Hi. It's Mr. Andersen. Today I'm going to go over the big idea of homeostasis. I'm going
to be using Prezi to do this. So if you want to follow along you could go to this address.
It's bit.ly/homeoprezi. And if you type that in it should bring you to the homeostasis
prezi that I created. Prezi, it's kind of like PowerPoint. It's a flash way to look
at material online. And so what I would always start with is if you go over here under more,
and click on full screen you're going to see exactly what's on the screen right now. And
so this is a concept map of the unit 4 which is on homeostasis. So basically this covers
the big parts of homeostasis. A few big features before we get into the details. There's this
cycle over here where life is constantly interacting with the environment. Both abiotic and biotic
factors. And through feedback mechanisms and response it's able to maintain this homeostasis.
And so what is this whole unit about? It's about homeostasis and how we maintain that.
And this regular cycle is going to be right over on this side. If we go over here that
response can either be behavioral, what we do or physiological. And some examples of
physiological I'll talk about is development and defense. And then behavioral is going
to be mechanisms of timing and control. But remember like everything in biology evolution
is driving this. Or evolution is that concept that sits at the root of all of biology. So
let me clear the screen. So I'm just going to arrow through this. So this is on homeostasis.
So homeostasis is how we maintain an internal stable environment. And so especially as we
left the ocean, as we left water behind, we had to start maintaining a lot of that homeostasis.
What do you call somebody who can't maintain homeostasis? Well you would call them somebody
who's dead. In other words if we can't maintain this stable internal environment we don't
last long. And so what we're doing is we're surrounded by our environment. And we're constantly
responding to changes in the environment. The two major factors, the only factors that
we respond to are called abiotic and biotic. Abiotic means without life. And so these are
going to be nonliving factors. And biotic factors are going to be living factors. So
what's an example of an abiotic factor that I have to respond to? A big one that jumps
out right away would be temperature. What about a biotic factor that I have to respond
to? Maybe the invasion of a virus would be a biotic factor. Or competing with other living
organisms. And so this is the podcast that's called biotic and abiotic factors. And so
if you're confused on what I just said you may want to check that out. Our environment
tends to stay relatively stable. But there are disruptions in our environment. And so
I talk about disruptions in our environmental or in our environment in this podcast. A couple
of things I talk about are like hurricanes and how that impacted life. Or invasive species
and how that can impact life. And so if you have major disruptions to the environment
that makes it hard for life to continue existing. But in general we use feedback loops to respond
to our environment. And those feedback loops are two ways. Remember we have negative feedback
loops. Negative feedback loops are going to keep our values near a set point. And so you
have a set point. And if it goes too high then we have one response. And then if it
goes to low then we have a separate response. And so a quick example of that, if we're talking
about temperature, that abiotic factor. What happens if our temperature goes too high?
Well then we're going to start to sweat. We're going to dilate blood. And then our temperature
is going to lower. But if our temperature goes too low, then we're going to start to
shiver. Constrict blood vessels. If we talk about positive feedback loops, positive feedback
loops are going to move us away from a set point. So the quintessential example I talk
about is childbirth. So when the head of the child starts to push on the cervix, that produces
contractions which produces more oxytocin which produces more contractions which puts
more pressure on the cervix. And so that's a positive feedback loop. When we're moving
away from a set point. Or in this podcast on feedback loops I talk about ethylene and
how fruit ripening can transfer from fruit to fruit. And so that can speed up reactions.
So feedback then remember results in a response. So that's a response from the organism itself.
And I talk about response to external environments in this podcast. Here it is a little water
bear. And water bears are really good at responding to changes in their environment and surviving.
Those responses can be either behavioral of physiological. And so that's worth defining
what those are. Physiological is going to be, well let's start with behavioral. Behavioral
response is going to be something that an organism does. So it's a response of an entire
organism. Physiological generally we're talking about its response of parts of an organism.
And so what would be a behavioral response to an increase in temperature? Well if I'm
too hot, I might take off a coat or I might sit in the shade. So that would be behavioral
response. What about a physiological response? That might be sweating or dilating of blood
vessels. And so those are the major types of responses. I talk a lot about behavioral
responses in the podcast on timing and control or mechanisms of timing and control. Right
here I'm talking about jet lag and how we use circadian rhythms. So that's a whole organism.
Also talk about plants and how they grow towards or away from light. When we're talking about
physiological responses the two big things I talk about are development and how developmental
changes in organisms have created organisms that are adapted to their environment and
can respond to changes. And then physiological I also talk about plant and animal defenses.
And so animals and plants and how they defend themselves. In the animal defense I really
get into so detail on acquired immunity. And so using lymphocytes. Using red blood, or
excuse white blood cells, B cells, T cells. And that's a little bit intense. And so you
may want to take another look at that. And so those are my responses, both behavioral
and physiological. To any environmental stimuli I'm probably going to have both behavioral
and physiological stimuli or responses. But remember, like everything in biology evolution
shapes both the behavioral responses and physiological. And so in this podcast on natural selection
and behavior I talk about how plants evolved that photoperiod or response to the amount
of light. Or this is a picture of a bower bird. And how a male bower bird can produce
this wonderful bower for the female. But it's been developed through natural selection.
And then also how evolution shapes physiological responses. So those are responses within the
body. And so the two major ones I talk about in this podcast are going to be showing how
our excretory system has remained the same through organisms over time. Basically moving
circulatory system. And through some kind of a tube where we create filtrate. But also
the evolution when you have changes that's reflected in physiological adaptations as
well. And so as we move from water on to land and we had to move from gills to lungs being
that structure we can see that in the evolutionary record. Or in the record of life on our planet.
And so that's homeostasis. It touches numerous chapters within our book. But that central
theme is how we can maintain an internal stable environment in the face of a changing environment.
And so I hope that's helpful.