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Honors Biology
KEY
Kingdom Plantæ Practice Exam
1. Describe the main characteristics of the organisms in the Plant Kingdom.
Plants are multicellular photoautotrophs with differentiated cells. (You can also
mention that they have cellulose cell walls and contain chloroplast.)
At the cellular level, describe at least two ways that plant cells differ from animal
cells.
Plant cell contain chloroplasts, organelles completely absent in animals. They have
an external cell wall made of cellulose. They often have large central vacuoles. They
do not have centrioles, while animals do.
2. The fungi have a very pronounced alteration of generations, where they live part
of their lives as haploids and part of their lives as diploids. This is also seen in
plants, though in varying degrees. Draw the life cycle of a fern, clearly labeling
haploid and diploid states.
This diagram should look similar to the one on page 417. You should have the adult,
diploid fern (the sporophyte). This produces haploid spores through meiosis, which
grow into heart-shaped haploid gametophyte plants. Two gametophytes produce
cells that then fuse into a diploid cell, which grows into the adult diploid fern.
How does this compare to the higher plants, like an angiosperm?
More advanced organisms spend less time as haploid gametophytes. The pollen
tubes that grow down the length of the style are the only haploid gametophyte stages
seen in angiosperms.
3. What is the key difference between a bryophyte and a fern (a pteropsida)?
The big difference is that ferns evolved a vascular system to carry water and
nutrients. Mosses lack this system, which is why they are so short.
4. The fact that plants always grow towards the light is well known. What hormone
controls phototropism? What causes a plant to actually bend toward the sun?
Auxin, the plant hormone that controls cell elongation, is responsible for
phototropism. It builds to high levels on the dark side of the plant, causing the cells
on this side of the plant to grow longer than the cells on the light side. This makes the
plant lean toward the light.
5. If you tie a clear plastic bag over the end of a tree branch completely sealing the
leaves inside, after a few hours you will see water condensing on the inside of the
bag. What plant process caused this? Why is it important?
You are seeing transpiration, or the evaporation of water through the leaves. This is
one of the three forces that power the circulatory system in plants.
6. Describe at least three differences between monocots and dicots.
Monocots have one cotyledon, dicots have two. Monocots have parallel veins in their
leaves, whereas dicots have netlike veins. The vascular bundles are scattered in
monocots, but neatly arranged in rings in dicots. Monocots have flower parts in
multiple of three; dicots have flower parts in multiples of four or five.
7. Circulation in plants is amazing. A two-hundred foot tall tree can move water
from the bottom of its roots to the tips of its leaves without a powered pump like
an animal heart. Describe what powers plant circulation.
Plants take advantage of the cohesive nature of water. Root pressure causes water to
constantly flow into the hypertonic roots. The polar nature of water molecules causes
them to stick to the sides of the xylem through adhesion, so they don’t fall back into
the roots. Most importantly, as water transpires out of the leaves the cohesive bonds
between water molecules cause them to be pulled upwards.
8. What is the function of stomata? Where are they found?
Stomata are openings in the leaf that provided passages for carbon dioxide to diffuse
in and oxygen to diffuse out. They also allow water vapor to escape through
transpiration. Though this is essential to power plant circulation, too much water loss
can be detrimental. That is why stomata can close. They are most often found on the
bottom side of leaves, which lessens water loss because the sunlight is less intense
there.
9. Describe two evolutionary advances in reproduction made by angiosperms over
gymnosperms.
You can discuss many things here. Gymnosperms are pollinated by the wind, a
random unreliable process. Angiosperms often use animal pollinators (like bees) to
carry pollen from one flower to another. Gymnosperms lack stored food for the
embryo; angiosperms have cotyledons, which store food for the seedling until it can
make its own. Gymnosperms rely on the wind to spread their seeds. Angiosperms
have adapted many mechanisms to get animals to spread their seeds great distances.
10. Describe the double fertilization that occurs when angiosperms reproduce.
The pollen grain of an angiosperm contains two haploid gametes (sperm). The ovule
of the angiosperm contains one egg nuclei and two polar bodies (all haploid as well).
When the pollen grain lands on the stigma, it begins to eat its way down toward the
ovary. When it reaches the ovule, one of the sperm nuclei fuses with the egg nuclei,
forming a normal, diploid (2n) embryonic plant. The other sperm nucleus fuses with
the two polar bodies, forming a triploid (3n) cell that will grow into the endosperm
which will nourish the embryonic plant.
11. Identify the type of plant described:
A short plant with no vascular tissue. Bryophyte or moss
It reproduces with seeds, and has parallel leaf veins. Monocot angiosperm
It has thin needles for leaves. Gymnosperm
Though it has vascular tissue, it still reproduces with spores. Fern