Question 2
- State three features of the small intestine that increase the rate of absorption of digested food. [3 marks]
- Explain briefly what happens to the glucose formed in a plant during photosynthesis. [3 marks]
- Explain briefly the mode of feeding in each of the following organisms:
- Euglena;
[4 marks]
- Spirogyra.
[4 marks]
- Euglena;
- State three characteristics of an Estuarine habitat. [3 marks]
- State three differences between an aquatic habitat and a terrestrial habitat.
[3 marks]
Just a few candidates could state the features of the small intestine that increases the rate of absorption of digested food.
Observation
Many candidates could not answer (b).
Candidates could not give proper answers to the mode of feeding in Euglena and Spirogyra.
Only a few candidates knew how to answer the question on Estuarine habitat.
The candidates that answered (e) could not correspond their answers properly.
The expected answers are:
(a)Features of the small intestine that increase the rate of absorption of digested food
- Ridges/furrows on inner linings;
- Small finger-like projections/villi;
- Minute projections/microvilli on the villi;
- Thin epithelial lining of the villi;
- Highly vascularised/well supplied with blood;
- Intestine is long/it has a large surface area.
(b)
Fate of glucose formed in a plant during photosynthesis
- Glucose combines with Nitrogen/Sulphur/Phosphorus to form proteins for growth;
- Glucose is stored as starch;
- Glucose is oxidised to form carbon dioxide/water/energy in respiration;
- Glucose is also converted into lipids/cellulose which is stored.
(c) Mode of feeding of
(i)Euglena
- Exhibits both autotrophic and heterotrophic modes of nutrition;
- In autotrophic mode of feeding, the chlorophyll in its stellate chloroplast absorbs sunlight energy
- And the dissolved carbon dioxide in the pond water diffuses into the cell of Euglena
- Inside the chloroplast, the absorbed solar energy/sunlight is used in the synthesis of glucose from water and carbon dioxide
- Glucose is converted into starch and stored in the paramylum granules
- In heterotrophic mode of feeding, it takes in organic matter/diatoms e.t.c.
- Through the gullet;
- And digests it in the reservoir.
(ii) Spirogyra
- Manufactures its own food through photosynthesis;
- Its spiral chloroplast/chlorophyll absorbs the sunlight energy;
- It absorbs carbon dioxide from water/its environment to manufacture food;
- The manufactured food is used;
- while the rest/excess is stored in its pyrenoid in the form of starch.
(d) Characteristics of an Estuarine Habitat
- It is shallow;
- It has a high level of nutrients;
- Salinity/pH/O2 level fluctuates;
- Turbidity is high during rainy season;
- It is affected by tides;
- Species diversity is low;
- Muddy/soft soil/substratum
(e) Differences between an aquatic and terrestrial habitat
Aquatic habitat |
Terrestrial habitat |
- Temperature is lower |
temperature is higher; |
Thoracic |
Chest/thorax |
- Water is the medium for growth/reproduction |
- Organisms are not affected by humidity |
- Organisms are affected by tide/waves/water current |
organisms are not affected by tide/waves/ water current |
- Organisms are not affected by wind action |
organisms are affected by wind action;x |
- Light affects the distribution of organisms more |
light affects the distribution of organisms less; |
- Water is abundant |
water is not abundant. |
Note: Points must correspond to score.
Correct vertebrae x 1 mark
Vertebrae spellings must be correct to score
(b) Function of
(i) Palisade
- Manufactures food/carries out photosynthesis/site of photosynthesis;.
- Contains chloroplasts for photosynthesis..
(ii) Vascular bundle.
- Contains xylem for transport of water/mineral salts/phloem for translocation of manufactured organic substances/hormones;.
- Provides mechanical support.
(iii) Epidermis
.
- It keeps the leaf’s shape;.
- Reduces water loss/evaporation;.
- Protects the internal structures of a leaf;.
- Contains stomata for gaseous exchange.
(c) Function of
(i)Sieve tube
Translocates/transports manufactured foods to other parts of the plant.
(ii) Cortex
- The cells of cortex store starch;
- Outer cortex cells of green stems contain chloroplasts and make food by photosynthesis/chlorophyllus cortex cells manufacture food.
(iii) Pith
- Cells of pith act as packing/food storage tissues;
- Supports the stem.
(d)Structural differences
(i) External structural differences between stem and root of a maize seedling
Just a few of the candidates could conveniently answer (d). others could not correspond their answers.