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Class7—Biology

Lesson 1—Tissue

Answers

Review your learning (pg 15, To be written in the book)

A. Answer in one word

1. Intercalary meristem

2. Sclerenchyma

3. Lacunae

4. Chondrocytes

5. Lymph

B. 1.Incorrect---Organs

Correct --- Tissues

2. Incorrect--- Different

Correct ---Common

3. Incorrect---Simple

Correct ---Complex

4. Incorrect---Epithelial

Correct--- Skeletal

6. Incorrect---Lymphatic vessels

Correct ---Bone marrow

C. Match the columns.

1. (b) 2.(e) 3.(d) 4.(c) 5(a)

D. Answer in short—(To be written in the interleaved copy)

1. Tissue—It is a group of similar cells performing specific function.

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2. (i) The main function of Meristematic tissue is to form a number of new cells by repeated

divisions.

(ii) Apical meristem increases the length of the plant.

(iii) Lateral meristem helps in increasing the width of the plants.

(iv) Intercalary meristem causes increase in the length of an organ of a plant.

3. Depending on their origin, permanent tissues can be classified as shown.

Permanent tissue

Simple Permanent

Tissue

Protective Tissue

Supporting Tissue

Parenchyma Collenchyma Sclerenchyma

Complex Permanent

Tissue

Xylem Phloem

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4. The three types of epithelial tissues are---

i) Squamous epithelium

ii) Cuboidal epithelium

iii) Columnar epithelium

5. Blood plasma is a straw-coloured fluid present in blood. It is composed of dissolved

proteins, glucose, various electrolytes and water.

.

E. Answer in detail-—(To be written in the interleaved copy)

1. Meristematic tissue is made up of a group of cells which divide continuously and very

fast. This tissue is found in the growing regions of plants such as tips of roots, stems and

branches. Their function is to make the plants grow.

On the basis of their position in the plants, meristematic tissues are of three types.

• Apical meristem: This tissue is located at the apex or tips of roots and stems. It is

responsible for increase in the length of the plant.

• Intercalary meristem: They are located at the base of nodes where leaves attach and the

region of the internodes where cell division occurs for longer time. They are

responsible for stem elongation or longitudinal growth.

• Lateral meristem: This tissue is found along the lateral sides of stems and roots, and is

responsible for increase in their circumference.

2. Complex permanent tissue is made up of more than one type of cells which work together

to perform a common function. Their main function is to conduct water and

transport food material to various parts of a plant. Complex tissues include xylem and

phloem. Together they constitute the vascular system of the plant

3. Connective tissue proper connects various parts of the body such as muscles to bones or

bones to other bones and so on. It gives support by filling up the spaces between the organs.

It is of the following three types.

Areolar tissue: It is the most widely distributed connective tissue in animals. It is

present under the skin as a continuous layer. It fills up the spaces between various

organs and acts as a packing material around the organs.

• Fibrous tissue: It is further divided into two types.

i) Yellow fibrous tissue is found in ligaments which join the bones. It is also found in

the walls of the arteries. This tissue is strong but not flexible.

ii) White fibrous tissue is present in tendons which connect muscles to bones. This

tissue is strong and highly elastic.

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iii) Adipose tissue: It is mainly located under the skin. It is also found around internal

organs. Its main role is to store fat. It also cushions and insulates the body. It provides

protective padding around the organs.

4. Nervous tissue—

Structure—

i) Nervous tissue is made up of long nerve cells called neurons.

ii) Each neuron consists of a cell body called cyton and a long, thread like structure

called axon.

iii) The cell body contains a nucleus and many small thread-like branches arise from it in

all directions.

iv) These are called dendrons which further divide to form dendrites.

v) Neurons join together and form the nerves.

vi) Nerves are connected to the brain and the spinal cord.

Location—

Nervous tissue is present in the brain, the spinal cord and the nerves.

Functions—

i) The nervous tissue helps in the control and coordination of the body.

ii) The neurons of sense organs detect changes in the environment and send this message

to brain or spinal cord in the form of nerve impulses for the appropriate response.

A Neuron

5. Muscular Tissues--

i) Muscular tissues constitute the muscles and are found in every part of the body.

ii) Muscles contract and relax, and thus help the body in all its movements.

iii) They are of the following three types—

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a) Voluntary Muscles—All types of movements are brought about by these muscles.

Structure---

i) Voluntary muscle is formed of long cylindrical multinucleated cells.

ii) These cells show alternate light and dark bands (striations).

iii) Its fibres are arranged in the form of bundles.

Location –

i) It is found attached to all the bones.

ii) They are mostly present in the arms, legs, body wall, face and neck.

Functions—

i) Voluntary muscles contract quickly, but can not remain contracted for a long time.

ii) They help in the movement of bones.

iii) They get tired soon.

iv) They are voluntary in their activity (they work according to the will of an organism)

b) Involuntary muscle-- They are also called as striated or smooth muscles.

Structure—

i) Involuntary muscles are formed of spindle shaped cells.(cells with tapering ends)

ii) Each muscle cell is uninucleate.

iii) They do not show light and dark bands.

Location—

They are present in the internal organs of our body such as stomach, intestine, lungs and

urinary bladder.

Functions—

i) They contract slowly, but can remain contracted for a long time.

ii) They do not get tired soon.

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iii) They are involuntary in action (they do not work according to the will

of an organism.

c) Cardiac muscle--Cardiac muscles are special type of involuntary muscles. They are

found only in the heart and are also called heart

Structure---

i) Cardiac muscle is formed of short uninucleated cells

ii) These cells have light and dark bands (striations)

iii) Cells are cylindrical and branched.

Location—

They are found in the walls of the heart.

Functions--

i) Cardiac muscles contract quickly and rhythmically to continuously pump blood to

various parts of the body.

ii) They do not get tired.

iii) They are involuntary in their activity (not under the control of one’s will)

Voluntary Muscle

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Involuntary Muscle

Cardiac Muscles