170
•
Student will restate (orally or written) Science and Biology definitions and main ideas using
content-specific terms.
•
Student will organize information using a variety of graphic organizers according to content-
specific expectations (e.g. Steps of The Scientific Method).
6.5 Reading Resources
#
1 Reproductive Development and Structure
#2 Male and Female Gametophytes
#3 Sexual Reproduction in Gymnosperms
A.
Warm-Up
Talk about the issues with a partner.
1)
What is a reproduction?
2)
How do plants reproduce?
3)
Is reproduction the same for all types plants?
6.5 Reading #1
: Reproductive Development and Structure
Different groups of plants all
engage in sexual reproduction,
though with a few minor
differences. The gametophyte stage and the sporophyte stage are the two distinct phases of a plant's
life cycle. The haploid
gametophyte
produces the male and female gametes by mitosis in distinct
multicellular structures. Fusion of the male and female’s gametes forms the diploid zygote, which
develops into the
sporophyte
. When a diploid
sporophyte reaches maturity,
it produces spores
through meiosis, which then divide through mitosis to create the haploid gametophyte. The cycle is
continued when a new gametophyte produces gametes. This is
a typical example of plant
reproduction—the alternation of generations (Figure 115).
Figure 115.
The diagram illustrates how angiosperm generations alternate.
86
.
The sporophyte stage, which is where the gametophyte is carried, dominates the life cycle of
higher plants. The gametophyte in ferns is free-living and structurally very
different from the diploid
sporophyte. The haploid gametophyte is more developed than the sporophyte in bryophytes like
mosses.
The vegetative stage of growth sees plants grow larger and develop
their root and shoot
systems. Some of the branches begin to produce flowers as they move into the reproductive stage.
86
(credit: modification of work by Peter Coxhead)
171
While some flowers are borne in clusters, many flowers are borne alone. The stalk that supports the
flower is called a receptacle. Taxonomists frequently use flower shape, color, and size to categorize
plants because they are specific to each species.
Dostları ilə paylaş: