Bi 101 (Fall 2006) The Diversity of Plants Dr.
Dutton
What Are the Key Features of Plants?
Most plants are _________________________ and use
_________________________ to
convert carbon dioxide and water into sugar and oxygen gas
They have
an _________________________ of
_________________________ life cycle
consisting of both a _________________________ sporophyte
generation (that
develops from a zygote and produces _________________________ spores by
meiosis) and a _________________________ gametophyte generation (that
develops from a spore and produces, by mitosis, gametes that fuse to produce a
diploid zygote) Figure 21-2
Plants produce separate _________________________ and
_________________________ generations
that alternate with each other
Generally, a diploid
zygote develops into a diploid sporophyte plant by
mitosis, which then produces haploid spores by meiosis
A haploid spore develops
into a haploid gametophyte plant by mitosis, then produces haploid gametes by
mitosis, followed by the fusion of sperm and egg to make a diploid zygote
The general trend in
plant evolution has been ...
increasing prominence of the _________________________ generation, accompanied
by decreasing size and duration of
the _________________________ generation
What Is the Evolutionary Origin of Plants?
KNOW
TABLE 21-1
Plant
ancestors were most likely aquatic, photosynthetic protists,
similar to present-day algae
Algae
lack true roots, stems, leaves, and complex reproductive structures like
flowers and cones
_________________________ _________________________ are plants closest living
relatives
Based
on DNA comparisons
Both
use the same type of chlorophyll and accessory pigments in photosynthesis
Both
store food as starch
Both
have cell walls made of cellulose
Figure
21-1
How Did Plants Invade and Flourish on Land?
The plant body increased
in complexity as plants invaded the land
Plants adaptated to dry land by
anchoring _________________________ to absorb water and nutrients;
developing conducting _________________________ to transport water and minerals
upwards from roots to leaves, and move sugars from leaves to other body parts;
and
by producing the stiffening polymer _________________________ in the conducting vessels to
support the plant body
They developed a waxy
waterproof _________________________ on leaf and stem
surfaces to limit water evaporation, and _________________________ (pores) in leaves and stems that
open for gas exchange and close when water is scarce to reduce evaporation
Instead of flagellated
gametes and spores (zoospores) that algae release into the water, plants
evolved
_________________________,
_________________________, and
later _________________________ and _________________________
to protect spores, gametes, and young
embryos from desiccation, attract pollinators, and aid in dispersion of
offspring
The Bryophytes (including mosses and liverworts) are _________________________ plants lacking true roots, stems, and
leaves
Anchoring structures (_________________________) bring water and nutrients into
the plant body and they then diffuse throughout the body which must remain
small (less than 1 inch tall)
Enclosed reproductive
structures are present to prevent desiccation:
_________________________ (in which eggs develop) and
_________________________ (in which sperm develop)
Sperm must swim to eggs through a film of
water; thus, most bryophytes are confined to moist areas
The leafy gametophyte
plant is larger than the leafless sporophyte, which develops
from zygotes growing upward out of the archegonia in the gametophyte plants
Figures 21-4 & 21-3
Adaptations that allowed
plants to grow tall included support structures for the body, and vessels to
conduct water and nutrients
Evolution of rigid
conducting cells ("_________________________ ") in the
_________________________ _________________________ allowed plants to live on dry land
In vascular plants, and
especially the seed plants, the diploid sporophyte
plant body is dominant over the smaller, shorter-lived gametophyte plants
Seedless vascular plants include the club mosses,
horsetails, and ferns
Ferns are the only seedless vascular plants with _________________________
_________________________
In ferns, the small
gametophyte plants _________________________ conducting vessels, and the sperm
must swim through water to reach the egg
Figures 21-6, 21-5, &
21-1
The seed plants dominate
the land due to the evolution of
_________________________ _________________________ (to allow for sperm to
find eggs without swimming through
water) and _________________________ (to allow embryos to develop
without being immersed in water)
The pollen grain,
containing sperm-producing cells, is all that remains of the
_________________________ _________________________ generation in seed plants
The _________________________
_________________________ plant is a small group of haploid
cells that produces an egg
Pollen grains are
dispersed by wind or by animal pollinators like bees
Analogous to the eggs of
birds and reptiles, seeds consist of:
(1) an
_________________________
_________________________;
(2) a
supply of _________________________ for the embryo; and
(3) a
protective outer _________________________
Figure 21-7
Gymnosperms evolved _________________________ than the flowering plants and
include the conifers and two smaller groups, the cycads
and gingkos
Conifers (pines, firs, spruces, hemlocks, and cypresses) are most abundant
in the far north and at high elevations
They are adapted to dry,
cold conditions due to:
(1) retention of green leaves throughout the
year (evergreens), allowing them to photosynthesize and grow all year long;
(2) leaves
that are thin _________________________ covered with a thick
_________________________ to
minimize evaporation; and
(3) production
of "antifreeze" in their sap to allow transport of nutrients in
sub-freezing temperatures
A pine tree is the sporophyte plant
It makes smaller male and
larger female cones
Male cones release pollen
(male gametophyte with sperm) carried by wind to female cones (female
gametophyte with eggs)
The pollen grain sends
out a pollen tube that burrows into the female cone
Eventually the pollen
tube reaches the egg cell, releases sperm and fertilization occurs
The fertilized egg is
enclosed in a seed and develops into an embryo
The seed is liberated
when the cone matures and its scales separate
Figures 21-8 & 21-1
Angiosperms (> 230,000 species) evolved from _________________________ ancestors that formed an
association with insects who carried pollen from tree to tree
Insects ate some pollen
for food and carried pollen from plant to plant
Angiosperms waste less
pollen than gymnosperms
Angiosperms are successful due to:
(l) _________________________ (sporophyte
structures containing the male and female gametophytes) where fertilizations
occur within the flower ovary (where the eggs are and the seeds develop);
(2) _________________________ (ripened flower ovaries containing
seeds) that attract animals and entice them to disperse seeds; and
(3) _________________________
_________________________ to increase the amount of sunlight
trapped for photosynthesis in warm, moist climates
Life Cycle Figure 21-11
To discourage animals
from eating tender leaves, angiosperms have evolved many
_________________________, including:
thorns, spines,
resins, and chemical defenses now harvested by humans (used in such substances
as aspirin, nicotine, caffeine, mustard, and peppermint)
Summary: Major Points
This Chapter has Covered:
Evolutionary
trends in plants
Bryophytes
Ferns
Conifers
Flowering
Plants (Angiosperms)
Including
basic differences in the life cycles of each group