Science Answer the questions.[Bio-3M]

We get a crunchy and granular feeling when we chew pear fruit due to the presence of sclerenchyma tissue. The cell walls of sclerenchyma are greatly thickened due to the presence of lignin. Lignin is a complex polymer with high tensile strength e., it does not breaks easily on stretching and a high compressional strength, it does not buckle easily.

It is difficult to pull out the husk of a coconut tree due to the presence of sclerenchyma tissue. The cells of sclerenchyma tissue are closely packed without intercellular spaces, a middle lamella exists between them. Middle lamella is a thin layer of connecting substance containing pectin, lignin and protein.

Collenchyma cells are characterised by the deposition of extra cellulose at corners of the cell. In collenchyma intercellular spaces are absent and ceils are elongated. It is a mechanical tissue which provides support and elasticity to the branches of a tree so that, they move and bend freely in high wind velocity.

Functions of Epithelial tissues are:

1. The cells of the body surface form the outer layer of skin. These cells protect the underlying cells from drying, injury, and chemical effects.
2. Inside the body, epithelial cells form lining of mouth and alimentary canal and protect these organs.
3. Epithelial tissues help in absorption of water and nutrients in small intestine.
4. Some epithelial tissues perform secretory function such as sweat, saliva in skin and mouth cavity.

It is fat storing connective tissue which is found mainly beneath the skin. The adipose tissue consists of several spherical or oval adipose cells (adipocytes or fat cells). Each adipose cell contains fat globules. It is found below the skin, around the internal organs like heart, kidneys and eyeballs.
Functions:

1. It acts as an insulator.
2. Provides support and protection to the vital organs.
3. It acts as a storage of fat.

Functions of the epithelial tissue are:

• The cells of the body surface (i.e., epidermis) from the outer layer of skin. These cells protect the underlying cells from drying, injury and chemical effects. They also protect the body from viral or bacteria infection.
• Epithelial tissues help in absorption of water and nutrients.
• Epithelial tissues help in elimination of waste products.
• Some epithelial tissues perform secretary function. They secrete a variety of substances such as sweat, saliva, (mucus), enzymes, etc.

The functions of blood:

1. Transport oxygen from the lungs to different parts of the body.
2. Transport CO₂ from the body tissues to the lungs.
3. Transport digested food i.e., glucose, amino acids, etc. from alimentary canal to various parts of the body for energy, growth and repair.
4. Transport excretory waste product called urea from the liver to the kidneys for removal as urine.
5. Plasma regulates water balance in the body.
6. Regulates the body temperature.

Sieve tubes, companion cells, phloem fibres and pholem parenchyma.

It is composed of a single layer of cube- like cells. It is found in kidney tubules and salivary glands. It provides mechanical support to organs and helps in absorption and excretion.

It is a fluid connective tissue that links different parts of the body. it helps to maintain the continuity of the body. it contains fluid matrix called plasma and blood cells such as RBCs (red blood cells/ corpuscles) WBCs (white blood cells/ corpuscles) and platelets suspended in it.
Plasma also contains proteins, salts, hormones and vitamins to various tissues of the body it carries excretory products from the tissue to excretory organs it also conducts heat and regulates body temperature.

Meristematic tissue: It is a group of cells which constantly divide and produce cells indefinitely throughout the life of a plant. Meristematic tissue is found in all the growing parts of a plant such as root tip, shoot tip, etc.
Characteristics of meristematic cells:

1. The cells of this tissue are very active. They have dense cytoplasm.
2. The cell wall is thin and made up of cellulose.
3. They lack vacuoles.
4. They have big nucleus.

There are total three types of meristems, they are:

1. Apical meristem: These are situated at the growing tip of stem and roots, i.e., at shoot apex & root apex respectively. It is responsible for the growth or elongation of the root and stem, & it is called primary growth.
   
2. Lateral meristem: These are found beneath the bark (called cork cambium) and in vascular bundle of dicot roots and stems (called vascular bundle). It is responsible for increase in girth, This is called secondary growth.
   
3. Intercalary meristems: They are located at the base of leaves or internodes. It is responsible for the increase in the length of a leaves and internodes.
   

These muscles are exclusively present in the heart. These muscles of the heart show rhythmic contraction and relaxation throughout life. They are striated but involuntary muscles. Heart muscle are cylindrical and uninucleated. They are branched and form a network in the walls of the heart.

1. It is simple and living parenchyma tissue.
2.  

1. Cytoplasm.
2. Nucleus.
3. Vacuole.
4. Intercellular space.
5. Cell wall.

3. The main function of parenchyma is the storage of food.

Usually it is because their leaves have some spongy cells full of air. Some of them have spongy stems filled with air. Many also have a water repellent surface, so they don't get soaking wet when they go under the surface. Some have minute scales that trap air and help the leaves bounce back to the surface after they get pushed under water.
Examples of the water repellent scales can be seen on Salvinia plants. Water repellent leaves are seen on water lilies. Spongy air filled stems appear on the floating water chestnut. Air filled leaves are seen in Amazon frogbit or duckweeds.