Maharashtra Board Class 9 Science Chapter 17 Introduction to Biotechnology PDF Download

Tissue

In the case of amoeba-like unicellular organisms, all functions are performed by organelles of that single cell. However, most of the organisms are multicellular. How are the various processes brought in their body? Groups of cells come together, so as to perform the various functions of the body.

Are you familiar with the sequence- letters → words → sentences → lessons → text book?

Similarly, organization of the body of organisms follows a definite hierarchy. You have already studied cells and cell organelles in that hierarchy.

A group of cells having the same origin, same structure and same function is called 'tissue'. Millions of cells are present in the body of multicellular organisms. These cells are divided into different groups and each group performs a definite function. For example, we can perform movements due to contraction-relaxation of muscles. Conducting tissues in plants transport water and food to all its parts. All functions of the body occur with full efficiency due to the specific organization of cells and their division of work.

1. Which components bring about important processes in the living organisms?

2. Which is the smallest structural and functional unit of the body of living organisms?

Teacher's Note

Tissue is a group of same cells doing the same work. Like when you play a sport with friends, everyone has one job to do.

Exam Trick

Remember: Tissue = Team. Each team member does same work. Like a cricket team - all bowlers, all batsmen.

Points to Remember

Tissue is made of cells that look the same and do the same job.
Millions of cells join together to make tissues.
Muscles help us move because of contraction and relaxation.
Plants have conducting tissues to move water and food.

Types Of Tissue

Are the structure and functions of the bodies of plants and animals the same?

Plants being sedentary, most of their tissues are of the type that give support. There are dead cells in some tissues and these do not need much attention. Growth of the plants occurs in specific parts of their body where the tissues contain dividing cells. As animals have to move from place to place in search of food, shelter and partners, their energy needs are greater. Most of the tissues of animals are made up of living cells. Uniform growth occurs through out the body of an animal and they do not have different dividing and non-dividing tissue. This means that plants and animals have different types of tissue to performing the necessary functions.

Teacher's Note

Plants stay in one place, so they need strong tissues for support. Animals move around, so they need living tissues that work fast.

Exam Trick

Remember: Plants = Still, need support tissues. Animals = Move, need living tissues with energy.

Points to Remember

Plants have dead cells in their tissues but animals have mostly living cells.
Plants grow only in some parts but animals grow all over.
Both have different tissues because they live differently.
Support tissues are more important for plants.

Animal Tissue

Why can we not see our organs like the heart, blood vessels and intestines?

In the body of animal different organs come together to perform a specific function. Organs like the lungs and trachea, with the help of the contraction and relaxation of some muscles bring about the function of respiration. Different tissues perform different functions in the organs. Accordingly, tissues are classified into different types.

There are four main types of animal tissues, namely epithelial tissue, connective tissue, muscular tissue and nervous tissue.

Blood is also a type of connective tissue. It circulates in our body from one part to another and transports different materials. For example, it transports oxygen and nutrients to all cells in the body. Similarly, it transports waste materials generated all over the body to the kidney for excretion.

Teacher's Note

Our body has four types of tissues like a school has teachers, students, office staff, and helpers. Each does different work.

Exam Trick

Remember: Four animal tissues = ECMN. Epithelial, Connective, Muscular, Nervous. Like four pillars holding a house.

Points to Remember

Epithelial tissue covers and protects the body.
Connective tissue joins different body parts.
Muscular tissue helps us move.
Nervous tissue helps us feel and think.
Blood is a connective tissue that moves in body.

Epithelial Tissue

Protective coverings in the animal body are called epithelial tissues. Cells in this tissue are closely packed and form continuous layers. Any material that enters the body first encounters epithelial tissue. Cells of epithelial tissue are separated from the cells of other underlying tissues by a fibrous membrane. The skin, mucous layer of the mouth cavity, inner surface of blood vessels, walls of the alveoli, etc. are made up of epithelial tissues.

Teacher's Note

Epithelial tissue is like the wall of your school. It protects everything inside. Your skin is epithelial tissue protecting your body.

Exam Trick

Remember: Epithelial = Exterior. It covers outside. Like paint on a wall protects the wall underneath.

Points to Remember

Epithelial tissue cells are tightly packed together.
It forms a protective layer on the body.
Skin, mouth lining, and blood vessels have epithelial tissue.
It is the first thing germs meet when entering body.

Teacher's Note

Different parts of body need different epithelial tissues. Your skin needs many layers, but your stomach lining needs tall cells to absorb food.

Exam Trick

Remember: Squamous = Flat and thin (like a stamp). Columnar = Tall and thin (like a column). Cuboidal = Cube shaped.

Points to Remember

Squamous cells are flat and help filter things.
Stratified epithelium has many layers for protection.
Glandular epithelium makes sweat and oil for skin.
Columnar epithelium is in stomach to absorb food.
Ciliated epithelium has hair-like parts to push mucus.

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