The Origins of Eukaryotic Diversity

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

eukaryote “kingdoms” in 3ds kingdoms	equivalent 5ks
Rhizopoda (amoebas, polyphyletic)	Protista
Diplomonadida (Giardia lamblia, Archaezoa; flagellates)	Protista
Parabasala* (Trichomonas vaginalis, Archaezoa; flagellate*)	Protista
Euglenozoa (Euglenoids, Kinetoplastids, Trypanosoma, Archaezoa; flagellates*)	Protista
Alveolata (some flagellates*, i.e, dinoflagellates; apicomplexans & ciliates)	Protista
Stramenopila (water molds, diatoms, golden algae, brown algae)	Protista
Rhodophyta (red algae)	Protista
Chlorophyta (green algae, Viridiplantae*)	Protista
Plantae (Viridiplantae*)	Plantae
Mycetozoa (slime molds, Myxogastrida, Dictyostelida)	Protista
Fungi	Fungi
Animalia	Animalia

(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]

PROTIST (5KS) OVERVIEW

(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

(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), Actinopoda (Heliozoans & Radiolarians)

· 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)???]

· Plasmodium (Apicomplexa)

· 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)

· Green Algae (Chlorophyta)

(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)

(v) Reproductively diverse

(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

(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

(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

(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]

(10) Mixotrophic

(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

OVERVIEW OF PROTIST REPRODUCTIVE STRATEGIES

(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]

(12) Syngamy

(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]

(13) Cysts

(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):

(c)

(d) [protist cysts (Google Search)] [index]

A BIT OF PROTIST ECOLOGY

(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]

PROTIST ORIGINS

(16) Origin of eukaryotes

(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

(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) Endosymbiotic theory

(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]

KINGDOM “ARCHAEZOA”

(18) (Archaezoa) ß not supplemental (Kingdom Parabasala ßsupplemental)

(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]

(d) [Kingdom Diplomonadida, Giardia, Diplomonads (Google Search)] [index]

“KINGDOM” EUGLENOZOA

(20) “Kingdom” Euglenozoa (Euglenoids, Kinetoplastids)

(a) “Kingdom” Euglenozoa includes the

(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.

(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)

“KINGDOM” ALVEOLATA

(22) ”Kingdom” Alveolata

(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) Dinoflagellates (Dinoflagellata )

(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

(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) Apicomplexa (Sporozoans) (malaria, Plasmodium spp.)

(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

(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]

“KINGDOM” STRAMENOPILA

(26) Kingdom Stramenopila

(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”

(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

(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

(30) Phaeophyta (brown algae)

(a) The Phaeophyta are the brown algae

(b) Characteristics of Phaeophyta include

(i) Multicellular, often very large

(ii) Brown or olive in color

(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

(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]

SOME TERMS AND CONCEPTS PERTINENT TO PROTIST LIFE CYCLES

(32) Alternation of generations

(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]

(33) Sporophyte

(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

(34) Gametophyte

(a) The haploid generation

(b) This generation is so named because it generates, via mitosis, the haploid gametes

(35) Isogamy

(a) Isogamy is the fusion (syngamy) of phenotypically indistinguishable gametes

(b) See Figure 28.24, The life cycle of Chlamydomonas

(d) [isogamy, isogamy and algae (Google Search)] [index]

(36) Anisogamy

(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

(37) Oogamy

(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

(38) Isomorphic

(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

(39) Heteromorphic

(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

“KINGDOM” RHODOPHYTA

(40) “Kingdom” Rhodophyta (red algae)

(a) Characteristics of Rhodophyta include

(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

“KINGDOM” CHLOROPHYTA

(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

(d)

(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]

AMOEBAS

(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]

(43) Pseudopodia

(a) Membrane-enclosed cytoplasmic extensions are called pseudopodia (pseudopods, i.e., false feet)

(b) See Figure 28.26, Use of pseudopodia for feeding

(i) Rhizopods (Amoebas)

(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]

(44) Foraminifera (forams)

(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

(d)

(e) [Foraminifera, forams, White Cliffs of Dover (Google Search)] [index]

“KINGDOM” MYCETOZOA

(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

(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]