Aim: How are plants adapted to
reproduce?
Flower
Alternation of
Generations
Alternation of Generations:
Plant generations alternate
between diploid (2n) and
haploid (n) forms.
The haploid generation of
plants is called the
gametophyte.
The diploid generation
produces spores & is called
the sporophyte.
In a plant’s life cycle, each of these generations “takes
turns” giving rise to the other.
Reproduction of Mosses:
Spores vs. Gametes:
1)Spores can develop
into a new organism
without fusing with
another cell.
2)Spores have hard coats
that resist harsh
environments.
Flowers & Reproduction:
Flowers are the reproductive structures found in
Angiosperms.
Sepal – protect the unopened
flower.
Petals – aid in pollination by
attracting pollinators.
Pistil/Carpel – female
reproductive organ:
1)Stigma – pollen lands
2)Style – connects stigma to
the ovary
3) Ovary – ovules are located
here & they produce female
gamete.
Flowers & Reproduction:
Stamen –
Male Reproductive Organ:
1)Anther – the male gametes
are produced and develop into
pollen grains.
2) Filament – stalk that
supports the anther
Angiosperm Reproduction:
1)Cells in the anther undergo meiosis
to produce pollen grains – the male
haploid gametophytes. Each pollen
grain consists of 2 haploid cells.
2)A diploid cell in the ovule undergoes
meiosis and forms 4 haploid cells.
Three of the four haploid cells die.
3) The surviving haploid cell enlarges
& undergoes mitosis. The resulting
structure is call an embryo sac.
Angiosperm Reproduction:
4)The embryo sac consists of an egg
cell & a cell with 2 haploid nuclei.
5)Pollination – pollen grains land on
the stigmata of flowers of the same
species. Wind or animals help.
6)Two male haploid cells reach the
embryo sac. 2 fertilizations take place.
One produces the zygote & the other
produce a triploid cell (3n) that will
nourish the developing embryo.
Seed Development & Dispersal:
• After the double fertilization, the
ovule develops into a seed.
• Seeds have a tough outer coat to
protect the embryo.
• Cotyledon develops, which
functions in the storage & the
transfer of nutrients to the embryo.
• Animals, wind, or water can help
spread seeds to other locations.
Seed Germination:
When conditions are favorable,
The plant embryo will grow.
This usually occurs when there
is an abundance of water.