In this video, we're going to talk about the characteristics of life. All living organisms, regardless of whether they are unicellular or multicellular, share 8 characteristics that distinguish these living organisms from the nonliving things that surround them. If we take a look at our table down below, notice we're listing the 8 characteristics that are shared by all living organisms, and we'll go through each one of these 8 characteristics one by one. The first characteristic shared by all living organisms is that all living organisms are composed of cells, or in other words, all living organisms are cellular. Recall from some of our previous lesson videos that we define cells as the smallest or the most basic fundamental unit of life, meaning that nothing smaller than the cell displays all of the characteristics of life and thus nothing smaller than the cell is considered alive. Notice over here we're showing you an image that is showing you cells. As we move forward in our course, we're going to talk a lot more about the structure and function of different types of cells. For now, you should just know that all living organisms are composed of cells.
The second characteristic that all living organisms share is that all living organisms are organized, and this organization allows all living organisms to use smaller structures to build larger, more complex structures. Those larger, more complex structures allow living organisms to survive. Just like over here in this image where this large brick wall is being built by using smaller individual bricks that are organized in a very specific way, all living organisms are also going to be organized. Later in our course, we're going to talk about the organizational hierarchy of life, which discusses how living things are organized on our planet.
The third characteristic that's shared by all living organisms is that all living organisms are able to respond to environmental stimuli, or in other words, all living organisms can respond to changes in the environment. The environment is constantly changing. For example, over here on the right, we're showing you a plant that is growing on the windowsill and notice that the plant is growing towards the window where the sunlight is shining through. This plant is responding to the environmental stimuli, which is the sunlight, and it is growing towards the sunlight. All living organisms are able to respond to environmental stimuli in one way or another.
The fourth characteristic shared by all living organisms is the ability to maintain homeostasis. This refers to the ability of all living organisms to stabilize or maintain suitable living conditions. Not only are all living organisms capable of responding to environmental stimuli, but they're capable of responding to the stimuli in such a way that it allows them to stabilize or maintain suitable living conditions. The environment surrounding living organisms is constantly changing. Some days when we go outside it's super hot, and other days it's really wet or really cold. The environment that's changing may not be the best environment for living organisms. Living organisms have to be able to respond to the changing environments in such a way that it allows them to maintain suitable living conditions. A classic example of maintaining homeostasis is when the human body sweats. In really hot environments, like on a hot summer day, your body will start to sweat in order to cool off and maintain living conditions. Sweating helps to cool off your body and allows your body to maintain more suitable living conditions, and once again all living organisms are capable of maintaining homeostasis.
The fifth characteristic shared by all living organisms is the ability to reproduce. Reproduction refers to the capacity to produce life or the ability to produce more life, and reproduction can either occur sexually or it can occur asexually. Sexually, of course, means that there are going to be two parents involved in the reproduction, and asexually means that there will only be one parent involved in the reproduction. We'll get to talk a lot more about the reproduction abilities of living organisms much later in our course when we're discussing mitosis and meiosis. But for now, you should just know that all living organisms have the ability to reproduce and create more life. Over here, notice that we're showing you an image of a baby to remind you of this characteristic of reproduction.
The sixth characteristic shared by all living organisms is the ability for all organisms to acquire and utilize energy from the environment or from the surroundings. Over here, we're showing you this kid that is eating a carrot to obtain energy from its environment. All living organisms have the ability to do this, obtain energy from their environment.
The seventh characteristic shared by all living organisms is that all living organisms contain genetic information, which is essentially hereditary information that can be passed down from one generation to the next. The molecule that serves as the genetic material is going to be DNA. We'll get to talk a lot more about DNA and genetics as we move forward in our course, but for now note that all living organisms contain genetic information, specifically DNA. Over here, we're showing you an image that represents the structure of DNA.
The eighth and final characteristic shared by all living organisms is the ability to evolve. Evolution refers to changes in the DNA of a population over really long periods of time, which allows the population to adapt and improve their survival in their environments. Evolution occurs in all living organisms and all populations of living organisms. We'll get to talk a lot more about evolution later in our course, but notice over here we're showing you a classic image that represents evolution, and how characteristics can be acquired and changed over time to lead to new species.
It is important to note that viruses, such as the coronavirus, for example, are not considered alive. This is because viruses lack some of the characteristics of life, mainly the ability to reproduce on their own without having to hijack other cells. We'll get to talk a lot more about viruses later in our course, but for now, you should note that viruses are generally not considered alive because they lack some of these characteristics of life. This concludes our brief lesson on the characteristic of life, and all living organisms from single-celled bacteria to you and I display these characteristics of life. We'll be able to get some practice applying these concepts as we move forward, so I'll see you all in our next video.
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