Transcript Reproduction of Seed Plants - Science Class: Mrs. Boulougouras

Reproduction of Seed Plants
Chapter 24: Biology II
Alternation of Generations
• Diploid sporophyte generation
alternates with a haploid
gametophyte generation
• Gametophyte plants produce
male and female gametes: sperm
and eggs
• Gametes join  zygote
• Zygote begins the next
sporophyte generation
Life Cycle of Gymnosperms
Life Cycle of Gymnosperms
• Pollen cone: cone that
produces male
gametophytes in the
form of pollen grains
• Seed cone: cone that
produces female
gametophytes
• Ovule: structure in
seed cones in which
female gametophytes
develop
Pollination
•
The gymnosperm life cycle
typically takes 2 years to complete
•
Male cones release pollen grains
and fertilizes some female cones
•
Pollen tube: structure grown by a
pollen grain; contains two haploid
sperm nuclei
•
Fertilization produces a diploid
zygote; the new sporophyte plant
•
The zygote embryo develops in a
seed
Structure of Flowers
• Reproductive organs
composed of 4 kinds of
specialized leaves:
• Sepals
• Petals
• Stamens
• Carpels
Sepal
• Outermost circle of
flower parts that
encloses a bud
before it opens and
protects the flower
while it is
developing
Petal
• Brightly-colored
structure just
inside the sepals;
attracts insects and
other pollinators to
a flower
Stamen
• Male part of the flower
• Anther
– flower structure in
which haploid male
gametophytes are
produced
• Filament
– a long, thin structure
that supports and
anther
Carpel
• Female part of the flower
• Pistil
– Several carpels fused together
• Stigma
– sticky portion at the top of the style where pollen grains frequently land
• Style
– supports the stigma
• Ovary
– a flower structure that contains one or more ovules from which female
gametophytes are produced
Perfect Flower
• Male and female
parts on the same
flower
Life Cycle of Angiosperms
•
Reproduction takes place
within the flower
•
After pollination and
fertilization, the seeds develop
inside protective structures
(fruit)
•
The mature sporophyte
produces flowers
•
Each flower contains anthers
and an ovary
•
4 pollen grains are produced
from the anther (male)
Life Cycle of Angiosperms
• The ovary contains ovules,
in which the female
gametophyte develops
• Embryo sac: female
gametophyte within the
ovule of a flowering plant
• If fertilized, a zygote will
form and grow into a new
sporophyte plant
Pollination
• Most angiosperms are
pollinated by animals; i.e.
insects, birds and bats
• Flowers have bright colors,
sweet nectars, etc.
• Insect pollination increases
chance that genes will be
passed on
Fertilization
• A pollen grain lands on
the stigma of an
appropriate flower,
producing a pollen tube
• Endosperm: food-rich
tissues that nourishes a
seedling as it grows
Fertilization
• Double fertilization: fertilization in angiosperms,
in which two distinct fertilization events take place
between the male and female gametophytes
Seed and Fruit Development
• As seeds mature,
the ovary walls
thicken to form a
fruit that encloses
the developing
seeds
• Fruit: ripened
ovary that
contains
angiosperm seeds
Seed Dispersal
• Animals
• Wind
• Water
Seed Dormancy
• Period of time during which a plant embryo is alive but not growing
• Environmental factors such as temperature and moisture can cause
a seed to end dormancy and germinate
Seed Germination
• Early growth stage of a plant
embryo
Vegetative Reproduction
• Method of asexual reproduction used
by many flowering plants
• Naturally occurring in many plants
• A technique used by many
horticulturalists to produce many
copies of an individual plant
• Production of new plants from
horizontal stems, plantlets and from
underground roots
Plant Propagation
• Identical copies of a plant are made
• Offspring produced from seedless plants
– Cutting
– Grafting: use of a stem as a scion
– Budding: process of attaching a bud to a plant to produce a new branch
Agriculture
• Most of the people of
the world depend on
a few crop plants
such as wheat, rice,
and corn for the
bulk of their food
supply