Heterotroph Flashcards
Heterotroph
The mode of nutrition in which organisms do not possess the ability to synthesize their own food from simple inorganic material and depend on other organism for its food is knowns as heterotrophic nutrition.
Types of Heterotrophic nutrition
1) Holozoic Nutrition-
In this mode of nutrition, organisms take in food material and break down inside their bodies. ex- Amoeba, Humans.
2) Saprophytic nutrition-
In this mode of nutrition, organisms feed on dead, decaying matter outside the body and absorb it. ex- Fungi, yeast, mushrooms.
3) Parasitic nutrition-
In this mode of nutrition, parasites derive nutrition by living on or in the body of host organism. ex- Cuscuta, Ticks, Lice.
Nutrition in Amoeba
> Amoeba takes in food using temporary finger-like extensions of the cell surface which fuse over
the food particle forming a food-vacuole.
> Inside the food vacuole, complex substances are broken down into simpler ones which then diffuse into the cytoplasm.
> The remaining undigested
material is moved to the surface of the cell and thrown out.
Nutrition in Paramoecium
> In Paramoecium, which is also a unicellular organism, the cell has a definite shape and food is taken in at a specific spot.
> Food is moved to this spot by the movement of cilia which cover the entire surface of the cell.
Mouth
> Food is first crushed with the teeth and mixed with saliva by the muscular tongue so that it can pass through the soft tube.
> Nature of food being complex needs to be broken down to simpler molecules using bio catalysts called enzymes.
> The saliva contains the salivary amylase enzyme which breaks down the complex starch to form simple sugar.
Oesophagus
> The oesophagus is a long, muscular tube that connects mouth to the stomach.
> Swallowed food is squeezed by the walls of the oesophagus.
> This type of contraction and expansion of the muscles of the oesophagus is called peristaltic movement.
> This moves the food down the oesophagus to the stomach.
Stomach
> Stomach is a J shaped organ present on the left side of the abdomen.
> Gastric glands present in the walls of the stomach secrete gastric juice.
Gastric juice contains three substances:
1. Hydrochloric acid - creates an acidic medium to facilitate the action of the enzyme pepsin, it also kills the germs that enter the alimentary canal along with the food
2. Pepsin - enzyme that breaks down proteins
3. Mucus - Protects the lining of the stomach from the acidic action of the acid
Small intestine
> Partially digested food from the stomach enters the small intestine.
> It is the longest part of the alimentary canal and arranged in coil form.
> Small intestine is the site of complete digestion of food.
> Small intestine receives the secretions of two glands: Liver and Pancreas
> Liver secretes bile.
a. Makes the acidic food coming from the stomach alkaline so that pancreatic enzymes can act.
b. Bile salts break down fats in the form of large globules into small globules. This is known as emulsification of fats.
Pancreas
> The pancreas secretes pancreatic juice which contains
enzymes like trypsin for digesting proteins and lipase for breaking down emulsified fats.
> The walls of the small intestine contain glands which
secrete intestinal juice.
> The enzymes present in it finally convert the proteins to amino acids, complex carbohydrates into glucose and fats
into fatty acids and glycerol.
Absorption
> The inner lining of the small intestine has numerous finger-like projections called villi which increase the surface area for absorption.
Assimilation
> The villi are richly supplied with blood vessels which take the absorbed food to each and every cell of the body, where it is utilized for obtaining energy, building up new tissues and the repair of old tissues.
Egestion
> The unabsorbed food is sent into the large intestine where its wall
absorb more water from this material. The rest of the material removed from the body via the anus.
> The exit of this waste material is regulated by the anal sphincter.
Size of small intestine
Herbivores eating grass need a longer small intestine to allow the cellulose to be digested. Meat is easier to digest, hence carnivores like tigers have a shorter small intestine.
