protistans & metazoans

protistans & metazoans - Independent life as a single...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
Biology 5B concentrates on multicellular eukaryotic organisms, but these are a small portion of biological diversity. Most life is unicellular , mainly prokaryotic: Three domains: Bacteria, Archaea, Eukarya Independent life as a single cell LUCA -Last Universal Common Ancestor A recent ‘tree of life’ phylogeny: In 5B we largely ignore the prokaryotic Bacteria and Archaea and focus on the Eukaryotes: Prokaryotes Eukaryotes Usually no membrane other numerous membranes than cell membrane, which within the cell membrane may be infolded DNA not contained in DNA in membrane-bound a discrete region nucleus Small genome large genome (~1000 X bigger) Few organelles (ribosome) lots of complex organelles The Protists: independent life as a single cell First question: what was the origin of eukaryotes? • presumably from a prokaryote ancestor, probably an Archaean. • some recent research suggests eukaryotes came from a ‘merging’ of genomes from both bacterial and archaean ancestors: • “Ring of life” Second question: How did the internal structure of eukaryotes -- lots of complex organelles and nucleus -- arise? • formation of endomembranes (membranes inside the cell membrane, especially around the DNA): DNA Cell membrane infolds…. and internalizes Ancestral prokaryote
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Second question: How did the internal structure of eukaryotes -- lots of complex organelles and nucleus -- arise? The Protists: independent life as a single cell Internalized membranes (especially around DNA = nucleus ) Engulfing (phagocytosis) evolution of of heterotrophic aerobic mitochondrion prokaryote Endosymbiosis other organelles (e.g., chloroplasts) evolved similarly The endosymbiont concept of the origin of eukaryotes. many organelles (chloroplast, mitochondrion) still contain some DNA, retained from independent ancestors. symbioses (mutually beneficial cooperations between species) are very common; we will see many examples in both plants and animals. Today: Protozoans ( proto = early or basal, zoa = animals, as in zoo logy). "Protozoa" is an informal name for "animal-like" protistan phyla. Ingestive, heterotrophic nutrition (as opposed to photosynthetic autotrophs ) Unicellular (sometimes colonial), often with complex and unique organelles. Many modes of locomotion: pseudopodal, flagellar, cilia; organisms may be sessile, crawling, or swimming Very ancient (originated possibly > 2 billion years ago); almost certainly ancestral to metazoan animals. Protistan phylogeny is complex and constantly revised with new data. They originated ‘deep’ in the “tree of life”.
Background image of page 2
Amoebozoans ( amebae ) Gymnamoebas, etc. free-living in many habitats.
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/17/2008 for the course BIO 005b taught by Professor Chappel during the Spring '07 term at UC Riverside.

Page1 / 8

protistans & metazoans - Independent life as a single...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online