9. KINGDOM PLANTAE
Introduction
Plants are eukaryotic, multicellular, photosynthetic organisms. Another
characteristic that all plants share is their mode of sexual reproduction.
Diploid plants produce haploid cells through meiosis. These haploid cells are
however not called gametes, but spores. The reason for this is the fact that
these haploid cells do not need to fuse with another haploid cell (like the
gametes, sperm and egg, of animals through the process of fertilization), but
can survive on their own. In plants, the haploid spores will go through
multiple rounds of mitosis to form multicellular haploid organisms. It is this
haploid multicellular generation of plants that will produce gametes (via
mitosis). Those gametes then fuse to form an embryo and the next diploid
plant generation.
This is the so-called Alternation of Generations of plants. The plant’s life cycle
is an alternation of a haploid generation and a diploid generation. The haploid
generation is referred to as the gametophyte (the plant that forms gametes).
The gametophyte produces gametes (sperm and egg cells), which fuse
(fertilization) to form a diploid zygote. The zygote develops into an embryo
while enclosed in maternal tissue (another name for plants is Embryophytes).
The embryo develops into a mature diploid plant, called the sporophyte (the
plant that forms spores). The sporophyte then again forms haploid spores,
through meiosis, which will develop into haploid gametophytes, completing
the life cycle of the plant.
Special attention shall be paid to this alternation of generations while
observing all plant objects. How would you know by looking at a plant, if
you’re observing the diploid stage (sporophyte) or the haploid stage
(gametophyte) of a plant? The answer depends on which phylum of plants
you’re observing. For most plants, the sporophyte is the dominant phase.
When you see a fern or a rose, or a maple tree, you’re looking at the
sporophyte. Their gametophytes are really small and cannot be observed
without a microscope and, in many cases, without dissecting parts of the
sporophyte. Only mosses have gametophytes that can be observed with the
naked eye. Those are relatively large and green. Sporophytes of mosses are
relatively small and not green. In the course of plant evolution we see a shift
from plants that have haploid gametophytes as the dominant part of the life
cycle towards plants that have diploid sporophytes as the dominant part of
the life cycle.
The Kingdom of Plants has 10 phyla with living representatives. Of these
phyla, 5 are combined as the seedless plants. Their reproduction is
characterized by gametes and spores only. The seed plants, represented by 5
phyla, all have gametes, spores and seeds as part of their reproduction.
9-1
A. THE SEEDLESS PLANTS
1. Non-vascular seedless plants or bryophytes
The plants in this group have leaf-like, stem-like, and root-like structures
without vascular tissue, i.e. they lack phloem and xylem (no “plumbing
system”). The dominant phase of their life cycle is the gametophyte. The
sporophyte starts its development inside tissue of the gametophyte. It
remains attached to the gametophyte, and gains some nutrition from it.
There are about 24,000 species of bryophytes divided over three phyla:
liverworts, mosses and hornworts. We’ll look at one example from the
bryophytes.
Polytrichum (from the Mosses phylum):
The dominant generation of this plant, like that of all bryophytes, is the
gametophyte. The life cycle is shown in figure 1.
Figure 1: Life cycle
of Polytrichum a
true moss (from
OpenStax Biology)
9-2
The gametophyte has gametangia, which are gamete-producing organs. The
gametangium that produces eggs is called the archegonium. The one that
produces sperm is the antheridium. Archegonia and antheridia are often on
separate plants.
The egg in the archegonium will be fertilized by a sperm cell from an
antheridium. The fertilized egg then becomes a zygote, which develops first
into an embryo and then into a sporophyte. The sporophyte stays attached to
the gametophyte and draws food from it. The sporophyte forms spores (in a
sporangium) from which new gametophytes develop.
Draw, name the plant and label the parts
1. Polytrichum gametophyte
1. Plant name:
2. Archegonium (eggproducing structure of
gametophyte; microscope
slide). Draw the tip of a
female gametophyte, and
label the archegonia.
2. Plant name and part:
9-3
3. Antheridium (spermproducing structure of
gametophyte; microscope
slide). Draw the tip of a male
gametophyte, and label the
antheridia.
3. Plant name and part:
4. Sporophyte with
sporangium. Label the
sporophyte and the
sporangium (the sporeproducing structure). Notice
that the sporophyte is
attached to a gametophyte.
4. Plant name and part:
2. Vascular seedless plants
These plants have true vascular tissue (phloem and xylem). The dominant
phase of their life cycle is the sporophyte (see figure 2). This phase does not
remain attached to the gametophyte, but is completely independent. The
gametophyte lacks vascular tissue. The seedless vascular plants need a
watery environment so its sperm with flagella can reach the eggs.
The classification of the vascular seedless plants forms the subject of a
continuous debate among plant biologists. Currently, two phyla are
recognized within this group, the lycophytes and the monilophytes.
9-4
2A. Phylum of the Lycophytes (Club mosses, spike mosses and
quillworts)
5. Club moss (Lycopodium
sp.). Draw and label the
sporophyte with strobilus with
sporangia. A strobilus is a
cluster of sporangia
5. Plant name:
2B. Phylum of the Monilophytes (Whisk ferns, Horsetails and
Ferns)
6. Horsetail (Equisetum
spec.). Draw and label the
sporophyte with strobilus
6. Plant name
9-5
FIGURE 25.22
This life cycle of a fern shows alternation of generations with a dominant sporophyte
stage. (credit “fern”: modification of work by Cory Zanker; credit “gametophyte”:
modification of work by “Vlmastra”/Wikimedia Commons)
Figure 2: Life cycle of a fern (from OpenStax Biology)
7. Draw an example of a fern
(the sporophyte) like:
Polypodium polypodioides,
Matteuccion struthiopteris
(ostrich fern), or Lemon baton
fern
7. Plant name:
9-6
8. Fern gametophyte:
Label the prothallium (which
is the gametophyte) with
archegonia and antheridia
(microscope slide).
8. Plant name:
B. THE SEED PLANTS
Introduction
The alternation of generations characterizes all plants, including the seed
plants. The sporophyte is the dominant generation in seed plants. The
gametophyte is reduced to a group of cells that for a long time were not
recognized as representing the haploid phase in the plant’s life cycle.
The seed plants show heterospory. They produce two types of spores,
microspores, and macrospores. Microspores are formed in the male
sporangia on the sporophyte. They become pollen grains, which represent
small sperm-bearing male gametophytes.
The female sporangium of the sporophyte is called the ovule. The ovule
develops a macrospore which develops into a female gametophyte with egg.
The gametophyte remains in the ovule. The egg will be fertilized by a sperm
that is delivered through a pollen grain. The fertilized egg develops into an
embryo. At the same time, the ovule develops into a seed. The seed serves
as protection for the embryo. It also contains food for the embryo. The seed
is naked in some groups of seed plants, the Gymnosperms: it is not covered
by a fruit. In other seed plants, the Angiosperms, the seed is covered. It is
encapsulated in a fruit.
The first gymnosperm seed plants evolved in the Devonian period about 360
million years ago. They do not become dominant until the Mesozoic Era (the
Era of the Gymnosperms). The angiosperms, with fruits and flowers, evolved
during the Mesozoic. They are now the dominant group of plants on earth.
9-7
1. GYMNOSPERMS
The dominant generation of the gymnosperms, or “naked-seed” plants, is the
sporophyte (2n) (figure 3). Gymnosperms are heterosporous. The male and
female spore-producing organs (sporangia, resp. ovules) develop within male
and female cones (or strobili) on the sporophyte. Botanists consider the
scales of the cones as leaf like structures (sporophylls) that bear sporeproducing sporangia. The seeds are”naked”, not covered, and are borne
totally exposed on the scales of the female cones.
Figure 3: Life cycle
of a conifer (from
OpenStax Biology)
Male cone (or strobilus)
Each scale of the male cone produces sporangia (named: male sporangium
or microsporangium). Meiosis takes place in the sporangia, leading to haploid
spores (microspores, n). A spore develops into a gametophyte (n).
The male gametophyte is very small and is named pollen grain. The pollen
grain (and therefore the entire gametophyte) is distributed by wind or
animals. Pollen will enter the ovule on a female cone.
9-8
Female cone (or strobilus)
Each scale of the female cone has two ovules. Each ovule is a sporangium
(named: female sporangium or megasporangium). Meiosis takes place in the
sporangium, leading to four megaspores (n). One of these spores develops
into a gametophyte (the female or macro gametophyte) (n). The other three
megaspores degenerate. A gametangium, or archegonium, develops on the
gametophyte. An egg develops within the gametangium.
Fertilization
The male gametophyte, or pollen grain, develops a sperm cell, after it lands
on the female sporangium. The egg is fertilized by the sperm and becomes
the zygote (2n). The zygote develops into an embryo. Fertilization and
embryo development takes place within the ovule. The ovule becomes the
seed.
The gymnosperms contain four living phyla.
1. PHYLUM CYCADOPHYTA
2. PHYLUM GINKGOPHYTA
3. PHYLUM GNETOPHYTA (no example in this lab)
4. PHYLUM CONIFEROPHYTA (or PINOPHYTA)
9. Phylum Cycadophyta
Cycad sporophyte
10. Phylum Ginkgophyta
Ginkgo sporophyte
4. PHYLUM CONIFEROPHYTA (or PINOPHYTA)
Draw, name plant and object and label the parts
11. Pinus sp. sporophyte
12. Pinus: male cone
13: Pinus: male gametophyte (pollen grain) (microscope slide)
14. Pinus: female cone
9-9
15. Pinus:
16. Pinus:
detail of female gametophyte (microscope slide); label
the gametophyte, archegonium and egg
pine seed with embryo
11.
12.
13.
14.
15.
16.
9 – 10
2. ANGIOSPERMS (OR FLOWERING PLANTS)
The dominant generation of the angiosperms, or “covered-seed” plants, is
the sporophyte (2n) (figure 4). They reproduce sexually by forming flowers
(with the reproductive organs, figure 5), and seeds within fruits.
Figure 4: Life
cycle of a
flowering plant
(from OpenStax
Biology)
Angiosperms are heterosporous. They produce female spores (megaspores),
and male spores (microspores). The gametophyte (n) is much reduced. A
distinction exists between the female gametophyte and the male
gametophyte. The female gametophyte develops on the sporophyte. The
male gametophyte develops into a pollen grain that is shed from the anther.
The reproductive organs of flowering plants can be found in the flower of the
sporophyte.
9 – 11
Figure 5: A perfect
flower (from
OpenStax Biology)
Stamen
The flower contains stamen with anthers. Each anther contains male
sporangia. They produce haploid spores through meiosis. Each spore
develops into a minuscule male gametophyte: the pollen grain. The male
gametophyte (n) does not produce a gametangium (or antheridium).
Carpel
The female reproductive structure is the carpel. The carpel contains the
ovary with the ovules. Meiosis in the ovule produces female haploid spores. A
spore becomes the female gametophyte or embryo sac (n). No gametangium
(or archegonium) is formed. The entire gametophyte is made up of only a
few cells. All cells are haploid. One of the cells becomes the egg.
9 – 12
Fertilization
The pollen is brought to the female part of a flower by wind or animal. The
pollen germinates, develops two sperm nuclei that move through the pollen
tube to the female gametophyte in an ovule. One sperm nucleus fuses with
the egg, forming a zygote (2n). The zygote becomes the embryo. The other
sperm nucleus fuses with the two nuclei of the central cell of the female
gametophyte. This triploid nucleus with cytoplasm becomes the endosperm,
which serves as food for the embryo. Because of these two fertilization
events, flowering plants are said to have double fertilization. The outer part
of the ovule becomes the seed coat after fertilization. The ovary becomes the
fruit after fertilization of the egg.
The angiosperms contain one phylum.
PHYLUM ANTHOPHYTA (or MAGNOLIOPHYTA)
This phylum is the largest of the Plant Kingdom with 260,000 species. The
variety among the flowering plants is enormous, from very small (the 1 mm
large Wolffia) to very large (some 130 m tall Eucalyptus), with pretty colorful
flowers (like many orchids) or with inconspicuous flowers (like those of many
grasses). The classification of all flowering plants is still the subject of a very
active field of research and biologists are learning more and more about how
all these flowering plants are related.
Draw, name plant and object and label the parts:
17. Lilium:
label the flower parts: sepals, petals, stamen
(filament plus anther), carpels (stigma, stylus, and
ovary)
18. Lilium:
anther with pollen (microscope slide)
19. Lilium:
cross section through ovary with ovules (prepared
slide)
20. Bean:
seed (bean) with embryo
9 – 13
17. Flower of Lily
18.
19.
20.
9 – 14
8. Protists
Objectives
1. Become familiar with and draw examples of protists
2. Understand the unique position of the protists within the Domain Eukarya
Introduction
The protists are a very diverse group of organisms that can be found in
many different environments. They are all eukaryotic organisms, they have
a nucleus in each of their cells (and some even more than one). The first
eukaryotic organism was a protist. From this protist all other eukaryotes
evolved. Therefore, all eukaryotic organisms form a natural group (or, as
present-day systematics would say, a monophyletic group or clade), which
is named the Domain Eukarya (figure 1). A natural group of organisms is a
group of organisms that are closely related through a shared evolutionary
history (or phylogeny). They can be traced back to a common ancestor.
Within the Domain Eukarya are nested other smaller but well-defined
monophyletic groups. These are the plants (Kingdom Plantae), animals
(Kingdom Animalia) and fungi (Kingdom Fungi), each with their own
evolutionary history (phylogeny). For instance, all present-day plants are
related to each other as they all share a common ancestor, the first plant.
They share an evolutionary history that goes back to the first plant. The
same is true for the fungi and animals. Biologists base their classification
system on the establishment of these natural groups or monophyletic
clades.
It has been very difficult to establish natural groups for the rest of the
eukaryotes. Therefore they have been lumped into the group called protists
(everything that is not an animal, plant or fungus). They were even elevated
to the status of Kingdom. We can no longer do this as they do not confirm to
the definition of a natural group. Now we refer to them with the more
informal name protists (with a small letter p). Of course, all protists are
linked to a common ancestor, and are part of a natural group. That group is
called the Domain Eukarya. To that group also belong the Kingdoms of
Plants, Animals and Fungi. Therefore the protists as a whole cannot be
referred to as a Kingdom itself (as it would include other Kingdoms).
Biologists are hard at work trying to define groups within the protists that
share evolutionary histories. Many characteristics of the organisms,
including DNA sequences, are used to establish these natural groups.
Progress has been made and some proposals have been published to
classify the protists (like figure 1). If you look at the right side of figure 1,
you’ll see Land plants, Fungi and Animals. These are the well-defined 3
Kingdoms. You also see many other names at the same level as these 3
kingdoms, like Diplomonads, Parabasilids, etcetera. Should all these groups
8-1
on the right side of figure 1 now also be considered Kingdoms? That’s the
question that is being debated among biologists. There is a lot of
disagreement about this. Some of these groups are small and some are not
completely supported by enough scientific evidence. We also have to deal
with tradition, as names like protists have been in use for many years. A
new hierarchical level has been introduced called Supergroups to sort of
structure the discussion around groups of organisms about which there is
some agreement. It is very likely that these 6 Supergroups within
themselves are monophyletic (well-defined clades). The position of
Supergroups is between Domain and Kingdom.
This lab is organized around these Supergroups to recognize the progress
that’s been made in classifying Eukarya according to the rules of
Classification or Systematics based on phylogeny.
You will have to draw examples of organisms of each of the Supergroups
(except plants, animals and fungi that will be covered in separate labs).
Some examples are on ready-made slides, others are in little jars that
contain live organisms (make a wet mount for those). Ask your instructor
for guidance in determining the names of the organisms (see also Fig. 2 at
the end of this lab chapter). Write the name of the organism above your
drawing. It helps you to memorize and spell the name of the organism.
8-2
Figure 1 Evolutionary tree (cladogram) of the Eukaryotes showing 6 Supergroups (names on the
right). The Plant, Animal and Fungi Kingdoms fall within the Supergroups. No consensus exists
about the position, level in the hierarchy, of the other groups. (From Biology by OpenStax).
8-3
1. SUPERGROUP EXCAVATA
These are single-celled organisms that all have a groove “excavated” on
their side. There is one example from this group.
1. Euglena:
The example is a photosynthetic euglena. The group to which Euglena
belongs (the Euglenozoans) also has heterotrophic, parasitic and
mixotrophic species. Our Euglena got its chloroplast through
secondary endosymbiosis of a green alga.
1. Name:
2. SUPERGROUP CHROMALVEOLATA
The Chromalveolata are divided into two well-defined groups that are strong
candidates to once be called kingdoms: the Alveolates and the
Straminopiles.
2.1
Alveolates
The Alveolates have an alveolus, a membrane-enclosed sac, beneath the cell
membrane. Two examples:
2. Dinoflagellate:
Dinoflagellates are unicellular, mostly photoautotroph algae. Some
are chemoautotrophic or chemoheterotrophic. They are covered with
plates made of cellulose. They have two flagella in perpendicular
grooves, producing a spinning movement of the organism. We have a
prepared slide for this organism.
3. Paramecium
Paramecium belongs to the group of ciliates, a group of mostly
unicellular protists characterized by the presence of many hair-like
cilia. They use these cilia to move and feed. We have live specimen of
this organism. Make a wet mount of a Paramecium as an example of
a ciliate protist and draw the organism.
8-4
2.Name:
3.Name
2.2 Straminopiles
The Straminopiles include photosynthetic single-celled and multicellular
algae and heterotrophic species. Two examples from this group:
4. Diatom
Diatoms are unicellular photosynthetic algae with cell walls made of
silica. The cell wall consists of two halves that fit together like the
bottom and lid of a box (or like the two halves of a petri dish). Some
form multicellular colonies. Our examples of diatoms are on a
prepared slide.
5. Brown alga: Rockweed (Ascophyllum)
Brown algae are multicellular algae. They are referred to, together
with the red algae and marine multicellular green algae, as seaweeds.
Some are very large and abundant along the edges of the oceans
where they form so-called forests of the sea. However, they are not
plants and lack true stems, leaves, roots, and a vascular system.
4.Name:
5. Name:
8-5
3. SUPERGROUP RHIZARIA
Rhizarians are unicellular heterotrophic protists that have tiny shells made of
calcium carbonate (in the foraminifers) or of glassy silica (in the
radiolarians). The shells contain tiny pores through which thread-like
pseudopodia extend that trap food particles. The shells fossilize very well
and can accumulate to tens of meters of sediment in the world’s oceans.
They are important in geologic studies and in climate reconstruction. The
O18/O16 ratios of oxygen isotopes in the CaCO3 of the foraminifer shells are
indicators of former temperatures. This isotope record plays an important
role in climate reconstruction.
6. Foraminifers
We have a ready-made slide with a mix of forams.
7. Radiolarians
We have a ready-made slide with a mix of radiolarians.
6.Name:
7.Name:
4. SUPERGROUP ARCHAEPLASTIDA
The Archaeplastida are the red algae, green algae and land plants. These
are all organisms that got their chloroplasts through primary endosymbiosis
of cyanobacteria. There are some indications that the red algae were the
first organisms with chloroplasts. Green algae and land plants must have
evolved from them. For some biologists, this is a reason to group the red
algae, green algae and land plants together in the Kingdom Plantae (Plants).
Many other biologists would like to reserve the name Kingdom Plantae to
the land plants, because of tradition and because the land plants are readily
recognizable. Another reason is that all land plants have an embryo as an
early developmental stage that is protected by the parent plant. Red and
green algae do not have that. They release their gametes in the water
where fertilization and development of the young alga takes place. Another
Kingdom name has been suggested for the land plants: Kingdom
Embryophyta. If red and green algae were to be included in the plant
8-6
kingdom, then we might want to use the name Kingdom Archaeplastida.
Biologists have not reach consensus about this matter. To be continued!
8. Red Algae
Some red algae are typically soft-bodied multicellular protists. Others
have walls encrusted with hard chalky deposits. Those are common on
coral reefs.
We have a preserved red alga named Chondrus crispus (“Irish moss”).
(Another red alga you may have heard of is nori, which is the dried
version of the red alga Porphyra and used in making sushi.)
9, 10 and 11. Green Algae
Many green algae are plant-like in even more respects than red algae.
Like plants, they photosynthesize using pigments chlorophyll a and b,
have starch and have cell walls with cellulose. Many green algae are
unicellular, others are colonial, while others are truly multicellular.
You have to draw 3 examples of unicellular or colonial green algae
from a jar with live phytoplankton.
The term plankton refers to tiny organisms. Phytoplankton are tiny
photosynthetic organisms like the single celled or colonial green algae
discussed here. Zooplankton includes single celled heterotrophic
protists and multicellular larval stages of some animals like the larvae
of arthropods like crabs.
Examples of algae that could be present in our live samples are:
Chlamydomonas, Desmid, Pediastrum, Hydrodictyon (water net),
Scenedesmus, Cosmarium, and Volvox. Ask your instructor for help in
identifying the green algae or use figure 2 at the end of this lab
chapter.
You also have to draw a multicellular alga.
12. Ulva
Ulva or sea lettuce is a multicellular marine alga
The land plants are covered by Lab topic 9.
8. Name:
9. Name
8-7
10. Name
11. Name
12. Name
5. SUPERGROUP AMOEBOZOA
All organisms in this group have a single-celled amoeba-like stage in their
life. This stage is a flexible cell that moves and feeds through the formation
of pseudopodia. These are temporary cytoplasm-filled projections of the cell
membrane. Some of the Amoebozoa remain single-celled their entire life
(the amoebas), others congregate into large multinuclear single cells, and
other congregate into multicellular slimy masses (the slime molds).
13. Amoeba
Most amoebas have a soft-bodied cell. They move and feed by means
of pseudopodia. There is a jar with live amoebas. Make a slide of a live
amoeba. They are quite large and can be found using the scanning lens
(4x objective). They move very slowly.
14. Plasmodial slime mold
Slime molds are somewhat similar to fungi because of the filamentous
feeding structures that they sometimes form. All similarities end there.
Slime molds are not fungi.
This organism has both a unicellular and multicellular life stage. The
unicellular amoeboid cells can congregate into a large multinuclear
mass of cytoplasm. This stage can form reproductive structures.
Draw the colony of a live slime mold growing on oatmeal.
8-8
13. Name:
14. Name:
6. SUPERGROUP OPISTHOKONTA
The Opisthokonta contain the Kingdoms of Fungi and Animals plus some
smaller groups like the choanoflagellates. One common aspect of these
organisms is the presence of a posterior flagellum sometimes in their live.
Posterior means that the flagellum is at the back or hind end of the
organism. An example is the sperm cell of the animals. A flagellum is
present in some fungi, the chytrids, but has been lost in other fungi. The
close relatedness of fungi and animals has been recognized only recently in
article published in 1987. The choanoflagellates are very similar to the
choanocytes of the sponges (animals).
There are no examples of Opisthokonta in this lab. We’ll dedicate separate
labs to the fungi and animals.
8-9
Fig. 2. Some Common Freshwater Plankton
8 – 10
Lab 8: Protists
Here are photos of organisms that were to be viewed on slides and a link to a
video of larger specimens.
Feel free to supplement these images with your own search in Google Images and
YouTube.
Make sure you read through the introduction provided in the lab packet before
you begin so that you have some idea about what you’re looking at.
Make your drawings of the organisms (with names) on a separate sheet of paper
that you can photograph and upload to the Lab 8 Assignment folder on D2L.
Link to YouTube video for part of the lab exercises:
1. Supergroup Excavata
1. Euglena
This Photo by Unknown Author is licensed under CC BY-SA
2. Supergroup Chromalveolata
2.1. Alveolates
2. Dinoflagellate
This Photo by Unknown Author is licensed under CC BY-SA
2. Supergroup Chromalveolata
2.1. Alveolates
3. Paramecium
2. Supergroup Chromalveolata
2.2. Stramenopiles
4. Diatoms
(5. Rockweed: dried specimen in video)
3. Supergroup Rhizaria
6. Foraminifers
3. Supergroup Rhizaria
7. Radiolarians
4. Supergroup Archaeplastida
Green Algae
9. Scenedesmus
4. Supergroup Archaeplastida
Green Algae
10. Volvox
This Photo by Unknown Author is licensed
under CC BY-SA-NC
5. Supergroup Amoebozoa
13. Amoeba
Purchase answer to see full
attachment
Introduction
Plants are eukaryotic, multicellular, photosynthetic organisms. Another
characteristic that all plants share is their mode of sexual reproduction.
Diploid plants produce haploid cells through meiosis. These haploid cells are
however not called gametes, but spores. The reason for this is the fact that
these haploid cells do not need to fuse with another haploid cell (like the
gametes, sperm and egg, of animals through the process of fertilization), but
can survive on their own. In plants, the haploid spores will go through
multiple rounds of mitosis to form multicellular haploid organisms. It is this
haploid multicellular generation of plants that will produce gametes (via
mitosis). Those gametes then fuse to form an embryo and the next diploid
plant generation.
This is the so-called Alternation of Generations of plants. The plant’s life cycle
is an alternation of a haploid generation and a diploid generation. The haploid
generation is referred to as the gametophyte (the plant that forms gametes).
The gametophyte produces gametes (sperm and egg cells), which fuse
(fertilization) to form a diploid zygote. The zygote develops into an embryo
while enclosed in maternal tissue (another name for plants is Embryophytes).
The embryo develops into a mature diploid plant, called the sporophyte (the
plant that forms spores). The sporophyte then again forms haploid spores,
through meiosis, which will develop into haploid gametophytes, completing
the life cycle of the plant.
Special attention shall be paid to this alternation of generations while
observing all plant objects. How would you know by looking at a plant, if
you’re observing the diploid stage (sporophyte) or the haploid stage
(gametophyte) of a plant? The answer depends on which phylum of plants
you’re observing. For most plants, the sporophyte is the dominant phase.
When you see a fern or a rose, or a maple tree, you’re looking at the
sporophyte. Their gametophytes are really small and cannot be observed
without a microscope and, in many cases, without dissecting parts of the
sporophyte. Only mosses have gametophytes that can be observed with the
naked eye. Those are relatively large and green. Sporophytes of mosses are
relatively small and not green. In the course of plant evolution we see a shift
from plants that have haploid gametophytes as the dominant part of the life
cycle towards plants that have diploid sporophytes as the dominant part of
the life cycle.
The Kingdom of Plants has 10 phyla with living representatives. Of these
phyla, 5 are combined as the seedless plants. Their reproduction is
characterized by gametes and spores only. The seed plants, represented by 5
phyla, all have gametes, spores and seeds as part of their reproduction.
9-1
A. THE SEEDLESS PLANTS
1. Non-vascular seedless plants or bryophytes
The plants in this group have leaf-like, stem-like, and root-like structures
without vascular tissue, i.e. they lack phloem and xylem (no “plumbing
system”). The dominant phase of their life cycle is the gametophyte. The
sporophyte starts its development inside tissue of the gametophyte. It
remains attached to the gametophyte, and gains some nutrition from it.
There are about 24,000 species of bryophytes divided over three phyla:
liverworts, mosses and hornworts. We’ll look at one example from the
bryophytes.
Polytrichum (from the Mosses phylum):
The dominant generation of this plant, like that of all bryophytes, is the
gametophyte. The life cycle is shown in figure 1.
Figure 1: Life cycle
of Polytrichum a
true moss (from
OpenStax Biology)
9-2
The gametophyte has gametangia, which are gamete-producing organs. The
gametangium that produces eggs is called the archegonium. The one that
produces sperm is the antheridium. Archegonia and antheridia are often on
separate plants.
The egg in the archegonium will be fertilized by a sperm cell from an
antheridium. The fertilized egg then becomes a zygote, which develops first
into an embryo and then into a sporophyte. The sporophyte stays attached to
the gametophyte and draws food from it. The sporophyte forms spores (in a
sporangium) from which new gametophytes develop.
Draw, name the plant and label the parts
1. Polytrichum gametophyte
1. Plant name:
2. Archegonium (eggproducing structure of
gametophyte; microscope
slide). Draw the tip of a
female gametophyte, and
label the archegonia.
2. Plant name and part:
9-3
3. Antheridium (spermproducing structure of
gametophyte; microscope
slide). Draw the tip of a male
gametophyte, and label the
antheridia.
3. Plant name and part:
4. Sporophyte with
sporangium. Label the
sporophyte and the
sporangium (the sporeproducing structure). Notice
that the sporophyte is
attached to a gametophyte.
4. Plant name and part:
2. Vascular seedless plants
These plants have true vascular tissue (phloem and xylem). The dominant
phase of their life cycle is the sporophyte (see figure 2). This phase does not
remain attached to the gametophyte, but is completely independent. The
gametophyte lacks vascular tissue. The seedless vascular plants need a
watery environment so its sperm with flagella can reach the eggs.
The classification of the vascular seedless plants forms the subject of a
continuous debate among plant biologists. Currently, two phyla are
recognized within this group, the lycophytes and the monilophytes.
9-4
2A. Phylum of the Lycophytes (Club mosses, spike mosses and
quillworts)
5. Club moss (Lycopodium
sp.). Draw and label the
sporophyte with strobilus with
sporangia. A strobilus is a
cluster of sporangia
5. Plant name:
2B. Phylum of the Monilophytes (Whisk ferns, Horsetails and
Ferns)
6. Horsetail (Equisetum
spec.). Draw and label the
sporophyte with strobilus
6. Plant name
9-5
FIGURE 25.22
This life cycle of a fern shows alternation of generations with a dominant sporophyte
stage. (credit “fern”: modification of work by Cory Zanker; credit “gametophyte”:
modification of work by “Vlmastra”/Wikimedia Commons)
Figure 2: Life cycle of a fern (from OpenStax Biology)
7. Draw an example of a fern
(the sporophyte) like:
Polypodium polypodioides,
Matteuccion struthiopteris
(ostrich fern), or Lemon baton
fern
7. Plant name:
9-6
8. Fern gametophyte:
Label the prothallium (which
is the gametophyte) with
archegonia and antheridia
(microscope slide).
8. Plant name:
B. THE SEED PLANTS
Introduction
The alternation of generations characterizes all plants, including the seed
plants. The sporophyte is the dominant generation in seed plants. The
gametophyte is reduced to a group of cells that for a long time were not
recognized as representing the haploid phase in the plant’s life cycle.
The seed plants show heterospory. They produce two types of spores,
microspores, and macrospores. Microspores are formed in the male
sporangia on the sporophyte. They become pollen grains, which represent
small sperm-bearing male gametophytes.
The female sporangium of the sporophyte is called the ovule. The ovule
develops a macrospore which develops into a female gametophyte with egg.
The gametophyte remains in the ovule. The egg will be fertilized by a sperm
that is delivered through a pollen grain. The fertilized egg develops into an
embryo. At the same time, the ovule develops into a seed. The seed serves
as protection for the embryo. It also contains food for the embryo. The seed
is naked in some groups of seed plants, the Gymnosperms: it is not covered
by a fruit. In other seed plants, the Angiosperms, the seed is covered. It is
encapsulated in a fruit.
The first gymnosperm seed plants evolved in the Devonian period about 360
million years ago. They do not become dominant until the Mesozoic Era (the
Era of the Gymnosperms). The angiosperms, with fruits and flowers, evolved
during the Mesozoic. They are now the dominant group of plants on earth.
9-7
1. GYMNOSPERMS
The dominant generation of the gymnosperms, or “naked-seed” plants, is the
sporophyte (2n) (figure 3). Gymnosperms are heterosporous. The male and
female spore-producing organs (sporangia, resp. ovules) develop within male
and female cones (or strobili) on the sporophyte. Botanists consider the
scales of the cones as leaf like structures (sporophylls) that bear sporeproducing sporangia. The seeds are”naked”, not covered, and are borne
totally exposed on the scales of the female cones.
Figure 3: Life cycle
of a conifer (from
OpenStax Biology)
Male cone (or strobilus)
Each scale of the male cone produces sporangia (named: male sporangium
or microsporangium). Meiosis takes place in the sporangia, leading to haploid
spores (microspores, n). A spore develops into a gametophyte (n).
The male gametophyte is very small and is named pollen grain. The pollen
grain (and therefore the entire gametophyte) is distributed by wind or
animals. Pollen will enter the ovule on a female cone.
9-8
Female cone (or strobilus)
Each scale of the female cone has two ovules. Each ovule is a sporangium
(named: female sporangium or megasporangium). Meiosis takes place in the
sporangium, leading to four megaspores (n). One of these spores develops
into a gametophyte (the female or macro gametophyte) (n). The other three
megaspores degenerate. A gametangium, or archegonium, develops on the
gametophyte. An egg develops within the gametangium.
Fertilization
The male gametophyte, or pollen grain, develops a sperm cell, after it lands
on the female sporangium. The egg is fertilized by the sperm and becomes
the zygote (2n). The zygote develops into an embryo. Fertilization and
embryo development takes place within the ovule. The ovule becomes the
seed.
The gymnosperms contain four living phyla.
1. PHYLUM CYCADOPHYTA
2. PHYLUM GINKGOPHYTA
3. PHYLUM GNETOPHYTA (no example in this lab)
4. PHYLUM CONIFEROPHYTA (or PINOPHYTA)
9. Phylum Cycadophyta
Cycad sporophyte
10. Phylum Ginkgophyta
Ginkgo sporophyte
4. PHYLUM CONIFEROPHYTA (or PINOPHYTA)
Draw, name plant and object and label the parts
11. Pinus sp. sporophyte
12. Pinus: male cone
13: Pinus: male gametophyte (pollen grain) (microscope slide)
14. Pinus: female cone
9-9
15. Pinus:
16. Pinus:
detail of female gametophyte (microscope slide); label
the gametophyte, archegonium and egg
pine seed with embryo
11.
12.
13.
14.
15.
16.
9 – 10
2. ANGIOSPERMS (OR FLOWERING PLANTS)
The dominant generation of the angiosperms, or “covered-seed” plants, is
the sporophyte (2n) (figure 4). They reproduce sexually by forming flowers
(with the reproductive organs, figure 5), and seeds within fruits.
Figure 4: Life
cycle of a
flowering plant
(from OpenStax
Biology)
Angiosperms are heterosporous. They produce female spores (megaspores),
and male spores (microspores). The gametophyte (n) is much reduced. A
distinction exists between the female gametophyte and the male
gametophyte. The female gametophyte develops on the sporophyte. The
male gametophyte develops into a pollen grain that is shed from the anther.
The reproductive organs of flowering plants can be found in the flower of the
sporophyte.
9 – 11
Figure 5: A perfect
flower (from
OpenStax Biology)
Stamen
The flower contains stamen with anthers. Each anther contains male
sporangia. They produce haploid spores through meiosis. Each spore
develops into a minuscule male gametophyte: the pollen grain. The male
gametophyte (n) does not produce a gametangium (or antheridium).
Carpel
The female reproductive structure is the carpel. The carpel contains the
ovary with the ovules. Meiosis in the ovule produces female haploid spores. A
spore becomes the female gametophyte or embryo sac (n). No gametangium
(or archegonium) is formed. The entire gametophyte is made up of only a
few cells. All cells are haploid. One of the cells becomes the egg.
9 – 12
Fertilization
The pollen is brought to the female part of a flower by wind or animal. The
pollen germinates, develops two sperm nuclei that move through the pollen
tube to the female gametophyte in an ovule. One sperm nucleus fuses with
the egg, forming a zygote (2n). The zygote becomes the embryo. The other
sperm nucleus fuses with the two nuclei of the central cell of the female
gametophyte. This triploid nucleus with cytoplasm becomes the endosperm,
which serves as food for the embryo. Because of these two fertilization
events, flowering plants are said to have double fertilization. The outer part
of the ovule becomes the seed coat after fertilization. The ovary becomes the
fruit after fertilization of the egg.
The angiosperms contain one phylum.
PHYLUM ANTHOPHYTA (or MAGNOLIOPHYTA)
This phylum is the largest of the Plant Kingdom with 260,000 species. The
variety among the flowering plants is enormous, from very small (the 1 mm
large Wolffia) to very large (some 130 m tall Eucalyptus), with pretty colorful
flowers (like many orchids) or with inconspicuous flowers (like those of many
grasses). The classification of all flowering plants is still the subject of a very
active field of research and biologists are learning more and more about how
all these flowering plants are related.
Draw, name plant and object and label the parts:
17. Lilium:
label the flower parts: sepals, petals, stamen
(filament plus anther), carpels (stigma, stylus, and
ovary)
18. Lilium:
anther with pollen (microscope slide)
19. Lilium:
cross section through ovary with ovules (prepared
slide)
20. Bean:
seed (bean) with embryo
9 – 13
17. Flower of Lily
18.
19.
20.
9 – 14
8. Protists
Objectives
1. Become familiar with and draw examples of protists
2. Understand the unique position of the protists within the Domain Eukarya
Introduction
The protists are a very diverse group of organisms that can be found in
many different environments. They are all eukaryotic organisms, they have
a nucleus in each of their cells (and some even more than one). The first
eukaryotic organism was a protist. From this protist all other eukaryotes
evolved. Therefore, all eukaryotic organisms form a natural group (or, as
present-day systematics would say, a monophyletic group or clade), which
is named the Domain Eukarya (figure 1). A natural group of organisms is a
group of organisms that are closely related through a shared evolutionary
history (or phylogeny). They can be traced back to a common ancestor.
Within the Domain Eukarya are nested other smaller but well-defined
monophyletic groups. These are the plants (Kingdom Plantae), animals
(Kingdom Animalia) and fungi (Kingdom Fungi), each with their own
evolutionary history (phylogeny). For instance, all present-day plants are
related to each other as they all share a common ancestor, the first plant.
They share an evolutionary history that goes back to the first plant. The
same is true for the fungi and animals. Biologists base their classification
system on the establishment of these natural groups or monophyletic
clades.
It has been very difficult to establish natural groups for the rest of the
eukaryotes. Therefore they have been lumped into the group called protists
(everything that is not an animal, plant or fungus). They were even elevated
to the status of Kingdom. We can no longer do this as they do not confirm to
the definition of a natural group. Now we refer to them with the more
informal name protists (with a small letter p). Of course, all protists are
linked to a common ancestor, and are part of a natural group. That group is
called the Domain Eukarya. To that group also belong the Kingdoms of
Plants, Animals and Fungi. Therefore the protists as a whole cannot be
referred to as a Kingdom itself (as it would include other Kingdoms).
Biologists are hard at work trying to define groups within the protists that
share evolutionary histories. Many characteristics of the organisms,
including DNA sequences, are used to establish these natural groups.
Progress has been made and some proposals have been published to
classify the protists (like figure 1). If you look at the right side of figure 1,
you’ll see Land plants, Fungi and Animals. These are the well-defined 3
Kingdoms. You also see many other names at the same level as these 3
kingdoms, like Diplomonads, Parabasilids, etcetera. Should all these groups
8-1
on the right side of figure 1 now also be considered Kingdoms? That’s the
question that is being debated among biologists. There is a lot of
disagreement about this. Some of these groups are small and some are not
completely supported by enough scientific evidence. We also have to deal
with tradition, as names like protists have been in use for many years. A
new hierarchical level has been introduced called Supergroups to sort of
structure the discussion around groups of organisms about which there is
some agreement. It is very likely that these 6 Supergroups within
themselves are monophyletic (well-defined clades). The position of
Supergroups is between Domain and Kingdom.
This lab is organized around these Supergroups to recognize the progress
that’s been made in classifying Eukarya according to the rules of
Classification or Systematics based on phylogeny.
You will have to draw examples of organisms of each of the Supergroups
(except plants, animals and fungi that will be covered in separate labs).
Some examples are on ready-made slides, others are in little jars that
contain live organisms (make a wet mount for those). Ask your instructor
for guidance in determining the names of the organisms (see also Fig. 2 at
the end of this lab chapter). Write the name of the organism above your
drawing. It helps you to memorize and spell the name of the organism.
8-2
Figure 1 Evolutionary tree (cladogram) of the Eukaryotes showing 6 Supergroups (names on the
right). The Plant, Animal and Fungi Kingdoms fall within the Supergroups. No consensus exists
about the position, level in the hierarchy, of the other groups. (From Biology by OpenStax).
8-3
1. SUPERGROUP EXCAVATA
These are single-celled organisms that all have a groove “excavated” on
their side. There is one example from this group.
1. Euglena:
The example is a photosynthetic euglena. The group to which Euglena
belongs (the Euglenozoans) also has heterotrophic, parasitic and
mixotrophic species. Our Euglena got its chloroplast through
secondary endosymbiosis of a green alga.
1. Name:
2. SUPERGROUP CHROMALVEOLATA
The Chromalveolata are divided into two well-defined groups that are strong
candidates to once be called kingdoms: the Alveolates and the
Straminopiles.
2.1
Alveolates
The Alveolates have an alveolus, a membrane-enclosed sac, beneath the cell
membrane. Two examples:
2. Dinoflagellate:
Dinoflagellates are unicellular, mostly photoautotroph algae. Some
are chemoautotrophic or chemoheterotrophic. They are covered with
plates made of cellulose. They have two flagella in perpendicular
grooves, producing a spinning movement of the organism. We have a
prepared slide for this organism.
3. Paramecium
Paramecium belongs to the group of ciliates, a group of mostly
unicellular protists characterized by the presence of many hair-like
cilia. They use these cilia to move and feed. We have live specimen of
this organism. Make a wet mount of a Paramecium as an example of
a ciliate protist and draw the organism.
8-4
2.Name:
3.Name
2.2 Straminopiles
The Straminopiles include photosynthetic single-celled and multicellular
algae and heterotrophic species. Two examples from this group:
4. Diatom
Diatoms are unicellular photosynthetic algae with cell walls made of
silica. The cell wall consists of two halves that fit together like the
bottom and lid of a box (or like the two halves of a petri dish). Some
form multicellular colonies. Our examples of diatoms are on a
prepared slide.
5. Brown alga: Rockweed (Ascophyllum)
Brown algae are multicellular algae. They are referred to, together
with the red algae and marine multicellular green algae, as seaweeds.
Some are very large and abundant along the edges of the oceans
where they form so-called forests of the sea. However, they are not
plants and lack true stems, leaves, roots, and a vascular system.
4.Name:
5. Name:
8-5
3. SUPERGROUP RHIZARIA
Rhizarians are unicellular heterotrophic protists that have tiny shells made of
calcium carbonate (in the foraminifers) or of glassy silica (in the
radiolarians). The shells contain tiny pores through which thread-like
pseudopodia extend that trap food particles. The shells fossilize very well
and can accumulate to tens of meters of sediment in the world’s oceans.
They are important in geologic studies and in climate reconstruction. The
O18/O16 ratios of oxygen isotopes in the CaCO3 of the foraminifer shells are
indicators of former temperatures. This isotope record plays an important
role in climate reconstruction.
6. Foraminifers
We have a ready-made slide with a mix of forams.
7. Radiolarians
We have a ready-made slide with a mix of radiolarians.
6.Name:
7.Name:
4. SUPERGROUP ARCHAEPLASTIDA
The Archaeplastida are the red algae, green algae and land plants. These
are all organisms that got their chloroplasts through primary endosymbiosis
of cyanobacteria. There are some indications that the red algae were the
first organisms with chloroplasts. Green algae and land plants must have
evolved from them. For some biologists, this is a reason to group the red
algae, green algae and land plants together in the Kingdom Plantae (Plants).
Many other biologists would like to reserve the name Kingdom Plantae to
the land plants, because of tradition and because the land plants are readily
recognizable. Another reason is that all land plants have an embryo as an
early developmental stage that is protected by the parent plant. Red and
green algae do not have that. They release their gametes in the water
where fertilization and development of the young alga takes place. Another
Kingdom name has been suggested for the land plants: Kingdom
Embryophyta. If red and green algae were to be included in the plant
8-6
kingdom, then we might want to use the name Kingdom Archaeplastida.
Biologists have not reach consensus about this matter. To be continued!
8. Red Algae
Some red algae are typically soft-bodied multicellular protists. Others
have walls encrusted with hard chalky deposits. Those are common on
coral reefs.
We have a preserved red alga named Chondrus crispus (“Irish moss”).
(Another red alga you may have heard of is nori, which is the dried
version of the red alga Porphyra and used in making sushi.)
9, 10 and 11. Green Algae
Many green algae are plant-like in even more respects than red algae.
Like plants, they photosynthesize using pigments chlorophyll a and b,
have starch and have cell walls with cellulose. Many green algae are
unicellular, others are colonial, while others are truly multicellular.
You have to draw 3 examples of unicellular or colonial green algae
from a jar with live phytoplankton.
The term plankton refers to tiny organisms. Phytoplankton are tiny
photosynthetic organisms like the single celled or colonial green algae
discussed here. Zooplankton includes single celled heterotrophic
protists and multicellular larval stages of some animals like the larvae
of arthropods like crabs.
Examples of algae that could be present in our live samples are:
Chlamydomonas, Desmid, Pediastrum, Hydrodictyon (water net),
Scenedesmus, Cosmarium, and Volvox. Ask your instructor for help in
identifying the green algae or use figure 2 at the end of this lab
chapter.
You also have to draw a multicellular alga.
12. Ulva
Ulva or sea lettuce is a multicellular marine alga
The land plants are covered by Lab topic 9.
8. Name:
9. Name
8-7
10. Name
11. Name
12. Name
5. SUPERGROUP AMOEBOZOA
All organisms in this group have a single-celled amoeba-like stage in their
life. This stage is a flexible cell that moves and feeds through the formation
of pseudopodia. These are temporary cytoplasm-filled projections of the cell
membrane. Some of the Amoebozoa remain single-celled their entire life
(the amoebas), others congregate into large multinuclear single cells, and
other congregate into multicellular slimy masses (the slime molds).
13. Amoeba
Most amoebas have a soft-bodied cell. They move and feed by means
of pseudopodia. There is a jar with live amoebas. Make a slide of a live
amoeba. They are quite large and can be found using the scanning lens
(4x objective). They move very slowly.
14. Plasmodial slime mold
Slime molds are somewhat similar to fungi because of the filamentous
feeding structures that they sometimes form. All similarities end there.
Slime molds are not fungi.
This organism has both a unicellular and multicellular life stage. The
unicellular amoeboid cells can congregate into a large multinuclear
mass of cytoplasm. This stage can form reproductive structures.
Draw the colony of a live slime mold growing on oatmeal.
8-8
13. Name:
14. Name:
6. SUPERGROUP OPISTHOKONTA
The Opisthokonta contain the Kingdoms of Fungi and Animals plus some
smaller groups like the choanoflagellates. One common aspect of these
organisms is the presence of a posterior flagellum sometimes in their live.
Posterior means that the flagellum is at the back or hind end of the
organism. An example is the sperm cell of the animals. A flagellum is
present in some fungi, the chytrids, but has been lost in other fungi. The
close relatedness of fungi and animals has been recognized only recently in
article published in 1987. The choanoflagellates are very similar to the
choanocytes of the sponges (animals).
There are no examples of Opisthokonta in this lab. We’ll dedicate separate
labs to the fungi and animals.
8-9
Fig. 2. Some Common Freshwater Plankton
8 – 10
Lab 8: Protists
Here are photos of organisms that were to be viewed on slides and a link to a
video of larger specimens.
Feel free to supplement these images with your own search in Google Images and
YouTube.
Make sure you read through the introduction provided in the lab packet before
you begin so that you have some idea about what you’re looking at.
Make your drawings of the organisms (with names) on a separate sheet of paper
that you can photograph and upload to the Lab 8 Assignment folder on D2L.
Link to YouTube video for part of the lab exercises:
1. Supergroup Excavata
1. Euglena
This Photo by Unknown Author is licensed under CC BY-SA
2. Supergroup Chromalveolata
2.1. Alveolates
2. Dinoflagellate
This Photo by Unknown Author is licensed under CC BY-SA
2. Supergroup Chromalveolata
2.1. Alveolates
3. Paramecium
2. Supergroup Chromalveolata
2.2. Stramenopiles
4. Diatoms
(5. Rockweed: dried specimen in video)
3. Supergroup Rhizaria
6. Foraminifers
3. Supergroup Rhizaria
7. Radiolarians
4. Supergroup Archaeplastida
Green Algae
9. Scenedesmus
4. Supergroup Archaeplastida
Green Algae
10. Volvox
This Photo by Unknown Author is licensed
under CC BY-SA-NC
5. Supergroup Amoebozoa
13. Amoeba
Purchase answer to see full
attachment
