How do you tell the difference between something that's alive or was alive, something that we call biotic, versus something that was never alive, something that we call abiotic? So what are the characteristics of living organisms that are shared amongst all of them? Try and take a quick second here and see if you can write down some of the characteristics of living organisms, or at least try and think of them really quickly. Feel free to pause the video if you want some time there. So we're going to call these the properties of life.
These are the criteria or characteristics that are shared amongst every living organism that we know of. They'll look different in various organisms, but these traits, these general traits, are shared amongst all of them. The first one is that life is highly organized.
Moving from the smallest structures, atoms, all the way up to clusters of individuals, organisms are highly organized. So we can start off at atoms, which are just individual units of... different elements, stuff like carbon and oxygen and nitrogen that we talked about previously.
You can combine those into molecules and create stuff like carbon dioxide or water or more complex stuff like proteins. You can then combine those molecules to make higher structures, stuff like organelles or organs of the cell, something like mitochondria or nuclei. You can then group the organelles, wrap them in a membrane and call those cells.
So the cells then create, or all living organisms are made up of cells. Some are made up of one cell, some are made up of many, many cells. But all living organisms are composed of cells. You can then combine cells to make tissues, and multiple tissue types combined together are organs. And so organs are clusters of cells, of different types of cells and different tissue types that work together to perform a function.
You then combine organs and organ systems and you can get whole organisms like us. We have a cardiovascular system, we have a nervous system, we have a heart and lungs and liver. You have all of that and you get an individual, and that's the organism.
Now, we also have terms for combinations of multiple organisms. If you have more than one, so you have at least two of one organism, say like you have over here with these mice, you have what we call a population. A population is the multiples of one type of species. So multiple of these little mice would be a population. Having two people would be a population, two or more people.
Having two or more oak trees would be a population. Now, we also have a biological community, which is at least two different species together. It can be a lot more than two species, but you have to have at least two.
So you can see in this picture down here, you have an owl, you have a little leged jerboa or kangaroo rat, can't really tell from here. And you have this grass in the background, so you have at least three species there. That would be a biological community.
Life also responds to stimuli. If you think about it, we respond to stimuli all the time. We can see the light, we can react to light, we react to hot and cold, we react to hunger, or a lot of different stimuli we respond to, and all of these things respond to some sort of stimuli.
They'll vary across the different species, but they respond in some way. And you can see that here. with this video showing how plants respond to light. So these plants grow towards the light in what we call phototropism. You can see they're growing to the light on the left, light shifts around and the light let the plants follow it.
So all living things will respond to stimuli in some way. Living organisms also need to make new generations. They have to pass on their genes to survive long term. And so all living things reproduce somehow.
It can be through acorns like they do in an oak tree wood. It can be like giving birth to a baby, something like we do or elephants do or a lot of animals will do. It can be through fungal spores like what happened in a fungi.
Or it could be through like a lot of protists will do where they just literally break in half and now you have two organisms, what we call binary fission. But they have to make new generations. All organisms also undergo evolution and adaptation. So this is a phylogeny.
You can imagine back here being the origin of all life. And life has divided out and split apart over billions of years. And they have evolved and adapted. And so all organisms that we know of undergo evolution and adaptation.
You should take a second and try to figure out where do you think humans would be at on this tree. All organisms also grow and develop. So they have to grow, they consume nutrients, they grow, they develop in some way. A good video of that here is this video of liverworts.
So you see these liverworts slowly growing and developing over this landscape. All organisms also have to regulate their body systems and keep some sort of homeostatic condition. So this is highly variable, but in some way all organisms have to regulate their body condition in some way. This could be maintaining salt balances, maintaining body temperature, maintaining water balances.
There's a large variety of different ways that organisms regulate themselves depending on their own physiology and ecology. A good example of this is sweating. When we work out, like this guy is here, he is working out, his muscles are working, they're producing a lot of heat, and he's starting to sweat. So his body's getting too hot, and his body's trying to regulate that by sweating, which cools him off. The word homeostasis means maintaining a stable environment.
The average human body temperature is somewhere around 98.6 degrees. His body temperature rose up. So to maintain homeostasis, his body's trying to cool him back down.
Now, why do you think this kangaroo over here is licking its forearms? What do you think it's trying to do there? Most mammals don't sweat. Humans are kind of unique in that way. Kangaroos need to cool themselves off often.
And so what they they have a lot of blood vessels right here in their forearm and it's a little bit shorter hair there so when they need to cool off rather than sweating they lick it and when they lick it it's essentially like sweating they're putting some liquid on their forearm and that form in that case saliva rather than sweat and when it evaporates it's going to take heat with it and cool off the individual. So rather than sweating kangaroo rats or kangaroos lick their forearms. All organisms also need to somehow acquire nutrients and process those nutrients.
Now a good way of thinking about this is through a food chain. You have light, or the sun, which emits light energy. The plants take in that light energy during photosynthesis.
which allows them to produce sugars and produce their body structures. The mouse, so the plant has then gotten energy, processed that energy. The mouse then eats the plant, so it takes the energy from the plant and processes it into its own body.
And then the hawk or whatever owl thing that's supposed to be there comes down, eats the mouse and acquires energy itself. All organisms, even unicellular ones, have to acquire energy in some way. And then lastly we have emergent properties. So the whole is always greater than the sum of the parts. Think about just an individual unicellular organism.
It's composed of atoms. Atoms have no inherent quality of life. Those atoms create molecules which also have no inherent property of life. But as you combine those pieces up you end up getting a living organism somehow.
And so that's an emergent property. A good way of thinking about this is the brain. You have a neuron. A neuron is just a cell.
So you have a cell that can transmit signals in one way. You combine all of those neurons together in a mass that we call the brain. The brain is just a big collection of neurons.
So all those neurons can only transmit signals, but when you put it in a brain you have this large organ that's highly sophisticated and perform a large variety of functions. And somehow out of that we get consciousness. The neuron isn't conscious.
The brain, individual parts of the brain, components of the brain are not conscious but somehow we get consciousness out of it. The whole is greater than some of the parts. Somehow consciousness is an emergent property of a combination of neurons in a really sophisticated collection called the brain.
So just to recap we talked about now the properties of life. We talked about order, response to stimuli, reproduction, adaptation, growth and development, regulating internal functions and homeostasis, and processing energy. So make sure you know the basic properties of life and how they relate to describing biotic versus abiotic entities.