Major Groups of Plants Video Lecture - Class 9

hi it's mr. Andersen and in this podcast
I'm going to talk about plants more
appropriately we're going to talk about
land plants and so they have a great
diversity on our planet if it weren't
for plants we literally would not be
able to survive on our planet and so
let's start with looking at their
phylogeny so here are all the eukaryotes
on our planet so basically these are all
things that have a nucleus and they're
going to have a organelles and so if we
break off of this this is a pretty
ancient lineage in other words plants
have been separated for a long time who
are the things they're more related to
well red algae b1 right next door but
we're gonna have green plants right here
most of these are all going to be
protists but you can see us right here
animals and then fungi right next to
that and so plants are important for the
role they play in our lives
if we zoom more into their phylogeny
itself they're going to be some things
that you're familiar with like mosses
and we'll maybe liverworts and hornworts
but we're also going to have seed plants
all the way down here you don't have to
learn all of these these are simply the
way that they're starting to be
classified but there are four groups you
should be familiar with that I've chosen
and those are going to be the bryophytes
so those are going to be like the mosses
the ferns the gymnosperms and then the
angiosperms and the reason I've chosen
those four is that they're monophyletic
in other words they share common
ancestry with each other so we know that
they're related but they also show these
four evolutionary steps in the movement
of plants from water to land alright
let's talk about some of their
characteristics so they're eukaryotic we
know that they have a nucleus and
organelles
there are also autotrophs in other words
they're going to take energy from the
Sun and they're going to use chlorophyll
a to make sugars for themselves and so
they are self feeders they all have cell
walls and that cell walls are going to
be made up of cellulose which is a
polysaccharide but it's going to have a
lot of extra bonds on there that make it
really really durable another chemical
that I could have written here is Spore
of pollen in that they have this really
resistant chemical that can also protect
their spores their terrestrial in other
words all of these plants are what do we
call land plants
sometimes refer to those as embryo
fights but they all live on land and so
things like seaweed aren't going to be
technically plants and things like kelp
are going to be protists and so they're
not plants as well and so all these
things on here live on land the only
exception to that would be like water
lilies which we think moved on to land
and then move back into the water all
plants are also going to show
alternating alternation of generations
that's part of their reproductive
structure and I'll show you that on the
next slide but the big thing is where
they actually get their name is that
they all have protected embryos land
plants in other words this would be a
baby plant protected by material around
the outside and so all plants are going
to have one structure in their life when
you have this little baby embryo fight
and that's what shares was shared
between all plants alternation of
generation is a term that you should
understand what specially when we're
talking about plants and basically what
it means is that there are two life
cycles in plants we have the haploid
life cycle remember that's going to be
when you have one set of all the
chromosomes and then the diploid now
botanists have given specific names to
these and so the haploid portion we call
the gametophyte and then the diploid
portion we're going to call the
sporophyte in humans let's think about
that what are the different diploid and
haploid parts of our life cycle well the
diploid is going to be me it's all the
cells in my body and then the haploid
portion is only going to be the gametes
or the sex cells but in plants lots of
times that gametophyte will actually be
a part of the plant multicellular part
of the plan so let's look how this plays
out in fern so basically what you're
going to have is meiosis which creates
spores since we've undergone meiosis
we've got some variability here but we
also now have reduced our chromosome
number down to N or haploid so now we
have mitotic growth of these and that's
going to create the gametophyte portion
that's going to be this really small
portion below of what you might think of
as the firm we're then are going to have
mitosis fertilization that's going to
create a sporophyte and that sporophyte
is going to be the diploid portion then
we have that cycle over and over again
things like mosses most of the what you
see in a moss is going to be gametophyte
but as we move up towards things like
fir tree like a big tree what you're
mostly looking at just like when you're
looking at in humans is going to be the
sporophyte or the diploid portion how do
they make energy well they're going to
make energy through a process process
called photosynthesis so they're taking
energy from the Sun and they're
converting that into sugars why are they
doing that they're doing that so they
can store the energy they can build
structures out of it but they can also
use cellular respiration to release the
energy in the form of ATP in other words
they are self-sufficient and we are
simply parasites on plants as I
mentioned before there are four big
groups that you should understand when
it comes to plants and those are also
going to show you the four major steps
that plants went through to dominate our
planet and so basically we're going to
start here deep in the ocean because
that's where plants started as something
similar to seaweed and so basically what
they were able to do is move on to land
they were able to move material around
they then came up with a seed and then
finally they came up with the flower and
so the movement on to land was the first
step some of the organisms on our planet
the bryophytes which I like the mosses
basically they're similar to what some
of the first plants on our planet had
they were definitely green but they
couldn't be very tall because in order
to move water around they could only do
it through diffusion they didn't have
vessels inside them that could move the
water and so these are generally really
really really short and they're also
found in areas where there's enough rain
water on the bryophytes that they can
actually get to get water that way next
movement then is the vascular tissues
show up and so the bryophytes are going
to be separated from these vascular
plants they have true tissues and so
basically what they're going to have are
the xylem and phloem that can move
material around once we can move
material especially water from our roots
to our shoots then sizes got really
really big we didn't have to live only
in really really wet areas and we didn't
have to be really low to the ground and
so the next big jump was the ferns next
thing is the evolution of the seed the
seed allowed them to protect that embryo
fight and it can dry out totally and
then we can eventually can start a new
plant cycads an example of gymnast sperm
but so are all these conifers over here
if we break down the word it's Nate
good seed and so that's going to be this
group and then finally we have what are
called the angiosperms and that's the
evolution of the flower what's the
function of a flower the flower
co-evolved with insects and it gave them
an ability to reproduce so basically
what are these flowers doing they're
advertising to insects to come here
we've got some nectar and then when you
go there you're going to pick up a
little pollen you're going to move it
somewhere else and this is allowed them
to be incredibly successful but even
though you might not be able to see a
flower almost every plant on our planet
you can think of is going to be an
angiosperm so let's think about grass
well they're pollinated by the wind and
so the winds going to move their pollen
and so they don't have to have a very
fancy flower because they're not
advertising for insects but that again
is the evolution of plants those four
big groups again are the bryophytes the
ferns the gymnosperms example would be
the conifer those were what were around
when the dinosaurs were around and then
finally we have the angiosperms and so
those are plants I love plants because I
eat them or I eat things that eat plants
and I hope that's helpful