a. Explain briefly the importance of the following factors and organisms in the nitrogen cycle...

Explanation

a. Importance of the following in the Nitrogen Cycle

(i) Lightning

- When lightning occurs, nitrogen reacts with oxygen in air to form nitrous oxide/oxides of nitrogen;

- which is further oxidised to form nitrogen (IV) oxide /nitrogen dioxide;

- which dissolves in rain water to form nitric and nitrous acids;

- (that fall to the ground) when it reaches the soil combines with bases/mineral salts to form nitrates;

- which the plants absorbs.

(ii) Nitrosomonas

- Is a nitrifying bacterium in the soil;

- that converts ammonia to nitrites in the soil.

(iii) Azotobacter

- Is a nitrogen-fixing bacterium in the soil;

- that converts nitrogen in the soil;

- into ammonium compounds/amino compounds and protein in the soil;

- converts nitrites to nitrates in the soil.

b. Excretory organs

Insects – malpighian tubules;

Earthworm – nephridium

c. Explanation of diseases

(i) Hepatitis

- Is the inflammation/destruction of liver cells;

- hepatitis can arise from bacteria/virus/an autoimmune disease;

- or from excess consumption of alcohol.

The symptoms include fatigue;

- loss of appetite/anorexia;

- muscle aches/pains;

- flu;

- fever;

- nausea;

- jaundice;

- and dark coloured urine/stool.

(ii) Kidney stones

- Are small solids/crystals of concentrated minerals/uric acid found in the urine;

- they are formed if there is an excessive loss of water/insufficient water intake;

- so that the solubility of minerals/calcium phosphate/calcium oxalate in the urine is reduced;

- high levels of uric acids/amino acids can lead to kidney stones;

- bacteria may be trapped in the kidney tubules as the kidney stones get bigger;

- symptoms are sharp pain at the flank of back;

- frequent urination;

- nausea;

- sweating;

- kidney stones can be treated by medications;

- change in diet of food rich in calcium;

- surgery;

- drinking plenty of water.

d. (i) Effects of lack of sense receptors in the skin

- Humans will not be able to sense/feel/perceive external stimuli in the environment;

- pain;

- touch;

- a change in temperature;

- pressure;

- danger which could lead to death.

(ii) Layers of the epidermis

- cornified layer/stratum corneum;

- granular layer/stratum granulosum;

- malpighian layer/stratum Malpighi.

e. (i) Metamorphosis

Is the development of some/certain organisms from the egg; to an adult stage; involving three to four stages.

(ii) Type of metamorphosis of listed insects