Is it alive?

Keystone Standard A.1.1.1:

Describe the characteristics of life shared by all organisms.

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Characteristics of Living Things
DSC00172.JPGAll living things have common traits, irrespective of plants and animals. Scroll down to know these common characteristics of living things.

All individuals which have life in them are known as living things. Broadly, these living things can be classified as plants and animals. They both have common characteristics as they depend on oxygen for life. These living things follow a universal circle of life with birth, reproduction and death. They need all the basic nutrients for growth and development and are prone to disturbances in their metabolism. They share a mutual bonding through the ecosystem they survive in i.e. plants depend on animals for carbon dioxide and animals depend on plants for oxygen. Take a look at some of the similar characteristics of living things given below.


The basic component present in every living thing is the cell. Both plants and animals are made up of one to countless number of cells, which carry out different sets of functions. Life before evolution began from a single cell. Similarly even today life is generated from a single cell, which then divides or multiplies to give rise to a complex living form. After fertilization, once the zygote is formed, the cells start differentiating into their types and over a certain period of time give rise to a fully developed, mature living thing.


One of the most important characteristics of living things is the energy that they need to survive. Plants and animals use various forms of energy for the development of their bodies. The complete use of chemical energy they use to carry out their life processes is called metabolism. Plants use the energy from the sun or solar energy to carry out photosynthesis, which is the process for making their food (glucose). They are hence known as autotrophs. Animals and humans however cannot produce their own food and are dependent on plants and other animals for their food and hence they are called the heterotrophs. Therefore, energy is a common characteristic needed by all living things.


One of the rule of nature is growth, which is followed by all living things. As development is an involuntary process, every cell in living things has to age. Growth and change is a part of all living organisms as cells divide to give rise to new and identical ones. Sometimes due to some genetic defects, during differentiation, some cells mutate to form other types of cells and result in complex organisms. This process of constant development and growth is also called as organogenesis.


All organisms reproduce to continue their species' life. This is also one of the main characteristics of living things. Plants and animals have a reproductive system. There are two types of reproduction prevalent in nature, sexual and asexual. The sexual reproduction involves the combination of genetic material to give rise to a single zygote that further develops into a bigger organism. The asexual reproduction involves the splitting of one organism or cell to form two separate individuals of the same species.


Every living thing is highly organized when it comes to the pattern or built of the body. Plants as well as animals have very complicated cell structures arranged very uniquely in the different organs. The cells form organelles, and organelles form organs. The organs make up the various parts of the organism. This is a network which every cell follows and thus living things are called highly organized beings.

All living thing need to maintain balance to survive. This is called homeostasis, which is the process to maintain stable internal conditions for survival. To maintain homeostasis means that an organism is responding internally to the changes outside. For example, when you are thirsty, your body needs water. The water that was in your cells has been removed and needs to be replaced. When you replenish the water, your cells return to their state of homeostasis. Other human internal conditions that must be maintained are body temperature, heart beat, blood pressure. When the homeostasis is regulated the metabolism of the body is regulated and the living things stay healthy and fit.

By Aparna Jadhav
Published: 2/8/2010—adapted

This activity supports the Keystone learning competency:
A.1.1.1. Describe the characteristics of life shared by all organisms.

1. What are the six characteristics of life?

2. Explain what is a cell.

3. What is the difference between homeostasis and metabolism?

4. How do Autotrophs get their own food? Name an example of an organism that is an autotroph.

5. How do heterotrophs get their own food? Name an example of an organism that is a heterotroph.

6. Explain the difference between growth and reproduction.

7. Discuss how Louie the Gecko is alive using the six characteristics of life.