Multicellular organism, an organism composed of many cells, which are to varying degrees integrated and independent.

Following are the important examples of multicellular organisms:

• Humans.
• Dogs.
• Cows.
• Cats.
• Chicken.
• Trees.
• Horse.

Mushroom is a multicellular organism.

The first evidence of multicellularity is from cyanobacteria-like organisms that lived 3–3.5 billion years ago.

Multicellular organisms are composed of many cells. Some multicellular organisms have different cells. For example, Human beings have different cells of different shapes and sizes in their body to perform different functions.

The study of cells is called cell biology, cellular biology, or cytology.

Osmosis is the passage ot water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration. If the medium has a lower water concentration then the cell will lose water by osmosis. Such a solution is known as hypertonic solution.

1 : movement of a solvent (such as water) through a semipermeable membrane (as of a living cell) into a solution of higher solute concentration that tends to equalize the concentrations of solute on the two sides of the membrane.

A hypertonic solution is one that has a higher solute concentration outside the cell than inside. If a cell is placed in a hypertonic solution, the cell will shrink due to water osmotically moving out. The outside solution has higher soluble concentration than inside the cell.

If a cell is placed in a hypertonic solution, there will be a net flow of water out of the cell, and the cell will lose volume. A solution will be hypertonic to a cell if its solute concentration is higher than that inside the cell, and the solutes cannot cross the membrane.

Plasma membrane is the outermost layer in cells. It separates the content of cell from their external environment. It controls the entry and exit of materials in nd out of cell and hence it is called selectively permeable membrane.

Plasma membrane refers to the membrane that surrounds the organelles of the cell, by creating a barrier between cell organelles and external environment. Plasma membrane is a thin membrane that surrounds every living cell, separating it from the external environment around it.

Every cell is covered by a thin sheet of skin which is called cell membrane or plasma membrane. 1)The cytoplasm and nucleus are enclosed within the cell membrane.It encloses the living part of the cell called protoplasm. 2)Cell membrane protects the cell and also gives shape to the cell.

There are three major parts of a cell: a cell membrane, a nucleus, and a cytoplasm between the two. There are hundreds or even thousands of complex structures of fine fibers or minuscule but distinct structures inside the cytoplasm, called organelles.

plasma membrane

Neurons, also known as nerve cells, send and receive signals from your brain. While neurons have a lot in common with other types of cells, they’re structurally and functionally unique. Specialized projections called axons allow neurons to transmit electrical and chemical signals to other cells.

Function of nerve cell – (a) it helps in the transfer of messages from various body parts to brain and from brain to various body parts of the body. (b) Nerve cells help in coordination of the functions of the organs of body. 3.

Neurons (also called neurones or nerve cells) are the fundamental units of the brain and nervous system, the cells responsible for receiving sensory input from the external world, for sending motor commands to our muscles, and for transforming and relaying the electrical signals at every step in between.

Neurons are the special name for nerve cells. Nerve cells make up the brain, nerves, and spinal cord.