Animal nutrition is the study of how animals obtain and utilize nutrients from their food.
It involves understanding how animals consume food and how their bodies digest and absorb nutrients.
Food components, such as carbohydrates, are complex and need to be broken down into simpler substances through digestion.
Different Ways of Taking Food
Each species or type of organism has their own way of taking in food. Bees and humming birds suck plant-nectars, infant of humans and some animals feed on mother’s milk, Snakes such as python consume the animals upon which they prey. Aquatic animals filter small food particles floating close by and feed on them.
All organisms have their unique ways of consuming food, tailored to their physiology. These methods include:
Chewing: This involves biting and grinding food using teeth within the mouth. Examples include humans and dogs.
Scraping: Here, an organ like the jaw scrapes food off a surface. Examples are seen in snails and ants.
Syphoning: Food is absorbed into the mouth. Butterflies use this method.
Capturing and swallowing: This involves seizing food and then swallowing it whole. Lizards are an example.
Sucking: Organisms pierce food and draw out liquid. Mosquitoes utilize this method.
Sponging: Saliva combines with food to dissolve it in the mouth. Houseflies demonstrate this approach.
Note: A starfish feeds on animals that have hard shells made of calcium carbonate. It opens the shell and then extends its stomach out through its mouth to eat the soft animal inside. Afterward, the stomach retracts back into the body, where the food is slowly digested.
Star Fish
Question for Chapter Notes: Nutrition in Animals
Try yourself:Which method of food intake involves an organism piercing its food to draw out liquid?
Explanation
The method of food intake where an organism pierces its food to draw out liquid is known as sucking. This process is utilized by organisms like mosquitoes, which use specialized mouthparts to extract fluids from their hosts.
Here's how the other methods compare:
Chewing involves biting and grinding food, as seen in humans and dogs.
Syphoning is when food is absorbed into the mouth, a method used by butterflies.
Sponging involves using saliva to dissolve food, as demonstrated by houseflies.
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Digestion in Humans
The food travels through a continuous canal that starts at the mouth and ends at the anus. The alimentary canal is a continuous passage starting from the buccal cavity and ending at the anus. Compartments of the alimentary canal include:
Human Digestive System
Buccal cavity
Food pipe or esophagus
Stomach
Small intestine
Large intestine terminating in the rectum
Anus
These parts collectively form the digestive tract.
Food components gradually get digested as they move through different compartments. The inner walls of the stomach and small intestine, along with associated glands like salivary glands, liver, and pancreas, secrete digestive juices. Digestive juices convert complex food substances into simpler ones. The digestive tract and associated glands constitute the digestive system.
The Mouth and Buccal Cavity
The process of ingesting food begins with the mouth, where food is taken in.
Teeth: Teeth play a crucial role in masticating food into small pieces through mechanical breakdown. Each tooth is anchored in a distinct socket within the gums and serves different functions. Two sets of teeth are present in humans: milk teeth, which are shed during childhood, and permanent teeth, which replace them.
Arrangement of teeth
Saliva:Salivary glands are present in the mouth which are responsible for secreting saliva. Saliva aids in breaking down starch into sugars, facilitating digestion.
Tongue: The tongue, a muscular organ in the buccal cavity, assists in speech, mixing food with saliva, swallowing, and tasting different flavors.
Tooth Decay: Bacteria naturally present in the mouth are typically not harmful. If oral hygiene is neglected after eating, harmful bacteria can thrive by breaking down sugars from leftover food, releasing acids that gradually damage teeth. This process, known as tooth decay, can lead to severe toothache and, in extreme cases, tooth loss.
The Foodpipe/Oesophagus
The food pipe, also known as the Oesophagus, is where swallowed food travels into the stomach. The food pipe is located along the neck and the chest.
Movement of food in Oesophagus
Movement: Food is propelled downwards in the food pipe by the contractions of its walls.
Function: This movement of pushing food downwards occurs throughout the entire digestive tract. At times, when the stomach rejects food, it can lead to vomiting.
The Stomach
The stomach is a thick-walled organ shaped like a flattened J and is the widest part of the alimentary canal.
Journey of Food: Food enters the stomach from the esophagus and exits into the small intestine.
Function: The inner lining of the stomach produces mucus, hydrochloric acid, and digestive juices. Mucus protects the stomach lining, while hydrochloric acid aids in killing bacteria and creating an acidic environment for digestion. Digestive juices in the stomach help break down proteins into simpler substances.
Question for Chapter Notes: Nutrition in Animals
Try yourself:Which part of the alimentary canal is responsible for the digestion of fats?
Explanation
Small intestineThe majority of fat digestion happens once it reaches the small intestine. This is also where the majority of nutrients are absorbed. Your pancreas produces enzymes that break down fats, carbohydrates, and proteins. Your liver produces bile that helps you digest fats and certain vitamins.
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The Small Intestine
The small intestine is approximately 7.5 meters long and highly coiled. It receives secretions from the liver, pancreas, and its own walls.
Small & Large Intestine
Liver: The liver, a reddish-brown gland in the upper right abdomen, is the largest gland in the body. It secretes bile juice stored in the gall bladder, crucial for fat digestion.
Pancreas: The pancreas, a large cream-colored gland beneath the stomach, produces pancreatic juice that aids in breaking down carbohydrates, fats, and proteins into simpler forms.
Function of Small Intestine: In the lower part of the small intestine, intestinal juice completes the digestion process, breaking down carbohydrates into glucose, fats into fatty acids and glycerol, and proteins into amino acids.
Absorption in the small intestine
After food is digested, it moves into the blood vessels lining the intestine through a process known as absorption.
Villi
Digestion and Absorption: After digestion, food moves into the blood vessels lining the small intestine through a process called absorption.
Role of Villi: The inner walls of the small intestine have finger-like projections called villi, which enhance the surface area for efficient absorption of digested food.
Transport of Nutrients: Each villus contains a network of small blood vessels that absorb digested nutrients and transport them to various body organs for assimilation.
Assimilation and Energy Production: Assimilation involves using absorbed substances, like proteins, to build complex molecules. Glucose is broken down into carbon dioxide and water in cells, releasing energy with the help of oxygen
Further Processing: Undigested and unabsorbed food moves into the large intestine for additional processing
Large Intestine
The large Intestine absorbs water and certain salts from undigested food material.
Structure and Length: The large intestine is wider and shorter than the small intestine, with an approximate length of 1.5 meters.
Absorption: It absorbs water and certain salts from undigested food material.
Formation of Feces: The remaining waste moves into the rectum, where it forms semi-solid feces.
Egestion: Fecal matter is regularly eliminated through the anus in a process known as egestion.
Question for Chapter Notes: Nutrition in Animals
Try yourself:
How does the process of digestion begin in the human body?
Explanation
- Digestion in the human body begins in the mouth where food is chewed and mixed with saliva. - The teeth play a crucial role in breaking down food into smaller pieces through mechanical breakdown. - Saliva in the mouth aids in breaking down starch into sugars, facilitating digestion. - The tongue assists in mixing food with saliva, swallowing, and tasting different flavors. - Therefore, the correct answer is Option B: Digestion begins in the mouth where food is chewed and mixed with saliva.
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Digestion in Grass-eating Animals
Grass-eating animals, such as cows and buffaloes, chew continuously even when not actively eating. This helps them break down the fibrous material in grass.
Storage in the Rumen: After being swallowed, grass is stored in the rumen, a specialized stomach compartment. In the rumen, food undergoes partial digestion and forms cud.
Rumination Process: The cud, which is partially digested food, is regurgitated in small lumps and chewed again. This process, known as rumination, is characteristic of ruminant animals.
Role of Bacteria in Digestion: Ruminants, including cattle and deer, benefit from bacteria in the rumen that help digest cellulose, a carbohydrate found abundantly in grass. These bacteria break down cellulose, which is otherwise indigestible for many animals, including humans.
Cellulose Digestion in Non-Ruminants:Animals like horses and rabbits, which are not ruminants, possess a large structure called the caecum. The caecum contains specific bacteria that assist in the digestion of cellulose.
Question for Chapter Notes: Nutrition in Animals
Try yourself:Why can't humans digest cellulose?
Explanation
Cellulose is an important component in the diet of herbivorous animals, but humans cannot digest cellulose. This is because humans do not have the necessary enzymes, such as cellulase, to break down the complex carbohydrate. While ruminant animals like cows have symbiotic bacteria in their digestive system to help digest cellulose. As a result, cellulose passes through the human digestive system undigested and is eliminated as waste.
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Diarrhea
Sometimes, individuals may experience frequent passing of watery stool, a condition known as diarrhea.
Diarrhea can be triggered by factors such as infection, food poisoning, or indigestion and is prevalent in India, especially among children.
Severe cases of diarrhea can potentially lead to fatality due to the excessive loss of water and salts from the body.
It is crucial not to overlook diarrhea; even before consulting a doctor, the patient should consume ample boiled and cooled water with a pinch of salt and sugar dissolved in it. This solution is referred to as Oral Rehydration Solution (ORS).
Feeding and Digestion in Amoeba
Amoeba is a tiny single-celled organism discovered in pond water. Characteristics of Amoeba include a cell membrane, a dense nucleus, and multiple small vacuoles within its cytoplasm.
Amoeba is known for its ability to change shape and position frequently.
For movement and food capture, Amoeba extends finger-like projections known as pseudopodia or false feet.
Amoeba primarily feeds on microscopic organisms, engulfing them by extending pseudopodia around the food particle, forming a food vacuole.
Upon trapping the food in a food vacuole, digestive juices are secreted into it, breaking down the food into simpler substances.
The digested food is gradually absorbed to be utilized for growth, maintenance, and reproduction.
Any undigested remains are expelled outside the cell through a vacuole.
The digestion process in Amoeba involves breaking down food into simpler substances to extract energy, a fundamental process similar across all animals.
The document Nutrition in Animals Class 7 Notes Science Chapter 2 is a part of the Class 7 Course Science Class 7.
FAQs on Nutrition in Animals Class 7 Notes Science Chapter 2
1. How do humans and grass-eating animals differ in their ways of taking food?
Ans. Humans take food through their mouth and break it down through chewing, whereas grass-eating animals have a specialized stomach with multiple chambers to digest tough plant material.
2. What is the process of digestion in humans?
Ans. In humans, digestion begins in the mouth where food is chewed and mixed with saliva. It then travels down the esophagus to the stomach where it is further broken down by stomach acids and enzymes. The nutrients are absorbed in the small intestine and waste is eliminated through the large intestine.
3. How do grass-eating animals digest their food?
Ans. Grass-eating animals have a specialized stomach with multiple chambers, such as the rumen and the reticulum, where bacteria help break down the tough plant material. This allows them to extract nutrients from grass and other plant material.
4. How does feeding and digestion occur in amoeba?
Ans. Amoeba engulfs food particles by surrounding them with its cell membrane, forming a food vacuole. Enzymes are then secreted into the food vacuole to break down the food into nutrients. The nutrients are absorbed by the cell while waste is eliminated through the cell membrane.
5. What are the similarities and differences in the feeding and digestion processes of humans, grass-eating animals, and amoeba?
Ans. The similarities include the breakdown of food into nutrients and the absorption of these nutrients. The differences lie in the specific organs and mechanisms used for digestion, such as chewing in humans, specialized stomach chambers in grass-eating animals, and engulfing food particles in amoeba.