Plants
Ch 21-23
Adapted from Prentice Hall
What are Plants?
•Plants are multicellular ,
autotrophic eukaryotes that have
cell walls made of cellulose.
•Plants develop from multicellular
embryos and carry out
photosynthesis using the green
pigments chlorophyll a and b
Plant
Life
Cycle
Plants go
through
Alternation
of
Generations
The Plant Life Cycle
•During the two phases of the life
cycle, mitosis and meiosis alternate to
produce the two types of reproductive
cells — gametes and spores.
•The diploid (2N) phase is called the
sporophyte, or spore-producing plant.
•The haploid (N) phase is called the
gametophyte, or gamete-producing
plant.
What Plants Need to
Survive
–In order to survive, plants need:
• sunlight
• water and minerals
• gas exchange (need CO2 & give
off O2)
• transport of water and nutrients
throughout the plant body
Early Plants
• The first plants
evolved from an
organism similar to
the multicellular
green algae living
today.
Early Plants
•The oldest known
plant fossils, about
450 million years old,
are similar to today’s
mosses.
•They had a simple
structure and grew
close to the ground.
Overview of the Plant
Kingdom
– Plants are divided into groups
based on these features:
– water-conducting tissues
– seeds
– flowers
Evolution of the Plant
Kingdom
Flowering plants
Cone-bearing plants
Ferns and
their
Mosses and relatives
their relatives
Flowers; Seeds
enclosed in fruit
Seeds
Water-conducting (vascular)
tissue
Green algae
ancestor
Bryophytes
Moss
Groups of Bryophytes
•Mosses and their relatives are called
bryophytes, or nonvascular plants.
•They do not have vascular tissues, or
specialized tissues that conduct water
and nutrients.
Groups of Bryophytes
–Bryophytes have life cycles
that depend on water for
reproduction. Gametophyte is
the dominant generation in non
vascular plants
–Bryophytes draw up water by
osmosis only a few centimeters
above the ground.
–Holdfast structures called
rhizoids
Phyla (Divisions) of non
vascular plants
– The three groups are:
• Mosses (Bryophytes)
• Liverworts (Hepatophyta)
• Hornworts (Antherophyta)
• In non vascular plants, the
GAMETOPHYTE is the
dominant generation
Groups of Bryophytes
– Mosses
• The most common bryophytes are
mosses.
• Mosses:
– are adapted to life in wet
habitats (flagellated sperm swims
to egg) and nutrient-poor soils.
– can tolerate low temperatures.
– are clumps of gametophytes
growing together.
Capsule
Structure
of a Moss
Plant
Stalk
Sporophyte
Stem like
structure
Leaf like
structure
Rhizoid
Gametophyte
Human Use of Mosses
– Sphagnum mosses thrive in the
acidic water of bogs.
– Dried sphagnum can accumulate to
form peat deposits.
– Peat can be used as fuel.
– Peat can be used to improve the
soil’s ability to retain water and to
increase soil acidity.