Biology Paper 2 Questions and Answers - Wahundura Boys Mock Examination 2023

INSTRUCTIONS

This paper contains THREE Sections. Answer ALL the questions in the spaces provided IN THIS PAPER.
ALL the answers must be clear and precise.
Answer all the questions using correct English.

QUESTIONS

The diagram below shows a part of a plant tissue.
1. Name cell X and Y. (2 marks)
  X
  Y
2. Diagram B is drawn to show the change that has occurred in A. State the change. (1mark)
3. Explain how light could bring the change you have stated in (b) above. (5 marks)
The diagram below shows a light microscope. On the diagram, label the part responsible for the following functions as X, Y, and Z as follows:
1. 1. Produce precise and fine focusing - X (1mk)
  2. Concentrate light on stage - Y. (1 mark)
  3. Change from one objective lens to the other - Z. (1 mark)
2. Give two functional differences between the above microscope and the electron microscope (2mks)
  
  Light microscope
  
  Electron microscope
3. Give the importance of the following in microscopy
  1. Cutting a thin section (1mk)
  2. Staining (1mk)
4. Write down the formula for obtaining magnification using a light microscope. (1 mark)
The chart below represents a feedback mechanism in the human.
1. Identify feedback mechanism A and C. (2mks)
  A
  C
2. Name the hormones involved in feedback A and B. (2mks)
  A
  B
3. Name two organs involved in feedback B. (2mks)
4. Pancreatic duct of an animal was cut. Digestion in the duodenum was affected but regulation of blood sugar remained normal. Explain. (2 marks)
In tulip plants, the petals can have markings called flecks. There are two alleles for flecks in tulip plants: with flecks F; and without flecks f.
1. Explain the meaning of the term dominant allele. (2 marks)
2. A tulip grower crosses two tulip plants. He finds that 76 of the offspring have petals with flecks and 23 of the offspring have petals without flecks. Make a genetic cross to explain the results. (4 marks)
3. The tulip grower wants to produce a pure-breeding variety of tulips with petals without flecks. State the genotypes of the parent plants he should use to produce tulip plants without flecks. Explain your answer. (2 marks)
  1. Parental genotypes
  2. Explanation
A Form three student came across an organism with the following characteristics;
- Have jointed appendages
- Segmented body
- Have open circulatory system
- Body covered with exoskeleton
  1. Classify the organism into the following taxa
    1. Kingdom …………………………………………… (1mk)
    2. Phylum ……………………………………………… (1mk)
  2. 1. Give any three importance of organisms in this phylum to plant life (3mks)
    2. Give three reasons why we should classify organisms (3mk)

SECTION B (40 MARKS)
Answer TWO questions ONLY. Question 6 is compulsory. Then ANSWER question 7 or 8.

The data below represents the level of progesterone hormone produced in a female’s body within a period of 34 days. Study the data and use it to answer the questions that follow. N/B: The days were counted from the 1^st day that menstruation was noticed.

Day	Progesterone hormone concentration in arbitrary units
1	6
2	5
3	3
4	2
5	1
6	1
8	1
10	2
12	4
14	7
16	8
20	9
22	10
24	10
26	10
28	10
30	11
32	11
34	11

Day Progesterone hormone concentration
in arbitrary units

Plot a graph of progesterone concentration against time using a suitable scale (6 marks)
Account for the progesterone levels in the blood stream between
1. Day 1 - day 5 (2 marks)
2. Day 14 - day 20 (3 marks)
3. Day 28 - day 35 (2 marks)
Name two structures that produce progesterone in females (2 marks)
Suggest the process that usually takes place at day 14 (1 mark)
Suggest two other hormones that were in high concentration in the body of the female between days 11 -- 15. Give reasons for your answer. (4 marks)

1. Giving examples discuss how the following evidences of organic evolution show that evolution has taken place.
  1. Comparative anatomy (6mks)
  2. Geographical distribution (4mks)
  3. Comparative cell Biology (3mks)
2. Describe how water moves from the soil to the xylem vessels. (7 marks)
Describe the structure and functions of various organelles in a mature animal cell. (20mks)

Marking Scheme.

1. X- Guard cell; (1mk) rej. Guard cells
  Y- Epidermal cell; (1 mk) rej. Epidermal cells
2. Stoma open;
3. Chloroplast in the guard cells carry out photosynthesis producing sugar/glucose; sugar accumulates in the sap vacuole of guard cells increasing the osmotic pressure; water is drawn into the guard cells from surrounding epidermal cells by osmosis; the guard cells become turgid;bulge outwards and stoma opens; 5marks

X- Fine adjustment knob
Y- Condenser
Z- Revolving nose piece/Turret

Light microscope

Electron microscope

Uses light for illumination

Have low magnification

Has low resolution power

Magnify both live and dead objects

Image observed directly

Specimen is placed on a slide and placed on a stage

Uses glass lenses

Uses beam of electron for illumination

Have a higher magnification

Has a high resolution power

Magnify dead objects

Image observed on a screen.

Specimen is placed on a slide and mounted on a vacuum

Use magnetic deflectors

NB: MARK FIRST TWO

(2mks)

1. To allow light to pass through. (1mk)
2. To distinguish/differentiate cell components (1mk)
Eye piece lens magnification × objective lens magnification

1. A- Negative feedback
  C- Positive Feedback
2. Hormone A- Insulin
  Hormone B- Glucagon
3. Liver and Pancreas
4. Cutting pancreatic duct prevents entry of digestive enzymes into duodenum; while pancreas secretes hormones (insulin and glucagon) into blood which is transported to liver cells and stimulate them to regulate blood sugar;
In tulip plants, the petals can have markings called flecks. There are two alleles for flecks in tulip plants: with flecks F; and without flecks f.
1. Explain the meaning of the term dominant allele. (2 marks)
  - The allele that expresses itself both in homozygous and heterozygous condition;
2. A tulip grower crosses two tulip plants. He finds that 76 of the offspring have petals with flecks and 23 of the offspring have petals without flecks. Make a genetic cross to explain the results. (4 marks)
3. The tulip grower wants to produce a pure-breeding variety of tulips with petals without flecks. State the genotypes of the parent plants he should use to produce tulip plants without flecks. Explain your answer. (1 marks)
  1. Parental genotypes
    - ff X ff ;
  2. Explanation. ( 1mrks)
    - both parents must have a recessive allele / (if ff × ff) no dominant or F allele, in either parent / (if ff × ff) both parents must be homozygous, recessive / without flecks no parent must be homozygous dominant / presence of (even) one dominant allele in parents could result in flecks; (OWTTE)
1. 1. Kingdom – Animalia; Rej: Wrong spelling; Animal(s); if begins with small letter a 1 mark
  2. Phylum – Arthropoda; Rej: Wrong spelling; if begins with small letter a 1 mark
2. 1. - Dispersal of seed;
    - Maintenance of soil structure/fertility;
    - Crop pest;
    - Aerate the soil;
    - Control population of other organisms;
    - Recycle nutrients;
    - Pollinate plants; 3mrks (mark any three)
  2. - To help in identifying organisms into their correct groups/taxa for reference;
    - Grouping brings together living organisms with similar characteristics but separate those with different features;
    - Helps in arranging information about living organisms I n an orderly manner to avoid chaos confusion if it were done arbitrarily;
    - Help us to understand evolutionary relationships between different organisms; 3 mark (mark first three)

SECTION B (40 MARKS)

The data below represents the level of progesterone hormone produced in a female’s body within a period of 34 days. Study the data and use it to answer the questions that follow.
N/B: The days were counted from the 1st day that menstruation was noticed.

Day	Progesterone hormone concentration in arbitrary units
1	6
2	5
3	3
4	2
5	1
6	1
8	1
10	2
12	4
14	7
16	8
20	9
22	10
24	10
26	10
28	10
30	11
32	11
34	11

Plot a graph of progesterone concentration against time using a suitable scale (7 marks)
Account for the progesterone levels in the blood stream between
1. Day 1 - day 5 ( 2mrks)
  Level of progesterone was going down; corpus luteum has disintergrated;
2. Day 14 - day 20 ( 3 mrks)
  Level of progesterone increasing rapidly; to stimulate thickening and increased blood supply in the endometrium; in preparation of implantation; (of the blastocyst)
3. Day 28 - day 35 (2marks)
  Level of progesterone increases further; this is because implantation has taken place and progesterone is required to maintain pregnancy;
Name two structures that produce progesterone in females ( 2mrks)
Ovaries;/ corpus luteum;
Placenta;
Suggest the process that usually takes place at day 14 ( 1mrk)
Ovulation;
Suggest two other hormones that were in high concentration in the body of the female between day 11 -- 15. Give reasons for your answer. ( 4mrks)
Oestrogen; Stimulate repair and healing of the endometrium;
Stimulate the anterior lobe of the pituitary gland to secrete luteinizing
hormone;
Luteinizing hormone; stimulates ovulation;

1. 1. COMPARATIVE ANATOMY
    Anatomy is the study of structures of living organisms. Comparative anatomy is comparison of internal structures of various organisms. Some show basic structural similarities and this suggests that the organisms have a common or related ancestry
    i.e. homologous structures, but are modified to perform different functions. They have gone through divergent evolution.
    Examples of homologous structures are beaks of birds, feet of birds, pentadtyl limb in mammals. Other structures show basic structural differences since they have different embryonic origin but have gone through convergent evolution and modified to perform similar function. This are analogous structures e.g. wings of bats, insects and birds.
    Others are vestigial structures- those structures in course of time become greatly reduced and become function less. This indicate that they were present in their ancestral forms which have since evolved e.g. Coccyx- tails in human, body hair, reduce wings in flightless birds like kiwi.
  2. GEOGRAPHICAL DISTRIBUTION
    The theory of continental drift supposes that at some time the present day continents were one single landmass which later broke up into parts which drifted apart. Closely related organisms were separated and isolated from one another thus evolving differently, with time leading to formation of different species through natural selection. Each group of organisms adapted to different set of environmental conditions e.g. camels in Africa and llama in South America.
  3. COMPARATIVE SEROLOGY/CELL BIOLOGY
    Comparative cell biology is a comparison of different blood proteins in different organisms. This study shows that organisms that are closely related or have a common ancestry have similar blood proteins which is tested using antigen-antibody reaction. Where precipitate from varies from one animal to another. Greater amount of precipitate shows many common antigen hence common antibodies hence more reaction. This indicates that the organisms have a common ancestry. Less amount of precipitate show that few or none antigen is common in organisms hence are apart i.e. common ancestry.
    Increase genetic variations to all organisms to adapt to environmental/heterozygosity Bring about beneficial/advantageous traits e.g. leads to malaria resistance in human with sickle cell trait and leads to antibiotic resistant strains of bacteria to allow them to survive in presence of drugs
2. Water exists as a thin film in the soil/between soil particles; The concentration of cell sap of root hair is greater than that of the surrounding solution in the soil; thus drawing the water molecules across the cell membrane into the root hair cell; by osmosis; water drawn into the root hair dilutes the cell sap/makes it less concentrated than that in the adjacent cortex cells; water then moves from cell to cell by osmosis; across the endodermis by active transport; finally into xylem vessels; (then conduct the water up into the xylem of the stem)
Mitochondria;
Has a double membrane surrounding it and inner membrane folded to form cristae which increases the surface area for attachment of respiratory golgi body/apparatus, are stack of membrane bound like sac/is a system of membranes sacs/hollow spaces; that transports glycoproteins/carbohydrates and proteins; They package glycoproteins; secrete mucus/enzymes/synthesized proteins.
Lysosomes
Are spherical in shape and enclosed by a single membrane; contain hydrolytic enzyme which destroy worn out organelles, micro-organism/ingest food/breakdown large molecules.
Endoplasmic reticulum
Are membrane bound cavities in cytoplasm; smooth endoplasmic reticulum site for lipid/sterot transport. Rough endoplasmic reticulum ahs ribosome on its surface; and transport proteins.
Centrioles
Rod shaped; located outside the nuclear membrane, for formation of fibs and cilia Cytoplasm;
It’s a fluid medium; where chemical reaction occurs, contains organelles and inclusions (e.g. glycogen granules, fat droplets and dissolved substances).
Cell membrane
Encloses all cell organelles; has phospholipid layer between two protein layers/it’s a lipoprotein layer has pores that selectively allows substances to pass in and out of the cell/its semipermeable.
Nucleus
Has a double membrane/nuclear membrane around it, which has pores to allow substances in and out of the nucleus; Has nucleoplasm, which contain nucleolus/chromatin, nucleus controls all cell activities, Nucleolus manufactures ribosomes and centrioles.
Ribosomes
Are spherical in shape and suspended in cytoplasm and attached on endoplasmic reticulum; synthesis proteins.