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MANGU HIGH SCHOOL

BIOLOGY PAPER 1 MARKING SCHEME

1.a)Why would you give an athlete glucose and not sucrose after a race?(1mk)

Glucose is highly soluble in water (blood) hence its faster and easily transported to the respiratory sites/glucose is very simple in structure than sucrose hence easy to oxidize to yield energy to the body cells.

b)What happens to lactic acid after oxygen debt recovery?(2mks)

Its oxidized to release energy / converted into glycogen for storage in liver.

2.(a)What is gene Mutation(1mk)

Sudden change in the structure of gene

(b)State two disorders in human beings caused by gene mutation(2mks)

Albinism-Sickle cell Anaemia

Haemophilia -Chondrodystrophic dwarfism

Colour blindness (Achondroplasia)

(c)What name is given to the factors in the environment that encourage or speed up mutation(1mk)

Mutagens /mutagenic agents.

3.State three features used in classifying arthroponds into classes.(3mks)

Number of limbs

Presence and number of antennae

Number of body parts

4.State three environmental factor that affect the rate of stomata transpiration(3mks)

Light intensity

Temperature

Wind

Humidity

Atmospheric pressure

5.The diagram below shows the structure of sperm cell. Identify the parts labeled A, B and C and state their functions.(6mks)

PART

IDENTITY

FUNCTION

A

Acrosome

Contain lytic enzymes to break/dissolve egg membrane during fertilization

B

Mitochondria

Site for respiration to generate energy for the sperm movement

C

Tail

Propels the sperm in the female reproductive system

6.(a)Define the following terms (2mks)

i)Species:

A group of organisms that can naturally /freely interbreed to produce viable / fertile offspring

(ii)Binomial nomenclature;

Scientific naming of the organisms using genetic/genus and species names ( rej without genus & species)

(b)A certain sea animal has smooth skin, lungs ,regulates its body temperature and gives birth to young ones .the animal belong to the clas(1mk)

Mammalia

7.For a leaf to efficient in photosynthesis it has to be broad and flattened. Explain (2mks)

Provide large surface area for trapping maximum amount of light of light/absorbing

maximum Carbon (IV) oxide; required for photosynthesis.

8.Give reasons for each of the following;

a)Constant body temperature maintained in mammals (2mks)

Most /all biological activities in the body are carried out by enzymes; Enzymes

function within narrow range of temperature / they require optimum temperature for them to function.

b)Low Blood sugar level is harmful to the body.(2mks)

Sugar is a substrate for respiration therefore less sugar leads to low rate of respiration;

hence less energy available to the body/ low rate of metabolism.

9.State the functions of the following structure of the human brain(3mks)

(i)Cerebrum

Controls senses such as hearing and taste; integrating of sensory impulse human individualistic vision intelligence memory.

(ii)Cerebellum

Co-ordinate body movement/ maintain balance and posture / dexterity in the movement.

(iii) Medula oblagata

Controls breathing / vomiting / swallowing involuntary movement /

salivation / body temperature / sleep and wakefulness / feeding and drinking.

10.In what form is oxygen transported from lungs to the tissues?(1mk)

Oxyhaemoglobin

11.The diagrams below shows an experiment set up using growing bean seedlings.

What type of response does the shoot above show?(1mk)

Positive phototropism rej phototrophism

(b) Account for the shape of the bean shoot after four days of growth.(2mks)

Auxin hormones are sensitive to the light they migrate / diffuse to the side without light, where their high concentration stimulates rapid cell elongation as opposed to the light side the seedling curves towards the light.

12.The diagram below shows half the lower jaw of mammal. (2mks)

a) Name the teeth labeled

A – Incisors rej Incisor

C- Premolars rej premolar

b) State the function of tooth B

Tearing flesh

13.State three factors that affect the rate of diffusion (3mks)

Temperature

Surface area to volume ratio

Size of the molecule

Thinness/thickness of membrane

Concentration gradient

Stirring

14.Explain how the biceps and triceps muscles bring about the movements at the hinge joint of below in a man.(2mks)

When biceps muscles contract triceps relax it pulls the forearm and the arm ends towards the body when the triceps contract biceps relax and therefore arm is stretched/ extended.

15.Name one mechanism that hinders self-pollination in flowering plants(1mk)

Protondry / protogyny / self-sterility / incapability/ separate sexes /dioecious / heterostly / brightly coloured petals / sepals / peranth and bract to attract insects as agents of cross pollination.

16(a)State what would happen to a cell if its nucleus was removed(1mk)

Would survive for a short time and then die

Reason (1mk)

It will not be able to carry out normal functions which are controlled by the nucleus

(b)Give the functions of nucleus. (1mk)

Synthesis of RNA/ Ribosomes

17a)Name the products of the light reaction stage (2mks)

Hydrogen ions rej atoms

Oxygen gas

Energy

b)State the site where the following stage of photosynthesis takes place (2mks)

Dark Stage

Stroma

Light Stage

Grana

18.(a)Name two nutrients that do not require digestion before they are absorbed. (2mks)

Water

Mineral salts

Rej drug/ alcohol

(b)What is assimilation?

Incorporation of the products of digestion into the cell metabolism.

19.(a)Give a reason why the left ventricle muscles are thicker than the right ventricles(1mk)

To generate pressure to pump blood to all parts of the body / to furthest distance.

State the form in which carbon (IV) oxide is transported in the blood (1mk)

Hydrogen carbonate

Carbonic acid

Carbaminohaemoglobin

20.The figure below represents a transverse section of a young root.

a)Identify parts labeled(2mks)

A- Root hair

B-Endodermis

b) State the function of the parts labeled.

C

Transports water and mineral salts from the soil to the leaves.

D

Transports manufactured food from the leaves to the other parts of the plant  (2mks)

21.Explain how the following adaptation reduces transpiration in xerophytes  

(2mks)

a)Sunken stomata

Sunken Stomata forms pit in which water vapour accumulates reducing the rate of transpiration.

b)Thick waxy cuticle.

Waterproof to reduce the rate of transpiration.

22.The table below shows the estimated number of organisms in a lake.

Type of organisms

Weight in gram

Mosquito larvae

800g

Aquatic plants

5000g

Bacteria

40g

Fishes

1200g

Use the tale to answer the questions below

a)Construct a possible food chain(1mk)

Aquatic plant → mosquito larvae → fish → bacteria

b)Construct a pyramid of biomass for given data (2mks)

23.What is sex linkage?  (1mk)

Genes located on sex chromosome that is transmitted along with those determining sex.

24.Explain why individuals with smaller sizes require more energy per kg of body weight

Their surface area to volume ratio is larger therefore losing more heat; they require more energy per kg unit to maintain constant body temperature rej replace lost heat.

25.State the importance of placenta and amniotic fluid during pregnancy.

Placenta

Exchange of gases rej substances

Entry of nutrients rej exchange of nutrients

Removal of metabolic waste products from foetus.

Secrete progesterone hormon

Amniotic fluid

Absorbs shock before it reaches the foetus

Prevent dissections of foetus

Provide optimum temperature / Maintain constant temperature

26.Distinguish between the two patterns of evolution;(1mk)

(a)Divergent and convergent evolution

Divergent evolution is a mechanism of evolution where structures have same embryonic origin but they evolve to perform different functions while convergent structures of different embryonic origin evolve to carry out same function

(b)Why Lamarck's theory of evolution was rejected (1mk)

They acquired characteristics are not inherited /passed on the next generation

27.Name the meristematic tissues responsible for

(a)Primary growth(1mk)

Apical meristem

(b)Secondary growth in plants(1mk)

Vascular cambium/ cork cambium / intravascular cambium

28.The diagram below represents an organ from a bony fish, study the diagram and answer the questions that follow

State the functions of each of the following A and B (2mks)

A

Traps solid food particles filters solid food from the water

B

Provide large surface area for the attachment of many gill filaments’ and gill rakers

How is the structure labeled C adapt to its function

Dense network of blood capillaries / highly vascular for efficient transportation of gases.

Thin epithelium for rapid diffusion of gases ( rej Membrane for epithelium)

Elongated to increase surface area for diffusion of gases.