Important words and concepts from Chapter 28,
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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(1) Chapter title: The Origins of Eukaryotic
Diversity
(a)
"The more complex a structure, the more structural variation
possible. The origin of eukaryotic cells
was a major breakthrough in the history of biological diversity. Some of the
eukaryotic 'experiments' led to plants,
animals,
and fungi
through divergent lineages of protistan ancestors. We see the products of other
evolutionary experiments in the dazzling diversity of modern protists."
(b)
Note that I will be using a few conventions throughout this document to
distinguish the three main classification systems with which we will be
dealing:
(i)
Five-kingdom system = 5ks =
five-kingdom “sense”
·
in which Protista = paraphyletic
kingdom
(ii)
Three-domain system = 3ds = three-domain “sense”
·
in which Eukarya = monophyletic domain
(c)
Thus, we may differentiate eukaryotic diversity as
|
eukaryote
“kingdoms” in 3ds kingdoms |
equivalent
5ks |
|
Rhizopoda (amoebas, polyphyletic) |
|
|
Diplomonadida (Giardia lamblia, Archaezoa*;
flagellates*) |
|
|
Parabasala* (Trichomonas vaginalis*, Archaezoa*; flagellate*) |
|
|
Euglenozoa (Euglenoids, Kinetoplastids, Trypanosoma*,
Archaezoa*; flagellates*) |
|
|
Alveolata (some flagellates*, i.e, dinoflagellates; apicomplexans & ciliates) |
|
|
Stramenopila (water molds, diatoms, golden algae, brown algae) |
|
|
Rhodophyta (red algae) |
|
|
Chlorophyta (green algae,
Viridiplantae*) |
|
|
Plantae
(Viridiplantae*) |
|
|
Mycetozoa (slime molds, Myxogastrida, Dictyostelida) |
|
(d)
*terms indicated with an asterisk need not be
memorized
(e)
See Figure 28.8, A tentative
phylogy of eukaryotes
(f)
[the origins of eukaryotic
diversity (Google Search)] [index]
(2) Eukarya = monophyletic domain
(a)
The eukaryotes represent a monophyletic domain, one made up
of the protista, the fungi, the animals, and the plants
(as named according to the five-kingdom system—5ks)
(b)
See Figure 28.6, Traditional
hypothesis for how the three domains of life are related
(c)
Note, however, that a major caveat to this state are considerations of
horizontal transfer that occurred both between free-living prokaryote and
eukaryote lineages and which occurred between the eukaryote nuclear DNA and the
DNA of endosymbionts (mostly from the latter to the former)
(d)
See Figure 28.7, An alternative
hypothesis for how the three domains of life are related
(e)
[eukaryotes monophyletic
(Google Search)]
(The Tree of Life)] [index]
(3)
Kingdom Protista (protists)
(a)
Kingdom Protista (in the 5ks)
consists of the single-celled eukaryotes as well as a variety of not very
morphologically complex multicellular eukaryotes
(b)
“All protists are eukaryotes, but
protists are so diverse that few other general characteristics can be cited
without exception. In fact, protists vary in structure and function more than
any other group of organisms… at the cellular level, many protists are
exceedingly complex—the most elaborate of all cells. We should expect this of
organisms that must carry out within the boundaries of a single cell all the
basic functions performed by the collective of specialized cells that makes up
the bodies of plants and animals.” p.
520, Campbell et al., 1999
(c)
See Figure 28.1, Too diverse
for one kingdom: a small sample of protests
(d)
See Figure 28.2, The kingdom
Protista problem
(e)
[kingdom protista (Google Search)]
[images of protists
(Biology 122 Laboratory
– Southwest Missouri State
Univerisity] [index]
(4) Protista = paraphyletic taxon
(a)
Kingdom protista in the five-kingdom system
is a paraphyletic kingdom, meaning that there
exist a number of taxa (kingdoms) that are not included among the protists but
nevertheless descended from protists (5ks)
(b)
See Figure 28.8, A tentative
phylogy of eukaryotes
(c)
Keep in mind that while plants (as well as fungi, and animals)
essentially are modified protists, nevertheless plants (as well as animals and
fungi) will be considered in subsequent chapters
(d)
[protista paraphyletic
(Google Search)]
[index]
(5) Nutrient-acquisition categories ( engulfers vs. nutrient
absorbers vs. algae)
(a)
We can differentiate the members of Kingdom Protista into three non-clade nutrient-acquisition categories:
(i)
Engulfers: Single-celled eukaryotes that obtain their nutrients by engulfing
particles of food (the protozoa); these include:
·
Amoeba (Rhizopoda) including Forams (Foraminifora),
·
Ciliates (Ciliophora)
·
Slime molds (Myxogastrida and Dictyostelida in Mycetozoa)
(ii)
Nutrient absorbers: Non-fungus, non-animal eukaryotes that obtain their nutrients by
absorption across their cell membrane (the fungus-like protists); these
include:
·
Diplomonads such as Giardia lamblia (Diplomonadadida)
·
[???Trichomonads (Parabasala)???]
·
Euglena (Euglenoids in Euglenozoa)
·
[???Dinoflagellates (Dinoflagellata in Alveolata)???]
·
Water molds (Oomycota)
(iii)
Algae:
Non-plant photosynthetic eukaryotes (the algae)
·
Euglena (Euglenoids in Euglenozoa)
·
Dinoflagellates (Dinoflagellata in Alveolata)
·
Diatoms (Bacillariophyta in Stramenopila)
·
Golden Algae (Chrysophyta
in Stramenopila)
·
Brown Algae (Phaeophyta
in Stramenopila)
·
Red Algae (Rhodophyta)
(b)
“Though commonly used, the terms protozoa and algae have
no basis in phylogeny and no significance in taxonomy.” p. 521, Campbell et al., 1999
(c)
[“When Robert Whittaker popularized the five-kingdom system of
classification in 1969, he assigned unicellular eukaryotes to Kingdom Protista.
The trend during the 1970s and 1980s was to expand the boundaries of Kingdom
Protista to include some groups of multicellular organisms, such as seaweeds,
classified in earlier versions of the five-kingdom system as either plants (in
the case of seaweeds) or fungi. These taxonomic transfers were based mainly on
comparisons of cell structure and details of life cycles. In its expanded form,
Kingdom Protista also encompassed phyla of funguslike organisms, such as the
forms known as slime molds and water molds, which may have their closest
relatives among the unicellular eukaryotes called amoebas. (Slime molds are
fungus-like only in the sense that a whale is fishlike; the resemblance is due
to convergent evolution of morphological adaptations, not to common ancestry.)
The tendency was to treat Kingdom Protista as the taxonomic home for all
eukaryotes that did not fit comfortably into the definitions of plants, fungi,
and animals.” p. 524, Campbell
et al., 1999]
(d)
[(Google Search)]
[index]
(6) Protista general characteristics
(a)
Protists are
(i)
Mostly aerobic respirators
(ii)
Mostly motile during at least some stage
(iii)
Mostly chemoheterotrophs (algae excepted)
(iv)
Mostly aquatic (or, at least, favoring moist
conditions)
(vi)
and, of course, are all eukaryotic
(b)
Note that part of understanding protist biology will be to understand
protist life cycles—be prepared to learn not just the names (and basic
characteristics) of various protist taxa, but also to learn, at least in
outline, various protist life cycles
(c)
[protista general
characteristics (Google Search)] [index]
(7)
Protists are mostly aerobic respirators
(a)
Most protists are aerobic respirators, possessing either endosymbiotic mitochondria or analogous intracellular bacteria
(b)
Exceptional are the Archaezoa which are protists that lack
mitochondria
(c)
[(Google Search)]
[index]
(8)
Prostists are mostly motile
(a)
Most protists possess a flagella, cilia, or pseudopods during at least some portion of
their life histories so consequently are motile
during at least some portion of their life histories (Rhodophyta, in
particular, are excepted)
(b)
This contrasts with nearly all fungi
which never possess flagella or cilia
(c)
[(Google Search)]
[index]
(9)
Protists are mostly chemoheterotrophs
(a)
Most protists are chemoheterotrophs
(b)
Exceptions include the various algae
(c)
Additionally, there are protists, the mixotrophs, that
combine chemoheterotrophy with photoautotrophy (e.g., Euglena) using chloroplasts to gather light when that is available and
absorbing nutrients when light is not available
(d)
Animals
and fungi,
too, are chemoheterotrophs
(e)
[(Google Search)]
[index]
(a)
Mixotrophs combine photosynthesis and chemoheterotrophic modes of
nutrient acquisition; that is, they obtain their energy both from photons and
from reduced carbon compounds, particularly the latter when the sun is not
shining, and vice versa
(11)
Protists diplay a great diversity of reproductive strategies
(a)
Reproductive strategies of protists include
(i)
Asexual (i.e., reproducing solely via mitosis)
(ii)
Sexual with no mitosis in the diploid state
(iii)
Alternation of generations
(b)
“Among eukaryotes, sexual life cycles are the most
varied among the protists.” p. 524, Campbell et al.,
1999
(c)
Sexual protists display syngamy and the life histories of many
protists are further complicated by an ability to differentiate into cysts
(d)
Note that part of understanding protist biology will be to understand
protist life cycles—be prepared to learn not just the names (and basic
characteristics) of various protist taxa, but also to learn, at least in
outline, various protist life cycles
(e)
[protist reproduction
(Google Search)]
[index]
(a)
Syngamy is the fusion of gametes to form the
diploid zygote (which founds the sporophyte
generation in plants
and some algae, or the diploid stage in animals)
(b)
[syngamy (Google Search)]
[index]
(a)
Many protists can form cysts which are cell types that are resist harsh
environmental conditions such as drying out or long periods without
reproduction (i.e., no mitosis)
(b)
Supplement: Below shows as Giardia cyst undergoing excystation,
i.e., conversion from the resistant state (cyst, on left) to the vegetative
state (trophozoite, on right):
(d)
[protist cysts (Google Search)]
[index]
(14)
Protists are mostly aquatic (benthic, planktonic)
(a)
Protists are adapted for the most part to lives spent either in aqueous
or very wet environments; that is, the kingdom protista (5ks) niche
is a wet one
(i)
Some protists attach to non-floating aqueous surfaces, e.g., rocks or
sand on the bottom of a body of water; these are described as benthic
(ii)
Some protists float within bodies of water; these are described as
planktonic
(iii)
The parasitic protists inhabit the body fluids of animals and others
can serve as plant pathogens; we would describe these as non-free living as
well as parasitic (though in some cases the parasites are actually carnivores:
killing their hosts before eating them)
(b)
[protist benthic, protist planktonic
(Google Search)]
[index]
(15)
Protists are important aquatic producers
(a)
“As a large group of autotrophs, the eukaryotic algae are extremely
important ecologically. Phytoplankton (planktonic algae, along with the
prokaryotic cyanobacteria) are the bases of most marine and freshwater food
webs. Accounting for at least half the protosynthetic production of organic
material globally, they support an enormous abundance and diversity of
heterotrophic protists and animals.” p. 521, Campbell
et al., 1999
(b)
[(Google Search)]
[index]
(a)
Two things distinguish eukaryotes from prokaryotes
(i)
Internal membranes (e.g., the endomembrane system)
(ii)
Endosymbionts (e.g., mitochondria and chloroplasts)
(b)
The endomembrane system includes, of course, the cell nucleus; all
extant eukaryotes possess an endomembrane system and a cell nucleus
(c)
These membranes probably were derived from infoldings of cytoplasmic membrane of the ancestral
prokaryote
(d)
See Figure 27.8, Specialized
membranes of prokaryotes
(e)
The latter (the endosymbionts) represent co-evolved, cytoplasmic-living, gram-negative bacteria
(f)
See Figure 28.4, A model of
the origin of eukaryotes
(g)
[origin of eukaryotes
(Google Search)]
[index]
(17)
(a)
The endosymbiotic theory is the idea that mitochondria and chloroplasts both
descended from free-living, ancestral bacteria
(b)
"Perhaps they gained entry to the larger cell as undigested prey
or internal parasites. By whatever means the
relationship began, it is not hard to imagine the symbiosis eventually becoming mutually beneficial.
A heterotrophic host could derive nourishment
from photosynthetic endosymbionts. And in a world
that was becoming increasingly aerobic, a cell that was itself an anaerobe
would have benefited from aerobic endosymbionts that turned the oxygen to
advantage (or, in fact, just consumed the oxygen, thus detoxifying it). As host
and endosymbiont became more interdependent, the conglomerate of prokaryotes would gradually be integrated into a single
organism, its parts inseparable."
(c)
(“The evidence supporting an endosymbiotic origin of chloroplasts and
mitochondria includes the existence of endosymbiotic relationships in the
modern world. Another line of evidence is the similarity between bacteria and
the chloroplasts and mitochondria of eukaryotes. Chloroplasts and mitochondria
are the appropriate size to be descendants of bacteria. The inner membranes of
chloroplasts and mitochondria, perhaps derived from the membranes of
endosymbiotic prokaryotes, have several enzymes and transport systems that
resemble those found on the plasma membranes of modern prokaryotes.
Chloroplasts and mitochondria contain a genome consisting of circular DNA
molecules not associated with histones or other proteins, as in most
prokaryotes. The organelles contain the transfer RNAs, ribosomes, and other
equipment needed to transcribe and translate their DNA into proteins. In terms
of size, biochemical characteristics, and sensitivity to certain antibiotics,
the ribosomes of chloroplasts are more similar to prokaryotic ribosomes than
they are to the ribosomes outside the chloroplast in the cytosol of the eukaryotic
cell.” p. 523, Campbell
et al., 1999)
(d)
See Figure 28.4, A model of
the origin of eukaryotes
(e)
[endosymbiotic theory
(Google Search)]
[index]
(18)
(a)
What formerly had been lumped into a kingdom
called “Archaezoa” are the Diplomonads and Parabasala (no need to
know latter)
(b)
The Archaezoa are primitive unicellular eukaryotes; primitive in the
sense that they may better resemble the ancestral eukaryote than do less
primitive eukaryotes
(c)
The Archaezoa lack mitochondria and chloroplasts (and therefore neither photosynthesize
nor employ an electron transport system
to generate ATP)
(d)
See Figure 28.10, Trichomonas vaginalis, a parabasalid
(e)
[Kingdom Archaezoa, Kingdom Parabasala,
Archaezoa, Trichomonads, Microsporidians (Google Search)]
[index]
(19)
“Kingdom” Diplomonadida (Diplomonads, Giardia lamblia)
(a)
The type species of “Kingdom” Diplomonodida is Giardia lamblia, the protozoa that causes the gastrointestinal disease,
giardia
(b)
[“One group of archaezoans called the diplomonads have flagella, two
separate nuclei, no mitochondria, no plastids, and a simple cytoskeleton
[compared to other eukaryotes]. One of the diplomonads, a parasite
called Giardia lamblia, infects the human intestine, causing abdominal
cramps and severe diarrhea. Giardia is transmitted mainly in water
contaminated with human feces.” p. 524, Campbell
et al., 1999]
(c)
See Figure 28.9, Giardia: a diplomonad (see also the image to the
right/above)
(d)
[Kingdom Diplomonadida,
Giardia, Diplomonads (Google Search)]
[index]
(20)
“Kingdom” Euglenozoa (Euglenoids, Kinetoplastids)
(a)
(i)
Euglenoids, e.g., Euglena, a chemoheterotrophic and
photoautotrophic aquatic protist
(ii)
Kinetoplastids, e.g., Trypanosoma, a symbiotic protists that
causes, among other things, African sleeping sickness which is infamously
spread via the bite of the Tsetse fly
(b)
Formerly members of “Kingdom” Euglenozoa were described simply as
flagellates and it is likely that you will see them described using this term
in other texts.
(c)
See Figure 28.3, Euglena:
an example of a single-celled protist
(d)
See Figure 28.11, Trypanosoma,
the kinetoplastid that causes sleeping sickness
(e)
[Kingdom Euglenozoa,
Euglenozoa, Euglena, Trypanosoma (Google Search)]
[index]
(21)
Flagelates (Zoomastigophora, Zooflagellates
à these latter two terms are
supplemental)
(a)
In the past some members of “Kingdom” Euglenozoa
(as well as “Kingdom” Archaeoas, etc.) were called flagellates or, more
formally for the various non-photosynthetic members, zooflagellates or members
of Zoomastigophora, etc.
(b)
Characteristics of flagellates include
(i)
They are chemoheterotrophs
(ii)
They locomote using whip-like flagella
(iii)
There are both free-living and symbiotic varieties of flagellates
(e.g., Trypanosoma, above)
(c)
[Flagelates, Zoomastigophora, Zooflagellates (Google Search)]
(a)
“Another monophyletic candidate kingdom that is emerging from molecular
systematics, the Alveolata, draws together a group of photosynthetic
flagellates (the dinoflagellates), a group of parasites (apicomplexans),
and a distinctive group of eukaryotes that move by means of cilia (the ciliates).
Alveolates have small membrane-bounded cavities (alveoli) under their cell
surfaces. The function of alveoli is unknown; they may help stabilize the cell
surface and regulate the cell’s water and ion content.” p. 527, Campbell
et al., 1999
(b)
[Kingdom Alveolata, Alveolata (Google Search)]
[index]
(23)
(a)
Characteristics of Dinoflagellates include
(i)
Typically photosynthetic
(ii)
Planktonic (but some symbiotic forms)
(iii)
Typically unicellular (but some colonial forms)
(iv)
Some have cellulose cell walls
(v)
Two flagella that beat within perpendicular
grooves
(b)
Dinoflagellates are extremely important
producers in the sea, forming the “foundation of most marine and many
freshwater food chains.” p. 527, Campbell
et al., 1999
(c)
Dinoflagellates are the cause of red tides
(d)
Dinoflagellates serve as photosynthetic symbionts of coral polyps
(e)
Some non-photosynthetic parasitic forms also exist
(f)
["Other dinoflagellates lack chloroplasts and
live as parasites within marine animals. There are even carnivorous species.
The existence of both photosynthetic and heterotrophic forms closely related
enough to be grouped in the same phylum reinforces the point made earlier that
the terms protozoa and algae,
although useful in an ecological context, have no basis in phylogeny."]
(g)
See Figure 28.12, A dinoflagellate
(h)
[dinoflagellates, Dinoflagellata, red tide, Pfiesteria (Google Search)]
[index]
(24)
(a)
Characteristics of Apicomplexa include
(i)
All unicellular
(ii)
All parasites of animals
(iii)
Includes the malaria parasite (Plasmodium
spp.)
(b)
See (and know) Figure 28.13, The two-host life history of Plasmodium,
the apicomplexan that causes malaria including, in particular,
the terms sporozoite, merozoite, gametes, zygote, and oocyst
(c)
Here is an
overview of some the stages in the human host: “In the first stage of malaria
infection, mosquitoes inject worm-like sporozoites into their human hosts as
they feed on blood. When the sporozoites invade liver cells, they mature into
merozoites. In the third stage, merozoites infiltrate red blood cells and
mature into egg-like gametocytes. These then burst out of blood cells and are
sucked out of infected individuals by feeding mosquitoes. Finally, the
gametocytes mature in mosquitoes and produce new sporozoites, which the insect
injects next time it feeds.”
(d)
Here is an
overview of the stages in the mosquito: “(1) Female Anopheles mosquito
bites a person infected with malaria and picks up Plasmodium gametocytes
along with blood. (2) Gametes form from male and female gametocytes;
fertilization occurs in the mosquito’s digestive tract, and a zygote forms. The
zygote is the only diploid stage in the life cycle. (3) An oocyst develops from
the zygote in the wall of the mosquito’s gut. Thousands of sporozoites develop
in the oocyst and then migrate to the mosquito’s salivary gland.” p. 528,
Campbell et al., 1999
(e)
[Apicomplexa, Sporozoa, Plasmodium, malaria (Google Search)]
[index]
(25)
Ciliates (Ciliophora)
(a)
Ciliates are among the most complex of cells
(b)
They employ cilia (or modified
cilia) for locomotion
(c)
Ciliates live mostly in fresh water
(d)
This taxon includes the paramecia
(e)
See Figure 28.14, Ciliates
(f)
See Figure 28.15, Conjugation and genetic recombination in Paramecium
caudatum
(g)
[ciliates, Ciliophora, paramecium, micronucleus and Paramecium
(Google Search)]
[index]
(a)
The Stramenopila are a mostly photosynthetic eukaryotic lineage that,
among the photosynthetic members, appear to possess endosymbiotic red
algae (and their associated chloroplasts)
rather than simply cyanobacteria directly derived
chloroplasts
(b)
They are named for their “hairy” flagella, which are typically present
at at least some life-history stage; these flagella typically are of a pair of
flagella, the other of which does not possess these “hairs”
(c)
See Figure 28.5, Secondary endosymbiosis and the origin of algal
diversity
(d)
See Figure 28.25, A hypothetical history of plastids in the
photosynthetic eukaryotes
(e)
Some members of Stramenopila lack these endosymbiotic red algae, though
this may be a derived conditions (i.e., ancestors possessed these
endosymbionts)
(f)
The Stramenopila include the
(i)
Water molds (Oomycota)
(ii)
Diatoms (Bacillariophyta)
(iii)
Golden algae (Chrysophyta)
(iv)
Brown algae (Phaeophyta)
(g)
[Chromista (Google Search)]
[index]
(27) Oomycota (water molds)
(a)
The Oomycota or water molds superficially resemble fungi, but differ from true fungi in a number of ways
including
(i)
Water molds have cellulose (not chitin) cell walls
(ii)
Water molds are flagellated at certain points in their life cycle
(iii)
Water molds are diploid throughout most of their life cycle
(b)
See Figure 28.16, The life cycle of a water mold
(c)
[Oomycota, water molds (Google Search)]
[index]
(28) Bacillariophyta (diatoms)
(a)
The diatoms are photosynthetic and planktonic,
found in both fresh and marine environments
(b)
"Diatom cells have unique glasslike walls consisting of hydrated
silica embedded in an organic matrix. Each wall is in two parts that overlap
like a shoe box and lid."
(c)
See Figure 28.17, Diatoms
(d)
“Massive quantities of fossilized diatom walls are major constituents
of the sediments known as diatomaceous earth, which is mined for its quality as
a filtering medium and for many other uses.” p. 535, Campbell
et al., 1999
(e)
[Bacillariophyta, diatoms, diatomaceous earth
(Google Search)]
[index]
(29)
Chrysophyta (golden algae)
(a)
The Chrysophyta or golden alage are unicellular or colonial algae
possessing golden-colored photosynthetic pigment
(b)
See Figure 28.18, A golden algae
(c)
[Chrysophyta, golden algae (Google Search)]
[index]
(a)
The Phaeophyta are the brown algae
(b)
Characteristics of Phaeophyta include
(i)
Multicellular, often very large
(ii)
Brown or olive in color
(c)
Included among the brown algae are the giant kelps and various other seaweeds
(d)
[Phaeophyta, brown algae (Google Search)]
[index]
(31) Seaweed (blade, holdfast, stipe, thallus)
(a)
Seaweeds are multicellular producers that inhabit the regions where
marine coastal waters meet land
(b)
Seaweeds include the brown, red, and green algae
(c)
They are anatomically complex algae, some of which possess true
differentiated tissues (i.e., like plants)
(d)
Seaweed descriptors include
(i)
Thallus (thalli = plural) = body of the seaweed
(ii)
Holdfast = root analog used to anchor the thallus
(iii)
Stipe = stem analog
(iv)
Blade = leaf analog
(e)
That is, the thallus, going from bottom to top, consists of the
holdfast, the stipe and the blade: Holdfast-Stipe-Blade » Root-Stem-Leaf (keeping in mind that these
are analogous rather than homologous to the structures found in terrestrial
plants)
(f)
See Figure 28.19, Seaweeds: adapted to life at the ocean’s margins
(g)
[seaweed, blade holdfast stipe thallus
(Google Search)]
[index]
(32)
(a)
The life cycle of many algae, as well as green plants, displays an alternation of generations
(b)
"The term 'alternation of generations' is reserved for life cycles
that include haploid and diploid stages that
are both multicellular organisms." (emphasis mine)
(c)
See Figure 28.21, The life cycle of Laminaria: an example of
heteromorphic alternation of generations
(d)
Note in the figure
(i)
the sporophyte
(ii)
the gametophyte
(iii)
the occurrence of a familiar form of anisogamy called oogamy,
and
(iv)
of heteromorphy
(e)
[alternation of generations,
"alternation of
generations" and algae (Google Search)]
[index]
(a)
The sporophyte is the diploid generation
(b)
This generation is so named because it generates, via meiosis, haploid reproductive cells called spores that go on to form haploid
multicellular organisms
(c)
[sporophyte, sporophyte and algae,
zoospores, zoospores and algae
(Google Search)]
[index]
(a)
The haploid generation
(b)
This generation is so named because it generates, via mitosis, the haploid gametes
(c)
[gametophyte, gametophyte and algae
(Google Search)]
[index]
(a)
Isogamy is the fusion (syngamy) of phenotypically indistinguishable gametes
(b)
See Figure 28.24, The life cycle of Chlamydomonas
(c)
See the life cycle of Ulva shown under the heading green
algae, below
(d)
[isogamy, isogamy and algae (Google Search)]
[index]
(a)
Anisogamy is the fusion (syngamy) of phenotypically dissimilar gametes
(b)
See Figure 28.21, The life cycle of Laminaria: an example of
heteromorphic alternation of generations
(c)
[anisogamy, anisogamy and algae
(Google Search)]
[index]
(a)
Oogamy (accent on second o) is the fertilization of an
egg by a sperm
(b)
See Figure 28.21, The life cycle of Laminaria: an example of
heteromorphic alternation of generations
(c)
[oogamy, oogamy and algae (Google Search)]
[index]
(a)
A variation on alternation of generations where both generations are phenotypically similar, though differing in ploidy
(b)
See the life cycle of Ulva shown under the heading green
algae, below
(c)
[isomorphic, isomorphic and algae
(Google Search)]
[index]
(a)
A variation on alternation of generations
where both generations are phenotypically
dissimilar (e.g., one large and the other small)
(b)
See Figure 28.21, The life cycle of Laminaria: an example of
heteromorphic alternation of generations
(c)
[heteromorphic, heteromorphic and algae
(Google Search)]
[index]
(40) “Kingdom”
Rhodophyta (red algae)
(a)
(i)
Often red in color
(ii)
Often adapted to growth in deep water (where only blue and green light
penetrates)
(iii)
Lack flagella throughout
life cycle
(b)
See Figure 28.22, Red algae
(c)
[Rhodophyta (Google Search)]
[index]
(41) “Kingdom” chlorophyta (green algae)
(a)
Characteristics of Chlorophyta
(i)
Green in color
(ii)
Most species have biflagellated gametes
(iii)
Adapted to shallow water
(iv)
Marine and freshwater species
(b)
"Most green algae have complex life histories, with both sexual and asexual reproductive stages. Nearly all
reproduce sexually by way of biflagellated gametes."
(c)
Shown as follows is the life cycle of Ulva, the sea lettuce;
note the biflagellated gametes, the fusion of which is very similar to that
seen Chlamydomonas in Figure 28.24, The life cycle of Chlamydomonas
(e)
Note also that though Ulva is a green
algae, not all green algae display an alternation of generations
and that by definition a unicellular organism (e.g., Chlamydomonas)
cannot display an alternation of generations
(f)
See Figure 28.24, The life cycle of Chlamydomonas
(g)
[Clorophyta (Google Search)]
[index]
(42) Rhizopoda (amoebas)
(a)
Characteristics of Rhizopoda include
(i)
All are unicellular
(ii)
Some have shells
(iii)
All employ pseudopodia to move or to obtain food
(iv)
Found in fresh water, marine environments, and soil
(v)
Some are parasites
(b)
[Rhizopoda, amoeba, amoebas (Google Search)]
[index]
(a)
Membrane-enclosed cytoplasmic extensions are called pseudopodia (pseudopods,
i.e., false feet)
(b)
See Figure 28.26, Use of pseudopodia for feeding
(c)
These are employed by a number of chemoheterotropic protists including
(ii)
Actinopods (Heliozoans and Radiolarians) (which your book covers but
which we shall ignore in lecture though not in lab) [Actinopoda, Heliozoans, Radiolarians (Google Search)]
(iii)
Foraminiferans (Forams)
(iv)
Plasmodial slime molds (Myxogastrida)
(v)
Cellular slime molds (Dictyostelida)
(d)
Food includes chunks of remains of larger organisms as well as
unicellular organisms such as bacteria and other protists
(e)
“Little is known about their phylogeny, although it is clear that they
represent several distinct eukaryotic lineages.” p. 530, Campbell
et al., 1999
(f)
[pseudopodia, pseudopod, pseudopods (Google Search)]
[index]
(a)
Characteristics of Foraminifera include
(i)
All unicellular
(ii)
Mostly marine
(iii)
Most benthic
but some planktonic
(iv)
Calcium carbonate shells
(v)
Some have symbiotic algae
(b)
See Figure 28.12, Foraminiferan
(c)
The chalky White Cliffs of Dover consist of fossil forams
(e)
[Foraminifera, forams, White Cliffs of Dover
(Google Search)]
[index]
(45) “Kingdom” Mycetozoa (slime
molds)
(a)
The slime molds may be distinguished into plasmodial and cellular types
(b)
Both types obtain their nutrients as engulfers
(c)
[Mycetozoa (Google Search)]
[index]
(46) Myxogastrida (plasmodial slime molds)
(formerly Myxomycota ßlatter
is supplement)
(a)
Feeding stage consists of a motile, multinucleated, amoeboid mass
called a plasmodium (don't confuse plasmodium with Plasmodium, the genus that causes malaria)
(b)
"If the habitat of a slime mold begins to dry up or there is no
food left, the plasmodium ceases growth and differentiates into a stage of the
life cycle that functions in sexual reproduction."
(c)
See Figure 28.29, The life cycle of a plasmodial slime mold, such as Physarum
(d)
[Myxogastrida, Myxomycota, plasmodial slime mold
(Google Search)]
[index]
(47)
Dictyostelida (cellular slime molds)
(formerly Acrasiomycota ßlatter
is supplement)
(a)
Unlike the plasmodial
slime molds, the cellular
slime molds exist as free-living individual cells that come together to
form a multicelled slug (rather than forming a multinucleated plasmodium via
multiple rounds of mitosis not followed by cytokinesis as do the plasmodial
slime molds)
(b)
Individual cells resemble amoebas
(c)
"The feeding stage of the life cycle consists of solitary cells
that function individually. When there is no more food, the cells form an
aggregate that functions as a unit. Although the mass of cells resembles a
plasmodial slime mold, the important distinction is that the cells of a
cellular slime mold maintain their identity and remain separated by their
membranes."
(d)
See Figure 28.30, The life cycle of a cellular slime mold (Dictyostelium)
(e)
[Dictyostelida, Acrasiomycota, cellular slime mold
(Google Search)]
[index]
(48)
Vocabulary [index]
(a)
Algae
(b)
Algal life cycles, examples
(c)
Alternation of generations
(d)
Alveolata
(e)
Amoebas
(f)
Anisogamy
(g)
Apicomplexa
(h)
Archaezoa
(i)
Bacillariophyta
(j)
Benthic
(k)
Blade
(l)
Brown algae
(n)
Chlorophyta
(o)
Chrysophyta
(p)
Ciliates
(q)
Ciliophora
(r)
Cysts
(s)
Diatoms
(t)
Dictyostelida
(u)
Dinoflagellata
(v)
Dinoflagellates
(w)
Diplomonads
(x)
Diplomonadida
(z)
Engulfers
(aa)
Euglenoids
(bb)
Euglenozoa
(cc)
Eukaryotes
(dd)
Flagellates
(ee)
Foraminifera
(ff)
Forams
(gg)
Gametophyte
(hh)
Giardia lamblia
(ii)
Golden algae
(jj)
Green algae
(kk)
Heteromorphic
(ll)
Holdfast
(mm)
Isogamy
(nn)
Isomorphic
(oo)
Kinetoplastids
(pp)
Mixotrophic
(qq)
Mycetozoa
(rr)
Myxogastrida
(ss)
Nutrient absorbers
(tt)
Nutrient-acquisition categories
(uu)
Oogamy
(vv)
Oomycota
(ww)
Origin of eukaryotes
(xx)
Parabasala
(yy)
Phaeophyta
(zz)
Phylogenic overview
(aaa)
Planktonic
(bbb)
Plasmodial slime molds
(ccc)
Protista general characteristics
(ddd)
Protista (5ks)
(eee)
Protista (8ks)
(fff)
Protists
(ggg)
Protists are important aquatic producers
(hhh)
Protists are mostly aerobic respirators
(iii)
Protists are mostly aquatic
(jjj)
Protists are mostly chemoheterotrophs
(kkk)
Protists are mostly motile
(lll)
Protists display a great diversity of reproductive
strategies
(mmm) Pseudopodia
(nnn)
Red algae
(ooo)
Rhizopoda
(ppp)
Rhodophyta
(qqq)
Seaweed
(rrr)
Slime molds
(sss)
Sporophyte
(ttt)
Stipe
(uuu)
Syngamy
(vvv)
Thallus
(www) Water molds