Heterotrophism, Dentition, and Dental Formula

- This is a mode of nutrition in which organisms take in already manufactured complex food substances such as carbohydrates, proteins and lipids.
- Heterotrophs are organisms that feed on already manufactured food substances.
- These substances are broken down in the bodies of the Heterotrophs into simple soluble food substances that can be absorbed and be utilized by the cells.

There are four main heterotrophic modes on nutrition as follows;

• Holozoic - Where organisms ingest, digest and assimilate solid complex food substances.
• Saprophytism – Where organisms feed on dead decaying matter causing decomposition.
• Parasitism - a feeding association in which one organism (parasite) feeds on or obtain nutrients on another organism, the host.
• Symbiosis/Mutualism - An association where two organisms live together and mutually benefit from each other.

- There are two main types of parasites:

• Endo parasites- Live inside the host
• Ecto-parasites- Found on the external surface of the host.

- The parasite benefits but the host does not. Some of the parasites cause diseases to the hosts and damage their tissues thereby weakening them.

- In saprophytism, both organisms benefit:
- Symbiotic relationships include

• Rhizobium and leguminous plants: rhizobium fixes nitrogen for the legume while the bacteria obtains manufactured food from the legumes.
• Lichen: association of fungi (absorbing water and nutrients) and algae (manufacturing food for the association.
• Catalase digesting bacteria and ruminants

- Large animals depend on complex manufactured food substances.
- These food substances once ingested must be broken down to simpler forms that can be utilized by the cells. The breakdown is both physical and chemical.
- Most of the large animals have teeth to enhance physical breakdown of the complex food substances.
- Dentition refers to the description of types of teeth, their arrangement and specialization.

• Homodont dentition - Teeth arrangement and description where an organism has teeth of the same size and shape. Fishes and birds have homodont dentition.

  

• Heterodont dentition - where an organism has teeth of different sizes and shapes that is incisors, canines, premolars and molars. Heterodont dentition is common with mammals and reptiles.

  

- Are flat and chisel shaped with sharp ridged edges for cutting and biting food.
- They have one root.

- Are conical teeth with sharp pointed edges modified for seizing and tearing prey among carnivores.
- They have one root.

- They have cusps on their surface to suit their grinding action.
- Premolars have two roots.
- Molars have either two or three roots.

- Holozoic heterotrophs are classified according to the type of food they consume.
- These are:

• Herbivores: heterotrophs that exclusively feed on vegetation.
• Carnivores: heterotrophs that exclusively feed on flesh.
• Omnivores: heterotrophs that feed on both flesh and vegetation.

- Dentition of heterotrophs is based on the kind of food they consume.

- This is the description of the number, type and position of teeth in the jaws of animals.
- Number of teeth recorded represents half the total teeth in the upper and lower jaws.
- The teeth names are abbreviated as;

• i-incisors
• c-canines
• pm-premolars
• m-molars

Example of a questions you might find
- An animal was found to have no incisors and canines on the upper jaw. It had six premolars and four molars on the upper jaw. On the lower jaw, it had eight incisors, no canines, six premolars and six molars.

• Write down its dental formula.
• State its mode of feeding.
• Give a reason.

- Most do not have upper incisors. Instead they have a horny pad against which grass is pressed and cut by the lower incisors.
- They have a long tongue that assists in the cutting and moving food.
- They have a gap in the lower jaw separating canines from premolars known as diastema which allows the tongue to manipulate food.
- Herbivore teeth have open enamel which allows for continuous growth to replace worn out surfaces due to grinding.
- Their incisors are wedge shaped to cut grass and vegetation together with the horny pad.
- The jaws have movable joints to allow the sideways movement of lower jaw to facilitate grinding of grass.

- Their incisors are chisel shaped and closely fitting to seize the prey.
- Their canines are long, conical and curved to hold, kill and tear the prey.
- Some of their premolars in the lower and upper jaw are modified into specialized carnassial teeth which have smooth sides and sharp edges to slice through flesh and crush bones.
- Premolars and molars are broad with cusps for crushing bones.
- Their jaws are attached to powerful muscles that move the jaws up and down.
- Carnivores are adapted to fast running by possessing well developed leg muscles.

• Dental Carries: Caused by lack of hard food, too much sweet or sugary food, lack of calcium in diet, lack of vitamin D, lack of cleaning teeth and general ill-health. The bacteria in the mouth break down the sugars to form energy and organic acids. The acids corrode the enamel.
• Periodontal Diseases: Caused by lack of vitamins A and C, lack of massage of the gums and imperfect cleaning of gums. The gums become flabby and soft so they do not support the teeth. Common in adults than children. They are two types as follows;
  • Gingivitis- Characterized by reddening of gums, bleeding and pus in the gums.
  • Pyorrhea- The teeth become loose due to infection of the fibres holding the teeth in the sockets.

- Proper teeth care requires the following;

1. Regular cleaning or brushing teeth after every meal
2. Avoid eating too much sugary foods.
3. Eating hard foods e.g. raw carrots, cassava, yams, sugar cane.
4. Eating diet rich in calcium, phosphate and vitamins A, C and D.
5. Teeth should be used for their correct purpose.
6. Regularly visit the dentist if necessary.