Gayathri Mani

Characteristics of Life Study Guide

We are surrounded by various things, but how do we differentiate between living and nonliving? Here are seven characteristics of life that separate them.

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Biology is that branch of science that studies life. However, have you ever sat back and wondered - what defines the term ‘life’? It might sound like a silly question at first, but in reality it is not easy to define the meaning of life.

You’ll be relieved to learn that you are not the only one still figuring out the exact meaning of life. Many scientists are yet to agree upon the meaning of life and what it is made of. Multiple characteristics of life separate a living being from a non living being.

Jungle-wildlife Source

Look at it this way. Both a car and a cat can move, and both a crystal and a cell have structure. But even with such similarities, one is a living being, and the other is nonliving. Biologists have discriminated between living and nonliving through seven characteristics of life. The presence of all seven of these characteristics makes a living being, while the absence of even one turns them into non-living things.

What are the 7 characteristics of life?

Whether it is the largest whale or the smallest bacteria, all living organisms share some common characteristics of life.

The 7 characteristics of living things are as follows:

Environmental response

One of the primary characteristics of all living things is their ability to respond to their surroundings. For instance, you step on rocks, and they will not feel hurt and move. But, if you step on your pet's tail while going to your room, they will react to it.

Living beings respond and adapt to the changes happening around them. These adaptations include behavioral, physiological, and structural traits that improve the organism's reproduction and survival capabilities.

Cells - Fundamental units

Now think about what all living things have in common. The answer is simple, cells! All organisms are made of cells. When you observe a leaf and a beetle under the microscope, they both will look similar at a cellular level.

Cell with Nucleus Source

All living organisms consist of one or multiple cells, and they are the basic unit of function and structure of life.

Change and Growth

Another characteristic of life is the capability of organisms to change and grow. A block of wood would not grow into a piece of furniture under any circumstances. But if you put a seed under the right circumstances, it will grow into a plant.

All living organisms change and grow. That is, even the smallest bacterium will grow under the right conditions.


One of the significant characteristics of living organisms that distinguishes them from others is that they can reproduce. Life creates more life on Earth, whether it is a bacterium, tree, rabbit, or human being.

Reproduction Source

Reproduction can take place through an asexual or sexual process. While sexual reproduction requires the fusion of gametes from two parents, asexual reproduction involves a single parent. That is, the organism will produce identical offspring without the fusion of gametes.

Complex Chemistry

What makes something living is its complex chemistry. Take the example of a rose. It has a beautiful yet complicated structure. If you look carefully, you will observe the rose transporting water and nutrients through its stem. The flower also produces pigment molecules and breaks down sugar to get the energy (metabolism) to stay alive.

Maintaining Homeostasis

The ideal body temperature of humans is 37 degrees Celsius. Hence, if the temperature is cold outside, you will automatically try to keep yourself warm. And if the temperature is warm outside, you will drink cold beverages to keep yourself cool.

Homeostasis Source

Living organisms try to keep their internal temperature stable despite changes in the external environment. Such a process is called homeostasis, and it is the sixth most important characteristic of life biology.

Energy processing

Living organisms use energy for performing metabolic activities. Some organisms, such as plants, capture the sun's energy and then convert it into chemical energy for food. This process is called photosynthesis. Others use chemical energy present in their food molecules. This is called cellular respiration.


  • The seven characteristics what makes an organism living are: Environmental responses, cells, change and growth, reproduction, having complex chemistry, and homeostasis and energy processing
  • Sometimes non-living things can portray some of the above characteristics, but a living being consists of all.


1. What are the 7 characteristics of life?

The seven characteristics are:

  • Environmental responses
  • Cells, change and growth
  • Reproduction
  • Having complex chemistry
  • Homeostasis
  • Energy processing

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  1. Characteristics of Life. https://flexbooks.ck12.org/cbook/ck-12-biology-flexbook-2.0/section/1.4/primary/lesson/characteristics-of-life-bio/. Accessed on 10 Dec, 2021.
  2. What are the characteristics of life?. https://astrobiology.nasa.gov/education/alp/characteristics-of-life/. Accessed on 10 Dec, 2021.
  3. The Characteristics of Life. https://courses.lumenlearning.com/suny-wmopen-biology1/chapter/the-characteristics-of-life/. Accessed on 10 Dec, 2021.