What are the 8 characteristics of life in biology? Learn these properties of life, and see examples of how to classify something as living or non-living.
Updated: 11/21/2023
8 Characteristics of Life in Biology | Properties & Examples
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Characteristics of Life: Word Search Activity
This activity will help you assess your knowledge of the eight characteristics that determine life.
Guidelines
For this activity, you'll need a printer to reproduce the following page. Search for and circle or highlight the words that will complete each of the given clues. Afterward, neatly write them in the appropriate blank spaces.
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Clues
- _____ reproduction occurs when an offspring is created without exchanging genetic information, such as in unicellular organisms.
- _____ are the basic building blocks of all living things.
- _____ is the change in the heritable characteristics of a population over successive generations.
- A change in the structure of an organism's internal or external environment that provokes a reaction is called a _____.
- _____ concerns the transformation of the organism as enters the growth process.
- The passing on of traits from parents to their offspring is called _____.
- The ability of a living organism to adjust its internal environment to maintain stability is termed _____.
- The components of a cell and the arrangements of these individual parts within the cell form the cellular _____.
- Something is considered _____ if it contains the eight characteristics of life.
- Cell division and protein synthesis are examples of chemical reactions in the body known as _____.
Answer Key
- ASEXUAL
- CELLS
- EVOLUTION
- STIMULI
- DEVELOPMENT
- HEREDITY
- HOMEOSTASIS
- ORGANIZATION
- ALIVE
- METABOLISM
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What are the eight characteristics of life and their examples?
1) Reproduction - Two cats mating and giving birth to kittens.
2) Metabolism - Photosynthesis in plants (creating usable energy).
3) Response to stimuli - Seeking shade when it becomes too hot.
4) Heredity - A guinea pig passing down her coat colors to her offspring.
5) Adaptation through evolution - A butterfly evolving eyespots on its wings over time.
6) Homeostasis - A person's body keeping a constant internal temperature.
7) Growth and development - A tadpole growing and developing into an adult frog.
8) Cellular organization - All living things are made of cells, like a dog.
How do you remember the eight characteristics of living things?
Remember the phrase: Remember My Red Hat And Happy Green Coat (R- reproduction, M - metabolism, R - response to stimuli, H - heredity, A - adaptation through evolution, H - homeostasis, G - growth and development, C - cellular organization).
Table of Contents
ShowBiology is the study of life. But what, exactly, does that mean? Although it may initially seem obvious whether something is alive or not, when approaching it scientifically, the definition and properties of life become far less obvious.
For example, this frog is sitting amongst lily pads floating in a pond. Which things in this picture are living, and which ones are non-living?
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Looking at this picture, it may seem obvious that the frog and the lily pads are alive, while the water is not. But what specifically makes the plants in this picture be considered alive and not the water? For example, if someone were to lightly tap the frog, the lily pad, and the water, the frog would respond to the touch by hopping away, while the lily pad and the water would not react in any obvious way: the water might ripple, and the leaf might shake, but aside from that, nothing would happen. Still, the lily pad is considered alive, and the water is not.
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In order to categorize objects as either living or not living in a strict, logical, scientific manner, biologists have determined a basic set of 8 characteristics of life. For any object to be considered alive, it must have all eight of these properties.
However, organisms might display these characteristics differently, which can make them difficult to spot at first. For example, one of these 8 characteristics is whether or not something responds to stimuli. In the frog and lily pad example, the frog hopped away when it was touched, while the lily pad did not noticeably move or respond in any other way. Still, although the lily pad did not react to this specific type of stimuli, it would respond to others: if the impact was violent enough to damage it, for example, it might adjust how it used its resources in order to either heal the tear or to preserve the rest of itself. Similarly, the leaves on many different types of trees change colors during the fall, and are often shed in order to conserve resources during the drastic changes in weather and climate. This, too, would be considered a response to stimuli.
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Everything can be classified as either biotic and abiotic. Abiotic things are nonliving, meaning that they are missing one or more of the 8 characteristics of life, while biotic things are living, which means they do have all 8 of these characteristics. These 8 characteristics are:
- Reproduction - For something to be considered alive, it must be able to reproduce and create offspring.
- Heredity - Heredity is the ability to pass on genetic material (DNA) from parent to offspring. This can be in the form of phenotypic traits (the way a living thing looks on the outside) and genotypic traits (the actual genetic code that determines how something behaves and looks).
- Cellular Organization - All living things are composed of one or more cells.
- Growth and Development - All organisms develop over time to become more physically and mentally mature.
- Adaptation Through Evolution - Every living thing has evolved at some point in time, and continues to do so in order to adapt to an everchanging environment.
- Response to Stimuli - Living things respond to stimuli in their environment.
- Homeostasis - Homeostasis is a living thing's ability to maintain stable internal factors, such as blood pressure, body temperature (thermoregulation), and water balance within cells.
- Metabolism - An organism must use chemical reactions to process and/or use resources from the environment in order to continue functioning.
Examples
Reproduction
Reproduction can be either sexual, where offspring inherits genetic material from multiple parents, or asexual, where an offspring inherits genetic material from only one parent.
For example, most introductory biology courses mention meiosis and mitosis. In the former, a cell divides to produce two cells with the same number of chromosomes, while the latter creates four cells with half the number of chromosomes of the parent. These processes would both be considered asexual reproduction, as one parent cell creates offspring alone.
However, not all reproduction takes place on such a microscopic scale. A baby guppy (or "fry") is a product of sexual reproduction. Two adult guppies have mated to produce this fish, and it will have inherited chromosomes from both of its parents. Although these two reproductive processes are different, both of them still qualify as reproduction, since both result in offspring. Thus, both the individual cells and the guppies have this characteristic of life.
Heredity
Small mammals such as guinea pigs are very interesting, because of the different breeds and how heredity affects them. For example, if a brown long-haired male guinea pig were to reproduce with a ginger-and-white short-haired female, they might have offspring with a variety of different inherited traits. These two guinea pigs could produce one short-haired brown baby, and another ginger-and-white long-haired baby. In this example, these adult guinea pigs have passed down DNA to their offspring, resulting in similarities in heritable traits such as fur length and color.
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Cellular Organization
How many cells organisms have can vary. Single-celled organisms have just the one, as the name suggests. Humans, on the other hand, have 37.2 trillion cells and 200 different types! Some of these cells make up muscles, others form tissue, some move through the bloodstream as blood cells, and more. Although the number and structure of cells can vary between different organisms, there must be some level of cellular organization for something to be considered alive.
Growth and Development
The life cycle of a frog is an obvious example of how organisms grow and develop over time. A tiny egg hatches and becomes a small, limbless, water-dwelling tadpole with gills. This tadpole will grow, sprout legs and arms, and will begin to breathe using lungs. Its tail shrinks until it disappears. After a variety of changes, the tadpole will become a young frog, which will continue to grow and reach an adult size.
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Adaption Through Evolution
Fossils are one of the best ways to view evolution over time; the oldest fossils discovered are of 3.5 billion years old cyanobacteria! Animals aren't the only living things found in fossils. Plants, too, can become fossilized, and their evolution can also be recorded through these records. Over the years, the organisms born with traits that increase their rate of survival are the ones able to reproduce, leading to more of the population having these traits. The evolution of adaptations that increases survival rate are the primary idea behind Darwin's famous "survival of the fittest."
The Peacock butterfly is an excellent modern-day example of adaptation through evolution. These butterflies have evolved eyespots on their wings in order to scare away predators, which helps them avoid being eaten or killed. Butterflies born with eyespots are more likely to live long enough to reproduce, leading to more generations of offspring to be born with these eyespots. Over time, a greater percentage of the population of butterflies will have these eyespots present on their wings.
Responses to Stimuli
A lot of behaviors seen in living things are, in fact, responses to stimuli. For example, a morning dove might sense that it is too hot to stay in the sun, responding by searching for shade so that she can rest in it. In this case, the external temperature is the stimulus, and the movement of the dove is the response. Animals are not the only organisms who display responses to stimuli: many flowering plants can be seen reaching towards sunlight at one point, then turning to face another way at another time of day. These responses may be slower and less noticeable than, say, the movement of a dove, but both display behaviors in order to respond to their environment.
Abiotic rocks, on the other hand, do not respond to stimuli; they do not seek shade, run from predators, nor anything else living things do. As long as something changes its behavior in response to an outside or inside factor, it is considered a response to stimuli.
Homeostasis
Endotherms, or warm-blooded organisms, regulate their internal temperature without relying on the external temperature (as ectotherms do). Humans use homeostasis to keep their internal temperature balanced and within the normal range. If someone's homeostatic body functions are not working properly, they are often prescribed medicine, because having these processes is essential to good health and life as a whole.
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Metabolism
Metabolism is somewhat similar to homeostasis, since both include bodily functions that need to be maintained to avoid illness. The most commonly known metabolic process is the conversion of food into energy. Many popular weight loss strategies include "boosting your metabolism," since having a faster metabolism means whatever is consumed is converted into energy (usually in the form of ATP, or adenosine triphosphate) more quickly, more effectively "burning" calories. Unfortunately, having a fast metabolism can also cause negative symptoms like consistent hunger and fatigue, since energy is being used up faster.
Photosynthesis is a major metabolic pathway in plants. This is the process of receiving energy from the sun and converting it into usable energy for the plant to grow and function. The energy is converted through two reactions, energy-fixing and carbon-fixing, to become glucose, a sugar compound used by organisms for energy.
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This lesson defines each of the 8 characteristics of life and explains how they can be seen within the real world. These characteristics are reproduction, heredity, cellular organization, growth and development, response to stimuli, adaptation through evolution, homeostasis, and metabolism. Something must have all 8 of these traits to be considered a living thing.
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Video Transcript
Characteristics of Life
Every fall for the past dozen years, I have begun my biology class in much the same way---with a question. How do you know if something is alive? Now this may seem like a straightforward question, but based on student responses, it isn't nearly that easy to answer. Students often tell me that something is alive if it moves, or breathes, or thinks. Well, these responses are largely all wrong. However, despite the disappointment shown on aspiring biology students' faces when they realize they can't yet distinguish between living and nonliving, there is hope. Fortunately biologists have developed a list of eight characteristics shared by all living organisms. Characteristics are traits or qualities. Here is the list of characteristics shared by living things:
- Cellular organization
- Reproduction
- Metabolism
- Homeostasis
- Heredity
- Response to stimuli
- Growth and development
- Adaptation through evolution
Now, let's take a moment and elaborate on each of these characteristics.
Characteristics of Life Defined
The first characteristic of life we listed was cellular organization. This simply means that living things are made of cells. Cells are the most basic unit of life. It doesn't matter if those cells are plants, animals, fungi, or bacteria. If something is going to be alive, it must be made of cells.
Second is reproduction. If something is alive it must be capable of reproducing. Multicellular life forms such as humans reproduce sexually, while unicellular life forms like bacteria reproduce asexually. The important thing to remember is that, in either case, living things reproduce.
Next, we come to our third characteristic, metabolism. This concept is a little difficult for some students to grasp. Metabolism is essentially a collection of chemical reactions occurring within the body (or cell). These reactions vary in form and function but promote processes such as protein synthesis, chemical digestion, cell division, or energy transformation. Because metabolism includes reactions that link to other characteristics, it is sometimes grouped with those other characteristics. However, for our purposes, we'll keep metabolism separate.
Our fourth characteristic is homeostasis. Homeostasis is the term used to describe maintaining a stable internal environment. In other words, think about how our bodies maintain a constant body temperature or how blood sugar levels are consistent. If homeostasis is disrupted, and we spike a fever, it's an indication that something is threatening life. The same holds true with blood sugar. When it gets too high or too low, homeostasis is disrupted, and unfortunately, this can be deadly. Therefore, maintaining homeostasis is a vital characteristic of life.
Next, we come to heredity. Heredity means that our genetic information can be passed from one generation to another. If either of your parents has dark eyes, and you also have dark eyes, it's because of heredity.
Response to stimuli is the next characteristic in our countdown. This is simply a reaction to an internal or external force. This is something you've probably witnessed already. Think about a sunflower tilting towards the sun, a dog panting when hot, or trees losing their leaves in the fall when sunlight levels decrease. All living things respond to stimuli in some manner; to see it, all we have to do is look.
Our seventh characteristic of life is that living things all grow and develop, which simply means they become bigger and mature. Consider yourself as an example. You were a baby, then a toddler, then a young child, etc… Today, you're probably an adult. Consider this butterfly as another example.
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While all living things may not share specific life stages, all life does grow and develop.
Finally, we come to life's ability to adapt through evolution. Evolution is the change in heritable traits within a population. It is an inescapable fact that all life forms adapt and undergo evolution. Consider how dogs were domesticated from wolves. This represents a change in heritable traits (tameness) within the population and is a form of evolution. All living things adapt though evolution.
Lesson Summary
Sometimes it is difficult to distinguish something that is alive from something that is not. Fortunately, biologists have developed a list of eight characteristics shared by all living things. Characteristics are traits or qualities. Those characteristics are cellular organization, reproduction, metabolism, homeostasis, heredity, response to stimuli, growth and development, and adaptation through evolution. Some things, such as a virus, demonstrate only a few of these characteristics and are, therefore, not alive. However, other things will demonstrate all eight characteristics and, thus, be considered alive.
Definitions of the 8 Characteristics of Life
- Characteristics of life: Traits or qualities shared by all living things
- Cellular organization: Cells make up all living things
- Reproduction: The process of procreating a species either sexually or asexually
- Metabolism:: The collection of chemical reactions within a body that promote specific body processes
- Homeostasis: The body's ability to maintain a stable internal environment
- Heredity: Genetic information that is passed from one generation to the next
- Response to stimuli: The reaction of living things to internal or external force.
- Growth and development: The ability for living things to grow and mature.
- Evolution: The change in heritable traits within a population.
Learning Outcome
As you complete the video lesson, make an effort to try to remember and expound upon each of the eight characteristics of life.
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8 Characteristics of Life in Biology | Properties & Examples
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