Chapter 26 - Protists

What are basic features of Diplomonands

clade. supergroup: excavate. Excavates that have one or two nuclei, no functional mitochondria, no golgi complex, and up to 8 flagella.

Briefly describe: cellular slime molds

feed as individual amoeboid cells. They reproduce by aggregating into an aggregate (slug), then forming asexual spores.

Briefly describe: plasmodial slime molds

seeding stage of plasmodial slime bolds is a multinucleate plasmodium. Reproduction is by haploid spores produced within sporangia.

How to Protists obtain nutrients?

Autotrophically, or heterotrophically. Protists are free-living, or symbiotic, with symbiotic relationships ranging from mutualism to parasitism.

Describe the kinds of data biologists use to classify eukaryotes.

Relationships among protists are determined largely by "ultrastructure" which are the fine details of cell structure revealed by electromicroscopy, and by comparative molecular data. Or they compare nuclear genes.

Contrast two main groups of chromalveolates: aveolates and stramenopiles.

Chromalveolates: Probably orginated as result of secondary endosymbiosis. Some DNA sequence data suggests chromalveolates are not monophyletic. Aveolates: have similar ribosomal DNA sequences and aveoli flattened vesticles located just inside the plasma membrane. Most stramenopiles have motile cells with two flagella, one of which has tiny hairline projections off the shaft.

Distinguish among the alveolates: Dinoflagellates, apicomplexans, and ciliates.

Dinoflagellates: Mostly unicellular, biflagellate, photosynthetic avelolates of great econogical importance as producers in marine ecosystems. Apicomplexans are parasites that produce sporozoits and are nonmotile. An atypical complex of microtublules attaches it to its host cell. The Apicomplexan Plasmodium causes malaria. Ciliates are Aveolates that move by hairlike cilia, have micronuclei (for sexual reproduction) and macronuclei(for controlling cell metabolism and growth), and undergo sexual process called conjugation.

How to Protists reproduce?

Many reproduce both sexual and asexually; others reproduce only asexually.

Discuss Protist locomotion:

Protists have various means of locomotion, pseudopodia, flagella, cillia; a few are nonmotile

Describe evidence supporting the hypothesis that red algae and green algae should be included in a monophyletic group with land plants.

Red and green algae and land plants, collectively called archaeplastids are considered a monphyletic group based on molecular data and on the presence of chloroplasts bounded by outer and inner membranes. Red Algae, mostly multicellular seaweeds, are ecologically important in warm tropical ocean waters. Green Algae, exhibit wide diversity in size, structural complexity, and reproduction. Botanists hypothesize that ancestral green algae give rise to land plants.

Briefly describe some evidence that supports endosymbiosis.

They think chloroplasts of red, and green algae and platns probably came from a single primary endosymbiotic event in which cyanobacterium was incorporated into a cell. Eventually this lead to euglenoids, dinoflagellates, diatoms, etc.

What are the basic features of excavates?

They're a diverse group of unicellular protists with an excavated oral groove, and atypical, greatly modified mitochondria.

What are the basic features of Parabasilids?

anaerobic, flaggellated excavtes that often live in animals. Trichonymphs and trichomonands are examples of parabasilids.

Describe the Stramenopile: water molds

have a coenocytic mycelium. They reproduce asexually by forming biflagellate zoospores and sexually by forming oospores.

Briefly describe Unikonts

include fungi and animals, share a single posterior flagellum in flagellate cells.

Discuss the hypothesis of serial endosymbiosis.

mitchondria and chloroplasts arose from symbiotic relationships between large cells and smaller bacteria were incorporated and lived within them.

Describe the Stramenopile: golden Algae

mostly unicellular, biflagellate freshwater and marine stramenopiles are of ecological importance as a component of the oceans extremely minute nanoplankton.

Briefly describe: choanoflagellates.

unikonts that are probably the closest living non-animal relative of animals. A collar of microvilli surrounds their single flagellum at the base.

What are typical habitats for Protists?

Most live in oceans, or in freshwater ponds, lakes, streams. Parasitic protists live in the body fluids or cells of their hosts.

Describe the forams and actinoods and explain why many biologists classify them in the rhizarian supergroup.

Rhizarians: are ameoboid cells that often have hard outer shells, called tests, through which cytoplasmic projections extend; molecular evidence indicates this group is monophyletic. Forams: secrete many-chambered tests with pores through which cytoplasmic projections extend to move and obtain food. Actinopods: mostly marine plankton that obtain food by means of axopods, slender cytoplasmic projections that extend through pores in their shells.

Euglenoids

Unicellular and flagellate. Some euglenoids are photosynthetic

Describe the Stramenopile: diatoms

mostly unicellular, with shells containing silica. Some diatoms are part of floating plankton, and others live on rocks and sediments where they move by gliding.

Briefly describe: ameobas

move and obtain food by phagocytosis, using cytoplasmic extensions called pseudopodia

Describe the Stramenopile: brown algae

multicellular stramenopiles that are ecologically important in cooler ocean waters. the largest brown algae (kelps) possess leaflike blades, stemlike stipes, achoring holdfasts, and gas-filled bladders for buoyancy.