Ecology introduction | Ecology | Khan Academy


– [Voiceover] We’re now
going to start looking at ecology, which is just the
study of how life interacts with other life or how
living things interact with each other and their environment. And you you could think of it well how is life interacting with living beings? So that’s the technical term often given as biotic factors, biotic factors, you have
the word bio in there signaling life, or non-living things, abiotic factor. A is the prefix often for not, so abiotic is not living, not living factors, and those
are just the technical terms, but if you even think about
yourself as you watch this video you are in an environment,
you are interacting with it. There are many abiotic
factors around you that you might notice, the air
that you are breathing, the temperature, your access to water, but there’s also biotic factors. Even if you think you’re in a room alone, you’re not fully, you’re
not completely alone. There is bacteria around you that you might not see. There might be other forms of life, you might have a plant in the room. Those are the biotic factors
that you are interacting with. That plant in that room
might be producing oxygen that you are then breathing, or you’re producing carbon
dioxide which that plant is able to fix and grow. And it might be interacting
with abiotic factors like sunlight to in
order to that it uses in photosynthesis in order to fix the carbon. We study all of that in
some depth in biology, and really ecology is a
bit of a synthesis of a lot of what we learn, if
anything, all of what we learn in biology because it’s taking life, it’s studying life at another level where it’s not just the
individual organism anymore, and it’s not even just the
population or the community, but we’re talking about
an even bigger system that is incredibly complex and that’s why it’s a really interesting thing to study. Now all of these images here
are things that folks would associate with an ecosystem. Over here you have a coral reef, and some of the life is obvious, you see the coral, you see the fish here, but there’s also life
that you’re not seeing. There’s going to be bacteria in this water that’s not visible at
least in the picture. And the abiotic factors are going to be things like the water temperature, or frankly, just even
the existence of water, or the salt content of the water, or other minerals that are in the water. In these pictures over here, you don’t necessarily see the animal life, but there is for sure
going to be if you were to dig into this grass or
look through those bushes you will find animal life, you will find insects, you
will find other animals. The trees are life, so that’s going to be
part of the ecosystem. If we’re studying ecology we think about well how do these trees
interact with the water, how do they interact
with the other species? How do they provide shelter for them? Or food? Or how are they dependent
on the other life in some way to grow? Same thing for in this case the mushrooms. How does the fungus living
on this tree branch, or in conjunction with the
moss and whatever else? All of this is the study of ecology, the study of ecosystems. Now when folks are talking about ecology they like to talk about different scales. And so let’s now think
about the different scales within an ecosystem, or
even beyond an ecosystem. So I have some pictures that
if you watch a wildlife show you typically see some images like this, and so since we at least
are familiar with it, at least on TV hopefully we
get to visit this at some point in our life, let’s just
think about the different characters here on the
different ecological scales. So at the most basic
scale is the individual. So let me write this down, you have the individual. So if we were talking
about these elephants, the individual would be
one individual elephant right over there. Now the next scale is the population, the next scale is the population, and if we were to stick with
our African savanna theme right over here, the population,
you have an individual elephant, the population
would be the members of that same species
that live in that area. So in this case the population would be, would at least include
these elephants that we see in this picture, there might
be a couple of elephants that are off the picture, and I should say in
particular these are going to be the African elephants. So it’s the members of the same species that are living in the same place. And it’s up for the classifier, or the scientist, whoever is studying it to define what do we mean by
living in the same place? We might define it as the people, you know, the people
(laughs), the elephants that live within a few
miles of this watering hole. You might define it as
the elephants that live within a broader area,
it could be you know, that live in East Africa, or South Africa, whatever it might be. And so defining the population is all the members of a species
that live in an area, but that area is up for definition. Now the next level up is the community, is the community. And that is all the living things that might live in that area
however we define the area. So for example, if this
lion and this giraffe lives in the area that we
used to define the population they would be members of the community. Let me circle that, so they would be members of the community. And it wouldn’t even
just be the big animals that you see here, it
would include all the life that is in that area. So it would include the
vegetation that is in the area, it would include the bacteria,
it would include the fungus, it would include any animals that are living inside of this
water that you would see there. Now if you go even one more
level of kind of inclusion, then we go to the ecosystem. So then we go, I’ll go down here, then you go to an ecosystem. And what an ecosystem is, it’s all of the living
things in that community, so all of the living things in an area, and then you’re also adding
the non-living things, the abiotic factors. So you’re including the rock, and the air, and the
weather, and the clouds, and the water itself that is
part of that watering hole. And a lot of times you
might think that the abiotic factors well they for sure affect, they for sure affect the biotic factors. If you don’t have water,
or if the temperature is too cold or too hot
it might be hard for a certain type of life to thrive, but it goes both ways. The biotic factors affect
the abiotic factors. We have oxygen in our
environment due to life on Earth. They might also affect the various, the chemical composition of
certain parts of the abiotic factors, say the water, or
the soil, or whatever else. And if you want to get a
level above an ecosystem, then sometimes you’ll hear
people talk about a biosphere. Biosphere, which is, you can think of it as a meta-ecosystem, or
oftentimes in my head I view it as a fully, it
contains all of the ecosystems that are in some way
connected to each other. So a fully enclosed,
fully contained ecosystem. And biospheres are actually, well I guess the most
famous biosphere (laughs) or the one that we’re
typically referring to is we could refer to the
whole Earth as a biosphere. It has multiple ecosystems, and once again,
ecosystems, it depends what the researcher wants to
define as an ecosystem. They could define it as you know, just something around a certain
river in a certain area, just like that, or they might define the ecosystem as a broader region. But all of the ecosystems in the world are part of the biosphere that we know as that is part of Earth. And it’s self-contained
because we don’t think that there are that many influences from outside of the earth. Although, even there, we
have to give some credit to the Sun that is providing
abiotic factors for sure. We wouldn’t have life
on Earth as we know it without the Sun. And there’s also things like the Moon the gravitational effect, you could consider that an abiotic factor, without the tides we would
not have life as we know it. But one thing that’s really fun, and as many of you all know
I enjoy science fiction, is to think about well
what kind of biospheres could you have if you think
about beyond the Earth? And this is a depiction here, this is actually from NASA’s website. How humans could create
biospheres outside of a planet, and it’s this interesting thing where you know that’s quote,
unquote land up here. Artificially created, and
then you would rotate it so that there’s the perception of gravity. But anyway, the study of ecosystems, the study of biospheres, the
study of ecology in general is incredibly, incredibly fascinating because when you have
all of this complexity, each living thing is incredibly complex. In fact if you want, you could even sometimes
consider part of a living thing as an ecosystem in and of itself. If you were to look even on
the surface of your hand, you have bacteria living
there that’s dependent on you in some way, and
you might actually benefit from the bacteria, or actually get hurt from the bacteria in some way. So there’s all sorts of different scales, but once you start factoring
everything in together it becomes these incredibly
beautiful, complex, often balanced, sometimes
imbalanced systems that have emergent
properties that start to, that start to have behaviors and I want to use that word very loosely that are somehow described, or I guess you could say properties that somehow describe
the ecosystem as a whole.

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