Science Que-Ans (Each of 2 Mark )

The number of blood platelets is 2,50,000-300,000 per cubic mm.

The cells of squamous epithelium tissue are extremely thin and flat and form a delicate lining. It is found in the alveoli of lungs and blood vessels and protects the underlying parts from germs, harmful chemicals and injury.

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

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.

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.

Squamous epithelium protects the underlying parts from germs, harmful chemicals and injury.

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.

The normal RBC range for men is 4.7 to 6.1 million cells per microliter. The normal RBC range for women is 4.2 to 5.4 million cells per microliter.

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.

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.

1. Adipose tissues.
2. Ciliated epithelium.

It has finger-like projections called cilia on the outer suface of columnar epithelial. These cilia can move, and their movement pushes the mucus forward to clear it.

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.

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

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

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.

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.

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.

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.

Cartilage contains chondrin and bone contains ossein respectively.

Bone marrow is responsible for the production of blood cells in the body. If bone marrow is destroyed, the formation of white blood cells, red blood corpuscles and platelets will stop.

Smooth muscles are found in alimentary canal and accomplish peristalsis movement.

The process of taking up a permanent shape, size and a function is called differentiation.

Functions of microvilli:

1. They increase the absorptive surface of the intestinal cell (enterocyte).
2. They increase the surface area available for reactions.

The various cells of connective tissue are fibroblasts, adipose cells, macrophages, mast cells and lymphocytes.

Adipose tissue forms blubber of whale and hump of camel.

1. Glandular epithelium is present in sweat gland.
2. Germinal epithelium is present in testis.

Apical meristems are the growing parts of the roots and stems and are present at the tips of roots, branches, leaves and shoots. If the apical meristems are damanged or cut, the growth of that part of the plant will stop.

1. Parenchyma:

2. Collenchyma:

Simple permanent tissues: These tissues are composed of cells which are structurally and functionally similar.

There are three types of simple permanent tissues:

1. Parenchyma: Parenchyma cells are living and posses the power of division. The cell wall is thin and encloses a dense cytoplasm which contains a small nucleus and surrounds a large central vacuole.

2. Collenchyma: Its tissues consists of living cells. It is characterized by the deposition of extra cellulose at the corners of the cells. In collenchymas, intercellular spaces are generally absent. Collenchyma cells are elongated in shape. They often contain a few chloroplasts.

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

Parenchyma is the common living component of two complex permanent tissues, xylem and phloem.

Xylem parenchyma store food and helps in later conduction of water.

Phloem parenchyma store food, latex, resins, etc.

1. Xylem helps in conduction of water and minerals.
2. Phloem helps in conduction of food.

Three types of muscles occur in animals namely striated muscles, smooth muscles and cardiac muscles.

1. Apical meristem: It brings about the elongation of the root and stem.

2. Lateral meristem: It causes the organ (stem or root) to increase in diameter and girth.