Basic Science

What are single-celled organisms? How do they survive?

What are single-celled organisms? How do they survive?

Single-celled organisms are living organisms. There are two categories of organisms- those made up of a single cell (single-celled organisms) and those made of multiple cells. Single cell organisms are called unicellular organisms. Most protists and some of the fungi are an example of single-celled organism. Single cell organisms can live independently. Single-celled organisms like amoeba and Paramecium carry out their own body functions such as respiration, excretion, digestion, and reproduction.

What are single-celled organisms? How do they survive?

While humans and many others are made up of billions of cells, there are also some living things that consist of only a single cell. Single celled organisms, as their name suggests have only a single cell. All that they need to survive is present in that one cell.

There are different types of cells. A eukaryotic cell is a larger cell and is more complex. It contain a nucleus to hold their chromosomes which is an important part of DNA as well as many parts or structures called organelles that help in the functioning of the cell. Prokaryotic cells are cells with no nucleus. Their chromosomes form little loops that float around the cell. They are also smaller and much less complex than the other kind and they lack the cellular structures called organelles.

Cells are organized. Even a single cell has organization of its structures within it. The cell contains a number of different structures called organelles. These organelles are like organs in our body. They are essential for the survival of the cell and are organized into groups for efficiency.

 How do these single celled organisms live and survive?

These organisms have many different ways of gaining energy. Some cells absorb energy directly into the cell body through the surface of the cell. A larger cell literally wraps its body around a smaller cell or nutrient, absorbs it into its body and digests the nutrient directly for energy. Other single cells have special structures called chloroplasts which can absorb energy directly from the sun and use it to make chemical food energy.

Single cells do respond to and interact with their environment. Although cells are small, they are aware of their environment. Whether they are detecting food or avoiding danger, cells can respond. Many cells even have methods of motion. Some cells use a flagellum to move. Flagella are whip like tails that a cell moves back and forth to swim. Another method is the use of cilia. Cilia are tiny little hairs that surround a cell. They wiggle back and forth to help a single celled organism move. Some cells extend a part of their body forward and move the rest of the body with it. The part extending forward is called a pseudopod. An amoeba has no definite shape. It moves by extending fingerlike extensions called pseudopods out from the rest of its body.

While many cells may not grow much larger in their life they certainly develop and change. Throughout what is called a cell cycle, a cell creates new proteins, builds new internal structures, copies its DNA and ultimately it divides to create two new cells.

Single celled organisms definitely adapt to their environments. They have many ways of changing their DNA to adapt to the environment.

For example, if a person takes an antibiotic to get rid of bacteria in their body, which is a single celled organism, the bacteria will change their DNA to survive and adapt to their new environment in which the antibiotic is present. Bacteria are an example of single celled organisms that can adapt to their environment.

All single cells have adaptations that help them survive in their environments.

Single celled organisms are living things so they must reproduce to make new organisms with the same or similar DNA. Some cells do this through the process of binary fission. In this process a single celled organism splits down the middle to create two identical cells. Another process is called budding. In this process, a single celled organism will slowly grow another cell on the outside of its body called the daughter cell. The nucleus of the main cell splits into two and becomes part of the daughter cell. When this new daughter cell is large enough to survive on its own, it breaks off from the bigger cell. Both of these processes enable a single cell to reproduce.

We have evolved from being single celled to being multi-cellular. All animals and creatures have evolved in such a manner. We must stop and see the beauty of these small living beings that we cannot see except under a microscope and appreciate the power of creation and nature.

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Ayesha Mendonca

I am Currently studying B. A. In English literature at St. Xavier’s College. I love reading, writing, singing and watching English movies. I love thinking about abstract concepts, about life and the universe. Writing for me is an outlet, a way to express my thoughts and opinions. I love having intellectual conversations with people and I make the best of such interactions.

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