Most taxonomists now recognize the
domain as the largest taxon. The
three taxa at the domain level are the
Bacteria, Archae, and Eukarya. All
eukaryotes are in the domain
Eukarya. Within those domains are
super groups. The kingdoms are
found within the super groups. Of the
five kingdoms three have survivedAnimalia, Plantae, and Fungi. The
Moneran and Protista kingdoms are
no longer recognized.The major
difference between prokaryotic and
eukaryotic cells is the existence of
membrane bound organelles. These
organelles include the nucleus, E.R.,
lysosome, Golgi apparatus,
mitochondrion and plastid. The
advantage of having
compartmentalization allows for
specialization of tasks and greater
efficiency.
The evolution of the organelles involves two different processes- involution of cell membranes to
form the cytomembrane (endomembrane) system and endosymbiosis.
Shown is the possible outline of sequence of events that led to the cytomembrane system which
led to the development of the nucleus, E.R., Golgi apparatus, lysosome, vacuoles and vesicles.
The origination of the mitochondrion is thought to have come about by a prokaryotic cell engulfing
another aerobic heterotrophic prokaryote. This cell took up residence and eventually became the
mitochondrion. Evidence for this includes that the mitochondrion like prokaryotic cells have
circular, nonhistone DNA. The mitochondrion has prokaryotic-like ribosomes and does proteins
synthesis like a prokaryotic cell. The mitochondrion
replicates doing binary fission like a prokaryotic cell.
The origination of plastids (chloroplasts, chromoplasts and
leukoplasts) thought to have come about by a prokaryotic
cell engulfing another photosynthetic, aerobic prokaryote.
This cell took up residence and eventually became the
chloroplast. Evidence for this includes that the plastids like
prokaryotic cells have circular, non-histone DNA. The
plastid has prokaryotic-like ribosomes and does proteins
synthesis like a prokaryotic cell. The plastid replicates doing
binary fission like a prokaryotic cell. In the course of
evolution this has happened many times.
The algae that were involved in a secondary endosymbiosis
have 3-4 membranes
on their chloroplasts.
The Protista Kingdom
no longer exists.
Protists though are
considered to be
unicellular (or
multicellular without
differentiation). In
other words any
eukaryote not
considered to be a
plant, animal or fungus is a protist. Remember, protists, animals, fungi, and plants are all in the
same domain, Eukarya. There are five recognized super groups in the domain Eukarya
1. Excavata
2. Chromalveolata
3. Rhizaria
4. Archaeplastida
(plant kingdom found in this group)
5. Unikonta
(Animal and Fungi Kingdom found in this group)
The super group
Excavata (relationship
in the Eukarya is not
clear)
a. Grove on one side
of the cell body
b. Diplomonads and Parabasalids have reduced mitochondria
c. Euglenozoans have flagella with unique spiral rod
i. Kinetoplastids-have large mitochondrion with large mass of DNA-feed on prokaryotesii.
Euglenid-some mixotrophs in light do photosynthesis
in the dark become heterotrophic. Have protein pellicle under the cell membrane.
Giardia intestinalis can cause intestinal distress and diarrhea.
Trichomonas vaginalis is a sexually transmitted parasite that can infect both males and females
causing tissue damage. Has the ability to change surface proteins to evade recognition by the
immune system. (tricky little suckers!)
The super group- Chromalveolata
I. Alveolates-have membrane bags under cell membrane
A. Dinoflagellates-cellulose plates with perpendicular
grooves with flagella. Cause of red tide. Some autotrophs,
heterotrophs and mixotrophs.
B. Apicomplexan-parasites (Plasmodium) causes malaria.
Complex life cycle
C. Ciliates-Covered with cilia (Paramecium caudatum) has
large and small nuclei
II. Stramenopiles-covered with numerous fine “hairy” flagella
which is paired with regular shorter flagellum
Stores energy in form of laminarin (polysaccharide) and oil.
A. Diatoms-cell walls of silicon dioxide (glass) that overlap
Petri dish. Very strong. Over 100,000 species.
B. Golden algae have yellow and brown carotenoids. Most
unicellular, some mixotrophs.
C. Brown algae-Most complex of all the algae. Somewhat
like plants (analogous structures) Kelp beds Used for
food in some countries.
The super group- Rhizaria
Many members have long, stringy pseudopods (fake extensions). Forams (foraminiferans) have
shells made of calcium carbonate. Pseudopods extend through the pores.
A. Forams (foraminiferans) have shells made of calcium carbonate. Pseudopods extend
through the pores.
B. Radiolarians internal skeletons of silica with pseudopods extending out.
The super group- Archaeplastida Contains red algae, green algae and Plant Kingdom
A. Red algae-contain photosynthetic accessory pigment, phycoerythrin. Makes the algae
appear red-green to red depending on the amount. Phycoerythrin absorbs blue and green
light so red algae can survive in deeper water that blue and green light penetrates. Mostly
multicellular and has alternation of generation life cycle with no flagellated gametes.
B. Green algae-contain chlorophyll A and B
1. Chlorophytes unicellular, colonial and multicellular species. Reproduction includes
alternation of generations.2. Charophytes rosette shaped cellulose synthesizing
complexes, and other characteristics in common with higher plants. Closest relative to
land plants.
Super group Unikonta-two major clades Amoebozoans and Opisthokonts. Include slime molds,
amoebas, fungi and animals.
I. AmoebozoansA. Gymnamoebas- amoebas with club-like pseudopods. Heterotrophs consuming prokaryotes
and other protists
B. Entamoebas- parasitic amoebas. Entamoeba histolytica causes dysentery.
C. Slime molds- Two types Plasmodial slime molds form acellular masses where as cellular
slime molds form cellular plasmodial masses. Can live as individual cells
II. Opisthokonts-Includes nucleariids, fungi, choanoflagellates and animals.
A. Nucleariids are amoeba-like protists and more closely related to fungi than other protists
B. Kingdom Fungi that are absorptive heterotrophs. Characterized by columns of cells called
hyphae. Most are multicellular.
C. Choanoflagellates are flagellated protists that will form colonies. Individuals look much like
sponge cells.
D. Kingdom Animalia are multicellular ingestive heterotrophic organisms.