Science Que-Ans (Each of 2 Mark )

1. Sensory neurons carry impulses towards brain.
2. Axon is long, branch process of neuron which carries impulses away from cyton.

Aerenchyma: It have spaces or air channels on the leaves, stems and roots of few plants that allows exchange of gases between the shoot and root. Chlorenchyma: It consists parenchyma cells that contain chloroplasts and forming the basic green tissue of plant leaves and stems.

Ligaments are connective tissue which are very similar in composition to tendons. However they connect bones with each other and are important in maintaining them in place especially at articulating joints. Without ligaments, the bones can be displaced upon muscle contraction or even during movement. Ligaments help in maintaing the bones in place and aid in controling the range of movement.

Group of cells that are similar in structure and perform same function is called a tissue. Tissue provide structural strength, mechanical strength and show division of labour.

Meristematic cells have dense cytoplasm and prominent nuclei because they are actively dividing cells, so they require cytoplasm and nucleus to control their activities.Schlerenchyma tissue lack vacuoles and intercellular spaces.

Skeletal and cardiac muscles are two types of striated muscle fibres.

Bone and cartilage cells reside in small spaces within the matrix that are called lacunae.

Sieve tube elements do not have nuclei but have cytoplasm. They are dependent on adjacent companion cells which contains dense and very active cytoplasm and a large elongated nucleus.

1. Skeletal or striated muscle fibre is multinucleated.
2. Smooth or unstriated muscle fibre is long and spindle shape.

Tracheids:

1. Single celled.
2. The end walls remain intact.

Vessels:

1. Made up of a row of cells.
2. End walls get dissolved and become perforated.

Writing with hand is voluntary muscles action.

Cell body receives impulse and is transmitted through axon and axon terminals. Following picture also depicts the same phenomenon:

There are certain plants which are living in extreme conditions and it is possible due to the presence of certain distinctive features:

• Plants living in extreme dry habitats have a thick epidermal layer which prevents the loss of water.
• In desert plants, they have a thick waxy cuticle over the outer surface which prevents the loss of water.

Skeletal connective tissue forms the endoskeleton of the body. It includes bones and cartilage.
Functions of skeletal connective tissue:

1. It provides support to the body.
2. Protects the vital organs of the body like brain, ear, heart, lungs etc.
3. It anchors the muscles and provide movement to animal body.

Plant tissue in husk of coconut is sclerenchvma fibres. Reason for stiffness of scrererrchyma is deposition of iig'in in cell walls of its cells.

1. Plants are stationary or fixed as they don’t move while animlas move around in search of food, mates and shelter.
2. The growth in plants is limited to certain regions, while this is not so in animals.

Epidermis is the protective covering of plant body. It protects the plants from desiccation and infection.

Xylem:

1. It conducts water and minerals.
2. Conducting channels or tracheary elements are tracheids and vessels.

Phloem:

1. It conducts organic solutes and food materials.
2. Conducting channels are sieve tubes.

The different types of elements present in the phloem are:

1. Sieve tubes: Sieve tubes are slender, tube-like structures composed of elongated thin-walled cells, placed end to end. Their end walls are perforated by numerous pores and are called sieve plates.
2. Companion cells: It is a small thin-walled cell containing dense and very active cytoplasm and large elongated nucleus.
3. Phloem parenchyma: These are thin-walled, living cells of parenchyma of phloem. They have two functions, storage and slow lateral conduction of food.
4. Phloem Fibre: These are thick-walled, elongated spindled shaped dead cells which posses narrow lumen. They provide mechanical strength to the tissue.

Collenchyma cells have thin primary walls with some areas of secondary thickening. Collenchyma provides extra mechanical and structural support, particularly in regions of new growth. Sclerenchyma cells have thick lignified secondary walls and often die when mature.

1. Adipose tissues.
2. Ciliated epithelium.

When blood circulates in the body, it passes through all the organs and thus connects different tissues and organs of the body. Hence it is considered to be a connective tissue.

Two simple permanent tissue in plants are parenchyma and collenchyma while two complex permanent tissue in plants are xylem and phloem.

The sclerenchyma fibers are of great economical importance since they constitute the source material for many fabrics, hemp, flex, jute.

Adipose tissue is the tissue that is filled with the fat globules and acts as an insulator.
Location of adipose tissue: It is present below the skin and in between the internal organs.

The protein fibres of connective tissue are white fibres of collagen, yellow fibres of elastin and reticular fibres of reticulin.

Skeletal connective tissue are the tissues which join skeletal organs like bones. These oragans include tendons, ligaments and bones and make the whole skeletal system of our body.
Function:

1. It helps in the movement of body.
2. Protects major organs of our body like skull and rib cage.

1. Sclerenchyma fibers.
2. Sclereids.

Lymph is a colorless or slightly yellowish fluid which is called the middleman between tissues cells and blood.

They are located at the base of leaves or internodes, e.g., stems of grasses and other monocots. Such tissues also occur below the nodes. It produces an increase in the length of an organ such as leaves and internodes.

Functions of Xylem:

1. The main function of xylem is to carry water and mineral salts upward from the root to different parts of shoots.
2. Since walls of tracheids, vessels and sclerenchyma of xylem are lignified, they give mechanical strength to the plant body.

Transpiration takes place through stomata. Water vapour comes out of leaves during transpiration. When a potted plant is covered with a glass jar, water vapour (coming out because of transpiration) condenses on the wall of glass jar and hence it appears as fine droplets.

Amoeba is a single cell unicellular organism. It performs all vital life activities like respiration, intake of food, exchange of respiratory gases, excretion, reproduction.

Connective tissues are most abundant and widely distributed in the body of complex animals. The cells of connective tissue are loosely spaced and embedded in an inercellular matrix. The matrix may be jelly like, fluid, dense or rigid.

A special type of parenchyma; called aernchyma is present in water hyacinth. This tissue has air filled spaces inside and because the air gets trapped inside especially in the stem part so it becomes buoyant. Due to this, water hyacinth floats on water surface.

The hair like projection in cuboidal epithelium is called cilia. it prevents the blockage of waste material.

	Fibres	Sclereids
Cell	Sclerenchyma fibres are elongated cells which have long tapered ends and are present in most parts of the plant.	Sclerenchyma Sclereids are cells which have a varying shape and are distributed in the cortex, pith, xylem, and phloem of the plants.
Cell Origin	Origin of the fibres is meristematic.	Sclereids origin from mature parenchymal cells.
Shape	Fibres are elongated.	Sclereids are broad and in varied shapes.
Endings	Fibres have tapering ends.	Sclereids have blunt ends.

Tendon is a fibrous (dense) connective tissue which connects a muscle with a bone.

The nerve fiber which is surrounded by a myelin sheath is called medullated nerve fiber. In this nerve fiber, conduction of nerve impulse is faster.

Eosinophils increases during worm infection.

	Voluntary muscles		Involuntary muscles
i.	Their action is under our concious control.	i.	Their action is not under our conscious control.
ii.	Cells are multinu cleate.	ii.	Cells are un inucleate.
iii.	Skeletal muscles.	iii.	Smooth muscle.

Sclerenchyma cells are dead cells and they are devoid of protoplasm. The cells walls of sclerenchyma are greatly thickened by lignin. The cells of sclerenchyma are closely packed without intercellular spaces.

White blood cells are protect our body from various germs that infact our body, hence they are known as soldiers of the body.

Schlerenchyma tissue lack vacuoles and intercellular spaces.

Cartilage contains chondrin and bone contains ossein respectively.