(a) What is dentition in animals? (b) Describe briefly the generalised structure of a tooth in animals. (c) List three food substances that plants manufactu...

Answer Details

(a) Dentition in animals

Dentition is the type, number, arrangement and pattern of the teeth in the jaws of an animal. The kind of dentition an animal has (for example the presence and development of incisors, canines, premolars and molars) is related to its mode of feeding.

(b) Generalised structure of a tooth

A tooth has two main regions: the crown, which projects above the gum, and the root, which is embedded in the socket of the jaw bone; the slightly narrowed part where they meet, at gum level, is the neck.

• Enamel - the hard, white, non-living outer covering of the crown; it is the hardest substance in the body and resists wear.
• Dentine - a bone-like living layer beneath the enamel that makes up the bulk of the tooth.
• Pulp cavity - the central space containing the pulp, which is made of blood vessels (supplying food and oxygen) and nerve fibres (sensitive to pain and temperature).
• Cement - a layer that covers the dentine of the root and, together with the periodontal fibres, fixes the tooth firmly in its socket.

(c) Three food substances plants manufacture from glucose

• Starch (for storage).
• Cellulose (for building cell walls).
• Sucrose (for transport); also fats/oils and, with nitrogen, proteins.

(d) Diagram of an experimental set-up to show that oxygen is produced during photosynthesis

Make a labelled drawing 6 - 8 cm long of the classic aquatic-plant set-up: a beaker of water containing sprigs of a water plant such as Elodea (or Hydrilla), the plant covered by an inverted glass funnel, and an inverted test tube full of water placed over the funnel stem to collect the gas. Label the water plant, the funnel, the test tube and the gas bubbles (oxygen) collecting at the top of the test tube. When placed in sunlight, bubbles of gas rise and collect in the tube; the collected gas relights a glowing splint, showing it is oxygen.