1 AP BIOLOGY 11 13. The Protists Classification • The protists are by far the most difficult group of organisms to classify. • It is the most artificial and disagreed upon by biologists. • We will not focus so much on the taxonomy as the diversity within this group. • We will divide them into three groups based upon their nutrition method. Classification 1. Ingestive Protists • These are animal like protists that bring food into cells (ingest) and digest it. • Examples include the Protozoa. A Paramecium Classification 2. Absorptive Protists • Fungus like protists that use extracellular digestion, ie. They secrete enzymes onto a food source, digest it, then absorb the digested products. • Ex: Water and slime molds. A plasmodial slime mold Classification 3. Photosynthetic Protists • Plant like protists that do photosynthesis. • Include most of the unicellular, colonial, and multicellular algae. Evolution • Protists represent the first eukaryotes. • Probably evolved from prokaryotes that didn’t have a cell wall (therefore flexible). • Maintained shape with their cytoskeleton. • This could also “pull” is some plasma membrane to surround their nuclear material - forming a nucleus (by process like phagocytosis).
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AP BIOLOGY 11 - · PDF fileAP BIOLOGY 11 13. The Protists Classification ... C. Euglenophyta • Contains Euglena and related organisms. • Combine auto and heterotroph character
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AP BIOLOGY 11
13. The Protists
Classification
• The protists are by far the most difficult group of organisms to classify.
• It is the most artificial and disagreed upon by biologists.
• We will not focus so much on the taxonomy as the diversity within this group.
• We will divide them into three groups based upon their nutrition method.
Classification
1. Ingestive Protists • These are animal
like protists that bring food into cells (ingest) and digest it.
• Examples include the Protozoa.
A Paramecium
Classification 2. Absorptive Protists • Fungus like protists that
use extracellular digestion, ie. They secrete enzymes onto a food source, digest it, then absorb the digested products.
• Ex: Water and slime molds.
A plasmodial slime mold
Classification
3. Photosynthetic Protists
• Plant like protists that do photosynthesis.
• Include most of the unicellular, colonial, and multicellular algae.
Evolution
• Protists represent the first eukaryotes. • Probably evolved from prokaryotes that didn’t
have a cell wall (therefore flexible). • Maintained shape with their cytoskeleton. • This could also “pull” is some plasma
membrane to surround their nuclear material - forming a nucleus (by process like phagocytosis).
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Evolution
• This started cytoplasmic compartmentalization which allows for internal specialization.
• Cytoskeleton also allowed for new mode of cell division - mitosis.
• This removed the restriction of one circular chromosome, allowing many linear chromosomes - this produces more genetic information and more complexity.
Evolution
• This also allowed for true sexual reproduction to occur with meiosis and fertilization - increasing variations!
• The evolution of mitochondria and chloroplasts probably involved the evolution of a symbiotic relationship between a prokaryote and the evolving eukaryote.