Question 1
In an experiment a group of students set up four glass jars as shown in the diagram below. Jar A,B and C were maintained at 250C for 7 days while Jar D was maintained at 00C for the same period of time.
- What was this setup supposed to investigate?
- Why was pyrogallic acid induced in glass jar A?
- Explain why glass jar C and D were included in the experiment?
- What results would you expect in glass jar A and B at the end of the experiment.
- State two artificial ways of breaking seed dormancy.
Answer
- Investigate conditions necessary for germination of seed/To show that Water oxygen and warmth / temperature are needed for germination
- To absorb all oxygen from the jar
-
C-To show that water is needed for germination of seeds
D-To show that warmth is needed for germination -
Jar A-Seeds would not germinate
Jar B-Seeds would have germinated -
- Scarification
- Varnilasation
Question 2
A student drew the diagram to represent the three major organs labeled A,B and C and the main blood vessels in mammalian circulatory system.He observed that the blood vessel R carries blood rich in oxygen while U is rich in Carbon (IV) Oxide.
- Identify organ labeled A and B
- Name the blood vessels labeled R,S,U and T
R-
U-
S-
T- -
- With the aid of arrows at vessel R,U,T and S show the direction ofblood flow
- Name the parts of organ C numbered 1 and 4
1-
4-
-
- Explain why the circulatory system illustrated is described as double
- How does blood in vessels T differ from that in vessel U?
Answer
-
A-Lungs
B-Body tissues/organs -
R-Pulmonary veins
S-Pulmonary artey
U-Vena cava
T-Aorta
- 1-Right atrium
4-Left ventricle
- Blood enters the heart twice in a complete circulation/has pulmonary and systematic circulation
- Blood in T rich in oxygen and at high pressure; blood in U rich in carbon(iv) oxide and at low pressure
Question 3
- Fresh protozoa have active contractile vacuoles while marine protozoa do not have. Explain
-
Fresh water animals excrete their nitrogenous waste in form of ammonia, mammalian form of urea, while reptiles, birds and insects it is in the form of uric acid. Explain the necessity of excreting nitrogenous waste in different forms by organism
- Fresh water animals
- Mammals
- Reptile, birds and insects
Answer
- Fresh water protozoa draw in water from the surrounding by osmosis sincecytoplasm is hypertonic; contractile vacuole discharge excess water; cytoplasm of marine protozoa is isotonic to sea water
-
- Fresh water: Ammonia highly toxic; hence diluted by excess water, ammonia require a lot of water to dilute/make it less toxic
- Mammals: Urea less toxic/less soluble, hence need less water for elimination
- Reptiles birds and insects: Uric acid non-toxic/insoluble; make organisms conserve water since it is scarce
Question 4
- Name three examples of disaccharides
- State the three properties of disaccharides
- State the different between reducing and non reducing sugars
Answer
-
-Sucrose
-Lactose
-Maltose -
-They are soluble in water
-Are Crystalline
-They are sweet tasting -
-Reducing sugars-form an orange precipitate with Benedict solution
-Non-reducing sugars-No colour change when reacted with Benedict solution i.e colour remains blue
-Reducing sugars are simple sugars are complex sugars
Question 5
A common species of rats has individuals with white, black or grey coats. During a study a rat with white coat was crossed with a rat with grey coat. Both parents were pure lines. All the off spring in F1 generation had grey coat. Using letter B to represent the gene for black coat and W for white coat, answer the following questions.
- Work out the phenotypic ratio of the F2 generation
- Give a genetic explanation for the appearance of rats with grey colour
- State the significance of the test cross in the study of genetics
- State two importance of crossing over in meiosis
- Name one example of a characteristics in man that is transmitted by multiple alleles
Answer
-
- Incomplete / partial dominance
- To establish the unknown genotypes of an organism
- -Results in new gene combination/recombination
-Leads to variation/hybrid vigour