Question 1
-
(i) Name the structure of the plant where translocation takes place
(ii) State three structural adaptations of the part named above - Explain the movement of water from the soil until it reaches the root xylem
Answer
-
i. Phloem/phloem tissue:
ii.- - Sieve tubes have cross-walls called sieve plates that are perforated: to allow the flow of synthesized food material from one sieve tube to the next
- - Presence of cytoplasmic strandal/ protein strands that allow the streaming / flow of synthesized food material along them during translocation
- - Presence of companion cells next to the sieve tubes, which have numerous mitochondria to produce energy for translocation;
-
In the soil water exists as a thin film in the soil particles /soil solution
The concentration of the cell sap of the root hair is greater than that of the surrounding solution in the soil
The water molecules from the soil solution are drawn into the cell sap of the root hair cells, through the cell wall; and semi-permeable cell membrane by osmosis; thus dilute the root hair cell sap causing it to become less concentrated than that of the adjacent cortex cell of the root; water enter the cortex cell by osmosis; then pumped across the endodermis into the root xylem;
Question 2.
The structure below is found in the members of a class in the kingdom Animalia
- Name the class from which the animal with the structure above is found
- State the functions of the parts labelled T and R
- Name the structure on the animal that protects S from mechanical injury
- State the adaptations of the part labelled S
Answer
- Pisces
- T – Gill rakers
– are used filtering food particles from the water before it flows over the gills; thus protect the gill filaments from mechanical damage /injury - Operculum
- Gill filament are numerous to provide large surface area for gaseous exchange; gill filaments have thin walls /one cell thick /epithelium wall to reduce the distance over which the gases diffuse; Gill filaments have moist surface/ covered by mucus to facilitate faster diffusion of respiratory gases; Gill filaments are highly vascularised / have dense network of blood capillaries to facilitate transport of respiratory gases to and from the gills.
Question 3
- Define the term autotrophism
- Explain what happens during the light stage of photosynthesis
- Explain three adaptations of the mesophyte leaf to photosynthesis using the following heading
(i) Palisade mesophyll layer
(ii) Spongy mesophyll layer - State the role of Carbon (IV) oxide during photosynthesis
Answer
- Is a type of nutrition where organisms especially green plant6s and some bacteria manufacture their own food; from simple inorganic materials with the help of sunlight/chemical reactions;
- Light stage. Light trapped by chlorophyll pigments is used to split water molecules chemically (in the granum) to produce hydrogen ions, and oxygen; some of the light Energy is used to produce ATP molecules
- i. Palisade mesophyll layer have cells with numerous chloroplasts; to provide large surface for maximum photosynthesis;
palisade mesophyll cells are numerous to provide large surface are for photosynthesis;
Palisade mesophyll cells are found next to the upper epidermis; for maximum absorption of sunlight for photosynthesis;
ii. Spongy mesophyll layer has cells that have irregular shape and loosely packed to provide large intercellular air spaces for free circulation of carbon (IV) oxide to reach the photosynthesis cells; chloroplasts that provide a site for photosynthesis. - Carbon (IV) oxide reacts with hydrogen ions/ atoms in the presence of ATP/ energy to form simple sugars
Question 4
- Differentiate between the mode of fertilization in higher plants and in mammals
- Explain the role of the following hormones in the female menstrual cycle
(i) Oestrogen
(ii) Luteinizing hormone - Give two functions of the placenta during pregnancy
Answer
-
Fertilization in higher plants –involves one male nucleus fusing with a functional; egg to form a zygote; while the other male nucleus fuses with the polar nuclei to form a triploid cell;
In animals, fertilization involves the fusion of the male nucleus and female ovum nucleus to form a zygote - Explain the role of the following hormones in the female menstrual cycle
(i) Oestrogen
(ii) Luteinizing hormone -
i. Oestrogen
- Promotes / causes /initiate the healing /repair of the endometrium/ uterine’
- Stimulates the pituitary gland to secrete Luteinising hormone
ii. Luteinising hormone (LH)
– Causes ovulation;
– Stimulates the Graafian follicle remains to change into the corpus lutevis;
– Stimulates/causes corpus luteum to secrete progesterone
Question 5
- What is mutation
- Explain why certain bacteria and other pathogens become resistant to drugs after some time
- Work out a cross between a Haemophiliac man married to a carrier woman for Haemophilia
- State the phenotypic ratio of the children
Answer
- Mutation is a sudden / spontaneous change; in the genetic make up of an organism
- Bacteria that survive the drug will undergo mutation; to produce bacteria which are resistance to the prevailing condition / drug
-
Phenotypic ratio:
1 male normal
1 male haemophiliac
1 female haemophiliac
1 female carrier
1male normal: 1male haemophiliac :1 female haemophiliac: 1 female carrier:
Download the whole paper (including marking scheme) as PDF