9.2-9.3 Model Organisms and their Morphological and Physiological Characteristics

Question 1

______
◼ group of all the eukaryotes that are not fungi, animals, or plants.
◼ have cross-kingdom characteristics that make it difficult to justify keeping them all in a single group or subgroup.

Answer 1

PROTISTS

Question 2

PROTIST DIVERSITY
Four Supergroup:
1.
2.
3.
4.

Answer 2

Excavata
SAR Clade
Archaeplastida
Unikonta

Question 3

◼ defined by an asymmetrical appearance with a feeding groove that is “excavated” from one side
◼ parasitic, photosynthetic and heterotrophic predators
◼ subgroups are the _______

Answer 3

EXCAVATA
diplomonads, parabasalids, and euglenozoans.

Question 4

◼ most of which are parasitic
◼ Identified with mitosomes
(mitochondrial remnant
organelles)
◼ exist in anaerobic env’t and
use glycolysis to generate
energy
◼ two identical nuclei and uses several flagella for locomotion

Answer 4

DIPLOMONADS, excavata

Question 5

◼ exhibit semi-functional mitochondria
◼ Hydrogenosomes (anaerobes)
◼ parasitic protists which move with flagella and membrane rippling
◼ Trichomonas vaginalis, a parabasalid that causes a sexually-transmitted disease (trichomoniasis)

Answer 5

PARABALASIDS, excavata

Question 6

◼ parasites, heterotrophs, autotrophs, and mixotrophs, ranging in size from 10 to 500 μm.
◼ move through their aquatic habitats using two long flagella toward light using eyespot
◼ familiar genus, Euglena, encompasses some mixotrophic species (photosynthetic when light is present and heterotrophic during dark)

Answer 6

EUGLENOZOANS, excavata

Question 7

◼ subgroup of Euglenozoa
◼ named after the kinetoplast, a DNA mass carried within
the single, oversized mitochondrion
◼ Includes several parasites, called trypanosomes
◼ human parasite, Trypanosoma brucei, which causes African sleeping sickness

Answer 7

KINETOPLASTIDS, excavata

Question 8

2. _______
   ◼ organisms with hairy and smooth flagella, or membrane-enclosed sacs (alveoli) beneath plasma membrane, or amoebas with threadlike pseudopodia
   ◼ ______ (Diatoms, Golden algae, Brown algae), ______ (Dinoflagellates, Apicomplexans, and Ciliates), ______ (Radiolarians, Forams, Cercozoans).

Answer 8

SAR CLADE
Stramenopiles
Alveolates
Rhizarians

Question 9

◼ characterized by the presence of a long, anteriorly directed flagellum with mastigonemes (a.k.a stramenopili), tiny tripartite bristles
◼ comprise a monophyletic cluster of autotrophic organisms (Ochrophyta) and several heterotrophic lineages
◼ heterotrophic clades include several unicellular members (e.g., bicosoecids, marine stramenopiles, placidids), parasitic species (e.g., Blastocystis, Peronosporomycetes, labyrinthulids), and endocommensals (e.g., Opalinida).

Answer 9

STRAMENOPHILES, sc

Question 10

◼ contains the three well-known lineages, Dinoflagellata, Apicomplexa, and Ciliophora
◼ mostly unicellular organisms, some form filaments or chains, and others have large and complex cells
◼ parasitic (e.g., apicomplexans), heterotrophic (e.g., ciliates, some dinoflagellates), autotrophic (e.g., some dinoflagellates), and mixotrophic

Answer 10

ALVEOLATES, sc

Question 11

◼ distinct shapes due to “frames” of cellulose within their cell walls
◼ Their cell surface is ridged
with perpendicular grooves
that house a pair of flagella ◼ Flagella, their defining
characteristics, move by rotation or whirling
◼ responsible for red tide events, or “harmful algal blooms”

Answer 11

DINOFLAGELLATES, sc a

Question 12

◼ parasites, specialized for living and reproducing within the tissues of animals
◼ with apical complex (cluster of microtubules and organelles) located in the apex of cells that are in the sporozoite (infectious stage)
◼ an apicomplexan transmitted by mosquitoes, the infamous Plasmodium, which causes malaria in humans and other animals

Answer 12

APICOMPLEXA, sc a

Question 13

◼ characterized by the presence of hair-like organelles called cilia, which are identical in structure to eukaryotic flagella, but are in general shorter and present in much larger numbers, with a different undulating pattern than flagella.

Answer 13

CILIATES, sc a

Question 14

◼ are heterotrophic, free-living, and are difficult to isolate and culture
◼ show clear sign of secondary endosymbiosis
◼ contains several amoeboid lineages (e.g., Foraminifera and “euglyphids”) that
have filose (fine) pseudopods varying from simple to branching and
anastomosing
◼ abundance of Cercozoa in some soils, represent an estimated 30–60% of the
total protist community

Answer 14

RHIZARIANS, sc

Question 15

3. ◼ literally means “ancient plastids”
   ◼ all share plastids/chloroplasts that were primarily acquired some billion years ago when a cyanobacteria-like organism was engulfed by a heterotrophic eukaryote
   ◼ Included ______, _______ (red algae), and _______ (green algae)

Answer 15

ARCHAEPLASTIDA
glaucophytes
rhodophytes
chloroplastida

Question 16

◼ inhabits near the surface of freshwater environments
◼ have retained a number of the ancestral traits of the cyanobacteria-like organism that developed into plastids (referred to as “cyanelles” or “muroplast”)

Answer 16

GLAUCOPHYTES, ap

Question 17

◼ red algae
◼ have at least 6,000 mostly marine
members
◼ Some are unicellular, but most are
filamentous or multicellular ones
◼ Phycoerythrin (red photosynthetic
pigment)
◼ Intensity of coloration depends on the depth where the species thrive; dark colored red algae which may sometimes appear black is usually observed in deep waters

Answer 17

RHODOPHYTES, ap

Question 18

◼ green algae
◼ with 12,000 green algae species recorded
◼ with varying photosynthetic pigments: xanthophyll, carotene, chlorophyll a, and chlorophyll b
◼ either motile or non-motile
◼ vary in size and form:
unicellular, colonial, multicellular, filamentous, or tubular

Answer 18

CHLOROPLASTIDA, ap

Question 19

What condition could have permitted the ancestral green algae to transition to land plants?

Answer 19

Evidence shows that plants evolved from freshwater green algae. In plants, the embryo develops inside of the female plant after fertilization. Algae do not keep the embryo inside of themselves but release it into water. This was the first feature to evolve that separated plants living on land from green algae

Question 20

◼ the most heterogeneous mix of members
◼ has two major clades: _____ and _____

Answer 20

UNIKONTA
Amoebozoa
Opisthokonta

Question 21

◼ are either amoebae for all or at least a huge chunk of their life cycle while employing their pseudopodia for movement
◼ most species from are lobopodian but a few non-fruiting amoebae are filose or reticulate
◼ capable of cyst formation when resources are inadequate but once the condition permits, they consume their prey through phagocytosis
◼ Fungus-like slime molds such as the Physarum also belong to this subgroup

Answer 21

AMOEBOZOA, u

Question 22

◼ With two distinctly protists members of the nucleariids and the choanoflagellates
◼ NUCLEARIIDS
◼ filose amoebae identified as the ancestral
group of fungi
◼ CHOANOFLAGELLATES
◼ only known closest relatives of animals. ◼ nutritional modality is heterotrophic
phagocytosis employing a collar of microvilli around a flagellum.
◼ The propulsion of the flagellum creates a current that allows suspended food particles to be filtered into the organism

Answer 22

OPISTOKHONTA, u