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
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Course-external links are in brackets Click [index] to access site index Click here to access text’s website Vocabulary words are found below |
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(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 tend to have swollen underground storage organs
(v)
Think of an onion or a lilly or lawn grass, etc.
(f)
[monocots (Google Search)]
[index]
(a)
The dicots include all of the
non-monocot
angiosperms
(b)
See Figure 30.11(f), Representatives of major angiosperm clades
(c)
The embryos of dicots have paired (di-) first leaves (a.k.a., seed
leaves or cotyledon)
(d)
Other characteristics of dicots
that distinguish them particularly from monocots include:
(i)
Dicot leaves have net-like leaf
vein structures called reticulate veins
(ii)
About one-half of all dicots
display woody growth
(iii)
About one-sixth of all dicots
are annuals
(iv)
Think of a maple tree or poison ivy or marigolds, etc.
(e)
[With only a little knowledge and experience it is possible to fairly
easily distinguish monocots from dicots. It is a skill that almost gives the
impression that one has a reasonably expansive knowledge of plant biology. In
fact, possessing only a little additional knowledge (as outlined above and in
the next chapter), and some experience, it is actually possible to fairly
consistently distinguish fungi, lichens, bryophytes, ferns, conifers, monocots,
and dicots!]
(f)
not responsible for following: 
(g)
[dicots (Google Search)]
[index]
NEAR “TRIUMPH” OF SPOROPHYTE OVER GAMETOPHYTE
(14) Life cycle of
an angiosperm (endosperm)
(a)
See Figure 30.17, The life
cycle of an angiosperm
(b)
Note particularly
(i)
Pollen is produced within the anther and is
transferred to the stigma (often not within the same flower)
(ii)
The pollen tube (which already contains the two sperm cells) grows into
the stigma and down the style, ultimately into the maternal tissue (sporophyte) holding the egg
(iii)
The pollen is the male gametophyte
(iv)
The female gametophyte consists of seven cells (product of three round
of replication), six haploid and one containing two nuclei, one of the former
of which (single nuclei) is an egg
(v)
Note that the female gametophyte (megagametophyte) is found embedded in
the sporophyte tissue, just as in the pine, but that the
sporophyte tissue is even further surrounded by grand-maternal sporophyte tissue
in the form of the ovary wall (i.e., see step four of the figure)
(vi)
Comparing Figure 30.17 between steps 6 and 7 and Figure 30.9 step 6,
note how similar the proximity of the pollen tube cell is to the female
gametophyte; the major difference is that in Figure 30.17 (the angiosperm)
the ovule
is in turn contained within the ovary (i.e., see Figure 30.13) whereas in
Figure 30.9 (the gymnosperm) the ovule is not contained within
sporophyte tissue but instead is exposed to the environment
(vii)
Double fertilization takes place with one sperm nuclei fertilizing the
egg (thus giving rise to the next sporophyte generation) and the other sperm
nuclei fertilizing the gametophyte cell containing two nuclei (thus giving rise
to triploid endosperm tissue)
·
both sperm are genetically identical, by the way, since they were
generated by mitotic division within the gametophyte
(viii)
The endosperm serves to nourish the embryo (sporophyte generation)
(ix)
The sporophyte is dispersed within a seed and generates the dominant (conspicuous) plant
(c)
Follow text rather than these images when studying except to the extent
that you find that these images are helpful: 
(d)
["In angiosperms, sexual reproduction entails cyclic alternation of generations: the plants, which comprise the sporophyte generation (2n), produce specialized reproductive structures (flowers) in which genetic recombination and reduction occur
during meiosis, yielding haploid microspores
(male) and megaspores (female) that undergo limited mitotic development
to form microgametophytes (pollen) and megagametophytes (embedded in a
maternal ovule). A microgametophyte delivers two haploid sperm cells
into a megagametophyte through an ovule-penetrating pollen tube. By processes
still not well understood, one sperm fertilizes the
central cell, which often is binucleate (n
+ n), to form the endosperm (3n), a terminal tissue with multiple
hormonal and nutritive functions critical to the embryo; the other sperm
fertilizes the egg cell (n) to form
the zygotic embryo (2n)."
Jean-Philippe Vielle Calzada, Charles F. Crane, and David M. Stelly, 1996,
Apomixis: The asexual revolution, Science
274:1322]
(e)
[life cycle of an angiosperm
(Google Search)]
[index]
PLANTS, SUMMARY
(a)
Note: The following table is intended to serve you as a helpful summary
rather than as a daunting burden; that is, all of the information contained you
would have been responsible for regardless, but with luck is more
understandable as summarized below
|
name4 |
||||
|
terminating event4 |
mitosis4 |
|||
|
ploidy4 |
diploid |
haploid |
haploid |
haploid |
|
Inconspicuous |
Wind dispersed |
Conspicuous; germinates
apart from parental sporophyte |
Sperm is motile; egg stays
in association with gametophyte |
|
|
Conspicuous |
Ditto |
Inconspicuous; Ditto |
Ditto |
|
|
Ditto; Embryos disperse,
packaged associated with grandparental sporophyte tissue (seeds) |
Megaspore not dispersed; Microspore is
wind dispersed with pollen |
Ditto; Microspore germinates as pollen tube, associated with female
sporophyte tissue, associated with ovule; Megaspore
germinates in parental sporophyte |
Sperm is non-motile; Both
gametes stay in close association with parental gametophytes |
|
|
Ditto except that seeds
are in turn packaged within grandparental-sporophyte tissue (fruit) |
Ditto |
Ditto except that the
ovule is surrounded by a grandparental-sporophyte ovary (i.e., ovary and
ovule are of same generation) |
Ditto |
(b)
Note that the seed-bearing plants disperse
following spore germination (and syngamy) while
non-seed-bearing plants disperse prior to spore germination; exception is male microspore, which disperses in association with male gametophyte, i.e., pollen
(c)
Note that in the seed-bearing plants the sperm stays in close
association with the male gametophyte while in the non-seed-bearing plants, the
sperm disperses from the male gametophyte
(d)
VOCABULARY
(a)
Angiosperms
(b)
Anther
(c)
Carpel
(d)
Dicot
(e)
Dicotyledon
(g)
Endosperm
(h)
Filament
(i)
Flowering plants
(j)
Flowers
(l)
Fruit
(n)
Gymnosperms
(o)
Integuments
(q)
Life cycle
of an angiosperm
(r)
Monocot
(s)
Monocotyledon
(t)
Ovary
(u)
Ovule
(v)
Petals
(w)
Pollen
(x)
Seeds
(y)
Sepals
(z)
Stamen
(aa)
Stigma
(bb)
Style
(cc)
Whorls