ADAPTATIONS FOR NUTRITION AND DIGESTION

'The human digestive system'                                                                            — illustration for About Science Book 3 by

Science Press                                                                                ---- by David Dickson

DIGESTION AND ABSORPTION

For a nutrient to be used by cells of an organism, it must pass through the cell membranes. This process is called absorption.

The nutrient molecules in food are usually too large to pass through cell membranes. Thus, to be absorbed by the cells, most food molecules must be broken down into smaller, simpler forms. The process by which food molecules are broken down is called digestion.

1. MECHANICAL DIGESTION

• Pieces of food are first cut,crushed or, broken into smaller particles without being changed chemically

• Mechanical break down increases the surface area of food and prepares the food for faster chemical digestion

DIGESTION AND ABSORPTION

Examples for mechanical breakdown

1. Cutting of food particles with teeth

2. Emulsification

Big oil small oil

Droplets droplets

DIGESTION AND ABSORPTION

bile

Sudan III has been used to stain oil. The effect of emulsification is shown below :

Large oil drops are physically broken down into numerous smaller oil droplets.

Numerous oil droplets are formed as a result of emulsification.

Numerous oil droplets are physically formed as a result of emulsification.

2.CHEMICAL DIGESTION • It is carried out by digestive enzymes

which act only on the surface of the food particles.

• Chemical digestion takes place in stages - large molecules are broken down into smaller molecules- smaller molecules are broken down into digestive end products

DIGESTION AND ABSORPTION

DIGESTION AND ABSORPTION

Examples for chemical digestion

lipid fatty acids+ glycerol

lipase

NUTRITION IN PROTISTS

Intracellular digestion takes place in protists

NUTRITION IN HYDRA

NUTRITION IN HYDRA

DIGESTION IN HYDRA IS BOTH INTRACELLULAR AND EXTRACELLULAR

NUTRITION IN PLANARIAN

The pharynx can suck small bits of food into the digestive cavity. Most digestion takes place within food vacuoles in the cells lining the intestine.

Digested food diffuses to all cells of the body. Indigestible materials are expelled through the pharynx and mouth.

NUTRITION IN EARTHWORM

Food is pulled into the

mouth by muscular

pharynx

Food passes through it

Chrushes the food and mechanical break down occur. By muscular movement , food and sand grains crush each other.

Storage chamber,

gradually releases food into the gizzard

NUTRITION IN EARTHWORM

Chemical digestion absorption take

place

Undigested materials and soil are removed

through the anus

NUTRITION IN INSECTS

Food is broken down

by mechanically

Food is stored

temporarily

Secrete saliva and food is mixed with saliva in mouth for chemical break down

Chemical digestion and

absorption occurs

Undigested material passes through intestine

The dried wastes are eliminated

Wastes stored

temporarily and water is

absorbedgizzard

It has teeth like plates made of chitin and food is ground in it

NUTRITION IN BIRDS

http://www.biologycorner.com/resources/bird_anatomy.jpg

http://numbat.murdoch.edu.au/Anatomy/avian/fig4.1.GIF

NUTRITION IN BIRDS

Food is stored and softened.

First part of stomach. Food is

partially digested by gastric juice.

Second part of stomach, thick-

walled and muscular. May contaion small stones. Food is ground up and

thoroughly mixed with gastric juice.

Digestion is completed, and

nutrients are absorbed into the

blood stream.

The digestive systems of different mammals reflect their diet

DIGESTION IN RUMINANTS

DIGESTION IN RUMINANTS