Prokaryotes and Protists CH 16

PROKARYOTES Prokaryotes have inhabited Earth for billions of years – Prokaryotes are the oldest life-forms and remain the most numerous and widespread organisms Colorized SEM 650  Figure 16.7

RNA might have acted as templates for the formation of polypeptides – Assisted in RNA replication First Cells Self-replication of RNA Self-replicating RNA acts as template on which poly- peptide forms. Polypeptide acts as primitive enzyme that aids RNA replication. RNA Polypeptide

Membranes may have separated various aggregates of self- replicating molecules which could be acted on by natural selection LM 650  Membrane Polypeptide RNA Figure 16.6B, C

Prokaryotes Small, relatively simple cells Do not have a membrane-bound nucleus Figure 4.3B

Branches of Prokaryote Evolution Bacteria and Archaea – Distinguished on the basis of nucleotide sequences and other molecular and cellular features

Prokaryote Shapes Cocci Bacilli Spirochetes

Structural Features Gram staining – Cell wall differences Gram + (purple) – Simple cell wall – Thick peptidogylcan layer Gram – (pink) – More complex cell wall with lipids bonded to carbohydrates – Thin peptidoglycan layer

Structural Features Capsule Pili Flagella

Growth & Reproduction Binary Fission Endospore

Innards Lacks membrane bound organelles Respiratory / photosynthetic membrane Small, circular genome Ribosomes

Nourishment Phototrophs & Chemotrophs Autotrophs & Heterotrophs Biofilms CO 2 Organic compounds Energy source Chemical Chemoautotrophs Photoautotrophs ChemoheterotrophsPhotoheterotrophs Light Carbon source

Archea Extremes Extremophiles – Halophiles – Thermophiles Methanogens

Bacteria Proteobacteria Spirochetes Gram-positive bacteria Cyanobacteria

Disease Exotoxins Endotoxins

Bacteria Uses Biological weaponry Bioremediation

Recycle chemicals and clean up the environment – Prokaryotes are decomposers in Sewage treatment and can clean up oil spills and toxic mine wastes Figure 16.16A, B Liquid wastes Outflow Rotating spray arm Rock bed coated with aerobic bacteria and fungi

Protists and Evolution Multicellularity evolved in several different lineages probably by specialization of the cells of colonial protists Unicellular protist ColonyEarly multicellular organism with specialized, interdepen- dent cells Later organism that produces gametes Food- synthesizing cells Locomotor cells Somatic cells Gamete 1 2 3

Protists are an extremely diverse assortment of mostly unicellular eukaryotes The parasitic Giardia Colorized SEM 4,000  Red blood cell Apex TEM 26,000  Plasmodium causes malaria SEM 2,300  Single celled algae

Symbiosis Endosymbiosis Secondary endosymbiosis Nucleus Primary endosymbiosis Cyanobacterium Heterotrophic eukaryote Evolved into chloroplast Autotrophic eukaryotes Nucleus Chloroplast Green alga Chloroplast Red alga Heterotrophic eukaryotes Secondary endosymbiosis Secondary endosymbiosis Remnant of green alga Euglenozoans Remnant of red alga Dinoflagellates Apicomplexans Stramenopiles

Protists Diplomanads – Parabasalids Euglenozoans Alveolates – Dinoflagellates – Ciliates – Apicomplexans

Protists Stramenopiles – Watermolds – Diatoms – Brown Algae Amoebozoans – Feed via pseudopodia – Plasmodial slime mold Plasmodium – Cellular slime molds

Protists Foraminiferans Radiolarians Algae – Red – Green