Name_________________________
BOT 101 ALE #6 Sexual life cycles of plants
1.
What is happening in the cell during each phase of the cell cycle?
Interphase:
G1
S
G2
M phase:
2.
Draw a series of cells depicting the stages of mitosis. Label the stages.
3. What are sister chromatids? How do sister chromatids compare genetically?
4. What are homologous chromosomes?
Meiosis
5. a. What is the function of meiosis?
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b. What kinds of cells are produced by meiosis in plants?
c. Are these cells haploid or diploid?
6. Overview of Meiosis…
a. How do the chromosomes align at metaphase I of meiosis?
b. What separates during anaphase I of meiosis?
c. How do the chromosomes align at metaphase II of meiosis?
d. What separates during anaphase II of meiosis?
e. Are the daughter cells haploid or diploid?
7. Compare mitosis and meiosis by completing the table below.
Mitosis
Type of cells involved
Number of cell divisions involved
Number of daughter cells
How do the daughter cells compare
genetically?
Are the daughter cells diploid (2n) or
haploid (n)?
Involves homologue pairing and cross
over?
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Meiosis
8. Draw and label the generalized diagram of the alternation of generations. Be sure to
label mitosis and meiosis, and indicate which parts of the cycle are haploid and
which are diploid
Item:
Cells:
single
or multi?
#chrom.
sets:
haploid or
diploid?
How form:
mitosis?
meiosis? fert?
spore
gametophyte
gamete
zygote
sporophyte
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What is reproductive job?
The moss lifecycle
Step 1. A tiny spore blows in the wind, lands in moist soil, and sprouts into a
leafy plant.
Step 2. At the top of the moss plant, hiding within its leaves, eggs form
within little cups. Neighboring moss plants make sperm inside little sacs.
Step 3. The eggs give off chemicals to beckon the sperm who swim within a
film of rain water.
Step 4. The fertilized egg (zygote) sprouts into a tall stalk, up into the air
currents. At the tip of the stalk is a capsule where spores are made via
meiosis and released into the wind.
B. Moss questions based upon the story above:
1. Does “sprouting” happen via mitosis?
2. Are moss gametes (eggs and sperm) made via meiosis as they are in
animals?
3. The spores are made via meiosis... so are the spores haploid or diploid?
4. The leafy plants are made from a sprouted spore... so are the leaves
haploid or diploid?
5. How is spore different from a gamete?
6. How does moss get up onto your roof?
FERNS ....will represent the SEEDLESS VASCULAR PLANTS
Their story sounds a lot like the moss story... with a few subtle twists.
A. The Fern lifecycle
Step 1. A tiny fern spore blows in the wind, lands in moist soil, and sprouts
into a little heart-shaped flat thing.
Step 2. The heart-shaped thing makes egg cups and sperm sacs on its
surface.
Step 3. The eggs give off chemicals to beckon the sperm who swim within a
film of rain water (from one “heart” to another).
Step 4. The fertilized egg (zygote) sprouts into a leafy fern plant. On the
surface of the leaves, many spore capsules form. Spores are made via
meiosis and tossed into the wind.
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B. Questions based upon the life cycle story
1. Is the flat heart-shaped thing diploid or haploid?
2. Are the fern leaves haploid or diploid?
4. Where would you find fern zygotes?
5. What is the “job” of a fern spore?
6. What is the technical name for the heart-shaped thing?
7. What is the technical name for the stage when ferns have roots, stems,
leaves and spore capsules?
8. What is the technical name for spore capsules?
PINES will represent the Gymnosperms
The general steps are the same in pines as they are in moss and ferns but
many of the stages are very small and happen inside cones. The scales of the
cones are modified leaves. On the surface of each leaf are sporangia.
A. The Pine Lifecycle
Step 1. Spores are made via meiosis within tiny male cones and tiny female
cones. The spores do not go anywhere.
Step 2. : In the male cones, the spores divide a few times then get coated
with a hard material. They have become pollen grains. They are sperm in a
capsule! They are the male gametophytes. They blow in the wind and the
male cones shrivel up and fall off. In the female cones’ sporangia, all the
spores die except one. That remaining spore divides many times, making an
egg or two within sacs, surrounded by nutritious tissue.
Step 3. The pollen lands on the female cones (usually before they are even
done making the eggs) and starts growing a tube towards the eggs. The
sperm nucleus slides down the tube and fertilizes the egg.
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Step 4. The fertilized egg (zygote) divides to form an embryo surrounded
by nutritious female gametophyte tissue. The sporangium sac hardens into a
seed coat. The seed falls out and grows into a new tree.
B. Questions based upon the life cycle story
1. Why is it adaptive for the sperm to be wrapped in a hard coat and travel
in the air?
2. Why is it adaptive for the embryo to be wrapped inside a seed?
FLOWERING PLANTS
Flower Lifecycle- : Fill in the blanks
Step 1. A plant has matured and formed a young flower.
Step 2. Within the sporangia sacs of the anthers, spores are made via
m_________. The spores each divide a few times to form pollen grains (the
male gametophytes).
Step 3. Meanwhile, in the ovules, spores are made via meiosis and only one
survives. The survivor divides three times to make 8 nuclei in communal cell.
One of these is the egg. These 8 nuclei are the female g_____________.
Step 4. Pollination: Pollen lands on the female’s stigma and grows a
p________ t______.
Step 5. Fertilization: the tube reaches the egg, and one sperm cell slides
down the tube and unites with the egg. Then a second sperm slides down
and unites with TWO other female nuclei to make a triploid (3n) cell in a
unique process called “d____________________”.
Step 6. The embryo grows. The triploid tissue grows also and is future food
for the baby. It is called “endosperm” and is a milky white fluid. The ovule
wall becomes a seed coat. The ovary (and sometimes other parts like the
receptacle) will mature to become the f_______.
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9. Compare and contrast Monocots & Dicots. What characteristics would you use to
identify a plant as one or the other?
10. Describe the move of plants onto land. What challenges did plants need to
overcome in order to successfully live & reproduce on land? What adaptations
allowed them to overcome these challenges?
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