Teeth

TEETH

Different animals have different teeth. Why?

Depends on the type of food that

they eat

1

2

3

4

5

1. Human2. Cow3. Cat4. Dog5. Horse

Animals are called:

Eat mainly vegetation

Eat other animals

Eat both vegetation

& flesh

Herbivores- sheep, rabbit

Carnivores- dog, tiger

Omnivores- bears, pigs

4 different types of teeth

These different teeth have different jobs!

incisor canine premolar molar

Incisors These are used for cutting & biting off pieces

of food

Chisel-shaped

Cutting by incisors

Canines These are long, pointed and sharp teeth that

are used to hold and tear at food; kill prey

Premolars are used to crush & grind soft food

premolars

Molars used for chewing &

grinding hard food

cusps

Fig. 1 Dog – a carnivore.

Carnassial teeth

Carnassial teethslide past each other in a scissor-like fashion as the

mouth is closedare adapted for shearing flesh

Fig. 2 Sheep – a herbivore.

(blunt)

Sheep & Cows have no upper incisors, unlike horses:

Horny pad of gum

horse

sheep

Function of the horny pad on upper jaw:

the lower teeth grind against the horny pad to cut grass.

Compare canines in herbivores and carnivores

Large, long and pointed: to kill prey & hold it

Small as in sheep OR absent as in cows:

no need to kill

sheep

cow

Diastema is a space where food collects before being pushed back by the tongue

Why are premolars & molars very flat in herbivores?

Provide a large surface area for crushing grass.

Teeth in:

Herbivores grow throughout life.

Carnivores & omnivores stop

growing.

Overgrown teeth in a

rabbit.

Enamel ridges

HerbivoreCarnivore

Human Jaw

Tooth FunctionIncisor To cut

Canine To tear flesh; to hold the prey; kill prey

Premolar To crush

Molar To crush

Look at the skull.

What type of food did the animal

eat?

Flesh

Plants

The lower jaw moves:

Up and down

Herbivores Carnivores & Omnivores Sideways and

back and forth

Question: SEP, 2007

The following diagram shows the skull of a lion.a. List TWO characteristics

of canines visible in the diagram. (2)

Long and pointed.b. i) What are the canines used for? (1)

To hold the prey in place / tear flesh.

ii) What are the carnassials used for? (1)Crush flesh and bones.

c. i) Explain why carnivores have a proportionally large liver. (1)Excess amino acids are deaminated in the liver.

ii) In a carnivore the upper and lower jaw fit

together so closely that they cannot be dislocated. Explain the benefit of this. (1)

So the jaw does not dislocate as the prey struggles to become free.

d. i) In sheep a horny pad replaces the incisors and canines on the upper jaw. Explain the function of the horny pad. (1)The lower teeth grind against the horny pad to cut grass.

ii) In herbivores such as sheep the upper and lower jaw

fit loosely. What is the benefit of this?To allow side to side movement during chewing. (2)

iii) Name the TWO types of teeth that herbivores use to grind and chew the vegetation.Molars and premolars. (2)

Question: MAY, 2010Give a biological explanation for the following statement:The dentition of a rabbit is adapted to its diet. (5) The front incisors are chisel-shaped and adapted for cutting. The molars and premolars have flat grinding surfaces that continue to grow throughout life as they are worn away by grinding. The upper and lower jaw fit together very loosely to allow side-to-side movement during chewing. Diastema to enable manipulation of food.Rabbit is a herbivore.

CELLULOSE DIGESTION IN

HERBIVORES

Most herbivores have a problem:

eat grass: principal component is cellulose cannot produce cellulases

Mutualistic bacteria in digestive system produce cellulases.

A ruminant has

FOUR stomach chambers

Fig. 3 A ruminant.

e.g. cow, sheep, goat, camel a ruminant has a stomach made of four

chambers, the biggest being the rumen

Where are the bacteria able to make cellulase found in rabbits & cows?

Non ruminants

Ruminants

Cow

Rabbit

The rumen contains mutualistic bacteria that produce the enzyme cellulase.

A ruminant:1. Cuts the grass and swallows it into the

rumen.2. Bacteria in rumen make cellulase to digest

the cellulose.3. The grass is regurgitated and chewed by the

flat molars and premolars.

Chewing the cud is whenthe grass is regurgitated and chewed by the flat

molars and premolars

A cow makes between 40,000-60,000 jaw

movements a day chewing

What’s up…I’m chewing my cud…Sometimes I chew

over 100 times before swallowing!

The length of the vertebrate digestive system is related with diet.

Explain why, in general herbivores &

omnivores have longer alimentary canals

relative to their body sizes than carnivores.

A longer alimentary canal provides more:1. time for digestion 2. surface area for absorption of nutrients.

Vegetation is more difficult to digest than meat because it contains cells walls.

Question: MAY, 2012The table below lists a number of characteristics related to the dentition of dogs and a sheep. For each statement in the tablemark the box with a tick () if correct and a cross () if incorrect. (4)

STATEMENT DOGS SHEEPIncisors found on both upper and lower jaws.Molars wear down to form enamel ridges.Strong jaw muscles that allow extensive chewing of food.Jaw joint only allows up and down movement.

STATEMENT DOGS SHEEPIncisors found on both upper and lower jaws. Molars wear down to form enamel ridges. Strong jaw muscles that allow extensive chewing of food. Jaw joint only allows up and down movement.

Question: SEP, 2008

Give a biological explanation for each of the following statements:Sheep have cellulose-digesting bacteria in their gut but lions do not. (4)Sheep are herbivores and eat grass with a high cellulose content. Bacteria produce cellulase to digest cellulose.Lions are carnivores and do not need the bacteria.

THE ENDMake sure

you do not END up in a

shark’s jaws!!