2012 Biology

Hint

1a.(i). Draw a large labelled diagram (8 — 10cm long) of a typical plant cell.

ii.       State THREE differences and TWO similarities between a plant and an animal cell.

Similarities between plant cell and animal cell

1. They both have nucleus
2. They both have cytoplasm
3. They both have cell membranes
4. They both have mitochondrion
5. They both have endoplasmic reticulum

iii       List FIVE functions of blood

1. Defends the body against diseases/ foreign bodies
2. Serves as a medium of transportation of soluble organic compounds / digested food from the small intestine to the various parts of the body
3. Transports oxygen from the lungs to all parts of the body or transports CO₂ produced by the tissues of the lungs
4. Distribution of heat and the equalization of body temperature
5. Aids in the clotting of blood i.e. prevents excess loss of blood
6. It transport soluble excretory waste such as urea, CO₂ to the organs of excretion such as kidney / lungs
7. It transport mineral salts
8. Transport water

Hint

2a.(i). Define Excretion.

it is the removal / elimination of waste products of metabolism from the protoplasm / body an organism

ii        Give TWO reasons why excretion is necessary in organisms

• It removes wastes products of metabolism from the body
• It helps to maintain water balance
• Some substance are harmful & should never be allowed to accumulate in the body

b.       For each of the following: carbohydrates, lipids and proteins

i.        Name TWO sources of each.

ii.       State ONE function of each.

Functions of carbohydrate

• It provides energy / oxidized to give energy
• It is the starting material for the synthesis of lipids & proteins
• Excess is stored as glycogen for later use

Functions of lipids

• It is oxidized to give energy / provides energy
• Stored under the skin / adipose / tissue / around organs to insulate or present loss to heat
• Formation of cell membrane
• Stored as food reserve

Functions of proteins

• For growth
• For repair / formation of tissues
• Oxidized to give energy / provides energy
• For synthesis / production of enzymes
• For synthesis of hormones / insulin
• Formation of blood proteins / fibrinogen

c. i.    Give FIVE ways by which forests can be conserved in Nigeria.

1. Establishment of forest reserve.
2. Carrying out awareness campaigns against deforestation
3. Replace felled mature tree with seedlings in plantation
4. Planting new forest tree (afforestation) where they have been completely destroyed.
5. Controlling plants diseases by using pesticides to kill pests
6. Regulation made to control excessive deforestation that only mature tree should be felled
7. Discouraging extensive use of natural forests as a source of timber since animals and some other plants are also displaced or destroyed.
8. Using trained forest guards to guard the forest against intruders or light fires
9. Prevention of forest fires/bush burning

ii.       State TWO differences between photosynthesis and respiration

Hint

3a.     State TWO effects each of the following agricultural activities on the ecosystem.

i.        Bush burning.

• Bush burning burns humus and litter on the ground, leading to loss of soil fertility
• Useful microorganism such as putrefying bacteria, earthworm which burn about decay are burnt by bush fires causing loss of soil fertility
• Leads to loss of soil moisture by evaporation
• Exposes the soil and promotes erosion
• Kills useful plants such as oil palm & orange trees in the area

ii.       Fertilizer application.

• Fertilizer applied to farms may be washed into streams where they cause pollution
• The continuous and exclusive use of fertilizers over the years leads to loss of organic humans deterioration of the soils crumb structures
• Excessive application can cause soil acidity
• It stimulates vegetative growth hence reduces erosion

iii.      Use of pesticides

• Pesticides application can cause environmental pollution
• It affects or destroys other useful plants
• Excessive use of pesticides may destroy crop plants.
• It reduced the population of the target insects / plants
• It may leave undesirable residue on the environment
• May cause death of aquatic animals when washed to the sea / water bodies

b i.     Define the term ‘ecological succession’.

Ecological succession is a gradual and orderly change / replacement of different species of plants and animal. Communities in a given area over a period of time until the conditions of the area become gradually modified by their activities so that a climax / equilibrium / bacteria community is reached / established.

ii.       Name TWO types of ecological succession.

• Primary succession
• Secondary succession

c. (i). Give FOUR differences between involuntary action and voluntary action.

ii.       List FOUR components of the mammalian blood.

• Red blood cells / erythrocytes / red blood corpuscles
• White blood cells / leucocytes / white blood corpuscles
• Blood platelets / thrombocytes
• Plasma / fluid matrix

iii.      State TWO reasons why a transport system is necessary in multicellular organisms.

• Many cells are situated far away from others, hence substance have to be moved over greater distances
• To connect isolated groups of cells
• It is importance because diffusion alone cannot be used to transport materials to isolated cells
• It is important especially when materials are transported in large quantities

Hint

4a. i. Define the term asexual reproduction.

It is the production of a new individual from a parent / organism/older organism/individual without fertilization / gametes / change in chromosome number / genetic contribution. It involves a single parent.

ii.       List TWO types of asexual reproduction.

• Binary fission
• Multiple fission
• Spore formation
• Natural vegetative
• Artificial vegetative propagation
• Fragmentation

b. i.    Make a labelled diagram (8 -10cm long) of the vertical section of the mammalian skin.

ii.       State TWO functions of the mammalian skin.

Protection: The epidermis of the skin contains melanin which protects the skin against harmful ultraviolet rays

Sensory: The skin has five sensory nerve endings which are sensitive to touch, pain, cold, heat and pressure.

Excretory: The skin excretes excess water, salts and a little urea (sweat) from the blood through the sweat pores.

Thermoregulation: The skin helps to regulate the internal body temperature.

Synthesis of vitamin D in sunlight

c.       Give FOUR differences between meiosis and mitosis.

Hint

5a. i. List FOUR supporting tissues in plants.

• Sclerenchyma
• Collenchyma
• Xylem (Wood)
• Turgid parenchyma (unspecialized plant cells)

ii.       State FOUR adaptive features of desert plants (xerophytes).

• Leaves are modified into spines to reduce water loss
• Succulent stem to conserve water
• Thick waxy cuticle on stems to prevent / reduce water loss
• Stem are green / chlorophyllons to manufacture food
• Flattened stem

b. i.    A pure breeding white cock (WW) was crossed with a pure breeding brown hen (ww). By means of crosses, show the phenotypic ratio of the F₁ and F₂ generations.

Pure breeding white cock   WW

Pure breeding brown cock ww

Phenotype All white cock

Phenotype ratio      4 : 0

Phenotypes 3white cocks and 1 brown cock

Phenotypic ratio 3   :        1

White           brown

ii.       State FOUR differences between an artery and a vein.