Download AP Biology, Chapter 28 Protists Living Small 28.1 Most eukaryotes

AP Biology, Chapter 28
Protists
Living Small
28.1 Most eukaryotes are single-celled organisms
Intro
Structural and Functional Diversity in Protists
1. Explain why protistan cells are not analogous to a single cell from a multicellular
organism.
Multicellular cells are specialized
Many protistan cell show elaborate adaptations for performing all life functions
2. Describe the general protistan life cycles, habitats, and nutritional modes.
Life cycles
Most can reproduce asexually; many also sexually
Haploids are the main vegetative stage in most
Many form cysts in harsh conditions
Habitats
Most are aquatic as free-living bottom dwellers or plankton
Many are symbionts
Nutrition
Photoautotrophs
Chemoheterotrophs
Mixotrophs: a combination depending on conditions
Endosymbiosis in Eukaryotic Evolution
3. Describe three evolutionary trends that occurred as some prokaryotic groups became
increasingly complex.
Multicellularity as in cyanobacteria
Complex communities of mutualistic prokaryotes
Intracellular compartmentalization of function
4. Review: describe the evidence that supports the theory that mitochondria and
plastids evolved by serial endosymbiosis. Explain what living organisms are the likely
relatives of the prokaryotes that gave rise to mitochondria and plastids.
Modern endosymbiotic relationships
Similarities between bacteria and mitochondria and chloroplasts
Cell / organelle size
Prokaryote-type membrane components
Replication by binary fission
Single, circular DNA without histones
Similar transcriptional and translational apparatus
Mitochondria most resemble proteobacteria; plastids cyanobacteria
5. Given the endosymbiosis theory, explain the modern collaboration between the
genome of the organelles and nucleus.
Genes have been transferred from the organelle to the nucleus
Transfer is common among prokaryotes
6. How does secondary endosymbiosis explain the diversity of plastids?
Sequential endosymbiotic fusions were involved
Explains >2 membranes around some algal plastids
Vestigial nuclei in chlorarachniophyte plastids
Five Supergroups of Eukaryotes
7. How do the five supergroups or major clades of protists relate to one another?
There is thought to have been a common ancestor of Domain Eukarya
Unresolved branching order after that
Shown on phylogenetic trees as a polytomy
28.2 Excavates include protists with modified mitochondria and protists with unique
flagella
Intro
8. What defines the Excavata?
Clade based on common cytoskeletal morphology
No molecular sequence confirmation
However, that may be a primitive derived character
9. Describe the key morphological characteristics and most important examples of
Excavates.
Diplomonads and Parabasalids
Morphology: modified mitochondria
Examples
Intestinal parasites (Giardia)
Sexually transmitted disease(Trichomonas)
Euglenozoans
Morphology: spiral or crystalline rod inside flagella
Kinetoplastids
Examples
Trypanosoma
Euglenids
Sleeping sickness spread by tsetse flies
Chagas disease spread by “kissing bugs”
Euglena freshwater mixotrophs
28.3 Chromalveolates may have originated by secondary endosymbiosis
Intro
10. What defines the Chromalveolata?
DNA sequence suggest a monophyletic group
May have arisen from secondary endosymbiosis of a red alga
11. Describe the key morphological characteristics and most important examples of
Chromalveolates.
Alveolates
Morphology: membrane-bound sacs under plasma membrane
Intro
Examples
Toxic dinoflagellates like Pfisteria
Plasmodium (malaria) spread by mosquitoes
Freshwater ciliates like Paramecium
Stramenopiles
Intro
Morphology: most have both a hairy and a smooth flagellum
Diatoms
Protected by overlapping silica shells
Major component of aquatic phytoplankton
Golden Algae
Brown Algae
Example: kelp forests
Thallus with holdfast, stipe, blades
Mainly coastal
Harvested for food, food additives, etc.
Oomycetes (Water Molds and Their Relatives)
Hyphae with cellulose cell walls
Water molds: potato blight
Alternation of Generations
12. Describe a life cycle including an alternation of multicellular generations.
Diploid sporophyte makes haploid zoospores by meiosis
Haploid gametophyte makes gametes by mitosis
Zygote gives rise to sporophyte
Sporophyte and gametophyte may look much different
28.4 Rhizarians are a diverse group of protists defined by DNA similarities
Intro
13. What defines the Rhizaria?
DNA sequence suggest a monophyletic group
Many have threadlike pseudopods
14. Describe the key morphological characteristics and most important examples of
Rhizarians.
Radiolarians
Morphology: many have silica shells
Aquatic heterotrophs
Forams
Morphology: multichambered, coiled, calcium carbonate shells with tiny holes
Aquatic heterotrophs
Cercozoans
Morphology: some with fresh cyanobacterial endosymbionts
28.5 Red algae and green algae are the closest relatives of land plants
Intro
15. What defines the Archaeplastida?
DNA sequence
Original mitochondria+plastid endosymbiont
16. Describe the key morphological characteristics and most important examples of
Archaeplastida.
Red Algae
Morphology
Color from phycoerythrin
Absorbs wavelengths that penetrate deeper water
Most are multicellular seaweeds
Example: nori sushi wrap
Green Algae
Morphology
Chloroplast structure and pigments homologous with plants
Examples
Unicellular Chlamydomonas
Colonial Volvox
Multicellular Ulva
28.6 Unikonts include protists that are closely related to fungi and animals
Intro
17. What defines the Unikonta?
Myosin sequence and multigene sequences
18. Describe the key morphological characteristics and most important examples of
Unikonta.
Amoebozoans
Intro
Morphology: lobe-shaped pseudopods
Slime Molds
Plasmodial Slime Molds
Physarum grows as a giant multinuclear cell or plasmodium
Forms fruiting bodies upon starvation
Cellular Slime Molds
Dictyostelium feeds as individual amoebae
Aggregates upon starvation
Multicellular mass migrates, the differentiates into fruiting body
Gynamoebas
Entamoebas
Opisthokonts
Parasitic amoebae
Example: Entamoeba histolytica causes amoebic dysentery
Morphology
Name means, “posterior flagellum”
Examples: fungi and animals
28.7 Protists play key roles in ecological communities
Intro
Symbiotic Protists
19. Exemplify the significant symbiotic protists.
Corals have mutualistic algae
Termite harbor wood-digesting protists
Plasmodium and Trypanosoma cause significant diseases
Photosynthetic Protists
20. Quantify the contributions of prokaryotes and plants to global productivity.
Protists 30%
Plants 50%
Prokaryotes 20%