Download The Plants

The Plants
The Origin of Plants
• Plants are believed to have
originated on the Earth about half
a billion years ago.
• They evolved from early algal
ancestors and adapted to the
wide variety of landforms,
transforming the land into soil
that would be suitable for its
offspring.
General Characteristics
• Eukaryotic organisms.
• Autotrophs – they carry out
photosynthesis.
• Cell wall made of cellulose.
• Mostly terrestrial – land-dwelling.
• Embryos are protected by tissues of the
parent plant. (Like an apple.)
• Lifecycles include an alternation of
generations. This sees the cycling
between a diploid and haploid form.
Alternation of Generations
• The plants alternate between a diploid form
and a haploid form – sometimes within the
same structure.
• The diploid form – called the sporophyte –
produces haploid spores which are the
reproductive cells of the plants. Sporophytes
tend to be the plants that you see when you
are walking around.
• The spores will grow into plants called
gamteophytes that will be haploid (like the
spore).
• The gametophytes will eventually produce
gametes – sex cells – that will fuse and form a
diploid zygote. This diploid zygote will
become the next sporophyte.
Alternation of Generations
Who Are These Plants?
• Plants can be divided into four major divisions/phyla –
the bryophytes, ferns, conifers and flowering plants.
The Bryophytes
• Bryophytes include mosses, liverworts and
hornworts.
• They do not have any vascular tissue so they are
small and must live near the water. A wet
environment is key to them.
• To reproduce, bryophytes must release sperm cells
into the water so they can swim to the female
reproductive structures and fertilize the eggs.
• Bryophytes are important because they form such
substances as peat – which can be used as a
fertilizer or fuel. The peat bogs are also huge
storage areas for atmospheric carbon dioixde.
Mosses
Vascular Plants
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•
Vascular Plants are also known as
tracheophytes. They have conducting
tissues called xylem and phloem that
carry water and food respectively.
The tracheophytes can be broken down
into three groups:
1. Spore producers (ferns)
2. Gymnosperms (“Naked Seeds” - Cones)
3. Angiosperms (Flowers & Seed in Fruit)
Spore Producing
Vascular Plants
• These plants have vascular tissue and
produce spores.
• Ferns, club mosses and horsetails are prime
examples.
• These plants must grow close to water or
where water gathers. Roots are not long and
water is needed to reproduce.
• Reproductive structures called sporangia
produce spores – these small cases can be
found on the underside of the ferns leaves.
• Ferns are a food source for many forest
creatures. They also look nice.
Ferns & Horsetails
Gymnosperms
• Gymnosperms are seed producing
plants that produce a “naked” seed
that is in the form of a cone.
• The cones can be female seed cones
or male pollen cones. The pollen grains
are carried in the wind to he female
cones.
• Gymnosperms are large trees and are
found pretty much everywhere.
• They are important in that they are a
major food source, provide shelter and
look pretty at Christmas.
Gymnosperms
Angiosperms
• Angiosperms are flowering plants with their
seeds encased in a fruit. The fruit is actually
the ripened ovary of the plant.
• They are the most successful plants on Earth
and dominate most habitats that plants are
able to exist within.
• Flowers are the sexual organs of
angiopserms. Flowers can be either male or
female but many of them contain both sexual
organs.
• Angiosperms also provide a major food
source for living things as well as flowers.
They may also be used for aesthetic
purposes.
Angiosperms
Flower Anatomy
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