Biology 1B - Lecture 2 - Algae, Mosses, Lower Vascular Plants


Uploaded by UCBerkeley on 21.01.2011

Transcript:
I want to make a couple of announcements. The first announcement is sitting to my left
to your right is a gentleman by the name of Mr. Terry Kern. Terry is a former biology
teacher at a community college. And he’s now retired. But every year he comes her in
gratis. He runs a review session, a question session. It will be held every Friday from
9 to 11 in 2017 VLSB. He gives you practice exam questions. He gives you practice lessons
in the class. So for those of you who are having a little hard time understanding some
of the concepts or just want to look at it from a different point of view, that is from
Terry’s point of view, I encourage you to go to those sessions. So again, Terry, I want
to thank you very much for doing this. Okay. And it starts today. Okay? Thanks a lot. Yeah,
we really should thank him.
And then I have a couple of announcements to make. Again for the class there are materials
to collect for next week’s lab. So make sure that you have those materials and you
read the lab ahead of time or else you won’t be able to do part of the lab exercise. And
your GSI will come up with a less than positive impression of you.
The second thing is that my office hours again are 9 to 10 Monday, Tuesday and Wednesday.
And last week I neglected to say the last time that they’re in 2017 VLSB the same
room that Mr. Kern will be in.
And finally we’ve been getting a lot of questions from students about the textbook.
In the assignments both Campbell Seventh and Campbell Eighth are fine for this class. We
give pages for reading in both of those textbooks. And several of you have asked me do you have
to buy Mastering of Biology, which is in the bookstore. And as far as I know we are not
going to use that for the class. We just need the textbook.
And then the other point I wanted to mention is some of you have asked me what emphasis
I’m going to put on the textbook with regard to exams. And I want to say to you that all
the exam questions will come from the lecture. The textbook is meant to supplement, to help
you clarify concepts that I might not explain too clearly. But most of all to give you a
lot of pictures, a lot of diagrams of the things that I talk about because the more
that I show you pictures of the more examples you’ll have. Am I doing something wrong,
Tim? Oh, okay. Microphone is quiet. So, does anybody have any questions about the class?
What do you want to do? Is that too loud? Okay. But I understand a lot of you read lips.
That’s okay. All right. So there are no questions, I gather? Yes, a question?
Well, I think what you’re going to have to do is just to look for the comparable pages
for the subject matter in the textbook that I talk about. And it’ll be pretty clear
I think.
And that question was since the free pages aren’t bound how are you going to know what
number of pages to look at if that’s what you’re reading? I think it will be pretty
obvious from the lecture material. Okay.
Last time I began by introducing you to the fungi. Which to remind you they’re classified
with the plants and even today are treated historically with the plants because that’s
where Linneaus placed them. And I mentioned to you that fungi have a number of generalized
characteristics, which lump them together. And we started making a list of those characteristics
last time. And now what I want to do is to continue with that list and to really expand
upon some of the points. And to begin, first of all, by giving you some terminology. And
I’m going to try to hold down the terminology in this class. I don’t want you to have
to remember terms. A lot of this will just stick with you. But we have to give you a
few terms. And the first term I want to do refers to the filaments that we talked about
in the fungi. We said the fungi are made up of filaments. And technically these filaments
are known as a hypha. A single filament is known as a hypha. Many filaments, the plural
is hyphae. And if you have many, many, many hyphae, have many, many, many hyphae we call
this, so if you have many times ten to the tenth hyphae, that’s just a number I made
up, we call this a mycelium. So, we will be referring to these terms and you will see
them in your textbook. And these are meant to indicate to you a specialized name for
the fungal filaments.
Now what I’d like to do is to begin by talking to you about reproduction in the fungi. We
mentioned last time that the fungi have both sexual and
asexual reproduction. In asexual reproduction we can produce spores. Fall to the ground
and make a new individual as we talked about last time. We can have asexual or sexual.
Another form of asexual reproduction is when the hyphae just breaks off and makes a new
organism just like the parent. What I’d like to spend time on now is talking to you
about the sexual lifecycle because the fungi have a particular aspect of their lifecycle,
which we don't find any place else in the biota, in the living
kingdom.
I’d like to begin with a hypha strand. And when we talk about sex and fungi, sex is different
in fungi because they don’t have just two sexes as many other organisms have. They have
many sexes. And we those sexes mating types. And so for this illustration of this example
I'm going to draw for you two mating types. We’ll make hyphae of two mating types. So
each of these is a hypha, a hypha. And we’re going to make some cells in each of the hypha.
And each cell is going to have a nucleus in it. And we're dealing with two
mating types. And as I said there are many in the fungi. And just to make it easy, we’ll
call this mating type minus and this mating type plus. Now notice that
each cell in the hyphal strand has one nucleus. We say that this cell has N with regard to
it's DNA. N with regard to its DNA. Or that it is haploid. And if these terms are unfamiliar
or you’re a little rusty with them, go back a little earlier in the textbook and look
at them, what they mean. So each of these cells is N having one nucleus in it and each
cell is haploid.
Now, fungi can grow for a long time in the soil as the haploid hypha. They absorb nutrients,
they secrete their materials and they grow for a long time. But if they meet a compatible
mating type, if there’s a compatible strain there, we can then get fusion of the hyphae
if there’s a compatible mating type which is a . In fusion we produce a new hyphal strand,
which again has cells in it. But now the unique aspect of the fungal lifecycle becomes evident.
In this particular case, the nuclei remain separate in a cell. Although the hyphae have
fused, the nuclei remain separate. Compared to before they fused where we had one nucleus
in there where they were haploid, we call this a monokaryon. Meaning one nucleus in
the cell.
This is compared to the fused situation where we have two nuclei in the cell. This is knows
and the dikaryon. This is a unique condition in the fungi, where the two different mating
strains or sex types remain separate. They don’t combine. Now fungi can exist in the
soil for years in this in this dikaryon state, continuing to absorb nutrients to continue
to enlarge. Then we believe, following some change
in the environment half the nutrients run out of the soil, that change in the
environment sends a signal to the fungus. And the signal results in the production of
the reproductive structure.
And so in this mushroom, which I have over here in front, this mushroom represents a
reproductive structure. If we cut the mushroom down the center and could put the mushroom
underneath a microscope, we would find that every place on the mushroom is made of dikaryotic
hyphae except for one region. And that region on this particular mushroom that I’m holding
up for you is on the gills because on the gills what happens and I will write this down
for you. On the gills, the nuclei, that is the plus and the minus,
fuse and they make a two-end nucleus. So the only place on the mushroom
where you have the two-end nucleus, which most of you know is called
the diploid, is on the gills. This is the time that sexual recombination
can occur when you can have genetic variation. But it’s a very short interval with regard
to the whole lifecycle of the fungus.
Following the diploid production, following the genetic recombination, we then get meiosis
occurring on the gills and that results in spores which are now N again. And they are
either plus or minus spores for this particular type. That's the basic lifecycle of the fungus.
These spores have to be dispersed. They’ve got to be sent around to the rest of the environment
so that the lifecycle can continue. In most cases fungal spores are very light, very tiny.
As they are produced they are usually carried away by the wind. They’re very easily transported.
Some fungi have developed unique ways of dispersing their spores or their spore masses. I would
like to give an example of one of the fungi, which disperses the spore mass in a unique
way. And that fungus is one, which is called pilobolus. It’s a fungus, which is about
5 to 10 millimeters high. Not a very big fungus. And I want to draw it for you.
This fungus has a stalk. It has its mycelium. This particular fungus grows and its mycelium
penetrate dung, excrement, a rich source of carbohydrate, a rich source of nutrients.
So we have the mycelium connected to a stalk. On the top of the stalk we have an inflated
region. On the very top of the inflated region we have the spore mass. You
need to know one other aspect of the biology of this fungus to be able to
understand how it reproduces, how it produces its spores. This fungus bends to
the light. Bend toward the light. Any organism, including us, that respond in
this way by bending or moving toward the light. We call
this response phototropism. Bends toward the light.
Let's consider now the lifecycle of this fungus having been introduced to
a couple of the features of the fungus. The fungus is now, in this particular case, bending
toward the light. Here is the fungus sitting over here. Here is the dung. It bends toward
the light. We have bending occurring or phototropism. The
second step is number two. This is number one. Number two pressure increases in the
inflated region.
Pressure increases in the inflated region. This region below, pressure
increases. Then in a blink of the eye, much faster than you can see, the
spore mass
is discharged. It's discharged toward the light. Usually in
the case that we are using here it will land on some grass. The grass will be eaten by a cow or some other
animal.
And the fungal mass, the spore, passes through the cow and is embedded in the dung.
So, in this particular case, once it’s in the dung, the whole lifecycle begins again.
The spore germinates and the process begins again. This is very interesting dispersal
mechanism. We are using another animal to move the spore to the area.
The question I have for you and I will present a number of questions throughout the lecture.
I won't give you the answer now, but you’ll get it before the midterm. It is
important to think about. The question I have is why is it important that this fungus show
or have the ability of phototropism for its lifecycle? Why does it have to be
phototrophic in order for the lifecycle to be successful?
Finally, what I want to briefly mention to you before we leave the
fungi is an unusual but a very marked association between fungi and other
organisms. In particular, I want to talk to you about an association
between fungi and photosynthetic organisms. I will write that. These
photosynthetic organisms are frequently, but not always, algae. This
association is a symbiotic association. At least we think it is. You know
of this association by the term a lichen. A lichen is a symbiotic
association between a fungus and some photosynthetic organism. Here is an
example and there are many examples of lichens growing outside. This is an example of a lichen.
They are very beautiful, very colorful where we now have an association between the fungus,
perhaps several fungi and one or more photosynthetic organisms to make these structures you know
of as lichen.
Lichens were first understood as being comprised by fungus and other organisms by a person
some of you may have heard of when you were three or four years old. Lichens were first
described, first appreciated Beatrix Potter in the early Nineteenth Century. Because she
was a great artist, she drew all of her own pictures in Peter Rabbit. She also drew beautiful
pictures of the lichens she identified. They are in the British Museum today.
Beatrix Potter is the first one to have shown and understood this association. What does
the association result in? Well, the fungus in the association provides
structure. It provides structure
and it absorbs nutrients. The photosynthetic organism, if it’s an alga or something else,
makes complex compounds like fats and oils and carbohydrates. The lichens grow very slowly.
However, they serve very important functions over the long-term. In
areas that are disturbed like, for example, when Mount St. Helens erupted up in Washington
State, large amounts of soil or earth were covered with volcanic lava and that soil was
no longer available to be colonized by other
plants.
Lichens secrete acids. And they actually over many, many years will regenerate soil as a
result of their activity. Lichens also are very sensitive indicators of pollution. In
areas where we have a large amount of pollution, we won't have many lichen. So, if you are
choosing a place to live, you’d like to choose a place were there are more lichens
growing because this would be an indication to you that the air is in pretty good shape.
Let me show you some pictures now of fungi. Three days later, here
we go, this fungus now is a fungus similar to the one that we have saw before. We
have the underground mycelium, which is absorbing nutrients. We have a stalk and on the end
of the stalk we have a spore mass, which I’ll show you in a little higher power. Here is
the spore mass.
Notice the many spores, which are being produced from this particular fungus. Now
let's talk about the reproduction of the fungus. This is the mushroom and
if we look at the mushroom, we have the stalk and the whole structure is
dikaryotic. Beneath the ground here, maybe we can turn the lights off a little bit. Maybe
we can’t. Can we dim the lights a little?
Beneath the surface here, that’s good, that's great, a good start. We have the spore mass,
I mean the mycelium and that's feeding that. If you look carefully at the reproductive
stage, you can see the mycelium. All dikaryotic hyphae here. And once the spores are produced
on the gills, they are carried away by the wind.
Now if we take this structure here and we make a cut across the plane of this structure
we can actually see the gills with the spores. This would be the center stalk. Here are the
gills, the portion of the mushroom where the fusion of two N plus nuclei occur to make
the two N level. And here you can see now the spores. This is a higher magnification
of one of the gills. These are the spores that have been produced after meiosis has
occurred. They are now N spores. And a higher picture of it will show you each of these
spores here which in this case could be either plus or minus depending upon what it is.
And this is a picture similar to the one, which is in your book. And I want to encourage
you to look at it where you can see the various stages of the lifecycle we talked about. Again,
there are terms here, which aren’t necessary for you to know. It is important for you to
understand what is going on.
Here is pilobolus. Here is this fungus growing on some dung. Here is the spore mass and the
inflated region and the stalk. In this particular case, it is bending toward the light, showing
phototropism. The next picture will show you a slide I put in to remind me to remind you
that I put on the web page, which has assignments some links to YouTube. And those YouTube links
have some pictures of actually the shooting off of the spore mass. They put some music
to it, which is a little corny. It’s still fun to have a look at it and see how fast
it occurs.
Finally, I want to show you a few pictures of the lichens. Many of you have seen lichens
before. This is a large rock. This surface is being colonized by a large number of lichens.
And again, these lichens are secreting acids and eventually could result in the disintegration
of the rock. Just to show you a few lichens. They are very highly colored. Why are they
so highly colored? One reason is that lichens are very poisonous for a lot of us. And so
they are quite toxic. Many animals still eat them. But this might be a warning. And then
finally, to give you another example of a very highly colored lichen, this one over
here, in which it is red.
Okay. Let's now move on to the next subject matter. Oh, great. And we can put the screen
up. Great. Thank you. That's the fungi. They are a very interesting group as I said. They
are a group that is relatively unexplored with a lot of work to be done. And for those
of you who are thinking about being physicians, we have big trouble treating fungal diseases.
It’s a really interesting area to go into. Fungal pharmacology if you want to look at
it this way.
Now I want to move on in the evolutionary scheme to the next group of organisms to talk
about. And this next group, just like the fungi, were classified with the plants because
of historical reasons. But as with the fungi, that’s good. As with the fungi this next
group is really artificial with regard to being grouped with the plants. And this next
group of organisms that we are going to talk about are the algae.
Based on some of the characteristics that Linnaeus had developed, many of the organisms,
which we initially considered as algae were put in with the plants. Again, based upon
more contemporary molecular techniques and other physiology and biochemistry that we
understand about these organisms, we now know that the algae are going to be placed not
only with the plants but they’re going to be dispersed on the eukarya branch in a way
similar to what we talked about in the fungi.
Some people have grouped the algae based upon molecular characteristics them into smaller
groups. For our purpose, because we are going to consider a large
group of organisms if we have to generalize. I'm going to generalize
using the characteristics of the algae, which are based on color. Sort of subdivide this
group of organisms. I'm going to take this large group of algae, all of the
organisms that Linnaeus grouped with the algae and divide them into smaller
subgroups. And these smaller subgroups actually have a reality based on biochemical characteristics.
And these smaller subgroups are the green algae, the red, the brown and then two other
groups, which we are going to talk about, the diatoms and the dinoflagellates. This breaking down or
subdividing the algae into smaller groups, this particular case is based upon the pigments,
what the color of the organism looks like, the
pigment. But there are other ways which have high correspondence to the molecular biology
of breaking down the algae into smaller subgroups. And let me just give you other ways people
break down the algae into small subgroups.
They break it down on the basis of the cell wall and its composition. Another way they
break it down is are flagella present. What are flagella? They are whip-like extensions
from the body used for movement, used in movement. So there are lots of ways of breaking the
algae down into smaller subgroups. Or what this original subgroup was for algae. I'm
going to give you a couple of examples here. Today, because we are going to be dealing
with this group of organisms, I would like to break them down in a slightly different
way, because I think it will help our discussion in the short time that we have and talk about
these organisms.
The way I would like to begin in breaking the algae down is to ask whether the organism's
lifecycle is predominantly or exclusively unicellular. That would be one group that
we are going to try and look at. The second one is versus multicellularity at some or
all points of the lifecycle. We think that the algae evolved in the ocean about one and
a half billion years ago. This group that we’re calling algae. One and a half billion
years ago. And today there are about 130,000 identified species that we would call algae
based upon Linnaeus' original grouping.
What I’d like to do is to begin first of all with a generalization for those that are
predominantly and exclusively unicellular and then move on to those that are
multicellular. Into the unicellar groups we are going to place the diatoms and the dinoflagellates.
These are unicellular. These organisms are essentially in a single cell a self-sufficient,
self-contained unit for life. And all they need is light, water and
some nutrients from the water, and that's it. They can be very happy.
These two groups are extremely important in our world. The diatoms and the
dinoflagellates and the small invertebrates make up the plankton in
the ocean. This is the base of the food chain. This is where it all
starts, guys. They are really, really important for our life here.
Secondly, the other major importance to us, is found here in the
diatoms. In the diatoms, it has been estimated that every year 50 to 80% of
the atmosphere or the oxygen in the atmosphere is renewed through the
activities of diatoms. So they renew the atmosphere. So they provide a
tremendous portion of the renewal of the atmosphere. This is why it is
important that the ocean have to be kept healthy. Because if we poison the
ocean we get rid of the plankton and we get rid of these organisms that are
renewing our atmosphere. This is something that is not obvious to a lot of people.
Now I’d like to begin by talking about the dinoflagellates. The dinoflagellates, and
this also applies to the diatoms. These are organisms which grow along the coast or along
edges of lakes. They grow at the surface of the waters, generally in
undisturbed areas. They tend to grow an equilibrium with their environment. So in the case of
dinoflagellates they tend to grow in equilibrium, not too much and not too little. But whenever
there is a storm or a disturbance to the water inflow
from the land to the ocean to the lakes so that many nutrients are now washed into the
ocean or to the lake, the dinoflagellates in particular grow rapidly. They multiply
tremendously. This is known as algal bloom. The more common term for an algal bloom is
called a red tide.
Now, why do we take note of red tide? It is because the dinoflagellates produce a nerve
toxin. When they are growing at their normal rate,
the nerve toxin is not very concentrated in the water. But when the red tide occurs, fish
ingest it. And for those of you who come from a coastal area especially along the Southern
California or southern part of the U.S. you can get massive fish kills because the fish
are overwhelmed by this nerve toxin.
Many of you know that beaches are closed when we have a red tide. The reason the beaches
are closed is in addition to fish eating the dinoflagellate, shellfish also filter the
dinoflagellate and consume a large number of them. But shellfish
are much less sensitive to the toxin. They can concentrate this toxin to extremely high
levels. When humans go to the beach and eat the shellfish, they die.
The beaches are closed mostly to prevent shellfish fishing because of the high concentration
of these toxins. Really important economically. These are the dinoflagellates.
The other group I want to talk to you about now is the diatoms. If I were going to choose
one group of algae to study it would be the diatoms. The reason I would choose it is because
they are extremely beautiful. It is because their outer cell wall has a part of the cell
wall imbedded in it silica, the material that makes sand. But what it does to the diatom’s
cell wall it makes it extremely like a snowflake. I will show you some pictures of it in a moment.
The wall is hard. Diatoms like the dinoflagellates grow near the surface of the water. As they
die, they settle in the base of the ocean, forming very, very thick layers, materials.
When the ocean floor is uplifted, we produce this material. I have
some examples here called diatomaceous earth. This consists of the outer silica walls of
billions and billions of diatoms that have collected and settled over years. We, as humans,
have exploited this in a number of ways. We use as an abrasive, for example, in silver
polish. We have diatomaceous earth. In tooth paste there is some diatomaceous earth. That’s
what gives tooth paste its kind of scrubbing action. And diatomaceous earth is used extensively
in filtering lots of water and other materials because of the small pore size between the
individual cell. This commercially is an important group of organisms, which we, as humans, have
exploited.
But I want to leave you again with the idea that even though these are only two minor
groups apparently, maybe never on your radar screen that they play a pivotal role, a central
role, in order for us being able to continue to live, open the atmosphere and provide the
basis in the food chain.
Now what I’d like to do is to move to the multicellular organisms. And in the multicellular
organisms we have the green, red and the brown algae. So multicellular has the green, the
red and the brown. The brown are the predominant seaweeds of California. They form the kelp
bed. Whereas the reds are found mostly in the tropics. What distinguishes this particular group of
organisms from the previous one, is that they are multicellular, they have more than one
cell which makes them up.
More importantly, besides being multicellular, they can be differentiated into many cell
types. Let me draw you and I will also show you a picture of one that is a
kelp. Some of you may have seen this off the coast in Monterey. We
have a structure on the kelp, it looks like a root at the bottom. From it is a stalk or
stem. It is called a stipe. It is called a holdfast because it holds the alga onto the
bottom of the ocean or a rock it is attached to. It is attached to a stalk. This stalk
can be variously modified differentiated cells. In this one we might have an air bladder.
This helps the organism to float in the water, to be near the surface where
the sunlight is. Finally, we might have something like that which is known as
blades where photosynthesis occurs. I have some examples up here. And you’ll be able
to see this again.
This is an alga which you can see the bladders. Here is the holdfast down at the bottom here.
It looks like a root but it really isn’t a root. What’s attached to a rock, which
held this in place. Here are the blades, which float near the water and the bladders are
filled with a gas to help the alga remain near the surface of the water where the sunlight
is. This is one of the interesting green algae. We as humans and one of the brown algae, we
as humans make tremendous use of the algae.
Those of you who come from Asian cultures or cultures that live near the water, algae
are consumed. They are an important source of trace elements and minerals. Many of us
use algal products every day. You use an alga product if you shaving cream, if you use whipping
cream, anything where we have thickeners and emulsifiers in foods generally have a product
known as an alginate, which is an abstract from algae growing in the ocean. Those of
you who have worked in labs have probably daily used a major product of the algae and
that’s agar. The material which is used to solidify the medium on culture plates.
Now, what I'd like to do is to begin by telling you a little bit
about the lifecycle of the algae. This lifecycle of the algae represents
a new development in the evolution of life. When I talk to you about this
lifecycle, it is going to be something that begins now and repeats and
continues up to the rest of the lecture. But what I also want to say to you is that this
lifecycle that I'm going to tell you about sounds alien. If you were to design a species
coming from another world you couldn't think of a weirder lifecycle
than the one I'm going to tell you about. In order for you to
appreciate this lifecycle, I want to take you to the lifecycle of a
human, to remind you what our lifecycle is.
We have the human and we have either the male or the female. We are diploid, two ends. Through
meiosis we make the gametes.
In the case of the male, this is the sperm, which is N. In the case of the female, it
is the egg, which is also N. As soon as the gametes are made we have fertilization.
I'm going to go over here, as soon as the gametes
are made, we get fertilization to make the new 2N embryo. So, you
make the gametes, the gametes are fusing directly after their made and we
get the embryo. This is the lifecycle of most organisms but it’s a lifecycle,
which is not found in all the plants. Let's talk about this unique lifecycle.
First of all, this lifecycle developed a number of times, originated a number of times in
the green algae. Not all of the algae have it, but this lifecycle is one which started
in the green algae. Let's talk to you about how it works. We are going to begin in
exactly the same place. We are going to begin with this 2N individual. Just like you have
sitting out there in the audience. We are going to start with a 2N individual. Just
like when you produce sperm or egg we have meiosis occurring to make something that is
N. Same thing as you saw over there. But this is where
the trick comes in. This end is not a gamete. It is not a sperm. It is not
an egg. This end is a spore. This is a spore. What goes on next is the
unique part. This spore germinates, I will put germ nation in quotes to
yield an N or haploid plant. This is the N haploid plant over here.
This haploid plant then, let's say that we have two haploid plants, this is
N because it came from an N spore. Now through mitosis, makes an egg and
the sperm, which are also, as in us, N. Now we have fertilization. Now
we have fertilization occurring and now make the 2N individuals.
I want you to all after you write down just think about this and look at me and think
about this for a second. What we have done in this particular lifecycle, introduced or
developed by the algae, is we have a lifecycle in which we have delayed
fertilization. We’ve delayed fertilization by producing a second plant. A second plant,
which has to be part of the lifecycle of a haploid plant. For every plant that you guys
see out there, every plant that you see out there you're seeing only one
generation. You’re seeing only this individual. This individual, the haploid
generation, you guys don't see, you don't realize it is there. But in all
plants that you see growing out you have to produce the second plant.
This evolution that we’re going to talk about in this particular system
changes as we move up the evolutionary scheme from the algae to higher plants we are going
to study. The relationship and the size of the second plant changes in relationship to
the plants outside.
What do we call these two different plants? This plant because it produces
spores, we call it the sporophyte. The plant, which produces the gamete, we
call the gametophyte. So, think of it gametophyte produces gametes and
the sporophyte produces spores. Because we an alternation of two
plants, between the sporophyte and the gametophyte, this whole lifecycle is called, we can go
down a little bit more, alternation. Can we go down a little bit more? Okay, I'm glad
I asked.
Called
alternation of generations. This is the lifecycle of the algae, not all of the
algae, but many of them. They developed and initiated this lifecycle. Let's
begin by looking at the slides. Turn the lights down, if you could. Oh, sorry. Alrighty.
Let's look at the algae and excellent. Here we go. This is one of the
unicellular algae. This is an alga where you can see the two flagella on it. This alga
spent its entire life as a single cell. And it is able to capture Co2, water and nutrients
and move through the water to new areas. As we go up the evolutionary scheme and look
into the multicellular, we find two cells joined together or one cell, which has been
elaborated if this is a single nucleus. If you look we can start to get colonial and
you are going to see this in the lab where you now have four cells formed together.
They don't seem to have any differentiation, but at least it’s one cell. It’s beginning
to get multicellular. And then you’re going to see large colonial algae. You will see
this one in the lab, which is made up of upwards 60,000 new cells which join together. They
all have flagella along the outside. And causes this colony to rotate and move. It looks like
a spaceship. Sometimes colonial algae can also be in the form of filaments in which
we have cells joined together. More than one cell but in this case it is filamentous.
Here is our alga that I showed you before which is a kelp. This holdfast or root-like
structure, the stipe, the blade and in this case, you don't see a float or a bladder to
help it stay upright.
Now here are some diatoms. These are the organisms which are always unicellular and which have
embedded in their cell wall this silica and they come in a
wide variety of sizes and shapes. And in Victorian days before television or the web or anything
that would entertain people in that way, people used to collect diatoms
and have contests arranging them on slides. And they would submit them and
get the best award for the particular diatom arrangements. Let me show you some other examples
here. Really beautiful. That's why I said I wanted to study these organisms if I had
a chance. Very nice. Here’s a dinoflagellate. I wanted to show you the dinoflagellate. These
are the organisms that cause the red tide, and these are the organisms that produce the
nerve toxin and they are completely unicellular in their lifecycle.
And finally I mentioned to you that algae have a great use in commercial and various
industries. This is looking down and there are some houses over here. And this is looking
down from an airplane view in an alga farm in Australia. These are ponds in which algae
are grown. Depending on the salt concentration that you have in the pond, you can get the
algae to take on different colors, different characteristics. The algae then are extracted
and that coloring is used to dye many of the pills and the vitamins and many of the cosmetics,
which we use come from the coloring from the alga pond.
Okay. Next time then we’ll move up through the algae to the next group. Have a nice weekend.