Transcript Pollination and Fertilization

Principles of Agricultural Science – Plant
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Principles of Agricultural Science – Plant
Pollination and Fertilization
Unit 7 – Sexual Reproduction
Lesson 7.2 Pollination and Fertilization
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If We Have Pollen…
pollination can occur.
Pollination is the transfer of pollen from the
anther to the stigma of a flower.
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Types of Pollination
Some plants use different methods to
achieve pollination:
 Self-pollination: Transfer of pollen from
the anther to the stigmas of the same
flower or to flowers on the same plant.
 Cross Pollination: Transfer of pollen
between two plants that are not of identical
genetic material.
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Mechanisms Used for Pollen
Transfer

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

Animals
Insects
Water
Wind
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Attracting Pollinators
The flower uses important features to attract
animals and especially insects to help the
pollination process:
 Bright petal colors
 Fragrance
 Nectar
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Fertilization
Fertilization is the union of pollen with the ovule to
produce seeds.
Once pollen grains are transferred to the stigma:
1. Pollen grains move through the pollen tube to
the ovule.
2. A pollen gamete unites with the egg cell
gamete in the ovule.
3. Ovary swells and forms the fruit.
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A Microscopic View: The Birth of
Pollen and Egg Cells
Pollen and egg cells must undergo the
process of Meiosis to become haploid.
Meiosis is a type of cell division that
reduces the number of chromosomes in
new cells by half.
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Start With a Sex Cell
• Male and female productive organs
produce sex cells also called germ cells
• The nucleus contains chromosomes,
which carry genes.
Chromosome
Nucleus
Chromatid
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Meiosis I
Diploid cells, which are cells with two sets of each
chromosome.
Diploid
Sex Cell
Matching chromosomes separate
Haploid
Cells
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Meiosis II
Cells divide again to produce haploid gametes.
This process
happens for
both pollen
and egg cells.
Four gametes are produced
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From Gametes Back to a Diploid
Pollen Gametes
I
I
I
Egg Gametes
I
I
I
I
I
Fertilization
This new
cell is called
a zygote.
II
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The Development of a Zygote
Cells undergo rapid mitosis
as the zygote grows.
Parent Cell
Replication
Cell Division
You will learn more about mitosis in a
later activity.
Daughter
Cells
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The Next Step
Following fertilization, division of the zygote
will continue the cell replication process.
This process is called mitosis.
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Mitosis
Mitosis is the division of cells to produce
daughter cells that contain a full set of
chromosomes.
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Phases to Mitosis
•
•
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•
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Interphase
Prophase
Metaphase
Anaphase
Telophase
Mitosis phases will be explored further in Activity
7.2.2 A Closer Look at Mitosis.
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References
Herren, R. V., & Donahue, R. L. (2000). Delmar’s
agriscience dictionary with searchable CD-ROM. Albany,
NY: Delmar.
Parker, R. (2004). Introduction to plant science (Rev. ed.).
Clifton Park, NY: Delmar.
Schooley, J. (1997). Introduction to botany. Albany, NY:
Delmar Publishers.
Toogood, A. R. (Ed.). (1999). American Horticultural
Society plant propagation: The fully illustrated plant-byplant manual of practical techniques. New York, NY:
Dorling Kindersley.
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