SECTION A (40 MARKS)
Answer ALL the questions in this section in the spaces provided.
- The flow diagram below represents passage of a meal through the human digestive system. Study the diagram and answer the questions that follow.
- Name the physical process that will occur in mouth cavity (1mk)
- Name the digestive juices B and C (2mks)
- Explain two ways in which the digestive system is protected from corrosive effects of digestive juices. (2mks)
- Name the hormone that stimulate secretion of juice B. (1mk)
- Identify two contents of digestive juice A (2mks)
- Examine the diagram below and answer the questions that follows
- Name the parts labeled A-D (4mks)
- State the type of germination exhibited by the seedling above (1mk)
- State and explain three environmental conditions necessary for germination. (3 marks)
- A cross between a red flowered plants and white flowered plants produced plants with pink flowers. Using letter R to represent the gene for red color and W for white.
- What were the parental genotypes? (2mks)
- Work out the cross between f1 generations (4mks)
- State the phenotypic and genotypic ratios of the f2 generations (2mks)
- What is meant by:
- Autecology (1mk)
- Synecology (1mk)
- Using the table below, answer the questions that follow
Number of stomata
Leaf
Upper epidermis
Lower epidermis
A
300
0
B
150
200
C
02
13
- Suggest the possible habitat of the plants from the leaves were obtained (3mks)
- State the modifications in the stomata of leaf C (3mks)
- What is meant by:
- The diagram below shows a section through the mammalian skin
- State the function of the parts labeled W and Z (2mks)
- Explain the changes that occur on the skin when it is cold (4mks)
SECTION B: (40MKS)
QUESTION 6 is COMPULSARY: Answer either question 7 or 8.
- In an experiment, three healthy rabbits were fed with equal amounts of carbohydrates. After 1 hour their blood sugar glucose concentration was measured at 30 minutes intervals for 3 hour. The results are as shown in the table below.
Glucose conce Mg/ml Rabbit
Initial time(minutes)
30 Minutes
60Minutes
90 Minutes
120 Minutes
150 Minutes
180 Minutes
P
1.6
1.55
1.43
1.36
1.3
1.19
1.11
Q
1.49
1.39
1.34
1.32
1.27
1.2
1.09
R
1.59
1.39
1.33
1.27
1.18
1.1
0.99
Mean
1.56
1.44
1.32
1.25
1.16
-
- On the grid provided plot a graph of mean glucose concentration against time. (6mk)
- What was the mean concentration in the blood after 75minutes? (1mks)
- Why was it necessary to use 3 rabbits in the experiment? (1mks)
- Account for differences in mean glucose concentration between initial time and 180 minutes
- Name three products of digestion other than glucose (3mks)
- What is the fate of excess glucose in:
- Plants? (2mks)
- Animals ? (2mks)
- Describe how the male reproductive system is adapted to its functions.(20mks)
- How are structures of the human eye adapted to their functions (14 marks)
- State three defects of the eye and how each can be corrected ( 6 marks)
MARKING SCHEME
-
- Mastication;/chewing;/grinding; any one (1mk)
- B – Gastric juice; (1mk)
C – Intestinal juice;/succusentericus; (1mk) reject wrong spelling - produces mucus;
- Enzymes produced in inactive from that is pepsinogen and trypsinogen (2mks) - Gastrin; (1mk)
- – Enzyme salivary amylase.Ptyalin;
- Mucin/Mucus;
- Water; (any two) (2mks)
- A- Foliage leave, C-Hypocotyl
B –Cotyledon, D-Roots - --Epigeal germination
- Optimum temperature----To activate the germination enzyme
- Oxygen –Oxidising the food material to release energy necessary for germination
- Water----solvent to dissolve substance weaken testa to enable germination to place and hydrolysis enzyme
- A- Foliage leave, C-Hypocotyl
- RR; WW; (2mks)
- Phenotypes Pink Pink (1mk)
- Phenotypic ratio; 1 Red flowered: 2 Pink flowered: 1 white flowered; Rej: 1:2:1 (1mk)
Genotypic ratio 1RR: 2RW:1WW; Rej: 1:2:1 (1mk)
- Autecology-study of a single species;
Synecology-study of many species;
A- aquatic/ fresh water;
B-terestrial/ forest;
C-arid/ semi-arid/ desert;
-Sunken stomata;
-Reversed stomatal rhythm;
-Mid-day closure;
- Small stomatal pore - Y-sweat pore;
X-Eractor pili muscles; (2mks) - W- produces sebum which keeps the skin supple/ antiseptic
Z- Secrets sweat which evaporates to bring about cooling/sweat also removes excretory products/excess salts/water (2mks) - vasoconstriction; hence less blood flows to the skin surface;reducing heat loss;no sweating;heat produced throught metabolisms/shievering;heat is retained in the body; ( 4 marks)
- Y-sweat pore;
- 60 minutes – 1.37;
180 minutes- 1.06; - On grid provided;
- 1.35+ 0.001mg/ml;
- To get more reliable results;
- initial glucose concentration was high because of absoption into the blood stream.
Glucose concentration decreased due to oxidation to release energy; excess converted to glycogen; under Influence of insulin;
- 60 minutes – 1.37;
- Amino acids; fatty acids; glycerol;
- Trans located; to storage organs; and converted into starch;
- translocated to the liver( 1mk); and converted to glycogen;
- Consist of testes; that lie outside the abdominal/location outside the body to provide cooler environment/ lower temperatures; suitable for sperm production/ spermatogenesis;
inside the testes there are seminiferous tubules; that are highly coiled and have actively dividing germinal epithelial cells; that form sperms;
Interstitial cells that produce male sex hormones/ Androgens/testosterone; that promotes development of secondary sexual characteristics; and maintain masculinity;
Epididymis form ducts that convey sperms out of the testes; testes they are highly coiled to increase surface area for the (temporary) storage of sperms;
Sperm duct/vas deferens has thick muscular walls that contracts to propel sperms to the urethra (during ejaculation)
Seminal vesicle; is a blind ending sac that produces alkali fluid; with nutrients for the spermatozoa/sperms; to provide energy for the sperms;
Prostate glands; secrete alkaline; fluid that neutralizes the acidic vaginal fluids; and activates the sperms;
Cowper’s gland; secrets alkaline fluid that neutralizes the acidity of urine in the urethra; :urethra is along tube along the penis; for conduction and expulsion of urine; and passage of sperms during copulation;
penis is made up of spongy erectile muscular tissue; consisting of numerous spaces that are filled with blood; making the penis to become erect during sexual stimulating/activity; to enable it penetrate the vagina; to deposit sperms;
tip of penis has gland; that is highly innervated for stimulation during sexual activity;
Scrotum/scrotal sac; is a sac like structure made of skin and it encloses testes protects the testes; (Total 20) -
Adaptation
Function
Conjunctiva - An epithelium colourless
Protects eyeball
Cornea: Transparent/curved
Allow light/ refract light entering the eye
Aqueous/vitreous: clear
Allow light to pass through/ refract light.
Maintain the shape of the eye
Iris. Opaque and contractile
Controls light intensity/amount of light entering the eye.
Ciliary muscle/ body contractile
Control curvature of lens, secretes humour
Suspensory ligaments: are fibrous
Hold lens in position
Lens is transparent; lens is biconvex
To allow light to go though/to refract light/ to focus light.
Retina- contain light sensitive cells
Where an image is formed which perceive light.
Cones: contain pigments
For colour vision/ bright light/ light of high intensity
Rods contain pigments
For dim light vision
Foreacentralis: High concentration of cones
For accurate vision
Choroid: Layer has blood vessels
For nutrition and pigments.
Reduce light reflection and absorb stray light
Sclera- Tough/ non elastic or fibrous
Gives eye shape and protects
Optic nerve
Contain sensory neurones for transmitting impulses from retina to brain.
Defect
Correct
Myopia/ short sightedness
Biconcave/diverging lenses
Hypermetropia/long sightedness
Biconvex/ converging lenses
Astigmation
Use of cylindrical lenses with combined curvature
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