class-7 chapter-2

Revision Notes on Nutrition in Animals

Quick Revision


The animals depend upon other plants and animals for their food.


Animal nutrition comprises the mode of taking in the food in the body, nutritional requirements of the body and how animals can utilize their food.


Digestion - it is a process by which animals break down complex food substances in simpler substances.



Different ways of taking the food



Figure 1: Mode of feeding in Animals

Digestion in Humans


The food that we eat passes through a Canal inside our body.


The food is processed and utilized in the body and unused food is collected inside the canal only.


This Canal is often called as the Alimentary Canal or the Digestive Tract.


The canal is divided into different parts:


The Mouth or Buccal Cavity


Food Pipe or Oesophagus


Stomach


Small Intestine


Large Intestine


Anus







Figure 2: Digestive Tract in Humans

There are three glands associated with the alimentary canal that secrete digestive juices that are used to convert the complex food substances into simpler substances.


liver


pancreas


salivary glands



The Digestive System - The alimentary canal and the digestive glands together form a system in the human body which is responsible for the digestion of food in the body. This system is called the Digestive System.

The Mouth or Buccal Cavity



Figure 3: The Mouth or Buccal Cavity


Ingestion - the process of taking in the food through the mouth is called ingestion.


The food is chewed with the help of teeth, saliva and the tongue present in the mouth.


The salivary glands present in our mouth secrete saliva which mixes with the food, moist it and breaks the starch present in the food into sugar.


The tongue present in the mouth helps in mixing the food with the saliva and helps in swallowing it inside the mouth. It also has taste buds which help in identifying the taste of anything that we eat. Besides this, the tongue also helps in talking.



The Teeth

Milk Teeth - In the early childhood a set of teeth growth in children that then fall off after certain age 6 to 8 years. These teeth are called Milk Teeth.

Permanent Teeth - The teeth that grow after milk teeth fall off are called Permanent Teeth. They generally remain during the lifetime of a person or at least until old age.

Different Types of Teeth



Figure 4: Different types of teeth

Tooth Decay –


A gradual damage of teeth is often called tooth decay.


The main cause of tooth decay is the presence of bacteria in the mouth that grow if we do not keep our mouth and teeth clean.


Any leftover food present inside our teeth is broken down by such bacteria.


As a result, an acid is released which damages the teeth slowly.


Tooth decay can cause severe pain and even toothless.


Tooth decay is caused mainly because of eating food with high sugar content, soft drinks and chocolates.





Figure 5: Stages of Tooth Decay

How can we prevent tooth decay?


Clean your teeth with a brush or dental floss at least twice a day


Rinse your mouth after every meal you eat


Do not put a dirty finger or any unwashed food items in your mouth



Food Pipe or Oesophagus


The food pipe starts from the neck region and runs until the chest area in animals.


The food, when the chewed, moves through the food pipe and reach the stomach through this path.


The food moves in download direction in the food pipe.



The Stomach



Figure 6: Stomach


It is the widest part of the alimentary canal.


It's a bag like structure in a flat U shape.


The stomach is connected with the food pipe and the small intestine.


The stomach’s inner lining produces three things:


Mucous: It protects the stomach lining


Hydrochloric Acid: It kills the bacteria present inside the stomach and activates the digestive juices


Digestive Juices: They help in digestion of the food by breaking down the proteins present in the food into simple substances (olympiads)





Small Intestine


It is a highly coiled structure.


The length of the small intestine is almost 7.5m.


The liver and pancreas release digestive juices into the small intestine.


The inner lining of the intestine also secretes some digestive juices on its own.


The small intestine breaks the carbohydrates into glucose, fats into fatty acids and proteins into amino acids.



The Liver


It is a gland reddish brown in colour.


It is known as the largest gland of the human body.


It secretes a digestive juice called bile juice.


The bile juice is stored in the gallbladder.


The bile juice makes it possible for the body to digest the fats.



The Pancreas


It is a cream coloured gland present in the human body.


It secretes pancreatic juice that helps in digestion of fats, carbohydrates and proteins.



How small intestine absorbs food?


Absorption: it is a process by which the digested food enters the blood vessels of the small intestine.


Villi in the intestine: the small intestine contains small finger-like structures called Villi. They increase the surface area of the intestine thereby increasing the amount of absorption. The digested food gets into the blood vessels through villi and then reaches the whole body. (Olympiads)





Figure 7: Villi in Small Intestine


Assimilation: The process by which the organs of the body utilize the digested food and form complex substances which the body needs such as proteins are called Assimilation.



Parts of Small Intestine

The small intestine has been divided into three parts:

1. Duodenum

It is the first part of the small intestine whose main function is to initiate the digestive process. In this process, the food that enters the small intestine from the stomach is mixed with the digestive juices (bile and pancreatic juice) and is further broken down into simpler substances.

2. Jejunum

It is the middle part of the small intestine that contains the villi and hence undergoes absorption and assimilation.

3. Ileum

It is the third and last part of the small intestine that contains villi-like structures. The ileum absorbs vitamin B12, bile acids and any other nutrients present in the food.

The Large Intestine


Any food that is left undigested passes through the small intestine and enters the large intestine.


It is a wide tube-like structure.


It is only 1.5 m long.


The main function of the large intestine is to absorb water and salts from the undigested food.


The rest of the waste, undigested food passes through the rectum.


Egestion: The process by which the waste, undigested food (the faecal matter) get out of the body through the anus.



 What is diarrhoea?


A condition when watery stools appear frequently is called Diarrhoea.


Food poisoning and infection are two main causes of diarrhoea.


It is a serious disease and can lead to death in severe cases because it involves extensive loss of water and salts from the body.


Generally, ORS (Oral Rehydration Solution) which is boiled cooled water in which a pinch of salt or sugar is added is recommended to the patients to maintain the water loss of the body.



Digestion in Grass Eating Animals



Figure 8: Digestive System in Cow


Rumen - It is a sac-like structure present between the food pipe and the small intestine in grass eating animals like cows and buffaloes.


At first, the animals do not chew their food (basically grass) and instead swallow it.


This partly digested food is stored in the rumen.


Cud: The partly digested food present in the rumen is called Cud.


Rumination: The cud returns to the mouth in these animals and then they chew it. This is called Rumination.


Ruminants: the animals that swallow their food at first and then chew it, later on, are called Ruminants.


Grass eating animals can digest cellulose while several other animals cannot. These animals have a different type of bacteria present in the stomach that helps in digesting the cellulose. (Olympiads)



Feeding and Digestion in Amoeba


The Amoeba is a microscopic organism which is made up of only one cell


The Amoeba has a cell membrane, cytoplasm, a nucleus which is round and dense and small vacuoles which are like bubbles present all over it.


The Amoeba is capable of changing its shape and position on its own.


 It uses false teeth called pseudopodia to take in the food present in the surroundings.


Whenever it wants to intake the food the pseudopodia or finger-like projections come out of its body.


The pseudopodia engulf the food in and the food gets stored in the food vacuoles.


Then it secretes some digestive juices inside the vacuoles that help in its digestion of the food.


The Amoeba then absorbs the digested food and uses it for fulfilling different life processes such as multiplication and growth.


The Amoeba also secretes out waste products or undigested food out of its body. (Olympiads)





Figure 9: How amoeba digests the food

class-7 chapter-1

Quick Revision


Living organisms such as plants and animals survive on food.


The food gives them the energy to perform several activities in their life and helps in the growth.


Nutrients - Certain substances are present in the foods that help in the survival of the organisms. These special substances are called nutrients for example, proteins, vitamins, carbohydrates, minerals and fats.


Some living organisms like plants synthesize their food by themselves by themselves while others such as animals depend upon the plants and other animals for their food.





Figure 1: Different Nutrients

Mode of Nutrition in Plants

What is nutrition?

Nutrition can be defined as a process by which organisms take in the food and utilize it in order to survive. Based on the mode of nutrition organisms can be divided into two categories:


Autotrophic Organisms - They can prepare their food by themselves such as plants


Heterotrophic Organisms - They depend upon other organisms for their food such as animals



How do plants prepare their food?

Plants prepare their food with the help of certain raw materials that they gather from their surroundings:


water


carbon dioxide


sunlight


minerals


chlorophyll



The process by which plants prepare their food by using these raw materials is called Photosynthesis.



Figure 2: Photosynthesis

Where is the food made in plants?


Leaves are also known as the Food Factories of the plants as they are the places where food is prepared.


Different parts of the plants like roots gather the raw materials from the environment and then transfer them to the leaves where photosynthesis takes place.


Transportation of water and Minerals in plants - The roots of the plants absorbs the water and minerals of the soil and then transports them to the leaves via stems and branches.





Figure 3: Transportation of water and Minerals in plants


Inhalation of Carbon Dioxide - There are tiny holes or pores present on the surface of the leaves called Stomata that take in the carbon dioxide present in the atmosphere.





Figure 4: Stomata on leaves and the Chlorophyll


Presences of Chlorophyll in the Leaves - A substance called Chlorophyll is present in the leaves of the plants. It is a green colour pigment. The chlorophyll not only provides green colour to the leaves but also helps in the process of photosynthesis. Chlorophyll captures the sunlight and along with other raw materials prepares the food in the leaves.


This process of photosynthesis only occurs in the daytime in the presence of Sunlight hence it is called Photosynthesis, photo means light.



Why sun is called the ultimate source of energy for all living organisms?

We know that the plants use solar energy to make their food. The herbivores animals depend upon the plants for their food. Animals (carnivores) that do not eat plants depend upon the herbivores animals. Therefore, all of the living organisms directly or indirectly receive their energy from the Sun.

Cells in Living Organisms

All living organisms are made up of tiny structures called cells. Some organisms (microscopic) contains only one cell while others plants and animals contain many cells of different kinds. Parts of a cell:


The Nucleus - Every cell has a nucleus present in the centre that performs various functions of the cell.


The Cell Membrane - Every cell has an outer boundary which protects the cell called the Cell Membrane.


The cytoplasm - Every cell has a gel-like structure present in it called the Cytoplasm.


Cell organelles: These are membrane bound structures found within a cell in the cytoplasm. The cell organelles have special function associated with them. Different cell organelles found in the cell are:


Mitochondria – Produces energy for the cell


Endoplasmic Reticulum – Produces lipids and proteins in cell


Golgi apparatus – Helps in exporting materials out of cell


Lysosomes – Help in digestion in the cell







Figure 5: Structure of Cell in Animals and Plants

Can photosynthesis take place in other parts of the plant?

Yes, green stems and branches of the plants can also undergo the process of photosynthesis. For example, plants in the desert area like cactus do not have leaves but they still exist there because their stem produces the food for the plant.

Why is the process of photosynthesis important?


There will be no food if the plants would stop conducting the photosynthesis process.


The plants take in carbon dioxide and produce oxygen during the process of photosynthesis. Hence, without this process, it would not be possible to survive on earth as they would be no oxygen.



Production of Oxygen and Carbohydrates by the Plants



Figure 6: Production of Oxygen and Carbohydrates

Plants use carbon dioxide and water in presence of the sunlight and chlorophyll to produce carbohydrates and oxygen. The carbohydrates thus produced by the plants are converted into starch.

Chloroplast and the Process of Photosynthesis



Figure 7: Structure of Chloroplast


Chloroplasts are special cell organelles that are found only in plant cells. They are called the food producers of the plant cells.


The chloroplasts are surrounded by two membranes called the Inner and Outer Membrane. The inner membrane surrounds stroma and thylakoid stacks.


The chlorophyll molecules are present on each of the thylakoids. The chloroplasts convert the sunlight into sugars that are used by the plant cells.


Hence, chloroplasts allow the conduction of the process of photosynthesis. The chlorophyll that can absorb the sunlight is present inside the chloroplasts.


When the light of the sun hits the chloroplasts and the chlorophyll, the light energy is converted into chemical energy found in compounds such as ATP and NADPH.


Then these energy molecules move into the stroma where carbon dioxide is attached to them. As a result of the molecular reactions, oxygen and glucose are created.



Can leaves which are red or Brown or violet in colour conduct photosynthesis?

Yes, the chlorophyll is also present in leaves that are not green in color. They are of different colours because the other colour pigments are more than the green colour pigments in such leaves.

Algae contain chlorophyll

Algae are green coloured organisms found in the stagnant water. They get their green color from chlorophyll. Since they have chlorophyll in them they are capable of conducting photosynthesis. (olympiads)



Figure 7: Algae in Water

How do plants generate proteins and fats?


Along with carbohydrates, plants can also produce proteins and fats which are formed with the help of Nitrogen.


Nitrogen is present in large amounts in the air but plants cannot consume the nitrogen directly from the atmosphere. 


The soil often contains some bacteria that are capable of converting the nitrogen into nitrates which can be the used by the plants.


Also, fertilizers used by farmers and gardeners contain a high amount of Nitrogen which mixes into the soil and is used by the plants.



Nutrition in Plants that do not contain Chlorophyll

Many plants do not contain any chlorophyll. Hence they are unable to prepare their food by themselves. Therefore, they rely on other plants and animals for their food.

1. Parasitic Plants - Some plants live on another plant for their nutrition. These are called parasites. The plants on which these parasitic plants survive are called the host. For Example, cuscuta is a parasitic plant.



Figure 8: Yellow color Cuscuta plant growing over green plants

2. Insectivorous Plants - Some plants depend upon insects for the food and thus are called Insectivorous. The leaves of these plants are modified into a pitcher like structure. The top part of the leaves acts as a lid which can open and close the pitcher. The pitcher contains hair in a downward direction which traps the insects. The pitcher on capturing the insect secretes some digestive juices which help in the digestion of the insect. For Example, Dischidia and Nepenthes

  

Figure 9: Insectivorous Plants

3. Saprotrophs - Some organisms survive on decaying food and organisms. This mode of nutrition is called saprotrophic nutrition and the organisms that survive because of the saprotrophic nutrition are called Saprophytes.

How do saprophytes obtain their nutrition?


The saprophytes secrete digestive juices on the decaying and dead matter.


These juices convert the matter into a solution.


The saprophytes that absorb the nutrients from the solution.


For Example, Fungi (yeast and mushrooms) are a saprophytes that can be found on stale food and pickles which are exposed to the hot and humid environment.





Figure 10: Fungi growing on Bread

4. Symbiotic Relationship - Sometimes organisms live together to share shelter and food with each other. These are said to have a symbiotic relationship.

Examples of organisms living in a symbiotic relationship:


Some fungi live in the roots of the trees. These fungi take food from the trees and in return help the trees in absorbing water and nutrients from the soil.


Sometimes an organism that contains chlorophyll such as algae lives in association with a fungus (together called as Lichens). The algae provide food and nutrition to the fungus while the fungus provides water, minerals and shelter to the algae.





Figure 11: Lichens

Replenishing the Soil with Nutrients


Plants get their nutrients from the soil mainly hence there is a need to replenish the soil again with nutrients so that the plants can survive on it.


Fertilizers and manure are often used to replenish the soil with the nutrients. They contain potassium, phosphorus and nitrogen all of which are important for the plants.


A bacterium called Rhizobium is present in the soil which can convert nitrogen present in it in the form that can be consumed by the plants.


The rhizobium generally lives in the roots of the plants such as peas, beans, grams and legumes and provides nitrogen to these plants. This again is an example of a symbiotic relationship. The farmers often do not need to use fertilizers while growing such crops. (Olympiads)





Figure 12: Rhizobium Bacteria in Soil