2. Nutrition in Animal
Plants make their food by the process of photosynthesis, so that they are known as autotrophs.
Animals cannot make their food themselves but the herbivorous animals that eat plants directly while some animals (carnivorous) eat plant eating animals.
Thus, animals get their food from plants either directly or indirectly.
All organisms require food for survival and to complete the life process as growth.
Requirement of nutrients, mode of intaking of food and its utilization in the body are collectively known as nutrition.
Nutrition in complex animals involves following steps: (1) Ingestion (2) Digestion (3) Absorption (4) Assimilation (5) Egestion.
1. Ingestion- The intaking of food in the body is called ingestion.
* Method of ingestion, i.e. taking of food, varies from one animal to another.
Bees and humming-birds suck the nectar of plants, infants of human and many other animals feed on mother’s milk. Snakes like the python swallow the animals. Some aquatic animals filter tiny food particles floating nearby and feed upon them.
Digestion - The process of breaking down of solid and complex component of food into simpler component is known as digestion.
The process of digestion is different in different animals like that human, grass eating animals, amoeba, etc.
Absorption – The process of absorving the digested food by the blood in the intestine is known as the absorption.
Assimilation – The utilisation of absorbed food is known as assimilation, as proteins and vitamins utilised by the body.
Through the process of assimilation our cells utilised the digested food supplied with oxygen and nutrients.
Egestion – Removal of waste food materials from the body is called egestion.
Since the waste of food left after digestion is called faeces, hence the process of egestion is also known as defecation. The faecal matter is removed through the anus from time-to-time.
Different Ways of Ingestion of Food:
Different organism takes food in different ways.
- A humming bird, butterflies,
sucks nectar of plants. - Lice, Mosquito sucks the blood
- House fly sucks the liquid material of food
- Human beings use their hands to put food into their mouth and swallow the food after chewing.
- Infants of human and many other animals feed upon their mother’s milk by sucking them.
- A snake swallows the animals they prey upon without chewing them.
- A frog captures prey with its sticky tongue joined outer parts of its jaw.
- An earthworm uses its muscular pharynx to swallow its food.
- Some aquatic animals filter tiny particles floating nearby and feed upon them.
- Amoeba, a unicellular animal, engulfs tiny particles of food by using pseudopodia. It surrounds the food by pseudopodia and then makes a food vacuole to engulf the food.
- Starfish feeds on animals covered by hard shells of calcium carbonate. After opening the shell, the starfish pops out its stomach through its mouth to eat the soft animal inside the shell. The stomach then goes back into the body and the food is slowly digested.
Digestion
The process of breaking down of complex component of food into simpler substances is called digestion.
After taking of food, food is digested and then it is passed to the different parts of body to complete the life process as the growth, repair and other vital functioning of body.
The food we take is primarily in the form of complex substances. Food in such complex form is not used as such by animals. Hence, they need to be first broken down into simpler soluble forms so that they can be absorbed by the cells of the body.
The process of digestion is different in human, grass eating animals, amoeba, hydra, etc.
Enzymes help in the breakdown of complex molecules like carbohydrates, protein, fats, etc. into simple molecules.
Digestion in unicellular animals; like Amoeba; is intracellular. The digestive enzymes are secreted in the food vacuoles.
Some Questions
Q. 1 What is ingestion?
Ans. - Ingestion- The intaking of food into the body is called ingestion.
* Method of ingestion, i.e. taking of food, varies from one animal to another.
Bees and humming-birds suck the nectar of plants, infants of human and many other animals feed on mother’s milk. Snakes like the python swallow the animals. Some aquatic animals filter tiny food particles floating nearby and feed upon them.
Q. 2 What is digestion?
Ans. Digestion - The process of breaking down of solid and complex component of food into simpler component is known as digestion.
The process of digestion is different in different animals like that human, grass eating animals, amoeba, etc.
Q. 3 What is absorption?
Ans.
Q. 4 What do you understand by assimilation?
Ans.
Through the process of assimilation our cells utilised the digested food supplied with oxygen and nutrients.
Q. 5 What do you understand by egestion?
Ans.
The waste of food left after digestion is called faeces, thus the process of egestion is also known as defecation. The faecal matter is removed through the anus from time-to-time.
Q. 6 What are the steps of nutrition involved in animals?
Ans. There is five steps of nutrition involved in animals. These are
(1) Ingestion
(2) Digestion
(3) Absorption
(4) Assimilation
(5) Egestion.
Q. 3 What are Pseudopodia?
Ans. The false feet of amoeba are called pseudopodia.
(The word pseudopodia is the formed with 'pseudo' and 'podus'. Pseudo means false and podus means feet. Singular of pseudoposida is pseudopodium)
Q. How the amoeba gets their food?
Ans. Amoeba, a unicellular animal, engulfs tiny particles of food by using pseudopodia. It surrounds the food by pseudopodia and then makes a food vacuole to engulf the food.
Digestion in Human
The system of the body which used to digest the food is known as the digestive system.
The digestive system of humans can be divided into various compartments, It consists of the gut or alimentary canal, along with many associated digestive glands.:
(1) the buccal cavity, (2) foodpipe or oesophagus (3) stomach, (4) small intestine, (5) large intestine large intestine ending in the rectum and (6) the anus.
1. Mouth: In humans the food is ingested through the mouth. The mouth contains tongue, teeth and salivary glands. Teeth break and chews the food into smaller particles. This process is called mastication. The chewed food is mixed with saliva with the help of the tongue. Saliva is a watery fluid secreted by the salivary glands. Saliva contains a type of enzyme called the salivary amylase, which converts starch into sugar. Thus the digestion of the food starts from the mouth
(a) Teeth: There are four types of teeth in our mouth. Our teeth cut, tear and grind the food before we swallow it. An adult human has 32 teeth in all; 16 in each jaw.
(i) Incisors: These are flat and chisel-shaped teeth, lie in the front of the mouth.
There are eight incisor teeth; four in the upper jaw and four in the lower jaw.
The incisor teeth are well adapted for cutting and biting of food items.
(ii) Canines: These are round shaped, sharp and pointed teeth.
There are four incisor teeth; two in the upper jaw and two in the lower jaw.
Canines are well adapted to hold and tear the food.
(iii) Premolars: The premolars are situated on each side of each jaw.
There are total 8 premolar teeth in an adult human. Two premolars are situated on each side of each jaw.
Premolars help in crushing and grinding the food.
(iv) Molars: The molars have almost a flat surface with small projections to chew the food. molars are meant for fine grinding of food.
There are two molars on both sides in both the jaws.
There are total 12 molar teeth including the wisdom teeth in an adult human.
The 4 molar teeth are also called wisdom teeth. Wisdom teeth usually grow between the ages of 18 to 21.
The tooth is covered with a white substance called enamel. It is the hardest substance in the human body.
Milk teeth and Permanent teeth
Humans get two sets of teeth in their lifetime.
The first set erupts when we are infant or babies, at the time of feeding of milk so that these teeth are called milk teeth. Milk teeth fall off at the age between six to eight.
Milk teeth are replaced by the second set of teeth and are called permanent teeth. The permanent teeth may last throughout life or fall off during the old age.
Q. 1 How many types of teeth are found in human beings?
Ans. There are four types of teeth in human beings. These are called incisors, canines, premolars and molars.
Q. 2 How many incisors are found in an adult human?
Ans. There are 8 incisors, 4 in lower and 4 in upper jaw, found in an adult human.
Q. 3 What is the function of incisors?
Ans. – Incisors are used to cut and bite the food.
Q. 4 How many canines are found in an adult human?
Ans. There are four canine found in an adult human.
Q. 4 What is the functions of Canines?
Ans. Canines are the type of teeth, which help to hold and tear the food.
Q. 5 – How many premolars are found in an adult human?
Ans. There are 8 premolars found in an adult human.
Q. 6 What is the function of premolars?
Ans. Premolars help in crushing and grinding the food.
Q. 7 How many molars are found in an adult human?
Ans. There are total 12 molars are found in an adult human.
Q. 8 What is wisdom tooth?
Ans. Wisdom teeth are molar teeth that grow usually between the age of 18 to 21 in an human.
Q. 9 How many teeth does a human adult have?
Ans. A human adult has 32 teeth in all; 16 teeth in each jaw.
Q. 10 What do you understand by milk and permanent teeth?
Ans. Humans get two sets of teeth in their lifetime.
The first set erupts when we are infant or babies, at the time of feeding of milk so that these teeth are called milk teeth. Milk teeth fall off at the age between six to eight.
Milk teeth are replaced by the second set of teeth and are called permanent teeth. The permanent teeth may last throughout life or fall off during the old age.
Q. 11 - What is Enamel?
Ans. The white substance that covers our teeth is called enamel. It is the hardest substances in the human body.
Tongue –
The tongue is a fleshy muscular organ attached at the back to the floor of the buccal cavity. It is free at the front and can be moved in all directions.
it helps in talking, mixing of saliva, swallowing food into food-pipe or oesophagus, finding the taste of food. It has taste buds that detect different tastes of food.
Oesophagus – It is a tube-like about 30 cm long structure connecting the mouth and the stomach.
Oesophagus has powerful muscles to push the food down to the stomach. The oseophagus contracts and relaxes in a rhythm to give the forward movement of food.
This movement also happens in other parts of the alimentary canal and is known peristalsis. No digestion is took place in oesophagus.
Stomach –It is a muscular U- shaped thick walled bag and the widest part of alimentary canal. It receives food at one end from food pipe and mother and open into the small intestine.
Stomach churns the food to mix digestive juices and convert it into semi solid. The churned semi-solid food is called chime.
The inner lining of the stomach s secretes mucous, hydrochloric acid and digestive gastric juices.
The mucous protects the inner lining of the stomach. The hydrochloric acid kills the harmful bacteria present in the food and provide the medium to the gastric enzymes to work. It makes the medium acidic.
Gastric juice contains some enzymes and hydrochloric acid. The enzymes present in the gastric juices break down protein from food.
Small intestine – The food leaves the stomach at certain intervals of time and enters into the small intestine. The small intestine is highly coiled and receives secretions from the liver and the pancreas. Its walls also secretes juices.
The small intestine is the longest part of the digestive system. It is about 20 feet or 7.5 meters long in an adult human. It consists of three parts: duodenum, jejunum and Ileum. In the duodenum, the liver and pancreas pour their secretions.
Liver is the largest gland in the body. It is a reddish brown gland situated in the upper part on the right side of the abdomen. It secretes bile juice which stored in a sac called the gall bladder. The bile of gall bladder plays an important role in the digestion of fats.
The pancreas is a large cream coloured gland located just below the stomach. The pancreatic juice acts on carbohydrates and proteins and changes them into simpler forms. The pancreatic juice contains several enzymes. The enzymes of the pancreatic juice break down starch into simple sugars and proteins into amino acids.
The bile juice contains the bile which carries out emulsification of fat. In this process, the fat is broken into tiny droplets. The carbohydrates get broken into simple sugars such as glucose, fats into fatty acids and glycerol, and proteins into amino acids.
Minerals and vitamins do not need to be changed because cells are able to absorb them easily.
From duodenum the food goes to the lower part of the intestine which has numerous finger-like projections on the wall of the small intestine called villi. They have fine blood capillaries to absorb the food. The villi increase the surface area for absorption of the digested food. After absorption; food mixes in the blood and carried to all the cells of the body.
In assimilation the cells, glucose breaks down with the help of oxygen into carbon dioxide and water, and energy is released.
The food that remains undigested and unabsorbed enters into the large intestine.
Large intestine: The food that remains undigested and unabsorbed enters into the large intestine. The large intestine is wider in size and shorter about 1.5 metre in length.
Its absorb water and some salts from the undigested food material. The semi solid and remaining waste passes residue is stored in the last part of the large intestine called rectum a semi-solid faeces. The faecal matter is removed through the anus from time-to-time. The throwing out of waste of digested food from rectum is called egestion. Egestionis also known as defecation.
Digestion in Grass Eating Animals -
Ruminants: Herbivores animal can digest cellulose which is a major component of the food eaten by them.
Q. Why Herbivores like cows, buffaloes and other grass-eating animals chewing continuously even when they are not eating grass?
Ans. Actually, they quickly swallow the grass and store it in a separate part of the stomach called rumen. Here the food gets partially digested and is called cud. But cud later the cud returns to the mouth in small lumps and the animal chews it.
This process is called rumination and these animals are called ruminants.
The grass is rich in cellulose, a type of carbohydrate. Many animals, including humans, cannot digest cellulose.
Ruminants have a large sac-like structure between the small intestine and large intestine. The cellulose of the food is digested here by the action of certain bacteria which are not present in humans.
The plant eating animals digest their food in two steps. Their stomach is divided into four chamber the rumen, reticulum, omasum and abomasum.
Rumen : It is the first chamber of rheumatoid animals. First of all, half chewed food is swallowed and it then goes from mouth to the rumen, the first chamber of the stomach. Here, it is acted upon by bacteria. These microorganisms digest the cellulose.
Reticulum: We can called it second chamber of stomach. This half digested food goes to the second muscular chamber; the reticulum. From the reticulum the food is sent back to the mouth; as cud; to be chewed again. Chewing of the cud is called rumination and such animals are called ruminating animals or ruminants as cow, goat, buffaloes, sheep, bison, etc.
Omasum: The re-chewed food is swallowed for the second time. After passing the first two chambers it enters the third chamber; the omasum. Here the food is further broken down into smaller pieces.
and finally enters the fourth chamber, the abomasum. Here, all enzymes act upon the food and the digestion is completed.
Abomasum: After further broken down into smaller pieces the food finally enters the fourth chamber, the abomasum. Here, all enzymes act upon the food and the digestion is completed.
After digestion and absorption, nutrients from food are taken to the cells in all parts of the body. The cells oxidize the food to release energy.
Amoeba
Amoeba constantly changes its shape and position. It pushes out one, or more finger-like projections, called pseudopodia or false feet for movement and capture of food.
Amoeba feeds on some microscopic organisms. When it senses food, it pushes out pseudopodia around the food particle and engulfs it. The food becomes trapped in a food vacuole.
Gradually the digested food absorbed which is used for growth, maintenance and multiplication.
The undigested residue of the food is expelled outside by the vacuole. The basic process of digestion of food and release of energy is the same in all animals.
Very short answer type question:
Q. 1.What is a carnivorous animal? Give two examples.
Ans. Animals, which eat the flesh of other animals, are called carnivorous, e.g. lion, tiger.
Q. 1 What is the function of the digestive juice secreted by the liver?
Ans. The digestive juice from the liver breaks up fat into tiny particle.
Q. 2 Name the organs that make up the alimentary canal.
Ans. Mouth, oesophagus, stomach, small intestine, large intestine and rectum are the parts of the alimentary canal.
Q. 3 Name the four types of teeth.
Ans. The four types of teeth are: Incisors, Canines, Premolars and Molars.
Q. 4 Name the four compartments in a ruminant’s stomach.
Ans. Four compartments in a ruminant’s stomach: Rumen, reticulum, omasum and abomasums.
Choose the correct answer:
Movement of food through alimentary canal is called Peristalsis.
2. Nutrition in Animals
Solution
Q -1 Fill in the blanks.
(a) The main steps of digestion in humans are _____ ____ _____ _____ ______
(b) The largest gland in human body is _______
(c) The stomach releases hydrochloric acid and _____ juices which act on food.
(d) The inner wall of the small intestine has many finger like structure called _______.
(e) Amoeba digest its food in the ________
Ans.(a) Ingestion digestion absorption assimilation egestion
(b) liver.
(c) digestive
(d) villi
(e) vacuoles
Q. 2 - Mark T if the statement is true and F if it is false.
(a). Digestion of starch starts in the stomach.
(b). The tongue helps in mixing food with sliva.
(c). The gall bladder temporarily stores bile.
(d). The ruminants bring back swallowed grass into their mouth and chew it for some time .
Ans. (a). F. (b). T. (c). T. (d). T
Q. 3 Tick (√) mark the correct answer in each of the following.
(A). Fat is completely digested in the
(a) Stomach
(b) Mouth
(c) Small intestine
(d) Large intestine
(B). Water from the undigested food is absorbed mainly in the
(a) stomach
(b) food pipe
(c) Small intestine
(d) Large intestine
Ans.
(A) (c) Small intestine
(B) (d)Large intestine
Q. 4 Match the items of Column I with those given in Column II:
Q. 5 What are villi? What is their location and function.
Ans. The lower part of the intestine has numerous finger-like projections on the wall of the small intestine called villi. They have fine blood capillaries to absorb the food. The villi increase the surface area for absorption of the digested food.
Q. 6 Where is the bile produced? Which component of the food does it digest?
Ans. Bile is produced in the liver. It helps in digestion of fats.
Q. 7 Name the type of carbohydrate that can be digested by ruminants but not by humans. Give the reason also.
Ans. Cellulose is the type of carbohydrates which is digested in ruminants but not in humans. Ruminants have a large sac –like structure between the small intestine and large intestine, in which cellulose of the food is digested by the action of certain bacteria.
Such structure is not present in human. Hence human cannot digest cellulose while ruminants can.
Q. 8 Why do we get instant energy from glucose?
Ans. Glucose is simple sugar so there is no need of digestion. It directly reaches the cells where it gives energy after respiration so
Q. 9 Which part of the digestive canal is involved in:
(a) Absorption of food ________
(b) Chewing of food ________
(c) Killing of bacteria ________
(d) Complete digestion of food _______
(e) Formation of faeces _________
Ans.
(a) Small Intestine
(b) Mouth
(c) Stomach
(d) Small Intestine
(e) Large Intestine
Q. 10. Write one similarity and one difference between the nutrition in amoeba and human beings.
Ans.
Similarity:
Both Amoeba and human beings are heterotrophs and derive nutrition from other organisms.
Dissimilarity:
Human beings have a complex digestive system and different nutrients are digested in separate regions digestive system.
Amoeba does not have special digestive system and all the nutrients are digested in the food vacuole.
Q. 11 Match the items of Column I with suitable items in Column II.
Q. 12 Lable the diagram of the digestive system.
Ans.
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