the diversity of life. i. a brief history of life ii. classifying life iii. the prokaryotic domains
TRANSCRIPT
The Diversity of Life
The Diversity of Life I. A Brief History of Life
II. Classifying Life
III. The Prokaryotic Domains
The Diversity of Life I. A Brief History of LifeA. Introduction
ATMOSPHERE
BIOSPHERE
LITHOSPHERE
N fixation Photosynthesis Respiration
DecompositionAbsorption
Energy harvest of animals and plants
Ecological Roles Played By Prokaryotes
The Diversity of Life I. A Brief History of LifeA.IntroductionB. Timeline
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Stromatolites - communities of layered 'bacteria'
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Grypania spiralis – possibly a multicellular algae, dating from 2.0 by
The classical model of endosymbiosis explains the origin of eukaryotes as the endosymbiotic absorption/parasitism of archaeans by free-living bacteria.
The Diversity of Life I. A Brief History of LifeA.IntroductionB. Timeline
The Diversity of Life I. A Brief History of LifeA.IntroductionB. Timeline
- Life was exclusively bacterial for ~40% of life’s 3.5 by history - Ecosystems evolved with bacterial producers, consumers, and decomposers. - Multicellular eukaryotic organisms evolved that use and depend on these bacteria
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The Diversity of Life I. A Brief History of LifeA.IntroductionB. Timeline
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4.5 million to present
(1/1000th of earth history)
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For ~40% of life’s history, life was exclusively bacterial
The Diversity of Life I. A Brief History of LifeII. Classifying LifeA.The Linnaean System
- a ‘nested’ hierarchy based on morphology
The Diversity of Life I. A Brief History of LifeII. Classifying LifeA.The Linnaean System
- a ‘nested’ hierarchy based on morphology
Genus Felis
Panthera
Family Felidae
Acinonyx
Lynx
The Diversity of Life I. A Brief History of LifeII. Classifying LifeA.The Linnaean SystemB.Cladistics and Phylogenetic Systematics
Evolution explained this nested pattern as a consequence of descent from common ancestors.
Modern biologists view the classification system as a means of showing the phylogenetic relationships among groups
Genus Felis
Panthera
Family Felidae
Acinonyx
Lynx
The Diversity of Life I. A Brief History of LifeII. Classifying LifeA.The Linnaean SystemB.Cladistics and Phylogenetic Systematics
But there are inconsistencies to correct:
Cougar (Felis concolor) is in the genus Felis but is biologically more closely related to Cheetah (which are in another genus), than to other members of the genus Felis.
The goal is to make a monophyletic classification system, in which descendants of a common ancestor are in the same taxonomic group.
Genus Felis
Genus Panthera
Family Felidae
*
*
The Diversity of Life I. A Brief History of LifeII. Classifying LifeA.The Linnaean SystemB.Cladistics and Phylogenetic Systematics
The goal is to make a monophyletic classification system, in which descendants of a common ancestor are in the same taxonomic group.
Now, all members of the genus Felis share one common ancestor.
The Diversity of Life I. A Brief History of LifeII. Classifying LifeA.The Linnaean SystemB.Cladistics and Phylogenetic Systematics
The goal is to make a monophyletic classification system, in which descendants of a common ancestor are in the same taxonomic group.
NEWHOMINIDAE
Genera: AustralopithecusHomo
PONGIDAE
Genera:PanGorillaPongo
OLD
The Diversity of Life I. A Brief History of LifeII. Classifying LifeA.The Linnaean SystemB.Cladistics and Phylogenetic Systematics
The goal is to make a monophyletic classification system, in which descendants of a common ancestor are in the same taxonomic group.
Phylum: Chordata
Subphylum: Vertebrata
Class: Reptilia
Class: Mammalia
Class: Aves
OLD
The Diversity of Life I. A Brief History of LifeII. Classifying LifeA.The Linnaean SystemB.Cladistics and Phylogenetic Systematics NEW
The Diversity of Life I. A Brief History of LifeII. Classifying LifeA.The Linnaean SystemB.Cladistics and Phylogenetic Systematics
The goal is to make a monophyletic classification system, in which descendants of a common ancestor are in the same taxonomic group.
OLD
NEW
The Diversity of Life I. A Brief History of LifeII. Classifying LifeA.The Linnaean SystemB.Cladistics and Phylogenetic Systematics
The goal is to make a monophyletic classification system, in which descendants of a common ancestor are in the same taxonomic group.
III. The Prokaryote Domains: Eubacteria and ArchaeaA.Overview
III. The Prokaryote Domains: Eubacteria and ArchaeaA.Overview
“Horizontal Gene Transfer” complicates phylogenetic reconstruction in prokaryotes and dating these vents by genetic similarity and divergence.
III. The Prokaryote Domains: Eubacteria and ArchaeaA.Overview
Bacteria Archaea Eukarya
No nucleus no nucleus nucleus
no organelles no organelles organelles
peptidoglycan no no
1 RNA Poly several several
F-methionine methionine methionine
Introns rare present common
No histones histones histones
Circular X’some Circular X’some Linear X’some
III. The Prokaryote Domains: Eubacteria and ArchaeaA.Overview 1. Archaea
“Extremeophiles”
- extreme thermophiles: sulphur springs and geothermal vents
- extreme halophiles: salt flats
“Methanogens”
Also archaeans that live in benign environments across the planet.
III. The Prokaryote Domains: Eubacteria and ArchaeaA.Overview 1. Archaea 2. Bacteria
- proteobacteria - Chlamydias - Spirochetes - Cyanobacteria - Gram-positive bacteria
III. The Prokaryote Domains: Eubacteria and ArchaeaA.Overview 1. Archaea 2. Bacteria
These groups are very diverse genetically and metabolically. Their genetic diversity is represented by the “branch lengths” of the groups, showing how different they are, genetically, from their closest relatives with whom they share a common ancestor.
The key thing about bacteria is their metabolic diversity. Although they didn't radiate much morphologically (spheres, rod, spirals), they DID radiate metabolically. As a group, they are the most metabolically diverse group of organisms.
III. The Prokaryote Domains: Eubacteria and ArchaeaA.OverviewB. Metabolic Diversity of the Prokaryotes
III. The Prokaryote Domains: Eubacteria and ArchaeaA.OverviewB. Metabolic Diversity of the Prokaryotes
1. Oxygen Demand
all eukaryotes require oxygen.
1. Responses to Oxygen:
all eukaryotes require oxygen.
bacteria show greater variability:
- obligate anaerobes - die in presence of O2
- aerotolerant - don't die, but don't use O2
- facultative aerobes - can use O2, but don't need it
- obligate aerobes - require O2 to live
III. The Prokaryote Domains: Eubacteria and ArchaeaA.OverviewB. Metabolic Diversity of the Prokaryotes
1. Responses to Oxygen:
2. Nutritional Categories:
- chemolithotrophs: use inorganics (H2S, etc.) as electron donors for electron transport chains and use energy to fix carbon dioxide. Only done by bacteria.
- photoheterotrophs: use light as source of energy, but harvest organics from environment. Only done by bacteria.
- photoautotrophs: use light as source of energy, and use this energy to fix carbon dioxide. bacteria and some eukaryotes.
- chemoheterotrophs: get energy and carbon from organics they consume. bacteria and some eukaryotes.
III. The Prokaryote Domains: Eubacteria and ArchaeaA.OverviewB. Metabolic Diversity of the Prokaryotes
III. The Prokaryote Domains: Eubacteria and ArchaeaA.OverviewB. Metabolic Diversity of the ProkaryotesC. Ecological Importance
- major photosynthetic contributors (with protists and plants)
- the only organisms that fix nitrogen into biologically useful forms that can be absorbed by plants.
- primary decomposers (with fungi)
- pathogens
- endosymbionts with animals, protists, and plants
Bacteria still drive major dynamics of the biosphere