Animal Survival

Animal Survival

The Need for Food

G Davidson

The Need for Food

All living organisms need food to survive.

Three examples of food types are

1. Carbohydrates

2. Fats

3. Proteins

The Need for Food

Carbohydrates contain the elements carbon, hydrogen & oxygen

Fats contain the elements carbon, hydrogen & oxygen

Proteins contain the elements carbon, hydrogen, oxygen & nitrogen

Carbohydrates

Carbohydrates provide us with energy for

our normal activities. They consist of long

chains of glucose molecules.

Glucose

Fats

Fats release some energy for our use if required

while the rest is stored in adipose tissue beneath

the skin. This is used as insulation. Each fat is

made up of a glycerol molecule joined to 3 fatty

acid molecules.

Gly

cero

l Fatty acid

Fatty acid

Fatty acid

Proteins

Our body requires protein to build it up and for repairing damaged tissue. Proteins are built up from long chains of amino acids. There are only about 20 different amino acids.

The Need for Food

Our food is a mixture of solids and liquids containing, among other things, carbohydrates and fats for energy and proteins for growth and repair.In order for the food to be of any use it has to reach every cell in the body.This is done by the blood, but in order to be carried in the blood the food must dissolve.Before the food leaves the gut, it must be soluble.

The Need for Food

Mammals, throughout the world, are adapted to almost every type of environment and the wide variety of food sources they contain.There are basically 3 types of mammal:

1. Herbivores – animals which eat only plants.2. Carnivores - animals which eat other

animals.3. Omnivores - animals which eat both plants

and other animals.

Herbivores

Teeth of a HerbivoreUpper jaw of a sheep

Lower jaw of a pig

Note the ridges on the molars & premolars

Note the gap between the incisors and the premolars

Skull of a Rabbit

Carnivores

Teeth of a CarnivoreSkull of a Fox

Note the large canines

Note the shape of the premolars and molars

Skull of a Dog

Omnivores

TeethThese mammals

basically have 4 types

of teeth – all suited to

special jobs.Incisors – found at the

front and used for biting,

gripping and pulling.Canines – used for

gripping and tearing.

Teeth

An animals teeth are suited to what it eats.An animals teeth are suited to what it eats.

Molars – found at the back and used for crushing and grinding.

Premolars – used for crushing and grinding.

Can YOU name the parts?Enamel

DentinePulp

Crown

Gum

Bone

Root

Nerves & Blood vessels

Location of Teeth

Digestive System

The human gut is sometimes called the alimentary canal.

It is a tube about 5m long.

It runs from the mouth to the anus.

It is coiled up to fit in the body.

Digestive System

1= Mouth

3= Tongue

2= Teeth

4= Stomach

5= Pancreas 6= Small intestine

7= Rectum 8= Salivary Glands

9= Oesophagus 10= Liver

11= Gall Bladder

12= Large intestine

13= Appendix

14= Anus

Can YOU name the Parts?Mouth

Oesophagus

LiverStomach

Gall Bladder

Colon

Appendix

Pancreas

Small intestine

Rectum

Anus

Digestive System

Food cannot move through the gut by itself.It must be pushed.This is done using the muscles in the gut wall which contract and relax to force the food along.This process is called peristalsis.If we drink water upside down it will not run back out.

Mouth

The food is physically broken down into manageable sizes by the teeth.

It is mixed with a fluid called SALIVA.

It contains enzymes to digest food.

This makes the food easier to swallow.

The food is then moved through the gullet (oesophagus) to the stomach.

Stomach

The stomach is a muscular bag with a valve at either end.The CARDIAC sphincter at the top allows food in.The PYLORIC sphincter at the bottom allows food to leave.The stomach wall produces digestive juices which chemically break down some of the large molecules of food.

Stomach

For digestion to work properly the food must be well mixed with the juices.

The stomach muscles contract and relax to mix up the juices and food.

Once the food has been in the stomach for a while, it is released slowly, small drops at a time into the small intestine.

Small Intestine (Duodenum & Ileum)

Digestion continues in the small intestine.

The final products are then absorbed through the intestine wall.

Absorption will happen quicker if the surface area of the inside of the small intestine is increased.

The length of the small intestine increases the surface area, but so also do the VILLI (small finger-like projections.)

Small Intestine (Duodenum & Ileum)

Once digestion is complete, the products pass through the thin wall into the blood capillaries to be transported away to other parts of the body for use.

The VILLI are adapted to absorbing food by their very thin wall, large surface area and excellent blood supply.

Absorption

Glucose and amino acids enter the blood capillaries.

The blood capillaries all enter the Hepatic Portal Vein which leads from the intestine to the liver.

Fatty acids and glycerol enter the LACTEAL which is a part of the lymphatic system.

Diagram of a Villus 

Large Intestine (Colon)

The undigested food passes from the small intestine into the colon.

The colon removes water from the undigested food to make it semi-solid.

After this, the food is stored in the rectum before it is eliminated through the anus.

Enzymes

Digestion in the gut involves the chemical breakdown of food. Each type of food is broken down by a different chemical (enzyme) e.g.

Amylase breaks down starch

Pepsin breaks down protein

Lipase breaks down fats

Digestive Enzymes

The main digestive juices are produced by the salivary glands, stomach, liver, pancreas and small intestine.Most digestive juices contain enzymes.Bile, which is produced by the liver and stored in the gall bladder, has no enzymes.There are 3 different groups of enzymes involved in digestion.

Digestive Enzymes

Each group acts on a different type of food, called the SUBSTRATE.

The substrate gets broken down by the enzymes to substances called PRODUCTS.

Digestive Enzymes

SubstrateSubstrate EnzymeEnzyme Product(s)Product(s)

StarchStarch AmylaseAmylase MaltoseMaltose

ProteinProtein PepsinPepsin PeptidesPeptides

FatsFats LipaseLipase Fatty acids Fatty acids & Glycerol& Glycerol

Size & SolubilityDuring digestion large molecules are broken down to small molecules to allow them to pass into the blood.

StarchStarch GlucoseGlucose

Large moleculeLarge molecule Small moleculeSmall molecule

InsolubleInsoluble SolubleSoluble

Cannot pass Cannot pass through gut wallthrough gut wall

Passes through gut Passes through gut wallwall

““Digestion is the breakdown of Digestion is the breakdown of large insoluble molecules to large insoluble molecules to

small soluble molecules so that small soluble molecules so that they can pass through the gut they can pass through the gut

wall.”wall.”

Peristalsis

The layers of muscle in the gut wall are required for the process of PERISTALSIS.

The wall of the gut constricts behind the food to push the food along.

The gut get wider in front of the food to let it through.

There is a wave of relaxation to push the food along – a bit like forcing a tennis ball into a sock.

Peristalsis occurs along the whole length of the gut from the mouth to the anus.

Peristalsis

Muscles contract

here

Food moves this way

Muscles relax here

Balanced DietA healthy diet must contain some food from all of the following groups:•CarbohydratesCarbohydrates

•ProteinsProteins

•FatsFats

•VitaminsVitamins

•MineralsMinerals

•FibreFibre

Balanced Diet

Carbohydrates and fats provide us with energy.Proteins are used to build and repair body tissue.Fibre gives the gut muscles something to work against to avoid constipation.Plant fibre is found in fruit and vegetables and especially bran which surrounds cereal grains.Vitamins and minerals are used to maintain health.

Food Additives

Some of the food we eat is fresh, e.g. apples and lettuce.Mostly, however, our food has been processed in some way to make it more attractive, to change its flavour, or to keep it longer.Processing food often involves adding chemicals called additives.

Vitamins

VitaminVitamin SourceSource Deficiency DiseaseDeficiency Disease

AA Milk, fresh veg.Milk, fresh veg. Night BlindnessNight Blindness

BB11 (Thiamine)(Thiamine) Cereal grainsCereal grains Beri beriBeri beri

BB33 (Niacin) (Niacin) Cereal, lean Cereal, lean meatmeat

PellagraPellagra

C C (Ascorbic (Ascorbic acid)acid)

Citrus fruitsCitrus fruits ScurvyScurvy

DD Liver, fish, milkLiver, fish, milk RicketsRickets

EE Wheat germWheat germ Reproductive Reproductive DisordersDisorders

KK Green veg.Green veg. Blood doesn’t clotBlood doesn’t clot

Minerals

MineralMineral Required For:Required For:

IronIron Haemoglobin in Red Blood CellsHaemoglobin in Red Blood Cells

IodineIodine ThyroxineThyroxine

SodiumSodium All cellsAll cells

CalciumCalcium Healthy teeth & bonesHealthy teeth & bones