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  1. 1. TEETH
  2. 2. Different animals have different teeth. Why? Depends on the type of food that they eat 3 1 4 2 5 1. 2. 3. 4. 5. Human Cow Cat Dog Horse
  3. 3. Animals are called: Eat mainly vegetation Herbivores Eat other animals Carnivores Eat both vegetation & flesh - sheep, rabbit - dog, tiger Omnivores - bears, pigs
  4. 4. 4 different types of teeth incisor canine premolar molar  These different teeth have different jobs!
  5. 5. Incisors  These are used for cutting & biting off pieces of food Chisel-shaped
  6. 6. Cutting by incisors
  7. 7. Canines  These are long, pointed and sharp teeth that are used to hold and tear at food; kill prey
  8. 8. Premolars  are used to crush & grind soft food premolars
  9. 9. Molars  used for chewing & grinding hard food cusps
  10. 10. Fig. 1 Dog – a carnivore. Carnassial teeth
  11. 11. Carnassial teeth slide past each other in a scissor-like fashion as the mouth is closed are adapted for shearing flesh
  12. 12. Fig. 2 Sheep – a herbivore. (blunt)
  13. 13. Sheep & Cows have no upper incisors, unlike horses: Horny pad of gum sheep horse
  14. 14. Function of the horny pad on upper jaw: the lower teeth grind against the horny pad to cut grass.
  15. 15. Compare canines in herbivores and carnivores sheep cow Small as in sheep OR absent as in cows: no need to kill Large, long and pointed: to kill prey & hold it
  16. 16. Diastema  is a space where food collects before being pushed back by the tongue
  17. 17. Why are premolars & molars very flat in herbivores? Provide a large surface area for crushing grass.
  18. 18. Teeth in: Herbivores grow throughout life. Carnivores & omnivores stop growing. Overgrown teeth in a rabbit.
  19. 19. Carnivore Herbivore Enamel ridges
  20. 20. Human Jaw
  21. 21. Tooth Function Incisor To cut Canine To tear flesh; to hold the prey; kill prey Premolar To crush Molar To crush
  22. 22. Look at the skull. What type of food did the animal eat? Flesh
  23. 23. Plants
  24. 24. The lower jaw moves: Carnivores & Omnivores Up and down Herbivores Sideways and back and forth
  25. 25. 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.
  26. 26. 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.
  27. 27. 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)
  28. 28. Question: MAY, 2010 Give 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.
  30. 30. Most herbivores have a problem:  eat grass: principal component is cellulose  cannot produce cellulases Mutualistic bacteria in digestive system produce cellulases.
  31. 31. A ruminant has FOUR stomach chambers
  32. 32. Fig. 3 A ruminant.  e.g. cow, sheep, goat, camel  a ruminant has a stomach made of four chambers, the biggest being the rumen
  33. 33. Where are the bacteria able to make cellulase found in rabbits & cows? Non ruminants Rabbit Ruminants Cow
  34. 34. The rumen contains mutualistic bacteria that produce the enzyme cellulase.
  35. 35. 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.
  36. 36. Chewing the cud is when the grass is regurgitated and chewed by the flat molars and premolars What’s up…I’m chewing my cud…Sometimes I chew over 100 times before swallowing! A cow makes between 40,000-60,000 jaw movements a day chewing
  37. 37. 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.
  38. 38.  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.
  39. 39. Question: MAY, 2012 The 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 Incisors 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. DOGS SHEEP
  40. 40. STATEMENT Incisors 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. DOGS SHEEP        
  41. 41. 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.
  42. 42. THE END Make sure you do not END up in a shark’s jaws!!
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