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
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
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
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.