (1mk)

(b) State the survival value of the response named in (a) above.                           (1mk)

(c) Give the role of calcium chloride in the experiment above.                               (1mk)

16    (a) What is accommodation?                                                                                   (1mk)

(b) Describe the sequence of events that occur in the eye for one to be able to see clearly

(i) a distant object                                                                                                   (4mks)

 (ii) if one moved from a dim lit room to bright light.                                       (3mks)

MARKING SCHEME STIMULUS AND RESPONSE REVISION QUESTIONS

1 (a) Motor neuron/Motor nerve cell;

(b) (i) cell body is terminally situated/located at the end of the axon;

    (ii) Arrow should point away from the cell body

2. (a)        A-Synaptic cleft

B- Mitochondria

  • Contains the transmitter substance/ Acetylcholine.

3.     a)     Show the effect of unilateral light on growth of seedling / plants;             (1mk)

                b)     (i)    Curvature of the tip of the shoot  toward the source light;

                        (ii)   Auxins / IAA/ Growth harmones; produced by the apical bud; move away from light / move to the dark side; causing faster elongation; hence curvature;

  •     In the roots / radicle higher  concentration of auxins / IAA inhibits growth; hence the upper side with less auxins grows faster than the lower side; (hence curvature downwards)                                                              (2mks)

4. Phototropisms;    -enables plant shoots to grow and get light for maximum photosynthesis; Allows for  leaf mosaic;

Chemotropism;   -Growth curvature in response to contact/ hard surface;

                 -Make plants with weak stems to get support on large plants /trees; this makes then to

                  reach and get light for maximum photosynthesis;

Geotropism;       -Growth curvature in response to gravity; enables plant roots to grow deep into the soil

                 to Maximum support/ anchorage;

Hydrotropism; – Growth curvature in response to moisture / water;

  • Enable plant roots to grow and find water in the soil; water is then used as a raw material   During photolysis stage;

Chemotropism; -Growth curvature in response to chemical concentration gradient;

  • Enables pollen tubes to grow down the style and into the ovary for fertilization to occur in plants flowers;

Thermo tropism; -Growth curvature in response to temperature changes;

 -Enables some plants to grow to where they can acquire optimum temperature for  effective plant processes; e.g. (Sunflower orientates towards the directions of the sun.

5        (a) 

  1. Dendrites
    1. Cell body
  2.  
  3. Has long axon to conduct impulses from CNs to effectors / muscles / glands;
  4. Axon enclosed with myelin sheath with nodes of ranvies to enhance speed of impulse conduction.
  5. Has dendrites which receive impulses from adjacent neurones.
  6.  
S.NM.N
– Cell body has no dendrites-Cell body has dendrites
– Cell body at a point  along nerve fibre;-Cell  body located at the top of nerve fiber;

6      a)     –       Hearing / detection of sound;

                                Body balance / posture;                                  (2marks.)

                b)     (i)    C- Ear canal / External auditory meetas;

                        (ii)   G- Semi – Circular canals;

                        (iii)  F- Auditory nerve;                                          (3marks)

                c)     (i)    Equalise air pressure between middle ear and outer ear / prevent damage of ear drum;                          (1mark)

                        (ii)   Cochlea/ E;                                                     (1mark)

                d)     –       Ear ossicles / D;                                              (1mark)

7.     a)     i)      Sensory neurons / afferent neurone

                ii)    Cell body located off the axon

        b)     N-    Axon

                P-     Cell body

                Q-    Myelin Sheath

                R-    Schwann cell

        c)     N-    Transmission of impulse

                Q-    Insulation / speed up impulse transmission.

8 a) Long sightedness / Hypermetropia ;                                                               1 mk)

b)     Short eye ball;

Weak lens (any one) ;1 mks

c)     Wearing of convex lens  / conveying lenses; 1 mk                                rj if a(i) is wrong

9 a) 1- Sensory neurone / Afferent neurone

2- Relay neurone     / intermediate neurone

3- Motor neurone/ efferent neurone                                                               3 mks

b)     Check on the diagram arrows show points towards neurone 3 from 2 and 1 :             1 mk

c)     Grey matter                                                                             1 mks

d)     Impulse reaching the dendrites  end of relay / Neurone 2 causes the synaptic vesicles, releases acetylcholine  / transmitter substancesü; into the synaptic  cleftü;the acetylcholine  / transmitter  chemical diffuses across the cleftü; and causes the depolarization of the  motor neuron/ neurone

  • Name the type of response (1mk)

10        Thigmotropism/Haptotropism;

  • Explain how the response named in (i) above occurs. (3mks)

Contact with support; causes migration of auxins to the outside; causing faster growth on the side away from contact surface; (Causing dendrils to curl around the support);

NB (a) (ii) is tied to (i)

  • What is the importance of tactic responses to microscopic plants? (1mk)

Escape injurious stimuli/seek favourable habitat

Rej. Seek mate and obtain food

11.   Describe how the mammalian ear is adapted to perform its functions. (20mks)                   

  • The pinna is flap made of skin and cartilage; for collection and concentration of sound waves;
    • Auditory canal/meatus is a tube lined with hairs which trap solid particles like dust; It has wax secreting cells; that secrete wax for trapping solids and insects entering the ear;
    • The eardrum/tympanic membrane is thin with double layer of epidermis; It vibrates translating sound waves into sound vibrations; Sound vibrations are transmitted to ear ossicles;
    • Ear ossicles are malleus, incus and stapes; they amplify and transmit vibrations to the oral window;
    • The oval window is a thin membrane which transmits sound vibrations to the fluid of the inner ear; perilymph and Endolymph;
    • Eustachian tube connects middle ear with pharynx equalizing air pressure in the ear with atmospheric pressure; to prevent distortion of the eardrum;
    • The cochlea is highly coiled tube with system of canals (and sensory cells) to occupy a small space/increase the surface area for accommodating many sensory cells to detect sounds vibrations; and generate impulses transmitted to the brain;
    • Auditory nerve transmits nerve impulses to the brain for interpretation;
    • Semicircular canals are tubular cavities containing fluid;
    • The canals are arranged at right angles to each other in the three planes of spaces; to detect changes in position of the body; the canals have ampulla: utriculus and sacculus; to detect position of body in relation to gravity;
    • Utriculus has otoliths attached to sensory cells which generate impulses which are then transmitted to the brain through the auditory nerve;
    • The perilymph and endolymph fluid in the inner ear absorb mechanical shock/transmit sound vibrations/protect delicate parts;                                        Total 25 max 20 marks

12             a)        i)      Conjunctiva transparent allow light to enter eye

    ii)    Cornea transparent / curved allow light / refracts light entering eye;

    iii)   Aqueous / vitreous humour – clear / allow light pass / refract light, hydrostatic pressure –

Maintain shape of eyeball. Contains sugars / proteins / salts – provide nutrients to eye.

    iv)    Iris – contractile – controls light intensity / amount of light entering eye;

    v)     Ciliary body glandular – secretes humuor

    vi)    Ciliary muscle contractile – controls curvature of lens;

    vii)  Suspensory ligament – fibrous – holds lens in position

    viii) Lens transparent / Biconvex – allow light go through to retina / refract light / focus light.

    ix)    Retina – rods – rhodopsin – for dim light vision;

                            – Iodopsin – for bright light vision

    x)     Fovea centralis – high concentration of cones – for accurate vision

    xi)    Choroid layer – blood vessels pigmented       – for nutrition

                            – reduce light reflection / absorb stray light

    xii)  Sclera – fibrous – protection / give eye shape;

    xiii) Optical nerves – sensory neurone – transmit impulse from retina to brain.

    xiv)  External eye muscle – contractile – move eyeball within socket

    xv)   Blind spot – cone and rods absent – no image is perceived

                                                    Correction

      b)   i)     Short sightedness;           biconcave / diverging lens

    ii)    Long sightedness;           converging lens / convex lens

    iii)   Astigmatism;                          use of cylindrical lens

    iv)    Squinting;                               surgery            (any 2 identifyü correctionü 4mks)

13.           Nervous communication                      Endocrine communication

– Nerve impulse to evoke a response              – Chemical substance/ hormone to evoke

   Response

                – High speed of transmission- Low speed of transmission;

                – Rapid response                             – Response delayed

                – Impulse transmitted through neurone  – Hormones transmitted in blood

                – Responses specific and localized to one      – Responses affects several parts of the

                  Target organ                                   body;

        Note: Comparison should come out clearly to award.

14.   a)     H – Eustachian tube;

                J – Semi-circular canals;

b)     H – Tube open/ connection to the pharynx and to the middle ear/ opens during swallowing/ yawning and vomiting to equalize the air pressure in the middle ear with the atmospheric air pressure;

                M – (pinna) curved/ funnel shaped to receive or collect and direct sound waves into the ear;

                N – (cochlea) – long/highly coiled/ spiral in form to increase surface area for sound Perception;

                – Has sensory hairs/ cells which convert sound vibrations to impulses/ generate impulses;

                – Has endolymph to transmit vibrations;

Mark one for each structure.

Rej. If the adaptation is not tied to function.

        c)     Total deafness;

        d)     Endolymph;

        e)     Balance; acc body balance/ posture.

15    (a) Tactic response;
(b) Move away from a harsh environment/move to favorable environment;

(c) To absorb any moisture from Petri dish A/OWTTE

16 .(a) A reflex mechanism/ability of the eye to adjust to bring an image from near or far object into sharp focus on the retina;
(b) Circular muscles of the iris contract; while the radial muscles relax; Ciliary muscles relax; increasing tension on suspensory ligaments; lens become thinner increasing the focal length; image focused onto the retina;
(ii) Circular muscles of the iris contract; pupil constrict/become smaller; and allows enough light for (sharp) image to be focused onto the retina;