Lecture 3- A Brief History Of Life On Earth Flashcards
What are the 6 kingdoms of life on earth
- archaea, eubacteria, protists, fungi, plantae,animalia
Out o f the six kingdoms, which are eukaryotes
Protists, plantae, animal, fungi
Out of the six kingdoms, which are prokaryotes
Archaea, eubacteria
Describe archaea
Prokaryotes lacking peptidoglycan cell walls
Eg. Methanogen
Describe eubacteria
-Prokaryotes with peptidoglycan cell walls
Eg. Cyanobacteria, pathogens
Describe protists
Eukaryotic singular celled organisms. Are either heterotrophic or photosynthetic
Describe fungi
Eukaryotic mostly multicellular organisms (except yeast). Heterotrophic and commonly non motile with chitin cell walls
Describe plantae
Eukaryotic multi cellular, non motile organisms
-photosynthetic (eg. Tree)
Describe anamalia
Eukaryotic, multicellular, motile, heterotrophic
Which as the four eukaryotes are motile?
Anamalia and some fungi
What is the key difference between archaea and eubacteria?
The presence of a peptidogloycan cell wall
How old is the earth?
4.5 billion years
Describe atmospheric conditions on the early earth
Extremely hostile, reducing atmosphere that allowed for the formation of carbon rich compounds and provided little protection against UV rays. This was incompatible to most life
What was the first types life to evolve when??
Prokaryotes 3.8 billion years ago. They dominated life from 3. 8- 2 billion years ago
When did Cyanobacteria first begin evolving?
- 5 billion years ago
What impact did Cyanobacteria evolution have on atmospheric composition?
They raised Oz concentration (as they are photosynthetic) about 2.4 billion years ago in the great oxygenation event
What happened to the oxygen released by Cyanobacteria (what did it form)
Free oxygen immedi ally dissolved into surrounding waters, and when its concentration within these waters was sufficient, it precipitated out as iron oxide. This accumulated in sediment in alternating with chert, forming banded iron formations
What happens when the oceans became supersaturated with oxygen
It began to gas out and changed atmospheric composition
When did the great oxygenation event occur?
It began with the evolution of Cyanobacteria around 2.7 billion years ago, but peaked 2.4 billion years ago
What was the first evidence of life on earth?
Stromatolites found in Australia. Stromatolites from when Cyanobacteria colonies group together, so provided the first evidence for life on earth
What were the impacts of the great oxygenation event?
Raised atmospheric oxygen levels over billions of years, formed the ozone layer which protects the earth from harmful UV rays, made conditions more favourable to many forms of life
What impact did the great oxygenation event have on the already present prokaryote populations (besides Cyanobacteria)
In pure form, oxygen attacks chemical bonds and can inhibit enzyme growth and damage cells. This was toxic to many prokaryotes, causing a large die off
How did organisms react to the great oxygenation event?
They had to adapt their physiology quickly in order to survive, such as evolving to use respiration as their main source of energy
When did Eukayotes first evolve?
Between 1.5 and 2.1 billion years ago, although there is evidence of them existing in 2.7 billion year old shale