Week 3 Flashcards
What are microorganisms?
- the oldest form of life on Earth
- They have evolved to preform critical functions that sustain the biosphere
How old is the Earth?
4.6 billion years old
when did microbial cells first appear?
between 3.8 and 4.3 billion years ago
During the first 2 billion years of earth…
its atmosphere was anoxic (O2 was absent), and only nitrogen carbon dioxide and a few other gases were present
What was the Earth’s origin like
sterile and anoxic
what was present 3.8 billion years ago?
bacteria and archaea
what caused Earth to become oxygenated over time
- The evolution of phototrophic bacteria called cyanobacteria
When were current levels of atmospheric O2 achieved?
500-800 million years ago
phototrophic microorganisms
organisms that harvest energy from sunlight
When did phototrophic microorganisms evolve?
within 1 billion years of the formation of Earth
what were the first phototrophs?
anoxygenic
Cyanobacteria
oxygen-producing phototrophs
When did cyanobacteria evolve
nearly a billion years later and began the slow process of oxygenating Earth’s atmosphere
Microbial Mats
Microbial Mats: The structures that these early phototrophs lived in structures and are still found on Earth today
Multicellular Life:
Evolved after the oxygenation of Earth’s atmosphere, culminating in the plants and animals we know today
How long have plants and animals existed?
about half a billion years
How much of life’s history was exclusively microbial?
80%
What can Earth be considered?
A microbial planet
Three major lineages of microbial cells:
- The Bacteria
- The Archaea
- The Eukarya
How many genes are present in cells of all 3 domains
approx 60 genes
- last universal common ancestor (LUCA):
- examination of the common genes reveals that all three domain have descended from a common ancestor
- Microorganisms fill every habitable environment on Earth
what constitutes a major fraction of global biomass?
Microbials
How many stars are there in space?
7x10 to the power of 22 stars
How many microbial cells are there on Earth?
2x10 to the power of 30 microbial cells
How much nitrogen and phosphorus are present within microbial cells
almost 4 times that in all plant and animal cells combined
Extremophiles
properties define the physiochemical limits to life
Microbes are abundant in:
- volcanic hot springs
- glaciers
- ice-covered regions
- high-salt environments
- extremely acidic or alkaline habitats
- deep in the sea
- deep in the earth at extremely high pressure