Hi. It's Mr. Andersen. And in this podcast I'm going to talk about the domain Eukarya.
That's the domain that you belong to. Because you, like a chimpanzee have a nucleus and
have organelles. But so do a bumble bee. So do these mushrooms. And this volvox. And these
flowers. And this yeast. We are all eukaryotic. And so this is just the first in a number
of podcasts that are going to talk about the diversity of eukaryotic life. And so what
is a eukaryotic life? It's basically things that have a nucleus. So they've got their
DNA contained within a nucleus. They'll have other things like endoplasmic reticulum. Or
golgi apparatus. Or mitochondria. But this is the domain that you belong to. Remember
there are other two domains. We've got the domain bacteria. And then we also have the
domain archaebacteria. And I've already talked about both of those. And so we are more related
to archaebacteria, if we look at this. So basically we share a common ancestor more
recently then we do with bacteria. But again, all life on our planet are going to have some
characteristics. We just happen to belong to the domain eukarya. So what are some other
things that are found inside here? Animals and fungi. But we're also going to have things
like slime molds, ciliates, flagellates. There's a bunch of things that are found in the domain
eukarya. But we're more related to archaebacteria. What are some of the characteristics of eukaryotic
cells? And here's just a typical animal like cell. Well we're going to have nucleus. So
we're going to have this nucleus right here. And the DNA is going to be found on the inside.
And then we're going to subdivide work. So we're going to have for example golgi apparatus
or endoplasmic reticulum or mitochondria. And so we're going to have organelles that
do individual jobs. Also we're going to be much larger then the cells of like a bacteria
for example. They just have their DNA in the middle. And they do all the same jobs that
we do, but we kind of divvy that up and give it to different parts of the cells. What's
another big characteristic that's different in eukaryotic cells is going to be our chromosomes.
Remember in bacteria and archaebacteria they're chromosome is a simple loop. But in us it's
going to be a linear stretch of DNA. There's is a loop. Ours is chromosome after chromosome
after chromosome. And so it's linear stretches. We also will have introns. Those are going
to be sections of our DNA that don't code for genes. Whereas on their DNA every little
bit of it is going to code for something. Another characteristic is going to be the
cytoskeleton. So the cytoskeleton, I'd point to these right here, are going to give us
structure on the inside of the eukaryotic cells. And now there is some structure in
bacteria and archaea, but it's not as definitive as that found in the cytoskeleton of eukaryotic
cells. How did they come to be? In other words we think eukaryotic cells came much later.
So how did we go from a simple cell to these complex cells? Well there's two ways that
we got there. And the first way is what's called the endosymbiotic theory of eukaryotic
evolution. That's a mouthful. It was first proposed by Dr. Lynn Margulis in I think 1967.
And basically what she said is that perhaps cells became more complex by having certain
cells ingesting or forming symbiotic relationships with prokaryotic cells. The two things that
she pointed to were the mitochondria and then the chloroplasts. That in 1967 was craziness.
But pretty much since then it's been accepted as close to scientific fact as you can. And
so what we have are these mitochondria and chloroplast which are almost, hijacked their
way into our cells. And they're living within our cells. What's some evidence that would
be, that could support endosymbiotic theory? Well, mitochondria and chloroplasts have their
own DNA. They have their own ribosomes. And they resemble both genetically and morphologically
they resemble bacteria. And so basically cells became more complex by grabbing two things.
I would point to this and the chloroplasts of the plant cell. And also to this, the mitochondria.
They became more complex that way. One of my favorite quotes of Lynn Margulis is that
cells became more complex not through combat or fighting each other, but through networking.
Through cooperation. Also they became more complex by infolding. And so if think about,
if we have a cell like this, what's one way that it could be complex? Well we could simply
fold it in on the side. And once you fold it in on the side, not only have you increased
the surface area, but you can give that organelle different jobs. And so all of these things
from the endoplasmic reticulum to the nucleus to the lysosomes, all these things we think
were formed by infolding. And so those two things gave us complexity in eukaryoitc cells.
Both this endosymbiotic working together. And then this infolding. What evidence would
we have that the endomembrane system was formed through folding? Well the proteins on the
outside and the proteins on the inside are going to be different. And so the proteins
on the outside, if we look on the inside of a golgi apparatus, are actually going to be
found on the inside of that. If you imagine it folding in. And those that were on the
inside are actually on the outside of this. And so that's pretty good evidence that endomembrane
systems formed through infolding. Now how do they make energy? In other words, how do
they make a living? Well their metabolism is going to be diverse in eukaryotic cells.
But two of the big things are going to be this process where autotrophs, so things like
plants and algae, and bacteria fall into this as well, are taking carbon dioxide, water
and using energy of the sun and converting that to compounds. And then we have the reverse
in cellular respiration. And so pretty much any niche on our planet is going to be filled
by eukaryotic cells. They're making a living however they can. The way they reproduce is
going to be different though, between bacteria and arachaeabacteria and bacteria. And so
basically they use the process of mitosis. Mitosis remember is copying those chromosomes.
You can see our linear chromosomes, we're copying it and then it's simply dividing in
half. And so we take one cell. In this case this would be a diploid cell. And we're making
two diploid cells that are exactly the same. And then we have meiosis. And so meiosis produces
gametes remember. In this case it could be four sperm cells or it could produce just
one egg cell. But regardless, if you're something like an anemone, so the would be an anemone
right here and you want to make a copy of yourself. In some eukaryotic cells they'll
simply just do mitosis. It will just divide in half. And you can see this one dividing
in half right here. Pretty soon what you get are two sea anemones that are exactly the
same. But we also can do sexual reproduction. So through the process of meiosis we can make
gametes. And then we can have fertilization. And then through mitosis we can get growth.
And so we can get genetic variability like we would have in this little child right here.
And so that's eukaryotic cells. Again they've got nucleus. They've got organelles. They've
got mitosis and meiosis. But the diversity of them is massive. And we're going to talk
about that over the next few podcasts. And I hope that's helpful.