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 Explain the sources and effects of water pollution. (20 marks)

Sources of water pollution

Domestic effluents-untreated sewage from urban centers gets discharged into rivers used for water supply for domestic purposes.

• This sewage contains disease causing micro-organisms such as bacteria, viruses and protozoa. It’s also full of faecal material and urine which encourage bacterial growth. Kitchen wastes also contain detergents that have a lot of phosphates.

Effects

• Water pollution may cause epidemics of water –borne diseases e.g. cholera, typhoid and amoebic dysentery.
• The faecal material is broken down by saprophytic bacteria and fungi which lead to depletion of dissolved oxygen in water. This in turn affects aquatic organisms such as fish and aquatic plants.
• Decomposition of wastes also releases nutrients into the water which causes rapid growth of water hyacinth e.g. L.victoria. This enrichment of the lake with nutrients and its effects is called eutrophication.

Industrial effluents

• Industries discharge various effluents into rivers, dams e.t.c.. The effluents contain toxic metallic compounds of mercury, arsenic and cadmium in addition to acids and other chemicals.

Effects

• The poisonous compounds directly kill aquatic organisms such as fish.
• This compound enter the food chain and accumulate to lethal levels in organisms higher up the trophic levels
• Heat
• Industries discharge hot water directly into the water bodies. Some of the effluents may react among themselves releasing heat into the water

Effects

• Heat reduces the amount of dissolved gases in water e.g. oxygen and carbon dioxide thus organisms may die from oxygen deficiency.
• The hot water may even kill the living organisms directly due to the high temperatures.

Oil Spillage

• Oil spillage occur in oceans from oil tankers accidents, 
• Marine organisms such as fish are killed by clogging on their respiratory surfaces.
• Marine birds get their feathers clogged hence have difficulty in flight.
• Oil coats photosynthetic phytoplankton’s till they die.
• There is reduced light penetration into the water hence photosynthesis of submerged plants is hindered

Agrochemicals

• They include inorganic fertilizers, herbicides, and pesticides.
• The inorganic fertilizers contains phosphates and nitrates
• Pesticides may contain heavy metals e.g. mercury and copper. other pesticides such as DDT contains CFC which are not easily broken down biologically(non-biodegradable)

Effects

Most of these chemicals contain heavy metals such as copper and mercury which affect respiratory activities of aquatic organisms.

• These chemicals accumulate in the body over a long time and reach toxic levels leading to death
• Nitrates and phosphates in fertilizers cause eutrophication

Lead 

• This is water pollutant mainly from pipes and tanks in domestic water supply system. through run-off it finds its way into water bodies like rivers, lakes and oceans

Mercury

• It’s a pollutant released by industries that manufacture chlorine, sodium hydroxide oves and vinyl plastics.
• Also released during combustion of coal and petroleum oils 
• Fungicides and some cosmetics also contain mercury 

Effects

• Methyl mercury is volatile and very toxicit is absorbed by aquatic organisms or though leaves hence entering the food web involving human beings animals eating plants will mercury are poisoned and killed
• Mercury poisoningin people results in accumulation of mercury in liver, kidney and brain affecting the physiological functioning and eventually causes death.
• Mercury also interferes with the process of melaline formation leading to skin lighting , blindness paralysis and even death
• SOIL EROSION 
• Silt is transported into water bodies 

Effects

• It makes water unclean and unfit for human consumption 
• The silt reduces light penetration hence hindering photosynthetic activities.
• It clog the respiratory surfaces of aquatic organisms e.g. gills in fish stomata in plants. This interferes with gaseous exchange.

Control of water pollution

• Legislation- relevant legislation should be enforced and provide for heavy penalties.
• Industries should control or treat the industries effluents before discharging into water bodies.
• Proper treatment and disposal of sewages there should be separate systems for disposal of sewage and drinking water.
• Latrines should be constructed and properly used in addition to proper personal hygiene to control diseases causing agent.
• Encourage use of unleaded fuels 
• The public should be educated on correct use of inorganic fertilizers and pesticide to be used and should offshore oil wells and refineries.

Effects

• Oil layer on the water surface reduces oxygen supply to the water and this may lead to death of aquatic life forms.
• be encourage using organic farming which biologically control pest.

Appropriate soil control methods to be put in place such as building of gabions.

8. a) Describe the process if hearing in man. (10 marks)

When sound waves are trapped by the pinna, they are directed inwards into the auditory canal then to the ear drum

Wax in the auditory canal trap dust particles and microorganisms in air

The sound waves cause the eardrum to vibrate with the same intensity as the sound waves; thereby converting the sound waves to vibrations

The vibrations cause the ear oscicles (malleus, incus and stapes) to vibrate in turn;

The oscicles amplify and transmits the vibrations to the oval window;

The vibration of the oval window is transmitted to the perilymph in the cochlea within the vestibular canal of the cochlea;

The perilymph transmits vibrations into the endolymph;

Displacement of the endolymph causes the movement of the sensory hair cells;

This movement of the hair generates impulses in the sensory hair cell;

The impulses are transmitted into the brain via auditory nerve;

The brain then translates the impulses to perception of sound;

 b) Describe how mammalian eye is adapted for accommodations. (10 marks)

- the iris; is opaque contractile; to control light intensity/amount of light entering the eye (by controlling the size of the pupil)

- ciliary body; contains ciliary muscles; which are contractile; for controlling the curvature and hence focal length of the lens;

- suspensory ligaments; are fibrous; to hold the lens in position;

- have a transparent; biconvex lens; to allow light to go through; to refract the light; and to focus the light;

- external eye muscles; is contractile; to move the eyeball (within the socket)

Distinguish between mutations, mutants, and mutagens.  (3mks)

Mutations are sudden, spontaneous, and permanent changes in an individual’s genetic material; 

Mutants are individuals who develop and exhibit unusual characteristics that were not previously present in the population due to mutations; mutagens are factors in the environment that cause the mutations to occur;

Give two causes of mutations (2mks)

• radiation such as gamma rays and ultraviolet rays;
• chemical substances such as mustard gas and other heavy metals (mercury, lead, asbestos);
• sudden extreme high or low temperatures;
• 
  

Describe the causes and effects of chromosomal mutations (15mks)

Deletion; refers to the absence of a portion of a chromosome; it results from breakage and falling off of a portion of a chromosome; leading to the loss of a group of genes that may have a disastrous effect on the development of an organism;

Inversion; refers to the reversal of the normal sequence of genes in a portion of a chromosome; occurs when a middle portion of a chromosome breaks, turns,the  or rotates (inverts) through 180o and joins up again; this does not change the genetic constitution of the organism; but may bring into proximity genes whose combined effects to an organism produce a beneficial effect to an organism, or cause disadvantages to the organism;

Translocation; attachment of a portion of a chromosome to a non-homologous chromosome; occurs when a chromosome breaks and the portion joins another non- homologous chromosome; this may lead to serious consequences, even death depending on what genes are missing;

Duplication; situation where a set of genes is represented twice in a chromosome; a part of a chromatid formed during cell division may replicate further to form an extra piece; which may attach onto the same or another chromatid; resulting to traits controlled by some genes being excessively expressed;

Non-disjunction; this is the failure of a pair of homologous chromosomes to separate during the first stage of meiosis; resulting in one of the daughter cells formed after the division of the cell having two of one kind of chromosome; while the other cell has less or none; diseases or disorders known as syndromes are known to result from this aberration e.g. Down’s Syndrome (Mongolism), Turner’s Syndrome, Klinefelter’s Syndrome; Polyploidy; this is the presence of more than two sets of chromosomes in a cell; occurs due to a failure of a cell to divide after the first stage of meiosis or after the chromosomes have replicated in mitosis; common in plants than animals; in plants, it causes some improvements such as resistance to drought, certain diseases and pests, improved yields and early maturity; 

Discuss the various ways in which anaerobic respiration is utilized in industries and homes.(20mks)

Bread making; yeast is used to ferment sugar in wheat flour into carbon (IV) oxide and energy; the carbon (IV) oxide is produced in form of bubbles that causes the dough to rise and become porous; 

Beer making; yeast is used to ferment sugars in malt/grapes/fruits; to form beer, wines and spirits; 

Sewage treatment; anaerobes break down raw sewage and harmful industrial effluents; to harmless products of water, energy/heat and carbon (IV) oxide; 

Silage formation; vegetation is fermented by bacteria to produce nutritious and good-scented/flavoured animal feed that increases production/yields;

Production of acids and strong liquors; special bacteria and fungi ferment food products; to produce acids such as citric acid, oxalic acid and vinegar; the products are used as food preservatives and flavouring agents; 

Manufacture of dairy products; under controlled environments; anaerobes help in fermentation hence manufacture of milk products such as butter, cheese, ghee and yoghurt; 

Production of fuels such as biogas; and gasohol; cane sugar is fermented by yeast; to produce gasohol for running engines or operating machinery; animal wastes such as guano and cow dung; can be used to produce a mixture of methane and carbon (IV) oxide gas; by exposing it to fermentation agents; methane is used to run simple machines such as water pumps and for cooking;

Production of fermented porridge and milk; maize or wheat flour and milk is exposed to microbes in the air, which ferment it; to produce sour and sweet tasting porridge or milk; 

Production of compost manure in agriculture, microorganisms breakdown organic matter to release nutrients for crops; 

Pharmaceutical industry; utilizes anaerobic respiration to produce drugs such as penicillin