a. State three features of the small intestine that increase the rate of absorption of digested food. [3 marks]
b. Explain briefly what happens to the glucose formed in a plant during photosynthesis. [3 marks]
c. Explain briefly the mode of feeding in each of the following organisms:
(i) Euglena; [4 marks]
(ii) Spirogyra. [4 marks]
d. State three characteristics of an Estuarine habitat. [3 marks]
e. State three differences between an aquatic habitat and a terrestrial habitat. [3 marks]
Explanation
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.
(i)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
d. Differences between an aquatic and terrestrial habitat
|
Aquatic habitat |
Terrestrial habitat |
|
Temperature is lower |
temperature is higher |
|
Water is the medium for growth/reproduction |
soil is a medium for growth |
|
Presence of dissolved oxygen |
presence of atmospheric oxygen |
|
Organisms are not affected by humidity |
organisms are 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 |
|
Light affects the distribution of organisms more |
light affects the distribution of organisms less |
|
Water is abundant |
water is not abundant |