TEST OF PRACTICAL KNOWLEDGE QUESTION (a)(i) Cut a pieces of specimen A, place it on the white tile. Add a few drops of iodine solution. Record the observati...
(a)(i) Cut a pieces of specimen A, place it on the white tile. Add a few drops of iodine solution. Record the observation and result in a tabular form.
(ii) Squeeze a few drops of specimen E on another clean white tile provided, add a few dre Record the observation and result in a tabular form.
(b)(i) State two observables differences between specimens A and B. (ii) Suggest two factors that are likely to be responsible for the state of specimen B.
(iii) With the aid of hand lens/magnifying lens, observe.specimen B. and name an organism that is likely growing on it. (iv) State the mode of feeding of the organism on specimen B (c) ) Make a drawing 6cm-8 cm long, of specimen C and label fully. one function each of any three parts labeled.
(a)(i) Iodine test on specimen A (bread)
Test
Observation
Result (inference)
A piece of specimen A is placed on the white tile and a few drops of iodine solution are added
The brown iodine solution turns blue-black
Starch is present in specimen A
(a)(ii) Iodine test on specimen E (orange juice)
Test
Observation
Result (inference)
A few drops of specimen E are squeezed onto a clean white tile and a few drops of iodine solution are added
The iodine solution remains brownish / yellowish (no colour change)
Starch is absent in specimen E
(b)(i) Two observable differences between specimens A and B
Specimen A (fresh bread)
Specimen B (stale bread)
White / cream in colour
Dark brown / black in colour
Soft in texture, fresh, with no mould
Hard in texture, stale / decaying, bearing mould (Rhizopus / Mucor)
(b)(ii) Two factors likely responsible for the state of specimen B
Presence of moisture / humidity.
Presence of warmth (a suitable temperature), together with fungal spores acting over time, which allowed micro-organisms to grow and spoil the bread.
(b)(iii) Organism likely growing on specimen B
A mould (fungus), for example Rhizopus (bread mould) or Mucor.
(b)(iv) Mode of feeding of the organism
Saprophytic: it feeds on the dead organic matter of the bread by secreting enzymes for external (extracellular) digestion and then absorbing the digested nutrients.
(c) Drawing of specimen C (boiled egg)
Below is a labelled drawing, 6 cm to 8 cm long, of the longitudinal section of the boiled egg (specimen C).
Labelled longitudinal section of the boiled egg (specimen C), 6-8 cm long.
(ii) One function of any three labelled parts
Labelled part
Function
Shell
Protects the egg and its contents, gives shape and allows gaseous exchange (aeration)
Albumen (egg white)
Supplies protein and water to, and cushions, the developing embryo
Yolk
Stores food (fat and protein) for the growth and nourishment of the embryo
Other parts labelled include the shell membrane and the air space, both of which aid gaseous exchange for the embryo.
A piece of specimen A is placed on the white tile and a few drops of iodine solution are added
The brown iodine solution turns blue-black
Starch is present in specimen A
(a)(ii) Iodine test on specimen E (orange juice)
Test
Observation
Result (inference)
A few drops of specimen E are squeezed onto a clean white tile and a few drops of iodine solution are added
The iodine solution remains brownish / yellowish (no colour change)
Starch is absent in specimen E
(b)(i) Two observable differences between specimens A and B
Specimen A (fresh bread)
Specimen B (stale bread)
White / cream in colour
Dark brown / black in colour
Soft in texture, fresh, with no mould
Hard in texture, stale / decaying, bearing mould (Rhizopus / Mucor)
(b)(ii) Two factors likely responsible for the state of specimen B
Presence of moisture / humidity.
Presence of warmth (a suitable temperature), together with fungal spores acting over time, which allowed micro-organisms to grow and spoil the bread.
(b)(iii) Organism likely growing on specimen B
A mould (fungus), for example Rhizopus (bread mould) or Mucor.
(b)(iv) Mode of feeding of the organism
Saprophytic: it feeds on the dead organic matter of the bread by secreting enzymes for external (extracellular) digestion and then absorbing the digested nutrients.
(c) Drawing of specimen C (boiled egg)
Below is a labelled drawing, 6 cm to 8 cm long, of the longitudinal section of the boiled egg (specimen C).
Labelled longitudinal section of the boiled egg (specimen C), 6-8 cm long.
(ii) One function of any three labelled parts
Labelled part
Function
Shell
Protects the egg and its contents, gives shape and allows gaseous exchange (aeration)
Albumen (egg white)
Supplies protein and water to, and cushions, the developing embryo
Yolk
Stores food (fat and protein) for the growth and nourishment of the embryo
Other parts labelled include the shell membrane and the air space, both of which aid gaseous exchange for the embryo.
