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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?
b. What kinds of cells are produced by meiosis in plants?
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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?
7. 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?
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
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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.
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.
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.
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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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