(a)   State the chemical composition of the following (3,3,3 marks)

i)     Proteins made from amino acid monomers comprising of Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Sulphur (S) and sometimes Phosphorus (P).

ii)    Fats made from Amino acids and Glycerol, they are composed of Carbon (C), Hydrogen (H) and Oxygen (O) only.

iii)   Carbohydrates made up of sugars, they comprise of Carbon (C), Hydrogen (H) and Oxygen (O) only.                                                                                          

(b)   How do you test for? (5,3,3 marks)

i)      The presence of reducing sugars in germinating maize seeds?

Aim: To test for reducing sugars in germinating seeds.

Requirements: Mortar, pistle, test tube, heat source, germinating seeds, water, Fehling’s (Benedict’s) reagent.

Procedure: Grind the germinating seeds in a mortar using a pistle. Add a little water and make a solution. Extract about 3ml of the solution into a test tube. Add about 2ml of Fehling’s reagent to the test tube. Boil and allow to cool.

Observation: A red precipitate is observed at the bottom of the test tube.

Conclusion: Reducing sugars are present in the germinating seeds used.

ii)    The presence of fats in meat?

Aim: To test for the presence of fats in meat using Sudan III test.

Requirements: Grinded meat sample, test tube, chloroform, Sudan III solution.

Procedure: The grinded meat sample is mixed with water and a solution is made. 0.5 ml of chloroform is put in a test tube and 0.5ml of the sample added and homogenised. 1 drop of Sudan III solution is added to the mixture.

Observation: A red colour is observed.

Conclusion: Fats are present in the meat sample used.

iii)   The presence of protein in meat?

Aim: To test for proteins in meat using the Biuret test.

Requirements: Grinded meat sample, NaOH, CuSO4, test tube, water.

Procedure: The grinded meat sample is mixed with water and a solution is made. 3ml of the solution is collected into a test tube. 1 ml of NaOH and 1 ml of CuSO4 are added to the test tube.

Observation: A brown ring forms at the top of the solution.

Conclusion: Proteins are present in the food sample.  (Total = 20 marks)

(a)   Draw a large and well labelled diagram of an insect pollinated flower.   (6 marks)

(b)   Distinguish between pollination and fertilization. (5 marks)

POLLINATION	FERTILISATION
Require external agents like wind,water	Does not require external agents
Takes place in plants only	Takes place in both plants and animals
Takes place externally	Takes place both internally and externally
It is the deposition of pollen grains on the anthers	It is the fusion of haploid male and female gametes to produce diploid zygotes.
A physical process	A cellular process

(c)    How is the ___________ Adapted to their various method of dispersal? (3, 3, 3 marks)

(i)         Coconut fruit

• It has air within to keep the fruit floating.
• Possess a hard shell that protects the seed as it falls off the tree.
• Seed shell is waterproof in nature to prevent water from entering the fruit.
• The fruit is round and can roll for meters after falling off.

(ii)        Cotton seed

• Seeds are small and light to be transported by wind.
• Seeds are feathery so they can be easily transported by wind.
• Seeds are resistant to harsh conditions.

(iii)       Mango fruit

• Seed is covered by juicy fruit.
• Fruits are sweet and colourful, with seeds within the fruit.
• Seed is slightly heariy and light so it can easily stick to animal fur and be transported.

(Total = 20 marks)

(a)   State the function of the human skeleton (5 marks)

• The skeleton functions in articulation or movement of body parts such as arms.
• The skeleton protects inner fragile organs like the brain, spinal cord, heart etc
• The long bone is the site of production of blood cells e.g. red blood cells are produced in the red bone marrow via a process called erythropoiesis.
• Site for storage of minerals like calcium.
• The skeleton gives shape
• The skeleton supports the body and keeps it in place

(b)   Make a labelled diagram of a typical synovial joint. (5 marks)

(c)   How does the eye function in vision? (5 marks)

For an object to be seen,light rays have to travel from the object into the eyes.

• Light travels from an object into the eye.
• The light is slightly refracted by the conea and aqueous humour.
• The light then passes to the lens where the most important amount of refraction is done.
• This light then passes through the vitreous humour before landing on the retina.
• The image formed on the retina is inverted. The signal is transferred via the optic nerves to the brain where the information is integrated.

(d)   What is  (2, 3 marks)

(i)         Long – sightedness

This is a condition where a person can see only distant objects. This is because the image of near objects are formed behind the retina.

(ii)        Astigmatism

This is a condition where a person sees blurry because of poor refraction of light at either the conea or lens or poor curvature at the retina. (Total =20 marks)

(a) Define the following terms (3,3,2 marks)

i)      Monohybrid cross

A monohybrid cross is a genetic cross between two individuals in which only one character or trait is studied.

ii)      Mutation

A mutation is any natural or induced change in the genetic make-up of an organism.

iii)      Homozygous

This is a condition whereby both alleles that make up a gene are similar e.g. “AA” or “aa”.

(b)   State the causes of mutation.   (4 marks)

• High energy radiation like UV rays, X rays, gamma rays etc.
• Cosmic rays from outer space.
• Radioactive radiations.
• Chemicals like mustard gas, caffeine, formaldehyde, cocaine etc.
• Tobacco, pesticides, drugs etc.
• Artificial or man induced

 

(c)   In a certain variety of squirrels, the fur colour is either grey or black. When a pure breeding black squirrel is crossed with a pure breeding grey squirrel, all the offspring produced had grey fur. When these offspring were allowed to interbred, the following results were obtained; 428 squirrels with grey fur and 152 squirrels with black fur.

Using appropriate symbols and diagrams explains the genetic of these crosses. (6 marks)

Let the dominant allele for skin colour (Grey) be G.

Let the recessive allele for skin colour (Black) be g.

(d)   How does bread mould reproduces asexually?    (2 marks)

Breadmould reproduces asexually by sporulation. The mould grows a sporangium that contains spores. When the spores mature, the sporangium burst. Releasing the spores which will later germinate to hyphae of bread mould. (Total = 20 marks)

(a)   Define the following terms as used in genetic engineering:          (3,3,3 marks)

i)      Restriction enzymes

These are enzymes used in genetic engineering to cleave/cut DNA into small, shorter and simpler units.

ii)     Recombinant DNA

This is a piece of DNA that has been produced artificially in the laboratory. It could comprise of one artificial and one natural strand of DNA or probably both strands being artificial.

iii)     Cloning.

This is the process by which an identical copy of a part or whole organism is artificially produced.

(b)     How are cereal plant important to mammals?     (6 marks)

Cereals are important to mammals in that;

• They reduce the chances of cancer and can stop any proliferations
• Help in digestion.
• Helps in the control of diabetes.
•  Very rich in nutritive content

(c)      Describe how atmospheric nitrogen is made available for plant use                  (5 marks)

Atmospheric nitrogen is converted to soil nitrogen via the following methods.

• Nitrogen fixing bacteria like Azobacter found in the root nodules of leguminous plants help to transform atmospheric nitrogen to soil nitrates which are absorbable and usable by the plant.
• Also, thunderstorms convert atmospheric nitrogen to soil nitrates. (Total = 20 marks)

---

---

DISCLAIMER

We at alstug.com assure the public that all answers provided are based on contributions from teachers around the nation and the world at large. The answers provided here are in no way gotten from the GCE marking guides. They are to be used as guides in your studies. Equally, these answers do not eliminate the teacher or the teachers information in any way. In a case of conflicting information, consult your teacher and/or the comment section of this site, or better still contact us directly with your information. We will be more than glad to be updated.

Remember that we are here for you.

---

---

By the ALSTUG Team.