Microbial Diversity

Describe 3 features of populations that experience Darwinian evolution

Multiplication: Specific traits can enable an individual to survive longer or reproduce more than others, so over time these traits become more common in the population leading to evolutionary change.

Heredity: Traits must be heritable otherwise they cannot be passed on through the generations.

Variation: Individuals have different traits which is crucial as it provides the material for natural selection to act upon.

Explain what conditions were like on Earth before the evolution of life.

Lots of rock and volcanos, Earth was hotter due to volcanic activity. Lack of O2 in the atmosphere making it toxic to aerobic organisms, lots of CO2. Water vapor which created the first oceans. RNA world.

Elaborate on ‘RNA world’

There were no enzymes or DNA. RNA was used as catalysts driving chemical reactions before enzymes. Used to store genetic information before DNA. DNA is a mutation of RNA that overtook as the information storing molecule as it’s more stable.

Describe the evidence that suggests the approximate time that microbial life evolved

Stromatolites (fossilized mats) containing ancient prokaryotes that date back 3.5bya proving fossil evidence of early life.

Carbon isotopes, suggest biological activity that dates back to around 3.85bya.

Compare and contrast the physical structure of Prokaryotes and Eukaryotes

Prokaryotes: No nucleus, no membrane-bound organelles, generally smaller, cell division by binary fission, cell wall made of peptidoglycan. Shapes can be spherical, rod-shaped or spiral. Bacteria and Archae.

Eukaryotes: True nucleus surrounded by nuclear membrane, generally larger, has membrane-bound organelles, cell division by meiosis or mitosis. Animals, plants, fungi, protists.

Describe the three pathways by which Horizontal Gene Transfer can take place

Transformation, Conjugation, Transduction.

Transformation: Some bacteria can take up free DNA fragments from the environment and can combine it into the bacterial chromosome which can give the recipient new genes/traits

Conjugation: Direct transfer of DNA between two bacterial cells via cell-cell contact use a conjugative plasmid that creates a ‘bridge’ to transfer DNA between cells.

Transduction: Transfer of DNA via bacteriophages (virus that infects bacteria), the phage infects a bacterial cell and accidentally packages its DNA into its viral particles which is can transfer to another bacteria

What are the consequences of HGT?

Disadvantageous - decrease fitness level of the cell, Advantageous - increase fitness level of the cell, neutral - no effect on fitness level of the cell

What is special about how bacteria can evolve?

Fast reproduction, increases chances of mutations, HGT so bacteria can gain genes from unrelated organisms

Explain how microorganisms have transformed the planet

Oxygenated the atmosphere, bacteria began producing oxygen as a byproduct of photosynthesis. Symbiosis and evolution, bacteria form mutualistic relations with animals, plants and fungi and enabled the evolution of eukaryotic life. Breakdown organic waste and regulate greenhouse gases.

Explain why Nitrogen Fixation is an important process

Converts atmospheric nitrogen gas (N2) into ammonia (NH3) that plants and organisms use. Organisms cannot use N2 directly from the atmosphere, but plants can use NH3 to support growth.

Describe how oxygen came to be enriched in Earth’s atmosphere

Oxygen became enriched in the earth’s atmosphere when cyanobacteria developed the ability to perform photosynthesis which produces oxygen as a byproduct, other time increasing the level of O2 in the atmosphere.

Describe the relationship between the Bobtail squid and Vibrio fischeri

The bobtail squid and the bacterium vibrio fischeri form a mutualistic relationship. VF is a bioilluminescent bacteria that colonizes a light producing organ in the squid. At night the bacteria produces bioilluminescence, emitting light that hides the bobtail squid’s shadow so it can avoid predators. In return the squid offers a nutrient rich environment to the bacteria allowing it to grow and reproduce.

Explain how the Quorum Sensing and Diffusion Sensing ideas are similar or dissimilar

Similar: