(a) Explain briefly the process of perceiving smell in humans.
(b) State the adaptive features of the egg of a domestic fowl
(c) (i) What are autotrophs?
(ii) Name two unicellular organisms that are autotrophs
(d) State five functions of the World Health Organisation
(e) Name two example each of plants and animals that live in a freshwater pond.
(f) In the table below, state five differences between the skin of a mammal and the epidermis of a leaf.
(g) A farmer has two plots of land; plots A and B. on Plot A the farmer planted several seeds of maize. On plot B, the farmer planted several seeds of maize and pepper in a small area. What type of competition would be observed on
(i) Plot A
(ii) Plot B
Explanation
(a) The process of perceiving smell
- Chemical substances/odour carried in the air pass through the air/nasal cavity
- The molecules dissolve in the moist membrane of the nasal cavity
- Sensory cells are stimulated
- Impulses are formed
- which pass through the nerves ending to the olfactory nerves
- which pass into the cerebrum of the brain/brain
- The brain interprets the impulses
- And the sensation of smell is produced/smell is perceived
(b)Adaptive features of the egg of a domestic fowl;
Porous: shell; for gaseous exchange/provides shelter/ protects the embryo against mechanical damage/ desiccation
Shell membranes; allow gaseous exchange/for protection
Yolk; contains high level of proteins and fats/provides food for embryonic-growth
Egg white/albumen; consists of water to absorb shock/ proteins/food
Air space; provides surface for gaseous exchange Chalaza; holds the yolk/embryo in position.
(c)i. Autotrophs: Organisms that do not rely on other organisms for food/they manufacture their own food; from using simple inorganic compounds; can be chernosyn-thetic/photosynthetic
ii. Examples of unicellular autotrophs Clamydomonas; Euglena; chemosynthetic; bacteria/ sulphur, bacteria; blue-green; algae/Anabaena; Nostoc/ Oscillatoria; Chlorella diatoms; Nitrosomonas; Nitrobacteria
(d) Functions of WHO
- provides grants for medical research
- Improves public health/promotes environmental health
- prevents the spread of diseases vaccination
- provides vaccines/drugs in cases of emergencies
- Informs/creates awareness/educates the public of any research findings/outbreak of diseases
- Assists by sending medical personnel/logistical sup-port to countries upon request
- Helps in the training of medical personnel
- keeps health statistics
- promotes nutritional/sanitary products.
(e) Examples of plants and animals that live in fresh water pond
Plants: Water arum; diatoms; Ceratophyllum/hornwort; utricularia/bladderwort. Arrowhead/sedge; Pistia; Salvinia/water fern; water lily; wolffish/duckweed any other correctly.
Animals: Cyclops; Daphnia/water flea; Hippopotamus; crocodile; water snake; tadpoles; pond skaters; zooplanktons; mosquito larvae; water bugs; water scorpions; leeches; water snails; catfish/Tilapia fishes etc.
(f) Differences between skin of a mammal and epidermis of leaf
| skin of a mammal | Epidermis of leaf |
| skin is made up of many layers/cells | made up of a single layer/cells |
| presence of sweat gland | absence of sweat gland |
| presence of sebaceous gland | absence of sebaceous gland |
| Absence of cuticle | presence of cuticle |
| Absence of guard cell stomata | Guard cells are present / stomata |
| Has blood cells capillaries | absence of blood vessels / capillaries |
| synthesizes vitamin D | does not make vitamin D |
| Fatty cells are present | absence of fatty cells |
| It is a sensory organ | its not a sensory organ |
| Hair follicle present | hair follicle absent |
| erector muscle present | erector muscle absent |
| presence of sweat pore | absence of sweat pore |
(g) Type of competition on
(i) Plot A: intra specific/intra species competition
(ii) Plot B: interspecific/interspecies competition