Life's Organizational Hierarchy - Online Tutor, Practice Problems & Exam Prep

Life's organizational hierarchy consists of various levels, starting from atoms, which combine to form molecules like water (H₂O). These molecules create organelles, leading to cells—the smallest unit of life. Cells group into tissues, which form organs, and multiple organs create organ systems. Together, these systems make multicellular organisms. Populations consist of the same species, while communities include different species. Ecosystems encompass both biotic (living) and abiotic (nonliving) components, culminating in the biosphere, which contains all ecosystems supporting life. Emergent properties arise at each level, demonstrating that the whole is greater than the sum of its parts.

Life's Organizational Hierarchy

So we already know from our last lesson video that one of the characteristics shared by all living organisms is organization. The ability to use smaller components to build larger, more complex functional components. In this video, we're going to continue to talk about that as we discuss life's organizational hierarchy. Life actually consists of multiple smaller parts that are organized into a hierarchical pattern. Notice that on the left-hand side of our image, we have a scale that is small at the top and gets larger as you go down towards the bottom. This scale applies to the hierarchy of life that we see on the left.

At the smallest scale of this hierarchy, you'll note that all life is composed of atoms, and at the opposite end, at the largest scale, is the biosphere, which we'll define further down in our image. Each of these rows represents a specific level of the hierarchy; towards the top, we have the smallest level, and as you go down, the levels get larger. Atoms make up both living and non-living matter, or anything that takes up space and has mass. We're going to talk more about atoms later in our course, and also about the basic chemistry of life. For now, we're defining atoms as the smallest particle of an element, and here we have an image that represents a typical atom.

Multiple atoms combined together begin to create molecules. Molecules are defined as a combination of atoms that are joined together. An example of a molecule is water, H₂O; it has 2 hydrogen atoms and 1 oxygen atom, creating a water molecule with 3 total atoms joined together. Some molecules, like water, have only a few atoms, while others can have hundreds of atoms joined together.

If you take multiple of the right types of molecules and join them correctly, you can begin to create organelles. The word "organelles" has roots in "organ" and a sound similar to "cell", indicating that organelles are the organs of cells, thus smaller than cells. They can be defined as specialized structures found within cells. Examples of organelles include the Golgi apparatus and the mitochondria. Later in our course, we will discuss these organelles in more detail and their functions.

If you combine several of the right types of organelles, you can create a cell. We've previously defined cells in our lesson videos as the smallest unit of life, and thus, nothing smaller than the cell—organelles, molecules, or atoms—are considered alive. It is the cell that is the smallest unit of life and displays all of the characteristics of life. Here, we're showing a cell with several different types of organelles within it.

Combining multiple of the same type of cell creates tissues. Tissues are groups of the same types of cells performing a specific function. We're showing you a bunch of cells forming tissues on the right-hand side. Multiple tissues can then create an organ. An organ is a group of tissues performing a specific function, like our heart, which has muscle and nervous tissues. Multiple different types of tissues can create an organ.

If you take multiple organs, you can create an organ system. For example, the cardiovascular system consists not just of the heart but also of blood vessels and arteries. An organ system is a group of organs working together to perform a specific function, such as the cardiovascular system of a deer or the nervous system, which includes the brain and spinal cord.

If you put all these systems together, you create a multicellular organism. It's important to note here that a cell is also an organism, but it is a unicellular organism consisting of just one single cell. Here at this level, we're talking about multicellular organisms such as humans or the deer shown in this image. A multicellular organism is an individual form of life composed of many cells.

If you take multiple of the same type of multicellular organisms, you can create a population. A population is defined as all of the organisms of the same species living together in the same area. Students often confuse a population with a community. A community consists of multiple populations, so if you take multiple populations, you get a community. Unlike a population, which includes only one species, a community includes multiple populations of different species living together in the same area.

While a community consists of different populations of living organisms, when you start to consider the non-living environment that surrounds those organisms, you are considering the ecosystem. The ecosystem includes the living community and the non-living environment, where "abiotic" just means non-living. Thus, the ecosystem not only includes the population of deer and the population of squirrels but also the non-living environment that surrounds those organisms, such as mountains, rivers, and rocks.

At the largest scale of this hierarchy, we have the biosphere. The biosphere consists of all the ecosystems on Earth that support life. This is the largest scale, and as you can see, we have the planet right here.

This concludes our lesson on life's organizational hierarchy. This is something you want to study and understand to correctly order, as there are usually multiple questions on your exams about this. We'll be able to get some practice applying these concepts as we move forward. See you all in our next video.

Life's Organizational Hierarchy Example 1

So here we have an example problem that says the image below represents the hierarchy of life. Which of the following options shows the correct order for 2 through 4? And we've got these 5 potential answer options down below. Notice that the image on the right does represent life's organizational hierarchy. However, you'll notice that not all of the levels are being shown in this image and that all the levels that come before organism are not being shown, and it starts with organism as the smallest level here, but it still wants us to correctly order items 2 through 4 here. So, we need to choose one of these 5 options. Notice here it's starting with organism. In number 2, you'll notice that there are a bunch of the same type of organism. In number 1 we have the organism which is a butterfly and in number 2 we have a bunch of butterflies. When you have a group of the same species, we refer to this as a population. We can label number 2 here as the population. Now, notice in the next image, number 3, what we have is a group of many different types of organisms or many different species of organisms. Not only do we have the butterflies, but we also have all these different types of plants, and we also have a mouse over here. Once you start to consider multiple populations of different species, you then have a community, and here we're looking at the community in number 3.

Taking a look at the fourth image here, what you'll notice is that it's not only showing the living community, the biotic community, but it's also including the non-living environment such as the mountains in the background and these rocks in the front. We can say here that number 4 is referring to the ecosystem because the ecosystem includes both the living community and the non-living or abiotic environment. You can see of course that at the largest scale here it's showing the biosphere, which is all of the ecosystems that support life on Earth.

For our answer options, we're only ordering 2 through 4 here so really we're looking for an option that reflects what we've determined here and you'll notice that it's option C that correlates with this. So 2 is population, 3 is community, and 4 is ecosystem just as we said here. This here concludes our example problem and we can indicate here that C is the correct answer. I'll see you all in our next video.

Which of the following options has the correct order in terms of the hierarchy of the organization?

• A. Ecosystem → Biosphere → Population → Community → Organism.
• B. Biosphere → Ecosystem → Population → Community → Organism.
• C. Ecosystem → Community → Biosphere → Population → Organism.
• D. Biosphere → Ecosystem →Community → Population → Organism.

Use the word bank to complete the pyramid of life's organizational hierarchy below.

Word Bank:
Population
Organelles
Organ System
Cell
Tissues
Ecosystem
Organ
Community
Molecules
Multicellular Organism

Alright. So this practice problem wants us to use the word bank over here on the left-hand side to complete the pyramid of life's organizational hierarchy down below over here on the right-hand side. Notice that at the very top of the pyramid we are showing the smallest scale of life’s organizational hierarchy with the atom, and at the very bottom of the pyramid, we're showing the largest scale of life's organizational hierarchy with the biosphere. Again, we need to use this word bank to fill in all the other levels of organization. There are many different ways that you can approach solving this problem, and we're just going to solve it starting from the smallest scale and building our way to the largest scale. If you take multiple atoms and link them together, you can build molecules, which are really just a combination of atoms. We can cross off molecules from our word bank over here. Then, if you take multiple molecules and put them together, you can build organelles, which, as their name implies, are really just the organs that are found inside of cells. If you take multiple organelles and put them together in the right way, you can build yourself a cell. Recall from our previous lesson videos that a cell is defined as the smallest unit of life. We can go ahead and cross off organelles and cell from our word bank. Now, if you take multiple of the same type of cell and put them together, you'll build a tissue, which is really just a group of the same type of cells specialized to perform a specific function. So we can cross off tissues from our list. If you take multiple tissues of different cell types, then you can build yourself an organ such as a heart, for example. We can cross off the organ. Then if you take multiple organs such as the heart, the blood vessels, the arteries, the blood, and things of that nature, then you can build yourself an organ system, such as the circulatory system that we just described. So we can cross off organ system here. Then, if you take multiple organ systems, such as the circulatory system, your digestive system, your immune system, your nervous system, and so on, you can actually build yourself a multicellular organism such as a human being or a deer, for instance. We can go ahead and cross off multicellular organism from our list. And then, of course, if you take multiple multicellular of the same species, you can build a population. If you take multiple populations of different species such as the population of deer and the population of squirrels, you'll get a community. We can go ahead and cross off community. Then, if you take the biotic community or the living community along with the nonliving surroundings or the abiotic portion, you'll get yourself an ecosystem. Of course, the biosphere represents all the ecosystems on earth that support life. This here represents the answers to this practice problem. That concludes this practice, so I'll see you guys in our next video.

Emergent Properties

In this video, we're going to introduce emergent properties. Emergent properties, as their name implies, are properties that emerge or arise upon combining smaller parts together. However, the individual smaller parts, when they are separate, do not display the emergent property. It's only when those individual smaller parts are combined that the emergent property arises. Now, emergent properties are incredibly relevant to life's organizational hierarchy that we covered in our previous lesson videos. At each new level of the hierarchy, there is going to be an emergent property that arises. The whole is going to be greater than the sum of its parts, and this is another way to explain emergent properties. Combining smaller parts together allows for a new emergent property to arise in the whole, and so the whole will be greater than the individual sum of the parts. To get a better understanding of emergent properties, let's take a look at our image down below.

Notice in the top half of the image here, there is an example of an emergent property. Notice over here on the left-hand side, we're showing you these bicycle parts, where you have a tire, pedals, a chain, and the bars that go along with a bicycle and notice that all of these parts are separate from one another. These are individual separate bike parts. Now, these individual separate bike parts do not allow for transportation. There's no way that you could go very far with these separate individual bike parts. However, when you combine those separate individual bike parts together in a very specific and proper way, then you can create a bicycle that allows for transportation efficiently. Transportation was not available with these individual separate bike parts. However, transportation is available when you combine these individual parts together. Transportation here, for that reason, is an example of an emergent property in that example.

In a very similar way, if we look at the bottom half you can see how these emergent properties also apply to life's organizational hierarchy. Notice on the left-hand side, we have these separate individual organelles or organs of cells such as, for example, the Golgi apparatus and the mitochondria. These separate individual organelles are not alive. There's no life here because these separate individual organelles do not display all of the characteristics of life. However, when you combine all of the organelles that are necessary in a very specific way, similar to how we combined all of the bike parts in a very specific way, an emergent property arises of life. Here what we're showing you is a cell that contains all of the necessary organelles that allow for life. Life here in this example is an emergent property that arose again moving forward in life's organizational hierarchy to a larger scale. Emergent properties arise at every single level of the scale as you increase in that hierarchy.

This here concludes our brief lesson on emergent properties, and 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.

Which of the following is the best example of an emergent property?

• A. Cells are the basic unit of life and all organisms are composed of one or more cells.
• B. Neurons can control which ions they keep inside and outside their membranes.
• C. Cells are made of simple molecules, but when organized together, these molecules can perform living functions.
• D. Molecules can form large chains by joining together multiple atoms.

At which point of the organizational hierarchy does life emerge?

• A. The molecular level.
• B. The population level.
• C. The multicellular organism level.
• D. The cellular level.
• E. The atomic level.

Here’s what students ask on this topic:

What is the smallest unit of life in life's organizational hierarchy?

The smallest unit of life in life's organizational hierarchy is the cell. Cells are the basic building blocks of all living organisms and are considered the smallest unit that exhibits all the characteristics of life. While atoms and molecules are smaller, they do not display the properties of life on their own. Cells can exist as unicellular organisms, like bacteria, or as part of multicellular organisms, like humans. Each cell contains organelles, such as the mitochondria and Golgi apparatus, which perform specific functions necessary for the cell's survival and operation.

How do emergent properties relate to life's organizational hierarchy?

Emergent properties are characteristics that arise when smaller components are combined to form a larger, more complex system. In life's organizational hierarchy, each level exhibits emergent properties that are not present in the individual components alone. For example, individual organelles within a cell are not alive, but when combined in a specific way, they form a living cell. Similarly, cells combine to form tissues, which have functions that individual cells do not. This concept illustrates that the whole is greater than the sum of its parts, and it is crucial for understanding biological complexity and the interdependence of life forms.

What is the difference between a population and a community in biological terms?

In biological terms, a population refers to a group of individuals of the same species living in a specific area. For example, a population of deer in a forest consists of all the deer in that forest. A community, on the other hand, includes multiple populations of different species living together in the same area. For instance, a forest community would include populations of deer, squirrels, birds, and various plants. While a population focuses on a single species, a community encompasses the interactions between different species within an ecosystem.

What constitutes an ecosystem in life's organizational hierarchy?

An ecosystem in life's organizational hierarchy consists of both the living (biotic) community and the non-living (abiotic) environment that interact in a specific area. The biotic components include all the different populations of organisms, such as plants, animals, and microorganisms. The abiotic components include non-living elements like water, soil, air, and minerals. Together, these components form a system where energy flows and nutrients cycle, supporting life. Ecosystems can vary in size and complexity, from a small pond to an entire forest, and they are integral to the biosphere, which encompasses all ecosystems on Earth.

What is the biosphere and how does it fit into life's organizational hierarchy?

The biosphere is the largest scale in life's organizational hierarchy and encompasses all ecosystems on Earth that support life. It includes every region of the planet where life exists, from the deepest oceans to the highest mountains. The biosphere integrates all living organisms and their interactions with the abiotic components of the Earth, such as the atmosphere, hydrosphere, and lithosphere. Understanding the biosphere is crucial for studying global ecological processes and the interdependence of life forms across different ecosystems. It represents the sum of all biological activity and the environments that sustain it.