This gives us a quick survey through animal nutrition. The presentation covers modes of nutrition and feeding, dentition and teeth structure.

1. HETEROTROPHISM

2. Heterotrophs are the organisms that use this mode of
nutrition. All animals are heterotrophs.
 Heterotrophism is a mode of nutrition where
organisms take in complex food substances
such as carbohydrates, proteins and fat
obtained from either plants or animals.
 They do not make their own food, therefore
feed on already made food.
 These materials are digested into simple
soluble and absorbable molecules.

3. Holozoic - where solid complex substances are
ingested, digested and assimilated in the body.
Saprophytism – where organisms obtain nutrients
from dead decaying matter thus causing
decomposition.
Parasitism – an association where the minor
organism (parasite) feeds on or obtain nutrients
from tissues of another living organism (host).
Symbiosis – an association where two organisms
live together and mutually benefit.
Heterotrophic modes of nutrition includes;

4. Nutrition in humans and other animals
 Animals are classified according to the type of food they
take.
 They include;
 Herbivores.
 Carnivores.
 Omnivores
 These animals have four different types of teeth (teeth with
different size and shape) thus referred to as heterodonts.
The teeth include;
Incisors
Canines
Pre-molars
Molars
 Homodonts have teeth of same size and shape.

5. Dentition
 Refers to description of types of teeth, their arrangement
on the jaw and their specialization (function).
 Incisors – flat, chisel shaped teeth with sharp ridged edges
for cutting and biting. Have one root as canines.
 Canines – conical shaped with sharp pointed tips for
seizing prey and tearing flesh especially in carnivores.
 Pre-molars – have broad surface and are ridged with
cusps. Are used for crushing and grinding food. Have two
roots.
 Molars – have the same characteristics and functions as
pre-molars only that they have three roots.

6. DENTAL FORMULA
 Describes the number, type and position of teeth in the jaw
of mammals.
 The record denotes half the total number on the upper and
lower jaws. Abbreviations are; incisors (i), canines (c), (pm)
premolars and (m) molars.
 Dentition determine the mode of feeding of an animal.
That is whether herbivorous, carnivorous or omnivorous.
e.g. i 0/4 , c 0/0 , pm 3/3 , m 2/3 = 30 tells the animal is a
herbivore (has a herbivorous mode of feeding) due to lack
of canines. To get 30; i(0+4)x2 + c(0+0)x2 + pm(3+3)x2 +
m(2+3)x2 = 8 + 0 + 12 + 10=30.

7. Herbivores
 Feed exclusively on vegetation.
 Are grouped into two;
Grazers – those feed on grasses e.g. zebras,
donkeys and cattle
Browsers – feed on shrubs and herbs e.g.
giraffes, goats and antelope.
 Their adaptations to this mode of feeding
includes the following.

8. Lack upper incisors and instead have a horny pad
against which lower incisors press and cut grass.
Have a long tongue that assist in cutting, turning and
moving grass during grinding.
Have a diastema (a toothless gap in the lower jaw
separating the canines and premolars) that assist the
tongue in the above functions.
Molars and premolars have broad cusps and ridges for
grinding.
Jaws move side by side to enhance grinding.
Enamel is continuously replenished to maintain teeth
height and counteract heavy wear and tear of teeth.

9. Carnivores
 Feed exclusively on flesh (meat) and most are hunters.
 Adaptations to this mode of feeding includes;
Are fast runners and have well developed leg muscles.
Have strong jaws to grasp prey.
Have chisel-shaped and closely fitting incisors to seize
prey and strip flesh from bones.
Canines are long conical (sharp) and curved to grasp,
kill and tear prey.
Have carnassial teeth – special premolars with
smooth sides and sharp edges to slice flesh and crush
bones.
Their strong jaws are attached to powerful muscles
that move the jaw up and down by snapping.

10. Omnivores
 Feed on both vegetation and flesh.
 Have two sets of teeth; milk(20 for human) and
permanent (32) teeth. Milk teeth are lost at of
between 6-12 years and replaced by the permanent
teeth.
 Teeth have characteristics of both carnivores and
herbivores.
Activity
Suggest the mode of feeding of animal with following
characteristics; long curved and sharply pointed
canines, small closely fitting incisors, narrow molars
and premolars with cusps.

11. STRUCTURE OF A TOOTH
EXTERNAL STRUCTURE
It is made up of three distinct regions;
Crown – the section that projects above the gum.
It is covered with hard, non-living material known
as enamel made of calcium carbonate and
phosphate. Enamel protects inner tooth and forms
the surface for biting and grinding.
Root - the part that is embedded in the jaw.
Neck – the region between the root and crown.

12. INTERNAL STRUCTURE
 Enamel - It is a white, hard and non-living material made of
calcium carbonate and phosphate. Enamel protects inner
tooth and forms the surface for biting and grinding.
 Dentine – It is a layer of tissue beneath the enamel and
surrounding the pulp cavity. It extends to form the root and
consists of living cells.
 Pulp cavity – It is found within the dentine. It contains nerve
endings and blood vessels. The blood vessels supply nutrients
to dentine and remove the waste products. Nerves detect heat,
cold and pain. Pulp plays part in nourishment, defense,
sensation of pain and formation of dentine.
 Cement – It is the outer layer of the root. It protects the tooth
and provides rough surface for anchorage of the tooth in the
jaw. It is surrounded by supporting fibres.

13. Structure of a tooth
Canine Molar

14. Dental Diseases
 Common dental diseases include the following;
Dental carries (tooth decay, cavities).
Periodontal disease. This disease is of two types;
Pyorrhoea.
Gingivitis.
Activity
Find out the causes and control (dental hygiene) of
the above diseases.

15. Dental Diseases links
 http://www.patient.co.uk/doctor/some-dental-and-
periodontal-diseases
 http://en.wikipedia.org/wiki/Tooth_pathology
 http://www.dentalgentlecare.com/picture_gum_disea
se.htm