Question 2
(a) List five stages of holozoic nutrition in humans.
[5 marks]
(b) Explain briefly the following nutrition in humans.
(i) secretion;[2 marks]
(ii) elimination;[2 marks]
(iii) excretion.[2 marks]
(c) Make a diagram, 8 cm to 10 cm long of the longitudinal section of the villus of a small intestine and label fully.
[9 marks]
Observation
Many candidates were able to state the five stages of holozoic feeding but lost marks to wrong spelling of the terms. Some also gave wrong definitions to secretion and elimination. Only a few were able to differentiate them and defined them correctly.
The diagram of villus of the intestine was poorly done as many did not give correct label, many did not adhere to the specification, many used wooly lines, some guidelines did not even touch the label and some did not give a title to the diagram.
The expected answers are:
- (a) Stages of Holozoic Nutrition in Humans
- ingestion
- digestion
- absorption
- assimilation
- egestion
5x1[5marks]
(b) Explanation of Terms
(i) Secretion
Production and release of specific substances into the external medium; by specialized cells/glands of organisms.
2x1[2marks]
(ii) Elimination
Removal of undigested food from the gut/body of organism
[2 marks]
(iii) Excretion
Removal of waste product of metabolism from the body/cells/tissues of an organism 2x1[2marks]
(c) Longitudinal Section of Villus of a Small Intestine
Title (Tl) Longitudinal Section of Villus [1mark]
Size (Sz) 8 – 10 cm long [1mark]
Quality (Q)
Clarity of Lines (CL) [1mark]
Neatness of Labels (NL) [1mark]
Details (D)
One-celled thick epithelium layer shown (EL) [1mark]
Conical shape of the villus (CV) [1mark]
Blood capillary shown (BC) [1mark]
Labels(L)
Epithelium layer, blood capillary, lacteal, lymphatic vessels