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13.3 Sexual Reproduction In Plants

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Chanell C

on 9 April 2015

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Transcript of 13.3 Sexual Reproduction In Plants

13.3 Sexual Reproduction in Seed Plants
Seed Function & Structure
Costs & Benefits of Sexual Reproduction
Sexual Reproduction in Gymnosperms
Sexual Reproduction in Angiosperms
Pollination & Fertilization
Pollination & Fertilization
Fruit Formation
Human Uses of Seeds & Fruits
The Flower
Life Cycle
Monocot & Eudicot Flowers
Seed Function
Seed Structure in Angiosperms
By: Chanell, Kristine & Joann
The products of sexual reproduction in angiosperms are seeds contained inside a
fruit
, which is a mature or ripened ovary.
Flowers are the key organs in
sexual reproduction
of angiosperms.
Structure of a Flower
Stamen:
the male reproductive floral part, comprising of an anther and a filament.
Anther:
the floral organ that produces pollen
Filament
: the thin stalk that supports the anther
Carpel
: the female reproductive floral part, comprising a stigma, a style, an ovary and a ovule
Stigma:
the sticky surface on top of the style
Style
: the stalk that leads to the ovary
Male
Female
In Angiosperms, pollination happens by
wind
or by
animals
, depending on the species
Animals that transfer pollen from one plant to another is called a
pollinator.
Angiosperms Pollination Varies:
1. Cross-Pollination:

the transfer of pollen grains from one plant to another
2. Self-Pollination:
the transfer of pollen from one flower to another on the same plant
Eudicot
Monocot
Dandelion seeds have a special structure that allows them to be
carried long distances by wind.
The nutrient-rich tissues of some seed-containing fruits,
attract mammals and birds
, which
carry them away from the parent plant
. The seeds can grow if they fall onto fertile ground.
Conifers can have both male and female cones:
The reproduction of cone-bearing gymnosperms provides us with most of the
wood
used in construction or
paper products
as well as other useful products.

Gymnosperms:

a vascular plant that
produces seeds
in special structures called
cones
; gymnosperms are a major plant group

Pollination
is the transfer of pollen grains to an ovule.
All gymnosperms pollination happens by
wind

Pollination
happens only
when a
pollen grain lands close to an ovule on a female cone
, which most pollen grains do not.
The Process
The pollen grain grows a hollow tube that grows out of a pollen grain and carries the pollen nucleus to the female sex cell also known as a
pollen tube.

As this tube grows, its haploid nucleus divides by mitosis, producing
two haploid sperm nuclei.

One sperm nucleus
fertilizes the egg
, the diploid zygote is formed.
The other sperm
nucleus degrades.

For the egg to be fertilized after the pollen grain lands on the ovule, it takes about 13 months for the ovule to develop various structures in the seed, and the
zygote develops into an embryo.
If this seed germinates, it can eventually
become a mature sporophyte
, and the cycle will be repeated.

Angiosperms:
a plant that
produces flowers
; angiosperms form the largest group of living plants
Since agriculture depended on individual farmers learning to collect and save seeds, many would gather seeds from each year’s crop to
carry out seed production.
• Most growers plant
monocultures

which
reduces biodiversity
and often relies on other uses of products such as fertilizers, watering systems, as well as machinery that use fossil fuels.
Changes that are being used to make

fruit production more sustainable
:
growing varieties
bred to be more resistance to pests, disease, or drought; covering soil to reduce
moisture loss
; and planting more than one species in an area.
We can all make fruit production more sustainable by
buying locally grown fruit in season
and
growing our own fruits
in our yards or in community gardens.
Seeds of Angiosperms such as wheat, rice, and corn serve as
food staples
for most humans.
Apple Orchid
Wheat Field
A plant must devote a lot of resources to sexual reproduction, therefore when resources are
limited
, sexual reproduction can
lower the chances of survival
of an individual organism.
However, the benefits of sexual reproduction outweigh the potential costs:
There is a
higher level of genetic diversity
in populations produced by sexual reproduction
Seedlings can be dispersed away from the parent plant, therefore they may have
less competition
for resources or better living conditions
Seeds can remain dormant for long periods and then germinate when conditions are favourable,
increasing their chance of survival
Finite Needs
Limited Resources
Examples of Monocultures:
Haploid cells called
microspores
are produced by meiosis within male cones. Each microspore develops into a
pollen grain containing a male gametophyte.

Meiosis in female cones produce
megaspores
that give rise to the
egg-producing female gametophytes.
Pollen grain from Scots pine (x1600 magnification)
How does Pollination occur?

The Main Difference- the number of petals/stamens
Monocot:
petals and stamens are always in multiples of
three
Eudicot:
petals and stamens are in multiples of
four or five
Many animal-pollinated flowers are very
showy
Example 1-
corn
has two types of flowers: the "tassels" on the top of the plant have male structures, while the cobs that grow lower on the plant are flowers that only have female structures
Example 2-
willows
, an individual plant produces only male flowers or only female flowers
Example 3-
pepper plants
have many ovaries that fuse together

Not all species of angiosperms have the same structure
For example
- The flower of the dragon arum plant is very large and smells like rotting flesh to attract flies
A
fruit
is a
mature ovary
of an angiosperm which contains seed(s)
Fruit Formation
Starts when an
ovule is fertilized
during double fertilization
Ovary develops into the fruit wall, call the
pericarp
.
A fruit helps
to protect and disperse seeds
, but the fruit does not provide nutrients to the developing embryo
1) To protect/nourish the enclosed embryo
Fruits help contain the seed for angiosperms (but not for gymnosperms)
Monocot and eudicot seeds contain an
embryo
, nutritive tissue to support embryo growth and a protective seed coat
2) To carry the embryo to a new location
A plant seed's ability to travel to a new location is important for introducing a species to a new area during
succession

Dispersal can move a plant's seed to a location where there is
less competition
from other plants for resources
The two main functions of a seed are:
The seeds of these plants contain an
embryo
, nutritive tissue to support embryo growth, and a protective seed coat
In angiosperms the nutritive tissue may be supplied either by
cotyledons or the endosperm
Endosperm:
the nutritive tissue in an angiosperm seed
Game Time
All About Gymnosperms
Player 1
Player 2
1. Conifers produce only male cones.
T or F

2. All gymnosperms pollination takes place by wind.
T or F

3. Pollination happens only when a pollen grain lands close to an ovule on a female cone.

T or F
Circle if the statement is True or False
1. A pollen grain contains a male gametophyte.
T or F

2. Pollination is the transfer of ovules to pollen grains.
T or F

3. In reproduction, the haploid nucleus is divided by meosis.
T or F
All About Seeds
Multiple Choice: Circle the correct answer
Player 1
Player 2
Monocots & Eudicots
Player 1
Player 2
Circle all the Monocots
Circle all the Eudicots
Thank you for watching!
Fruits
All About Angiosperms
Answer the question
Player 1
Player 2
Q: Name four pollinators
1.

2.

3.

4
Fill in the Blanks
Player 1
Player 2
1. A fruit is a mature
_ _ _ r _

2. The
_ e _ i _ _ _ _
is a fruit wall

3. Fruit development starts when an ovule is fertilized during
_ _ u _ _ _
fertilization
1. A fruit is a mature
_ _ _ r _

2. The
_ e _ i _ _ _ _
is a fruit wall

3. Fruit development starts when an ovule is fertilized during
_ _ u _ _ _
fertilization
Q: Name four pollinators
1.

2.

3.

4
1. The main function of a seed is to
a) Protect the embryo
b) Carry the embryo to a new location
c) All of the above
d) None of the above

2. The endosperm is...
a) the hollow tube that grows out of a pollen grain
b) the nutritive tissue in an angiosperm seed
c) the sticky surface on top of the style
d) the fruit wall, which develops from the ovary wall of fertilized angiosperm

3. The seeds of angiosperms are contained in...
a) embryo
b) flower petals
c) fruit
d) cotyledons
1. The main function of a seed is to
a) Protect the embryo
b) Carry the embryo to a new location
c) All of the above
d) None of the above

2. The endosperm is...
a) the hollow tube that grows out of a pollen grain
b) the nutritive tissue in an angiosperm seed
c) the sticky surface on top of the style
d) the fruit wall, which develops from the ovary wall of fertilized angiosperm

3. The seeds of angiosperms are contained in...
a) embryo
b) fruit
c) flower petals
d) cotyledons
Full transcript