Ch.25 Protists p.530-533

Evolution of the eukaryotes

protists were the first eukaryotic cells to evolve from ancestral prokaryotes.

monophyletic

evolved from a common ancestor electron microscopy reveals similar structural patterns among these protist taxa that comparative molecular evidence suggests are monophyletic

ultra structure

the fine details of cell structure revealed by electron microscopy

most biologists regard the protist kingdom as a paraphyletic group

the protist kingdom contains some but not all, of the descendants of a common eukaryotic ancestor.

Protists

unicellular, colonial, or simple multicellular organisms that have a eukaryotic cell organization.

parasitism

where one partner (the parasite) lives on or in another (the host) and metabolicaly depends on them

commensalism

where one partner benefits and the other is unaffected

most protists are unicellular

with each cell forming a complete organism capable of preforming all the functions characteristic of life.

Describe the kinds of data biologists use to classify eukaryotes.

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Discuss the hypothesis of serial endosymbiosis, and briefly describe some of the evidence that supports it.

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Introduction to the protists

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a consensus is emerging in eukaryote classification

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Key Concepts

Protists are a divers group of eukaryotic organisms, most of them are microscopic. Protists carry in body plan (unicellular, colonial, coenocytic, multicellular), method of motility (pseudopodia, cilia, flagella), nutrition type (autotrophic, heterotrophic) and mode of reproduction (asexual, sexual). Protists are descendants of early eukaryotes. Animals, fungi, and plants evolved from protist ancestors. Biologists are making a progress in understanding the evolutionary relationships among various protist taxa.

Characterize the features common to the members of kingdom Protista

Protists are mostly unicellular eukaryotic organisms that live in aquatic environments. Protists range in size from microscopic unicellular organisms to colonies ( loosely connected groups of cells) to coencytes (multinucleate masses of cytoplasm) to multicellular organisms (composed of many cells).

mutualism

a more or less equal partnership where both partners benefit

coenocytic

colonies that consist of multinucleate mass of cytoplasm.

some protists are multicellular

composed of many cells, but with simple body forms without specialized tissues

planktons

floating, often microscopic organisms that inhabit surface waters and are the base of the food web in aquatic ecosystems.

some protists form colonies

loosely connected groups of cells

Discuss in general terms the diversity inherent in the protist kingdom, including means of locomotion, modes of nutrition, interactions with other organisms, habitats, and modes of reproduction.

protist have various means of locomotion, including pseudopodia, flagella, and cilia. a few are nonmotile. protist obtain their nutrients autotrophically or heterotrophically. protists are free-living or symbiotic, with symbiotic relationships ranging from mutualism to parasitism. Most protists live in the ocean or in freshwater ponds, lakes and streams. Parasitic protists live in the body fluids of their hosts. Many protists reproduce both sexually or asexually; others reproduce only asexually.

protist work with other organisms

protists that form stable symbiotic associations with unrelated organisms.