Observations of Bryophytes (mosses)
Observe (Figure 19, pg 143) the moss life cycle diagram. Make observations from the various slides and specimens found on this tray.
I. External features.
A. Looking at the live
moss, make sure you identify the 'leafy' stage as well as the capsule and stalk.
Which stage of the life cycle do these structures represent?
B. Which stage appears to be more
dominant in this life cycle? Why?
C. Look at the moss capsule slide.
Name the structures inside the capsule. Are these produced from meiosis or
mitosis? What ploidy (N or 2N) level are these structures?
II. Internal structures of the gametophyte.
A. Polytrichum is a genus
of moss. Using the Polytrichum slide, observe the “leaves”.
1. How many layers of cells do you see? Why is this important?
Remember to compare this with 'true' leaves of ferns and angiosperms. What structures do the moss 'leaves' lack that fern or angiosperm leaves posses (if you haven't looked at the angiosperm slide yet, come back to this question later)?
There is space for you to draw a picture of what you see in Figure 18 on page 142.
2. What does it mean for the moss
to be “non-vascular”?
3. What is the function of these
leaf-like structures? How would a cuticle prevent moss 'leaves' from performing
their function?
B. Look at the moss
bulbils slide (bulbils are the ball-shaped things, mosses can reproduce asexually,
forming bulbils). The stringy filaments attached to the moss bulbils are the
rhizoids.
1. What is the function of rhizoids?
There is space for you to draw a picture of what you see in Figure 18 on page
142.
III. Reproductive structures.
A. Use the Moss archegonial head slide to find the female gamete producing
organ (archegonia) and eggs. Find these structures in the life cycle diagram
(Figures 18 and 19). What is the ploidy level of the arhchegonium and the eggs?
B. Using the moss sperm
slide, draw the multi-flagellated sperm. What is the ploidy level of these structures?
C. Once fertilization occurs a _____________
is formed. This structure is located on the top of the female gametophyte and
grows to become the_________________stage.
D. Do mosses produce seeds?
Observations of Ferns (and their allies)
Observe (Figure 15 pg 139) the fern life cycle diagram. Make observations from the various slides and specimens found on this tray, and the ferns located around the room.
I. External features.
A. Notice that ferns do
not have wood. Instead, they have a hard substance called lignin imbedded in
the cellulose matrix in the rhizome and “branch” of the fronds. Explain what
function lignin may have.
B. Using the live fern(s), locate
the frond, sorus, rhizome and roots. Draw a picture if it helps you to learn
the structures.
C. Is the frond the sporophyte or
gametophyte stage? In ferns, is this the dominant stage or less prevalent life
stage? How is this different from mosses?
II. Internal structures of frond,
stems and roots.
A. Using
the compound microscope and the Pteridium leaflet, examine part of the
frond. Locate the epidermis, stomata, cuticle, sporangium, xylem and phloem
(arranged in vascular bundles). Note that chloroplasts are also located in
the leaves and this is where photosynthesis occurs. There is space in Figure
14 on page 138 for you to draw a picture of what you see.
1. What is the function of the xylem
and phloem in this plant?
2. Where are the sori located on
the frond (top or bottom)? Why do you think this is important?
3. What is the function of the frond?
B. Using Figure 16 on page 140 as
your guide, observe the Pteridium rhizome (underground stem) with the
compound microscope. Find and observe the epidermis, xylem, phloem, inner cortex
and outer cortex.
C. Looking at the Pteridium
root slide and using Figure 17 on page 140 as a guide, find and observe the
epidermis, parenchyma cells, sclerenchyma cells, xylem and phloem. What functions
do these types of cells have? How can you tell the difference between xylem
and phloem cells (hint, they stain different colors)?
III. Reproductive structures.
A. Using figure 15 on page
139 as your guide, examine the fern antheridia and archegonia slide. These
are the reproductive structures that give rise to the “male” gametes (antheridia)
and the female gametes (archegonia).
1. On the prothallus, find
the antheridia, rhizoids and archegonia. This microscopic structure is which
stage of the fern life cycle and what ploidy level? How would you describe
the overall shape of the prothallus?
2. Observe and sraw the fern
sperm. What ploidy are these structures?
B. Once fertilization occurs a _________________
is formed. This structure is located in the archegonium on the prothallus and
grows to become the __________________________stage.
C. Do ferns produce seeds?
Observations of Gymnosperms
Observe Figure 9 (page 134) in the lab book. This is the gymnosperm life cycle. Make observations from the various slides and specimens found on this tray.
I. External features.
A. Woody trees are the
sporophyte state in gymnosperms. What are some functions of wood?
B. Are gymnosperm trees diploid or
haploid? Where is the gametophyte stage located on this organism?
C . Look at the live pine sapling and notice the characteristics of the needles.
These are modified leaves, which means they possess some of the common attributes
of a leaf. What internal structures would you expect to find in these needles
that would indicate they are really modified leaves?
II. Internal structures of needles, stems and roots.
A. Use the compound microscope,
Figure 10 on page 135, and the Pine five-needle leaf slide to examine the needles
more closely. Locate the xylem, phloem, cuticle, resin ducts and stomata.
Note that chloroplasts are also located in the needles and this is where photosynthesis
occurs.
1. What is the difference between
the epidermis and the cuticle? What is the function of the cuticle?
2. What is the function of the phloem
and the xylem in this plant?
3. What is special about the stomata
of this particular gymnosperm? Why do you think these stomata have this particular
morphology?
B. Using Figure 11 on page 135 and
pine stem slide, locate the resin ducts, primary and secondary xylem and secondary
phloem (vascular cambium). Primary growth elongates a stem while secondary
growth makes the stem larger (increases girth).
C. Look at the pine young root
slide. Using Figure 12 on page
136, identify the secondary xylem, secondary phloem, resin ducts and vascular
cambium. How is the internal structure of the root different or similar to
that of the stem?
1. Explain how the water gets
from the roots to the needles (hint, see Figure 36.1 on page 749 of the text
book).
III. Reproductive structures.
A. The cones
(part of the sporophyte) are the reproductive parts of the gymnosperms. The
microscopic female gametophyte is located inside the female cone (sporophyte).
Refer to lifecycle diagram (Fig. 9 page 134).
1. Using the pine archegonium
slide, locate the archegonium, egg and megagametophyte. What is the ploidy
of these labeled structures? Measure the size of the egg with your micrometer.
B. The microscopic microspores produce
the pollen, by meiosis. Pollen is released into the air. Using the pine mature
pollen slide, draw the pollen.
1. What do the pollen look
like? What does the pollen shape have to do with how it is dispersed? What
ploidy is the pollen?
C. Examine the pine seeds on the
tray. What stage (gametophyte or sporophyte) of the life cycle are these seeds?
Observations of Angiosperms
Observe the angiosperm life cycle diagram (Figure 4, pg 129). Make
observations from the various slides and specimens found on this tray.
I. External features.
A. Look at your tree sapling, what
external structures are visible (Figure 35.2, pg 722 in text book)? What defining
features of angiosperms (consider their common name) is missing in the sapling
that would be present in the adult (especially in the Spring)?
B.
Since this is the sporophyte, is this sapling diploid or haploid?
II. Internal structures of leaves, stems and roots.
There are two kinds of angiosperm plants: monocots and dicots. The two groups have differences in leaf, stem, and flower morphology
A. Using the compound microscope and the typical Monocot and Dicot leaves slide, locate the monocot leaf. There is space in Figure 3 on page 128 to make a sketch and label the xylem, phloem, upper and lower epidermis, mesophyll, cuticle, and stomata. Note that chloroplasts are also located in the leaves and this is where photosynthesis occurs.
1. What is the function of the xylem
and phloem in this plant?
2. How can you tell these two structures
apart based on staining?
B. Now find the dicot leaf (Fig. 35.19 on page 734 of the text). Locate and identify the upper and lower epidermis, mesophyll, cuticle, stomata, and guard cells. There is space in Figure 3 on page 128 to make a sketch of what you observe. Where are the vascular bundles located? Use the 40X objective to find them.
1. Compare the cross sections of
the monocot and dicot leaves. What are the similarities and differences? What
does the phrase 'monocot monkeyface' mean to you?
2. What is the function of a cuticle?
3. What do the stomata do?
4. What do the guard cells do?
5. What is the function of leaves
in an angiosperm?
C. Looking at the typical monocot and dicot stems slide, does this angiosperm (sporophyte) possess vascular tissue? Using Figure 5 on page 130 as well as the Monocot and Dicot stems slide, locate the sclerenchyma (fiber cells), epidermis, and vascular bundle for both stems.
1. For the monocot stem, focus on
the vascular bundle. Using the 40X objective locate and identify the xylem,
phloem, and sclerenchyma tissue. What is the function of the sclerenchyma tissue?
2. For the dicot stem, focus on one
of the vascular bundles with the 10X objective. Identifyl the xylem, phloem,
sclerenchyma tissue, and cambium.
3. What do you notice is different
between the two stem cross sections? Are the vascular bundles arranged in a
similar way?
D. Looking at the typical
monocot and dicot roots slide, does this angiosperm (sporophyte) possess vascular
tissue? Using Figure 6 page 130, identify the monocot and dicot roots. For
both the monocot and dicot roots, locate and identify the epidermis,
cortex, phloem, and xylem.
1. Describe the differences between
the monocot and dicot root.
2. What is the function of the root
system for this plant?
III. Reproductive structures.
A. The flower (sporophyte)
is the reproductive part of the angiosperms (see Figure 4 page 129). The microscopic
female gametophyte (egg) is located in the ovule (sporophyte) which is contained
within the ovary (sporophyte). Try to find the ovule and the egg in the ovary
slide. What ploidy is the egg?
B. The microscopic male gametophyte called the pollen is produced in the anther (sporophyte) of the flower, by meiosis. Pollen may be released into the air or picked up by a pollinator. Using the lily pollen slide, draw the pollen. What ploidy is the pollen?
Complete parts VI in your lab book, too! I will have review charts posted to the web site.