teeth
TRANSCRIPT
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.
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!!