Science Answer the questions.[Bio-2M]

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.

• Sieve tube.
• Companion cells.
• Phloem fibres.
• Phloem parenchyma.

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.
   

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.

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

These muscles are seen in hollow internal organs (viscera) such as stomach, intestine, blood vessels, urinary bladder, uterus etc.

In contrast to this , the muscle which shows cross striations are called striated muscles or striped muscles.

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.

• 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.

• 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.

1. Adipose tissues.
2. Ciliated epithelium.

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

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

• 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.

1. Tracheids.
2. Vessels or tracheae.
3. Xylem parenchyma.
4. Xylem Sclerenchyma.

Except xylem parenchyma, all other xylem elements are dead and bounded by thick lignified walls. Vessels are shorter and wider than tracheids. Vessels are very long tube-like structures formed by a row of cells placed end to end. Tracheids are elongated cells with tapering ends. They also conduct water.

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

Phloem is a vascular bundel in plants which helps in the transportation of food.

• 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.

1. 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.

2. Cardiac muscles have cylindrical branched cells and shows rhythmic contraction and relaxation throughout the life.

Location- Cardiac muscle cells are present in heart.

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