Revision: Organisation of Life Science SSLC (English Medium) Class 8 Tamil Nadu Board of Secondary Education

A tissue, in biology, is defined as a group of cells that have a similar structure and perform a specific function. The word tissue originates from French, which means "to weave."

• Cells that perform a particular function always live in a group. This group of cells is called a tissue.
• For example, blood, phloem, muscle, etc. are examples of tissues.

A group of similar cells which perform a specific function.
example: Muscular tissue in animals.

A tissue is a group of cells that are similar in structure and are organized together to perform a specific task.

The tissue is a group of cells of similar structure and function.

Vascular tissue is the complex plant tissue in higher plants that are composed of xylem and phloem and is concerned with conducting water, minerals, and organic food throughout the plant body.

Diffusion is the free movement of molecules of a substance (solute or solvent, gas, or liquid) from the region of their higher concentration to the region of their lower concentration when the two are in direct contact.

Example: Perfume fills a whole room.

Diffusion is the free movement of molecules of a substance (solute or solvent, gas, liquid) from the region of their higher concentration to the region of their lower concentration when the two are in a direct contact.

Osmosis is the movement of water molecules from their region of higher concentration (dilute solution or with a lower solute concentration) to their region of lower concentration (concentrated solution or with a higher solute concentration) through a semi-permeable membrane.

Osmosis is the movement of water molecules from their region of higher concentration (dilute solution or with a lower solute concentration) to their region of lower concentration (concentrated solution or with a higher solute concentration) through a semi-permeable membrane.

The function of the kidney that involves regulating the composition of blood, including the percentage of water and salts, while removing wastes like urea, is called osmoregulation.

1. Metabolism is the sum of chemical reactions by which living organisms sustain their life.
2. Metabolism consists of anabolism (the buildup of substances) and catabolism (the breakdown of substances).

1. Kidneys help maintain the balance of water and salts in the blood, a process known as osmoregulation.
2. In summer, more water is lost through sweat, so urine becomes thicker and less frequent due to increased water reabsorption.
3. In winter, water loss through sweat is less, so more urine is passed, and it is more diluted.
4. In cholera, severe water loss through vomiting and diarrhoea reduces water absorption into the blood.
5. Kidneys reabsorb almost all available water, but urea may also accumulate, leading to uremia (urea poisoning).
6. Immediate treatment includes oral rehydration solution (ORS) or glucose-saline drips to restore fluid balance.