Important words and concepts from Chapter 30, Campbell & Reece, 2002 (3/25/2005):
by Stephen T. Abedon (abedon.1@osu.edu) for Biology 113 at the Ohio State University
|
|
|
Course-external links are in brackets Click [index] to access site index Click here to access text’s website Vocabulary words are found below |
|
|
(1) Chapter title: Plant Diversity II: The
Evolution of Seed Plants
(a)
[the evolution of seed plants
(Google Search)]
[index]
BREAKING FREE OF REQUIREMENT FOR STANDING WATER
(a)
Primitive plants reproduce using flagellated sperm
which must swim through water to find and then fertilize ova (see life cycle of a moss, life cycle of a fern)
(b)
This obviously puts great limitations on where a plant might live and
still reproduce
(c)
The solution is the development of a desiccation-resistant capsule that
is capable of transporting sperm through the air
(d)
This innovation we call pollen
(e)
Pollen consists of the male gametophyte and the
haploid mitotic product of that gametophyte: sperm nuclei
(f)
“Microspores develop into pollen grains, which mature to become the
male gametophytes of seed plants. The pollen grains… can be carried away by
wind or animals after their release from the microsporangium… In seed plants,
the use of resistant, far-traveling, airborne pollen to bring gametes together
is a terrestrial adaptation that led to even greater success and diversity of
plants on land.” p. 600, Campbell & Reece, 2002
(g)
Pollen and pollen with pollen tube: 
(h)
Note haploid male nuclei (shadows in middle of tube): 
(i)
[pollen plant reproduction
(Google Search)]
[index]
(a)
More-primitive plants disperse employing haploid spores which establish the gametophyte
generation
(b)
“Spores were the main way that plants spread over the Earth for the
first 200 million years of plant life on land.” Campbell & Reece, 2002
(c)
Less-primitive plants disperse the gametophyte following it's
germination from its spore, with the sporophyte generation already begun (via
fertilization)
(d)
This gametophyte generation associated with an embryonic sporophyte
which in turn is protectively encased in desiccation-resistant capsules
(derived from grandparental sporophyte tissue) we call seeds
(e)
“What distinguishes seed plants is that the megaspores, and hence the
female gametophytes, are retained on the parent sporophyte.” p. 599, Campbell
& Reece, 2002
(f)
“One advantage of this arrangement is that the delicate female
gametophyte do not have to cope with many environmental stresses.” p. 599, Campbell & Reece, 2002
(g)
See Figure 30.1, Overview: three variations on gametophyte/sporophyte
relationships
(h)
[seeds plant reproduction
(Google Search)]
[index]
FURTHER INTRODUCTION TO SEEDS PLUS FLOWERS AND FRUIT
(4) 
Ovule (integuments)
(a)
“In seed plants, layers of sporophyte tissues called integuments
envelop the megasporangium. Thus a megaspore formed within the megasporangium
is very well protected. The whole structure—integuments, megasporangium, and
megaspore—is called an ovule… A seed’s protective coat is derived from the
integuments of the ovule.” p. 599, Campbell & Reece, 2002
(b)
See Figure 30.2, From ovule to seed
(c)
Note that the integuments of the ovule, the megasporangium, the female
gametophyte, and the next-generation embryo together form a seed
(d)
[ovule, integuments (Google Search)]
[index]
(a)
Flowers represent an innovation that increases the efficiency by which pollen
may be transferred to ova
(b)
Particularly, flowers allow plants to
effectively employ animals as pollen disseminators (syn: transferers or distributors
or dispersers)
(c)
Flowers are considered in greater detail below
(a)
Bare seeds are limited in their ability to disperse
(b)
Just as flowers have allowed plants to
take advantage of animals in the dissemination of pollen, fruits
allow plants to take advantage of animals in the dissemination of seeds (though not all fruits employ animals as
dispersers)
(c)
Fruit is considered in greater detail below
SEEDS BUT NO FLOWERS NOR FRUIT
(7) Division Coniferophyta [gymnosperms]
(a)
If one posits the plant-ancestral green algae as the
"fish" stage of plant evolution (i.e., aquatic), then the bryophytes (such as the mosses) and later the seedless, vascular plants (such as the ferns) represent the "amphibian" stage since these (terrestrial) plants are
still tied to water, particularly for their reproduction
(b)
Successful conquest of terrestrial environments required the evolution
of a truly terrestrial plant, one not tied to standing water for reproduction
(c)
The two key innovations that allowed plants to break their ties with
standing water were the evolution of pollen and the evolution of seeds
(for vertebrates, continuing the above analogy, the innovations included
desiccation-resistant skin and the amniote egg, but
more about that later)
(d)
Of the living seed-bearing, but non-flowering vascular plants, division Coniferophyta is by
far the most successful
(e)
See Figure 30.8, Phylum Coniferophyta: A sampling of conifer diversity
(f)
Another name for seed-bearing, non-flowering, vascular plants is
gymnosperm
(g)
Division Coniferophyta is one division of the gymnosperms, and includes
the conifers, i.e., the pines, spruces, yews, redwoods, cypress, junipers, etc.
[pine, spruce, yew, redwood, cypress, juniper (Google Search)]
(h)
These are typically evergreen trees and shrubs that reproduce using
cones
(i)
The conifers tend to be highly adapted to dryer as well as colder
environments
(j)
The gymnosperms dominated terrestrial ecosystems during the Mesozoic era
(k)
[coniferophyta, gymnosperms (Google Search)]
[index]
(a)
See Figure 30.9, The life
cycle of a pine
(b)
Note particularly
(i)
Pine trees typically produce both pollen and eggs on
the same trees, but in different cones
(ii)
The pine tree is the sporophyte generation
(iii)
Less conspicuous male cones produce and release pollen
(iv)
Pollen disperses on the wind and adheres directly to the female gametophyte
found within the more conspicuous female cone
(v)
The pollen then forms a tube (the pollen tube) which passes into female
gametophyte tissue to the egg; formation of this tube takes about a year
(vi)
During the growth of the pollen tube, the male gametophyte completes
its development by generating two sperm cells through mitotic division, and
these two sperm cells are found within the cytoplasm of the pollen tube cell
(the two sperm and pollen tube cell, all three cells, make up the male pine
gametophyte)
(vii)
The pollen tube completes its growth (and job) by depositing a sperm
nuclei in the female egg, thus fertilizing the egg
(viii)
The thus-formed zygote gives rise to the sporophyte generation, which ultimately sprouts
from within the female gametophyte (which together make up the dispersible pine
seed)
(ix)
Note that at the eighth step of this figure you have three generations
in close association, the new sporophyte, which
is intimately surrounded by the mother gametophyte, which in turn is associated with surrounding
grandmother sporophyte generation tissue
(c)
See Figure 30.10, A closer look at pine cones (Pinus sp.)
(d)
[life cycle of a pine
(Google Search)]
[index]
SEEDS AND FLOWERS AND FRUIT
(9)
Division Anthophyta [angiosperms, flowering plants]
(a)
The age of the reptiles came to a
close 65 million years ago and was replaced by
the age of the mammals, the latter noted, in most cases
today, for their embryonic development completely within the body of the mother
(b)
Perhaps coincidentally, at approximately the same time the age of the seed-bearing,
non-flowering
plants came to an end and was replaced by the age of the
flowering plants, the latter noted for their embryonic development completely
within sporophytic (grand-) maternal tissue
(c)
The flowering plants are the dominant plants on earth today
(d)
They possess all of the innovations listed above, plus they employ both
flowers
and fruit
(e)
Another name for members of this division Anthophyta is angiosperm
(f)
The flowering plants can be distinguished into varieties called monocots
and dicots
(g)
See Figure 30.11,
Representatives of major angiosperm clades
(h)
[“About 135 million years ago… nonflowering plants—perhaps similar to
today’s pines—hit an evolutionary fork in the road, with some veering off
toward Amborella and later angiosperms while others continued life sans petals.
¶ Found only on
(i)
Amborella: 
(j)
[“…new data strike a blow to the foundation of [plant systematics]: the
250 year-old system , designed by botanist Carolus Linnaeus, which groups species by the
number and arrangement of their reproductive organs, the stamens and pistils… A
vocal band [argues] that the Linnaean system should be thrown out, or at least
overhauled, because many plants presumed by their appearance to be closely
related—such as the water lily and the lotus—are in fact quite different
genetically.” Kathryn S. Brown, 1999, Deep Green rewrites
evolutionary history of plants. Science 285:990-991]
(k)
[anthophyta (Google Search)]
[plant systematics (Google Search)]
[index]
(10) Flowers in
more detail (whorls,
sepals, petals, stamen,
carpel, anther, filament, stigma, style,
ovary)
(a)
Flowers are optimized for the fertilization of ova by pollen
(b)
This fertilization may be achieved via the movement of pollen on wind
or the movement of pollen via animals (in the case of birds and flying insects,
a.k.a., flying penises) [flying penises (Google Search)]
(c)
Flowers consist of layers of modified leaves called whorls [flowers whorls (Google Search)]
(d)
See Figure 30.13, The
structure of a flower (this is a figure that you should take the time to learn)
(e)
A flower (note: "pistil"="carpel"):
(f)
Starting from the outside going in, whorls are called
(i)
Sepals, the typically green outer covering of the bud [flowers sepals (Google Search)]
(ii)
Petals, the typically colored-other-than-green sepal [flowers petals (Google Search)]
(iii)
Stamen, the male reproductive organs (anther and filament) [flowers stamen (Google Search)]
(iv)
Carpel, the female reproductive organs (stigma, style, and ovary) [flowers carpel (Google Search)]
(g)
The stamen, in turn, consists of the anther and filament, the
pollen-containing organ and the stalk it sits on, respectively [flowers anther, flowers filament (Google Search)]
(h)
The carpel consists of
(i)
The stigma, a sticky pad to which pollen adheres [flowers stigma (Google Search)]
(ii)
The style, a stalk upon which the stigma sits [flowers style (Google Search)]
(iii)
The eggs reside in separate ovules which are found within a flowers
ovary [flowers ovary (Google Search)]
(i)
Carpel evolution (not responsible for): 
(j)
(Figure 30.14, Hypothesis for the origin of the carpel from a
reproductive leaf (sporophyll))
(k)
[flowers plant reproduction
(Google Search)]
[flower anatomy (Google Search)]
[images: flower anatomy
(click on the various terms to see images) (Botany 301 – Texas A&M)] [index]
(a)
A fruit is a mature ovary, which has a thickened ovary wall
capable of protecting the embryo
(b)
See Figure 30.15, Relationship between a pea flower and a fruit (pea
pod)
(c)
Fruits can have many functions and structures in addition to the
familiar edible fruit variety, including the wings of maple seeds, the pod of a
pea, the shell of a peanut, etc.
(d)
A primary function of fruits typically is seed-dispersal
(e)
An example of a seed with some indication of anatomy: 
(f)
See Figure 30.16, Fruit adaptations that enhance seed dispersal
(g)
“The cereal grains of wheat, rice, corn, and other grasses are easily
mistaken for seeds, but each is actually a fruit with a dry pericarp that
adheres tightly to the seed coat of a single seed within.” p. 609, Campbell
& Reece, 2002
(h)
See Table 30.1, Classification of Fleshy Fruits
(i)
[fruit plant reproduction
(Google Search)]
[images: types of fruit
(you will need to scroll down a ways to find the list; click on the various
terms to see images) (Botany 301 – Texas A&M)] [index]
MONOCOTS VERSUS DICOTS
(a)
The monocots are grass and "grass-like" angiosperms
(flowering plants)
(b)
See Figure 30.11(e), Representatives of major angiosperm clades
(c)
Particularly, the embryos of monocots have only a single (mono-) first
leaf (a.k.a., seed leaves or cotyledon)
(d)
This single first leaf is a derived trait; the monocots are actually
derived from primitive dicots with which they share various characters
(e)
Other characteristics of monocots that distinguish them particularly
from dicots include:
(i)
Monocot leaves have parallel veins
(ii)
Few monocots display woody growth
(iii)
Few monocots are annuals
(iv) Monocots te