Land Plants I how land plants colonized land Ch' 29

1
Learning goals Lecture 3, Biological Diversity
(Plants and Fungi)
Readings Chapters 29, 30, and 31 (read all of
these, but the parts covered in lecture are most
likely to be on a test ).
Land plants II - Seed plants (Ch.30) Tiny
gametophytes protected in ovules and pollen
advantages of seeds Gymnosperms have naked
seeds Angiosperms have seeds in fruits
Monocots, Eudicots Fungi (Ch. 31) Characteristic
s fungi reproduce by spores fungal origins and
relationships importance  
Land Plants I- how land plants colonized land
(Ch. 29) Land plants evolved from green algae
terrestrial adaptations alternation of
generations bryophytes dominated by gametophyte
generation ferns dominated by sporophyte
2
Land Plants (Ch. 29) land plants evolved from
green algae terrestrial adaptations alternation
of generations bryophtes mostly
gametophyte ferns mostly sporophyte
Back to Lecture 2 for a moment - the key to
understanding the evolution of land plants lies
in the very diverse green algae. Fig. 28.3 Note
that some are rather plant-like in appearance.
A particular group of green algae, called
charyophyceans, seem to be the closest living
species to a possible land plant ancestor. Two
genera of charyophyceans are shown in Fig. 29.3.
Several unique features are shared between
charyophyceans and land plants.
3
Land Plants (Ch. 29) land plants evolved from
green algae terrestrial adaptations alternation
of generations bryophtes mostly
gametophyte ferns mostly sporophyte
Two important (of several) derived features of
all true plants are an apical meristerm (area of
growth at the tips of shoots and roots), and
alternation of generations. Fig. 29.5
Apical meristem allows plants to grow down into
the soil for nutrients and up to the light.
4
Land Plants (Ch. 29) land plants evolved from
green algae terrestrial adaptations alternation
of generations bryophtes mostly
gametophyte ferns mostly sporophyte
Alternation of generations should not be confused
with just sexual reproduction. Alteration of
generations means that in a species there is both
a haploid organism with many differentiated
cells, and a diploid organism with many
differentiated cells. The sporophyte generation
is not dependent on water to reproduce. Note that
syngamy fertilization when there are
differentiated eggs and sperm.
Fig. 29.5
5
Land Plants (Ch. 29) land plants evolved from
green algae terrestrial adaptations alternation
of generations bryophtes mostly
gametophyte ferns mostly sporophyte
Bryophytes are the mosses and plants like them.
Fig. 29.8 is terrible, with far more detail than
you need to know! Lets go through what you do
need to know, step by step.
6
Land Plants (Ch. 29) land plants evolved from
green algae terrestrial adaptations alternation
of generations bryophtes mostly
gametophyte ferns mostly sporophyte
Start at the top. The moss plants you see in the
woods are gametophytes (haploid plants). Some
are male, and some are female. Male gametophytes
make sperm, and female gametophytes male eggs -
by simple cell division. (Remember that the
collective term for eggs and sperm is gamete).
7
Land Plants (Ch. 29) land plants evolved from
green algae terrestrial adaptations alternation
of generations bryophtes mostly
gametophyte ferns mostly sporophyte
There must be moisture for the gametophytes to
reproduce, because the sperm have to swim to the
eggs on a different gametophyte! The egg sits in
a little vase called an archegonium.
Fertilization happens there.
8
Land Plants (Ch. 29) land plants evolved from
green algae terrestrial adaptations alternation
of generations bryophtes mostly
gametophyte ferns mostly sporophyte
The zygote (fertilized egg) grows, in the
archegonium, into a funny diploid plant - the
sporophyte. The sporophyte is the brown thing
sticking up from the mosses you see in the woods.
9
Land Plants (Ch. 29) land plants evolved from
green algae terrestrial adaptations alternation
of generations bryophtes mostly
gametophyte ferns mostly sporophyte
Finally, meiosis happens in the sporophyte to
make haploid spores that grow into new
gametophtes. Dont worry about the details,
know the big picture. Mosses are the only
bryophyte you have to know.
10
Land Plants (Ch. 29) land plants evolved from
green algae terrestrial adaptations alternation
of generations bryophtes mostly
gametophyte ferns mostly sporophyte

• Ferns differ from mosses in two ways
• The have vascular bundles (xylem, phloem) for
  moving fluids
• The sporophyte generation is the important one

Again, dont fret the details - the BIG PICTURE
is that a fern life cycle is like that of mosses,
but with the importance of gametophyte and
sporophyte reversed.
Fig. 29.12
11
Other seedless vascular plants related to ferns
(see also Fig. 29.14)
Land Plants (Ch. 29) land plants evolved from
green algae terrestrial adaptations alternation
of generations bryophtes mostly
gametophyte ferns mostly sporophyte
Up to 90 ft. tall! Extinct, makes up a lot of
coal beds.
www.ncstate.edu
www.anselm.edu
Horsetails, Equisetum
Club moss
12
Seed plants (Ch.30) Tiny gametophytes protected
in ovules and pollen grains Advantages of
seeds Gymnosperms have naked seeds Angiosperms
have seeds in fruits Monocots Eudicots
13
Seed plants (Ch.30) protected gametophytes
advantages of seeds gymnosperms angiosperms
monocots eudicots
Fig. 30.2 Notice how the importance of the
gametophypte dwindles as we move from mosses to
ferns to seed plants. The gametophyte of a seed
plant is microscopic and not green (does not
carry out photosynthesis)
14
Seed plants (Ch.30) protected gametophytes
advantages of seeds gymnosperms angiosperms
monocots eudicots
Lots of specialized terms are used to describe
the life cycle of see plants. Here, we will use
the fewest we can, and simply drastically. Fig.
30.3.
This whole structure is a ovule (integument, the
cells of the megasporangium, and the cells of the
megaspore). The megaspore is formed by meiosis,
so is a haploid gametophyte, the rest is diploid
sporophyte.
15
Seed plants (Ch.30) protected gametophytes
advantages of seeds gymnosperms angiosperms
monocots eudicots
Lots of specialized terms are used to describe
the life cycle of see plants. Here, we will use
the fewest we can, and simply drastically. Fig.
30.3.
One of the female gametophyte cells becomes an
egg (n). The rest divide to produce the rest of
the cells of the female gametophyte. A male
gametophyte (n), or pollen grain, enters the
ovule, and the nucleus of one of its cells acts
like a sperm, and fertilizes the egg ( zygote).
16
Seed plants (Ch.30) protected gametophytes
advantages of seeds gymnosperms angiosperms
monocots eudicots
Lots of specialized terms are used to describe
the life cycle of see plants. Here, we will use
the fewest we can, and simply drastically. Fig.
30.3.
The haploid female gametophyte (minus the cell
that became the egg) becomes a mass of tissue
that will provide a food supply for the new
embryo developing from the zygote. The
integument becomes a hard seed coat. Note that
the embryo stops developing until it germinates -
thus the baby plant in a peanut!
17
Seed plants (Ch.30) protected gametophytes
advantages of seeds gymnosperms angiosperms
monocots eudicots
The advantages of seeds are pretty obvious -
there is no need for the gametophyte to live in a
damp place so sperm can swim to the egg - seed
plants can, and do, live everywhere.
18
Seed plants (Ch.30) protected gametophytes
advantages of seeds gymnosperms angiosperms
monocots eudicots
Gymnosperms are seed plants that do not have a
fruit around the seed, and thus have naked
seeds. Most of us think of gymnosperms as just
pines (or conifers), but there is quite a
diversity. Ginkos live on campus - have you seen
one? The fruit is not really a fruit, but part
of the ovule..
pine
gingko
19
Seed plants (Ch.30) protected gametophytes
advantages of seeds gymnosperms angiosperms
monocots eudicots
Angiosperms do not have naked seeds, but seeds
surrounded by a n extra layer of tissue that
forms a fruit (which may be juicy or dry). Fig.
30.8, 30.9
20
Seed plants (Ch.30) protected gametophytes
advantages of seeds gymnosperms angiosperms
monocots eudicots
But of course, angiosperms also have flowers!
Fig. 30.7. You do not have to memorize all the
parts, but know that that most flowers have both
male, pollen producing parts, and female ovules.
21
Seed plants (Ch.30) protected gametophytes
advantages of seeds gymnosperms angiosperms
monocots eudicots
Almost all angiosperms fall naturally into two
groups, monocots (one cotyledon, or seed leaf)
and dicots (two cotyledons). A few dicots dont
form a clade, but the huge majoroty that do are
called true dicots, or eudicots. Fig. 30.12 (p.
603)
22
Seed plants (Ch.30) protected gametophytes
advantages of seeds gymnosperms angiosperms
monocots eudicots
Fig. 30.13. Angiosperms and animals have evolved
very intricate mutualistic interactions involving
pollination - interactions that benefit both.
23
Fungi (Ch. 31) Characteristics Fungi reproduce by
spores Fungal origins and relationships We dont
pay enough attention to fungi
24
Fungi (Ch. 31) characteristics reproduce by
spores origins and relationships importance
Fig. 31.5. The fundamental structure of many
fungi is the hypha (plural hyphae), thin
threadlike structures a mass of hyphae is called
a mycelium. Many fungi produce a reproductive
structure like the common mushroom.
Fungi are all heterotrophs - they obtain
nutrition by metabolizing complex biochemicals.
25
Fungi (Ch. 31) characteristics reproduce by
spores origins and relationships importance
Fig. 31.6, 31.7. But not all fungi make
mushrooms. This is the mold Penicillium (top)
and yeast, a single celled fungus.
26
Fungi (Ch. 31) characteristics reproduce by
spores origins and relationships importance
Fig. 31.23, 31.25. But some are mutualistic, and
some are parasites.
27
Fungi (Ch. 31) characteristics reproduce by
spores origins and relationships importance
Fig. 31.5 Fungi reproduce using tiny spores.
But there can be sexual or asexual reproduction,
or both. Note that most of the life cycle of a
fungus is haploid. For the test you can ignore
the terms plasmogamy, heterokaryotic,and
karyogamy (you can of course read about them, it
is quite interesting). The key feature of fungal
reproduction is that tough spores can be formed
in either the sexual or asexual part of the life
cycle.
28
Fig. 26..22
Fungi (Ch. 31) characteristics reproduce by
spores origins and relationships importance
Fungi seem to have arisen from a flagellated
protozoan ancestor. Oddly enough, the evidence
indicates that animals are more closely related
to fungi than to plants. Fungi are not plants!
29
Fungi (Ch. 31) characteristics reproduce by
spores origins and relationships importance
Fig. 31.21. Mycorrhizal fungi live in a
mutualistic, symbiotic relationship with almost
all land plants. Most land plants grow much
slower without micorrhizal fungi.
Fig. 31.26. Penicillium produces penicillin,
which inhibits the growth of the bacterium in
this Petrie dish.
30
Learning goals Lecture 3, Biological Diversity
(Plants and Fungi)
Readings Chapters 29, 30, and 31 (read all of
these, but the parts covered in lecture are most
likely to be on a test ).
Land plants II - Seed plants (Ch.30) Tiny
gametophytes protected in ovules and pollen
advantages of seeds Gymnosperms have naked
seeds Angiosperms have seeds in fruits
Monocots, Eudicots Fungi (Ch. 31) Characteristic
s fungi reproduce by spores fungal origins and
relationships importance  
Land Plants I- how land plants colonized land
(Ch. 29) Land plants evolved from green algae
terrestrial adaptations alternation of
generations bryophytes dominated by gametophyte
generation ferns dominated by sporophyte
31
(No Transcript)