Download Lectures 3 and 4 Exam I Answers

01-23-12
Lectures 3 and 4, Exam I
Warm Up
1. Gymnosperms and angiosperms have the following in common except: D.
a. seeds b. pollen c. vascular tissue d. ovaries
e. ovules
What are ovaries? A fruit is essentially an ovary, but can contain other parts as well. It
contains a mature ovary, nutritive material, and a protective coat. Fruit protect dormant
seeds and help disperse by being attractive to animals after ripening. Seeds are found in
both, as well as ovules, vascular tissue, and pollen.
2. What is the difference between the gametophyte in a seedless, vascular plant and a seed plant? And
where are the male and female gametophytes located within the gymnosperms and the angiosperms?
The gametophyte in a seedless vascular plant is reduced, independent, photosynthetic, and
free-living. The gametophyte in a seed plant is reduced, almost microscopic, smaller than
the ones in the seedless, vascular plants, and depends upon the sporophyte for nutrition.
Don’t confuse with the Bryophyte sporophyte depending upon the gametophyte for
nutrition. In the gymnosperms, the female gametophytes are found inside the ovulate cone.
The male gametophytes are found within the pollen cone. Remember these are adapted to
be smaller so they are enabled to hide within these structures. In the angiosperms, the
female gametophytes are found within the carpel. The male gametophytes are found within
the stamen.
What’s the Big Picture?
3. Overtime, we have seen the ______________ phase become increasingly dominant.
Sporophyte.
4. What two major adaptations (concerning reproduction) have emerged in plant history?
Why are they important?
Seed has been developed as the resistant, dispersible stage of life. Allows for
dispersal of the embryo (2N). Pollen has been developed as a resistant structure for
dispersing male gametes (sperm!); no longer need moisture or flagellated sperm for
reproduction.
Warm-Up Definitions:
5. Micro/Megasporangia
6. Mega/Microsporocytes
01-23-12
7. Micropyle:
8. Integument:
9. Which group of plants has a dominant sporophyte, an independent gametophyte, and
depends on moisture for reproduction? Seedless, vascular plants: ferns.
10. What are two “sterile” parts of the angiosperm flower structure that aren’t involved in
reproduction? Petals, sepals. Petals attract pollinators, great adaptation for angiosperms.
Sepals enclose the flower before it opens.
Lectures 3 and 4, Exam I Worksheet
Life cycle of the pine
1. Mature sporophyte, that looks like a pine tree, is standing tall with two types of cones: ovulate cone
(M/F), and a pollen cone (M/F).
2. Path of the male cone: The cone contains multiple organs called microsporangia (1N/2N) which
contain mother cells called microsporocytes that produce(2/4) microspores (1N/2N) by the process of
meiosis. Each spore develops into a pollen grain (1N/2N) when it contains a protective coat and a set of
wings, then disperses.
3. Path of the female cone: The cone contains multiple scales which each contain multiple ovules
which each contain one megasporangium, (1N/2N) which each contains mother cells called
megasporocytes. Surrounding these mother cells is integument with a hole in it called a micropyle.
Each cell divided by meiosis to make (3/4) megaspores. ( Only one survives!). This spore develops into a
female gametophyte (1N/2N) by the process of mitosis. This structure contains an egg- producing
structure called a archegonium which produces one egg each by mitosis.
4. Paths converge, pollination. The pollen grain reaches the micropyle on the female cone. The pollen
grain then divides by mitosis to produce a group of cells collectively called the male gametophyte
(1N/2N). One cell of the male gametophyte divides by mitosis to become a pollen tube. The remainder
of the cells becomes sperm cells. (1N/2N). One enters the tube. Fertilization occurs whenever the two
types of gametes unite which forms a diploid zygote which develops into an embryo. The ovule becomes
the seed consisting of the embryo, food supply from the tissue of the female gametophyte(1N), and seed
coat derived from the integument. The seeds are dispersed, form a seedling, and gives rise to a
SPOROPHYTE(1N/2N) by mitosis.
Life cycle of the angiosperm
1. A mature flower is a sporophyte(1N/2N).
2. The stame: male portion of the sporophyte: The filament leads to the anther which contains the
organ the microsporangium which contains cells called microsporocytes. Each of the cells divides by
01-23-12
meiosis to produce 4 microspores (2N/1N). Each of these develops a protective coat and is now called a
pollen grain. Each microspore divides by mitosis to form two cells: the tube cell and the generative cell.
The generative cell undergoes meiosis to form two sperm cells.
3. The male gametophyte is composed of what three portions?
Protective coat + tube cell + two sperm cells
4. What exactly is pollination? What has to happen first?
Male gametophyte attaching to the stigma, actually the pollen grain specifically attaching to the
stigma. Then the pollen tube elongates down to the style toward the ovary and carries two sperm
cells with it.
5. The carpel: the female portion of the sporophyte: The ovary contains an ovule which each contain
the organ the megasporangium which contains cells called megasporocytes. Each cell divides by
meiosis to produce four megaspores. (1, 2, 3) survive(s). The surviving cell(s) undergo 3 rounds of
nuclear division without cytokinesis. Then asymmetrical cytokinesis occurs which creates 6 1N cells and
one 2N cell, (two cells weren’t separated).
6. What is mean by double fertilization? What is each cell fertilized destined to become?
One sperm cell fertilizes the one 2N cell which creates a 3N endosperm, which becomes a food
source for the growing embryo.
One sperm cell fertilizes one of the 1N cells, (one of the 6 left). This creates a 2N embryo.
7. What are three parts of a seed?
Protective coat + 2N embryo + 3N endosperm (food source)
8. Female gametophyte is composed of what structures? Which parts creates a 1N egg?
The 6 1N cells + the one 2N cell. One of the six 1N cells becomes the egg.