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Relative ages of Earth and 1st prokaryotic and eukaryotic fossils
~4.6 billion years ago= Earth
~3.5 BYA= Prokaryotes appeared
~2.1 BYA= Single celled eukaryotes appeared
~1.2 BYA= Multicellular eukaryotes appeared
Do prokaryotes or eukaryotes have more total biomass on Earth?
- Prokaryote biomass is ~10x higher than eukaryotes
Review features of prokaryotic cells
-smaller than eukaryotes cell
-lack membrane-enclosed nucleus
-lack other membrane-enclosed organelles
-typically have cell walls
Classification of prokaryotes: shapes, associations or attachments, mobility, survival in extreme conditions (endospores), modes of nutrition
- Coccus or cicci-SPHERICAL
- Bacillus or bacilli- ROD
- Spiral or curved shape
- Association or attachment
- with other cells
- May form chains or clumps
- Spiral or curved shape
- Pilli, capsule, flagella,
- Survival of extreme
- Endospore: a thick,
- protected cell wall which can survive extreme heat and cold, even boiling water
- Modes of nutrition-How
- organisms obtain:
- i. Phototroph-obtains energy from light
- ii. Chemotroph-obtains energy from chemical bonds
- i. Autotroph-obtains carbon from carbon dioxide
- ii. Heterotroph-obtains carbon from organic molecules such as
- **Multicellular organisms are either
- Chemoheterotrophs (animals, fungi) or Photoautotrophs (plants, algae)
What is a biofilm and why are they important to people?
- A special association of one or several species
- of prokaryotes, and/or protists and fungi which can divide labor and defense
- against invaders
- on rocks, metal and teeth
- devices, dental plaque, UTI, sinusitis, plants: nitrogen fixation, plants: crop
- disease, microbial fuel cells, sewage treatment plants
What are the two basic ways that bacteria cause disease?
Exotixins: proteins secreted into the environment
Endotoxins: chemical components of the outermembrane of certain bacteria that cause illness
How are archaea related to bacteria and eukarya?
Archaea has similarities with:
- -bacteria (small cells, no nucleus, circular
- genome, no introns)
- (similar DNA replications, histones)
How are archaea classified?
- There are currently 4 Phyla of Archaea
- -becausethey occupy extreme habitats, they are the most poorly characterized domain
Why are protists placed in the same group? Is this appropriate?
Protists are Eukaryotes which are not fungi,animals, not plants. They are notgrouped together because they are closely related, but because they were notwell understood in the past
Where do most protists live?
- -Oceans, lakes and ponds
- -damp soil and leaf litter
- -the bodies of host organisms with which they mayhelp or harm
What are some of the differences among protists?
Be able to recognize the groups of protists by their types and properties: protozoans, slime molds, unicellular and colonial algae, seaweeds
- Protozoans: protists that live primarily by
- ingesting food most free-living, but a few parasites
Slime molds: decomposers- NOT FUNGUS
-plasmoidial slime molds: only have one cell, but many nuclei
-cellular slime molds: complex life history
Unicellular and Colonial algae:
- portists whose chloroplasts support food chains in aquatic
-Dinoflagellates: have external plates made of cellulose
-Diatoms: have glassy cell walls
-Green algae: unicellular or colonial in fresh water
Seaweeds: large, multicellular marine algae
- based on pigments of chloroplasts
-brown algae-including kelp
Potential exam question: What two processes likely created the membrane-bound organelles in eukaryotic cells? Briefly explain how each works.