Fig. 22-1 - ScienceToGo

Plants are multicellular eukaryotes that have cell
walls made of cellulose. (Fig. 22-1)
A. They develop from multicellular embryos and
carry out photosynthesis using the green
pigments chlorophyll a and b.
B. Most are autotrophs (some are parasites or
saprobes that live on decaying materials)
C. Provide the base for food chains, provide shade,
shelter, and oxygen.
Alternation of Generations – process in which
plants switch back and forth between haploid (n)
and diploid (2n) stages of their life cycles
A. Sporophyte – diploid phase or spore-producing
B. Gametophyte – haploid phase or gameteproducing plant
C. In plants, meiosis results in the production of
spores, not gametes.
A. Sunlight – Plants convert the energy from the
sun into chemical energy in the process of
photosynthesis. The shape and arrangement of
leaves enhances their ability to make their own
B. Water & minerals – Water and minerals are taken
up by the plant roots and transported to all other
cells. Plants have developed structures that
limit water loss.
C. Gas exchange – Plants exchange oxygen and
carbon dioxide with the atmosphere
D. Movement of water and minerals – Most plants
have specialized tissues that carry water and
minerals from one place to another
Plants had to adapt to the conditions of life on land,
mainly they had to evolve structures that acquire,
transport, and conserve water.
Plants evolved from a multicellular green
algae, similar to the algae below
Overview of the Plant Kingdom
 This cladogram shows the evolutionary
relationships among the various groups of plants.
Plants are divided into four major groups based on:
A. Presence of absence of water-conducting tissue
know as vascular tissues
1. mosses have no vascular tissue
2. ferns, conifers, and flowering plants all have
vascular tissue
B. Presence of seeds
1. mosses and ferns do not have seeds
2. conifers and flowering plants have seeds
C. Flowers; seeds enclosed in fruit – only flowering
plants have this feature
Plant Kingdom
Flowering Plants
Cone Bearing
Bryophytes must have water to reproduce. They
lack vascular tissue and must draw up water by
Because of the absence of vascular tissue,
bryophytes are relatively small and they must live in
moist places. Water is needed for fertilization.
A. The gametophyte is the dominant generation
(most visible)
B. The sporophyte generation depends on the
gametophyte for water and nutrients
A. Sphagnum – group of mosses that absorbs many
times its own weight in water and is used by
B. Peat moss – also very absorbent and increases
soil acidity, also used by gardeners
The evolution of vascular tissue, which is
specialized to conduct water and nutrients
throughout the plant, allowed plants to grow larger
than bryophytes.
Fig. 22-13
A. Xylem – water conducting tissue; transports
water from the roots  stems  leaves
B. Xylem also provides some support to the plant
C. Phloem – sugar (sap) conducting tissue;
transports sugar in two different directions
D. Sugar can be transported from the root  stems
 leaves or from the leaves  stems  roots
Ferns and other
vascular plants have a
life cycle in which the
diploid sporophyte is
the dominant
A. Spores are produced in sporangium which are
located on the underside of the leaf
A. Spores are released and grow into the haploid
gametophyte generation (very small and not
easily visible)
B. Gametophytes produce the sperm and egg.
Water is still needed for the sperm to be able to
swim to the egg and fertilize it.
C. After fertilization a sporophyte develops on the
gametophyte and eventually matures into an
adult fern.