The Diversity of Life. I. A Brief History of Life II. Classifying Life III. The Prokaryotic Domains.

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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

Stromatolites - communities of layered 'bacteria'

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.

- 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

4.5 million to present

(1/1000th of earth history)

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

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

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

Now, all members of the genus Felis share one common ancestor.

NEWHOMINIDAE

Genera: AustralopithecusHomo

PONGIDAE

Genera:PanGorillaPongo

Phylum: Chordata

Subphylum: Vertebrata

Class: Reptilia

Class: Mammalia

Class: Aves

The Diversity of Life I. A Brief History of LifeII. Classifying LifeA.The Linnaean SystemB.Cladistics and Phylogenetic Systematics NEW

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

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

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 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

The Diversity of Life. I. A Brief History of Life II. Classifying Life III. The Prokaryotic Domains.

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