Brief history of life on Earth, Lecture 3 Flashcards
Three domains of life
Bacteria, eukaryotes, archaea
Six kingdoms
- Archeabacteria
- Eubacteria
- Protists
- fungi
- plantae
- animalia
Archaaebacteria
six kindgoms of life
Prokaryotes that lack a peptido-glycan cell wall, eg: extreme halophiles, thermophiles and methanogens.
Eubacteria
six kindgoms of life
Prokaryotes with a peptidoglycan cell wall, eg: cyanobacteria, soil bacteria, nitrogen-fixing bacteria and pathogenic bacteria
Protists
six kindgoms of life
Eukaryotic, primarily unicellular organisms, heterotrophic or photosynthetic organisms
Fungi
six kindgoms of life
Heterotrophic, eukaryotic, chitin cell walls, mostly multicellular, usually non-motile
Plantae
six kindgoms of life
eukaryotic, multicellular, photosynthetic, non-motile
Animalia
six kindgoms of life
Eukaryotic, heterotrophic, multicellular, motile
Early Earth
4.5 billion years old
Characteristics of early earth
hostile, hot environment
reducing atmosphere - enabled formation of carbon rich compounds
When did life begin?
3.8 billion years ago
Earliest fossils
- are of prokaryotes, 3.5 billion years ago,
- simple structure, no nucleus and few internal structures
- dominant between 3.5-2 billion years ago
Stromatolites
precambrian ‘colonies’ of cyanobacteria
Photosynthesis
oxygen production
Which two main evolutionary branches do prokaryotes comprise?
bacteria and archaea
Which groups are included in the archaea?
3
methane producers, thermophiles and halophiles
these are found in very hostile anaerobic environments
When did cyanobacteria evolve?
around 3.5 billion years ago
Cyanobacteria
oxygen generating photosynthetic algae
Role of cyanobacteria in early earth?
raised atmosphere oxygen levels
enabled the ozone layer to form
protected the earth from UV radiation
Characteristics of eukaryotes
nucleus, chloroplasts, mitochondria
The origin of eukaryotes
5
- ancestral prokaryote
- infoldings of plasma membrane
- engulfing of aerobic heterotrophic prokaryote
- engulfing of photosynthetic prokaryote
- endosymbiotic relationships between bacteria
Multicellular eukaryotes
6
- evolved from single-celled eukaryotes living in association with each other
- development of specialised cells
- most are aerobic
- sexual reproduction was generally well developed
- the fusion of gametes enabled genetic recombination
- sex generates variation, enabling faster evolution
When was there an explosion in eukaryotic diversity?
at the end of the ice age, early cambrian period, about 570 million years ago
When was land colonised by plants, animals and fungi?
about 500 million years ago
When were most of the orders of modern mammals, inc. the primates, established?
50-60 MYA
When did the human lineage diverge from other primates?
5 - 6.5 mya
Which events shape evolution?
mass extinctions
Impact of extinction events
4
- create ‘ecological space’
- removes organisms occupying some niches
- the survivors descendants could evolve into those spaces with fewer constraints
- adaptive radiation may occur after mass extinctions or when new opportunities arise, eg: new islands
Adaptive radiation meaning
A process in which organisms diversify rapidly from an ancestral species into a multitude of new forms
When does adaptive radiation often occur?w
when a change in the environment makes new resources available
Example of adaptive radiation
Dawin’s finches
5
- ancestral finches arrive on island
- lack of small birds so no competition for food etc.
- finches diverged to occupy different habitats
- some evolved into different species
- finches with different beaks and feeding habits
