Science Que-Ans (Each of 2 Mark )

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.

• They are cylindrical and branched.
• They are uninucleated.
• Involuntary muscles.
• They contract and relax throughout life in rhythm.

There are four different types of cells that make up the xylem tissue. They are:

1. Tracheids.
2. Vessels.
3. xylem parenchyma.
4. Xylem fibres.

Functions of microvilli:

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

Cell wall has the prominent middle lamella. A major function of the cell wallis to give the cell strength and structure, and to filter molecules that pass in and out of the cell.

Features of sclerenchyma fibers:

• These are dead elements.
• They have thick wall of lignin, are elongated and pointed at ends.
• They have pits also.
• They mostly occur in groups.

Features of sclereids:

• These are dead elements.
• These are oval, spherical and are thickened due to lognin deposition.
• They have very narrow cavities at the centre.

Because adipose tissue stores fats ,storage of fats act as insulator.

1. It helps in transpiration in plants.
2. It helps in exchanging gases with the atmosphere.
3. The gas exchange that occurs when stomata are open facilitates photosynthesis.

1. Intercalated discs.
2. Lignin.

• Skin: Stratified squamous epithelial tissue.
• Bark of tree: Simple permanent tissue.
• Bone: Connective tissue.
• Lining of kidney tubule: Cuboidal epithelial tissue.
• Vascular bundle: Complex permanent tissue.

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

Cells of bark are dead and compactly arranged without intercellular spaces. They have a chemical called suberin in their walls that make them impervious to gases and water.

Xylem components tracheids and vessels transport the water and minerals in the plants. Following are the characteristic feature of the xylem tracheids and vessels:

• Tracheids and vessels are dead elements of xylem.
• They have thick walls and are tubular structures.
• Tracheids and vessels provide unidirectional flow of water and minerals.

Meristematic tissue consist of actively dividing cell and leads to increase in length and thickness of plant. The primary growth of plant occur only in specific region such as the tips of roots and stems because in these region meristematic tissue is present.

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.

In multicellular organisms, the different types of tissues perform different functions. Since a particular group of cells carry out only a particular function, they do it very efficiently. So, multicellular organisms possess a definite division of labour.

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:

1. Meristematic tissue developed from parent cell.
2. Meristematic tissue take part in growth.
3. The place of injury is held up by the formation of new cell.

Fat acts as subcutaneous insulation of body for thermoregulation. The animals living in cold regions have various layers of fat so that the temperature of the body can be maintained and also because fats do not allow the internal heat to escape out of the body.

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.

The outer protective layer or bark of a tree is known as the cork. It is made up of dead cells. Therefore, it protects the plant against mechanical injury, temperature extremes, etc. It also prevents the loss of water by evaporation.

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.

Pumping of heart involuntary, e., it is controlled by cardiac muscles.

Simple squamous epithelial cells are extremely thin and flat which allows diffusion of substances through it.

Two characteristics of nerve cells are:

1. They are highly specialised unit cells.
2. Neurons have the ability to receive stimuli from within or outside the body and to conduct (send) impulses (signals) to different parts of the body.

Function of fluid connective tissue: Blood a fluid connective tissue provides transport system within our body and other important substance. cartilage provides strong support and connection for our skeletal framework and function of bones is to support and protect soft tissue and organs in our body.

Cork cambium and vascular cambium help in secondary growth of stem and root.

Functions of Phloem: Phloem transports photosynthetically prepared food materials from the leaves to the storage organs and later from storage organs to the growing regions of the plant body.

Areolar connective tissue is present in bone marrow.

Types of white blood cells (WBCs) are:

• Eosinophils.
• Basophils.
• Neutrophils.
• Monocytes.
• Lymphocytes.

1. Muscular tissue.
2.  

1. Sarcoplasm.
2. Intercalated disc.
3. Nucleus.

3. It is cardiac muscles which are exclusively present in the wall of heart.

Ciliated Epithelium: When the columnar epithelial tissues have cilia, then they are called the ciliated epithelium. Their main function is to move particles or mucus in a specific direction. The rhythmic movement of the cilia helps in the movement of material in one direction. This tissue is found in the inner surface of organs like bronchioles and fallopian tubes.

Serum is blood plasma of blood from which fibrinogen is removed.

The cell wall of cork is coated with suberin, a waxy substance which which makes these impermeable to water and gases.

It is specialized in providing mechanical support. They often get specialized in secretions through the epithelium and therefore are known as gland cells. Sometimes by folding inwards they form multicellular gland and is termed as glandular cells.

A neuron consists of a cell body or cyton with a nucleus and cytoplasm, from which long thin hair-like parts arise.

The cells of stratified squamous epithelium are arranged in many layers to prevent any kind of wearing and tearing for providing protection.

Simple squamous epithelium forms the inner lining of the alveoli. Following functions are given below:

• These cells provide protection for underlying tissues.
• They forms a barrier between the body and the exterior environment.
• Simple squamous epithelial cells(glomerulus) in nephrons of kidneys enable rapid filtration of blood and diffusion of small molecules.
• Squamous epithelial cells of lungs (alveoli of lungs) helps to reduce friction and controls vessel permeability.
• It also helps in absorption and filtration.