-
7/30/2019 BIO1 - Gymno and Angio Life Cycles
1/4
Pine trees are 2N sporophytes
w/ pollen (male) & seed/ovulate (female) cones.
Pollen cones carry 2N structures
called microsporangia.
Through MEIOSIS,
microsporangia produce
N microspores.
MEIOSIS
Microspores undergo
MITOSIS to produce
winged male
gametophytes:pollen grains.
Seed cones carry 2N structures
called megasporangia.
Through
MEIOSIS,
megasporangia
produce
N megaspores.
MEIOSIS
N megaspores undergo mitosis to produce
the female gametophyte, w/c in turn produces
the ovule (structures in w/c egg cells come from).
POLLINATION is accomplished when pollen grains
are carried by the wind to seed cones.
The pollen grain grows a pollen tube into the ovule
and delivers the sperm to the egg cell.
FERTILIZATION is accomplished asone sperm fuses w/ the egg
cell,
forming a 2N zygote.
FERTILIZATION
The seed contains
the young embryo
(new sporophyte)
and its food supply
(female gametophyte),
and is surrounded by
a tough seed coat
(old sporophyte).
The seed falls to the ground
and eventually germinates.
The young embryo will grow
into a mature sporophyte.
Gymnosperm Life Cycle
-
7/30/2019 BIO1 - Gymno and Angio Life Cycles
2/4
Mature sporophyte (2N)
Pollen cones
w/ microsporangia (2N)
MEIOSIS: 2N microsporangia
N microspores
MEIOSIS
MITOSIS:
N microspores
N pollen grains
Seed cones
w/ megasporangia (2N).
MEIOSIS:2N megasporangia
N megaspores
MEIOSIS
MITOSIS: N megasporesfemale gphyte w/ ovule
POLLINATION:
pollen grains carried by the wind to seed cones
Pollen tube grows into the ovule,
delivers the sperm to the egg.
FERTILIZATION:N sperm + N egg = 2N zygote
FERTILIZATION
Seed:
1. Embryo (new 2N)
2. Seed coat (old 2N)
3. Food (female N)
GERMINATION:
embryomature sphyte
Gymnosperm Life Cycle
-
7/30/2019 BIO1 - Gymno and Angio Life Cycles
3/4
Angiosperm Life Cycle
Ovary contains
one or more
megasporangia
called ovules,
each w/ a 2Nmegaspore
mother cell.
The 2N
megaspore
mother cell
undergoes
MEIOSIS to
produce 4
N megaspores;only 1 surives.
MEIOSIS
N megaspore
undergoes MITOSIS
to produce 8 N nuclei.
The female gametophyte is the embryo sac
w/c contains 8 N nuclei; the 2 at the center
are the polar nuclei.
Anther contains microsporangia
w/c produce many 2N
microspore mother cells.
Each microspore mother cell undergoes MEIOSIS
to produce 4 N microspores.
N microspore undergoes MITOSIS to produce 2
N sperm cells. These, together w/ a protective wall,
make up the male gametophyte.
Anther dries out and releases mature
pollen grains, w/c stop growing
until deposited on a stigma.
Pollen grain lands on stigma, and a
pollen tube grows down the style,
eventually entering the ovule.
Sperm nuclei enter
the embryo sac.
One fuses w/the egg cell to form
the 2N zygote.
The other fuses
w/ the polar nuclei
to form the
3N endosperm.
DOUBLE
FERTILIZATION
The seed contains
the young embryo
(new 2N sporophyte)
and its food supply
(3N endosperm),
and is surrounded by
a tough seed coat
(old 2N sporophyte).
The seeds are actually
the mature ovules,
and the fruit is a
mature ovary.
The seed is dispersed and
eventually germinates.
The young embryo will
grow into a new plant.
-
7/30/2019 BIO1 - Gymno and Angio Life Cycles
4/4
Angiosperm Life Cycle
Ovary
= ovules
(megasporangia)
w/ 2N megaspore
mother cell.
MEIOSIS:
2N megaspore
mother cell
4 N
megaspores;
only 1 surives.
MEIOSIS
MITOSIS:
N megaspore
8 N nuclei.
Female gphyte =
embryo sac + 8 N nuclei;
the polar nuclei: 2 @ center
Anther w/ microsporangia
w/ 2N microspore mother cells.
MEIOSIS:
2N microspore mother 4 N microspores
MITOSIS: N microspore 2 N sperm cells.
Male gphyte = pollen grain = 2 sperm cells + wall
POLLINATION:
release of pollen grains
and landing onto stigma
Pollen tube grows
down the style,
enters the ovule.
N sperm + N egg
= 2N zygote
N sperm+ polar nuclei (N+N)
= 3N endosperm
DOUBLE
FERTILIZATION
Seed = mature ovule
Fruit = mature ovary
Dispersal & germination;
growth of new plant
Seed:
1. Embryo (new 2N)
2. Food (3N endosperm)
3. Seed coat (old 2N)
