What are Living Organisms Made Up of?

Robert Hooke discovered the cells in the year 1965. He was examining a thin slice of a cork, he saw that the cork resembled the structure of a honeycomb with too many little compartments. Then with the microscope, he observed these compartments and called them cells, meaning “little room” in Latin. This small incident is a very significant step taken in the history of science. This is the first time that someone has observed that living things are made up of smaller units.

The living organism is made up of a simple functional unit known as cells. It is the basic unit and has all the essential components to perform all functions need to survive

Cells

In higher organisms like humans, the cells are found in different structures according to their need and necessity of performing functions.

Robert Hooke in 1965 discovered the cell with the help of a primitive microscope. Later in the year, 1674 Leeuwenhoek discovered free-living cells in bond water for the first time with the help of an improved microscope. Robert Brown in the year 1831 discovered the nucleus of the cell later Purkinje in 1839 named the term ‘protoplasm’ for the fluid substance of the cell. The cell theory which explains that all plants and animals are composed of cells which is the basic unit of life was presented by two biologists Schleiden and Schwann. As the electron microscope was discovered the complex structure of a cell and its other various organelles were observed. The invention of magnifying lenses led to the huge discovery of the microscopic world. As in amoeba, it was found that a single cell may constitute a whole organism. Chlamydomonas, Paramecium and bacteria are some more examples of unicellular organisms (uni meaning single). We can also see that a group of cells together form a single body and perform different functions of the body and these organisms are called multicellular organisms (multi means many).

What are cells made up of?

Cells are the basic structure and units of living organisms. All living things or made up of cells. A cell is made up of three main components like cell membrane, cytoplasm and nucleus. The cell is outer covered by a membrane called a cell membrane which is responsible for controlling the substances that travel in and out of the cell and respond to signalling. Each cell is filled with a fluid substance in which all other organelles float known as cytoplasm. The cytoplasm is a thick solution which mostly made up of water salts and protein. The nucleus is like a brain which controls all the functions of a cell. This nucleus is having DNA which will carry the information from the parent to the young ones.

In higher organisms like humans, the cells are having different structures according to their needs and the necessity of performing a particular or specific function. The shape and size of cells are mostly related to the functions they perform in that body. Sometimes like amoebas have indefinite shapes, changing continuously. In some organisms the cell shape is more or less has the same structure throughout, for example, nerve cells have a particular typical shape.

 Organisms can be differentiated into unicellular and multicellular depending on the cells. Each living cell has the capacity to perform certain functions as a characteristic of living organisms. In higher multicellular organisms like humans, there is a division of labour in cells. Different parts of the human body are assigned to perform different functions like the heart pump blood throughout the body, the stomach digests the food and so on. In a single cellular organism, all these functions are to be performed by a single cell. Each cell has different components which are called cell organelle and they can perform different functions as a division of labour in a cell. Each kind of cell organelle performs special functions, such as intake of food material, excretion of waste material, digestion of the food material etc. A person can live only if it performs all the functions which are performed with the help of the cell organelles. Some of the cell organelles are cell membrane, nucleus, cell wall, mitochondria, lysosome, ribosome, centriole etc. These cell organelles together constitute a cell.

Characteristics of Living Things

• Cells– All living things are made up of basic structural units called cells.
• Growth– All living things grow from birth to death.
• Movement– All living things make movements in order to get food or to support their metabolic activities.
• Sensitivity– All living things respond to the environment and change around their environment.
• Reproduction– All living organisms tend to reproduce so as to ensure survival.
• Metabolic activities– Living things will have a set of functions which they have to perform to live. These functions are metabolic activities.

Conceptual Questions

Question 1: Who discovered cells and how did their structure develop?

Answer: 

Robert Hooke discovered the cells in the year 1965. Later in the year, 1674 Leeuwenhoek discovered free-living cells in bond water for the first time with the help of an improved microscope. Robert Brown in the year 1831 discovered the nucleus of the cell later Purkinje in 1839 named the term ‘protoplasm’ for the fluid substance of the cell.

Question 2: What are cell organelles? Explain with examples.

Answer:

The functional units present inside a cell or different structures present inside a cell which perform different tasks are called cell organelles. Some of the cell organelles are cell membrane, nucleus, cell wall, mitochondria, lysosome, ribosome, centriole etc.

Question 3: How initially cell was discovered by Robert Hooke? explain.

Answer:

Once Robert Hooke was examining a thin slice of a cork, he saw that the cork resembled the structure of honeycomb with too many little compartments. Then with the self-designed microscope, he observed these compartments and called them cells, meaning “little room” in Latin. This small incident is a very significant step taken in the history of science. This is the first time that someone has observed that living things are made up of smaller units.

Question 4: Do all cells of an organism have a similar structure throughout the body?

Answer:

The cells are found in different structures according to their need and the necessity of performing operations. The shape and size of cells are mostly related to the functions they perform in that body. Sometimes like amoebas have indefinite shapes, changing continuously. In some organisms the cell shape is more or less has the same structure, for example, nerve cells have a particular typical shape.

Question 5: Explain an experiment to see the presence of cells.

Answer:

Take a small piece from an onion bulb. With a pair of forceps peel off the skin which is the epidermis of the concave side of the onion. Immediately place it on a watch glass containing some water so as to prevent it from folding or getting dry. No, we can cut the peel into smaller pieces. Now try to transfer a smaller piece into a new slide.

Question 6: Explain the division of labour in cells for performing different functions in both unicellular and multicellular organisms.

Answer:

In higher multicellular organisms like humans, there is a division of labour in cells. Different parts of the human body are assigned to perform different functions like the heart pump blood throughout the body, the stomach digests food and so on. In a single cellular organism, all these functions are to be performed by a single cell. Each cell has different components which are called cell organelle and they can perform different functions as a division of labour in a cell.