Origin of Life
Define continental drift.
The concept of landmasses drifting closer together or farther apart over time.
Define an extremophile.
Extremophiles are organisms that thrive in extreme conditions (extremely high/low temperature, salinity, acidity, et cetera).
Define peptidoglycan.
A polymer of amino sugars in bacterial cell walls, used as a target for combating pathogenic bacteria. Gram-positive bacteria have a thicker peptidoglycan layer than Gram-negative bacteria.
State the main characteristics of viruses.
Main components are a protein coat and either RNA or DNA. They are not made up of cells and have no organelles or ribosomes, and cannot make proteins on their own, and thus are not considered to be living.
Define protists.
A non-monophyletic group consisting of all Eukarya that are not plants, fungi, or animals. They are mostly microbial and have diverse lifestyles (some being autotrophs and others being heterotrophs).
Explain how fossils form.
A dead organism is trapped in a site with no oxygen, rendering decomposition slow or nonexistent.
List the 3 common shapes of bacteria and the names given for each shape.
Cocci (spheres), bacilli (rods), and spirilla (spirals).
Describe the practice of environmental genomics.
In environmental genomics, a researcher takes a sample of soil or water and sequences all the DNA found in the sample and compares to known sequences. Any sequence without a match represents an undiscovered species.
Explain how viruses are classified (phylogeny) and why.
Viruses are classified based on their type of genome rather than evolutionary relationships, because the following makes classification based on evolutionary relationships difficult: tiny genomes, no fossil viruses, HUGE diversity, and extremely fast mutation rate.
Describe the pathway from primary to secondary to tertiary endosymbiosis in chloroplasts.
In primary endosymbiosis, a cyanobacterium was engulfed by an early eukaryotic cell.
In secondary endosymbiosis, an algal cell that already had a chloroplast was engulfed by another early eukaryote.
In tertiary endosymbiosis, a protist that already had a chloroplast through secondary endosymbiosis was engulfed by a heterotrophic eukaryote.
State how long ago the following major events occurred: Earth's formation and the first life on Earth.
Earth's formation: 4.5 bya (billion years ago)
First life on Earth: 3.8 bya (billion years ago)
Explain lateral gene transfer.
Lateral gene transfer is a transfer of genes from one species to another, usually in bacteria or archaea. This can happen through picking up DNA from the environment, acquiring genetic information from viral infection (bacteriophages), or through conjugation, where individuals (normally same species) transfer genetic material between one another.
Define methanogens and state what archaea group contains methanogens.
Methanogens are organisms that produce methane as a byproduct of energy production. Some Euryarchaeota are methanogens.
Describe the difference between a positive-sense and negative-sense RNA virus.
Positive-sense RNA viruses have RNA that is ready for translation, so the host cell can immediately start translating it into viral proteins.
Negative-sense RNA viruses have RNA that is a complement of mRNA, so the host cell must first make the mRNA using the viral genetic material and then use that mRNA to make viral proteins.
Describe the difference between plasmodial and cellular slime molds and state what larger protist clade they are a part of.
Plasmodial slime molds form large structures with many nuclei but only one cell, while cellular slime molds are made up of separate cells that swarm to act as one. They are Amoebozoans.
Earth's formation, formation of the oceans, first life on Earth, photosynthetic organisms evolved, first continents arose, first eukaryotes evolved, first multicellular eukaryotes evolved, first fossils of multicellular animals.
What are myoplasmas?
Myoplasmas are firmicutes (a type of bacteria) which represent the smallest known organisms, having perhaps the smallest amount of DNA required to create proteins required for life.
Name one example of a specific hadobacterium and explain what is special about it.
Example 1: Deinococcus genus. Can survive radiation and break down nuclear waste.
Example 2: Thermus aquaticus. Source of an enzyme called Taq polymerase, which is used in PCR.
Explain the two hypotheses for virus origin.
RNA viruses are hypothesised to be cellular components that "escaped" the cells to exist on their own, only returning as parasites.
DNA viruses are hypothesised to be highly reduced parasite organisms that lost their cellular structure and ability to survive on their own.
Describe the life cycle of Plasmodium and state what larger protist group it is a part of.
Plasmodium, which causes malaria, has two hosts over the course of its life cycle. For part of its life cycle, it lives within human red blood cells, and in the other part of its life cycle it uses a mosquito as a host. It is transferred between human and mosquito through mosquito bites.
Describe the changes in O2 concentration from Earth's formation to the present day (include commentary on the ozone layer).
There was essentially no oxygen gas for early Earth, but when photosynthesis evolved in the late Precambrian period it started to accumulate in the atmosphere. In the Cambrian period, there was enough O2 for aerobic respiration to evolve, and as O2 accumulated O3 began to as well, forming the ozone layer in the stratosphere. O2 concentration was at its highest in the Permian period, but at the end of this period (when Pangaea formed) climate change led to it plummeting. The evolution of flowering plants led to O2 concentration slowly increasing again over the past 200 million years up until the present day.
Describe what is special about the Streptomyces genus, state what bacterial group it is a part of, and describe some additional characteristics of that group.
Streptomyces produces hundreds of antibiotics such as streptomycin. It is an actinobacteria.
Actinobacteria have an odd shape (branchy structure), include some disease-causing members such as Mycobacterium tuberculosis (which causes tuberculosis -- I know, impossible to guess by the name!), and most of our antibiotics come from them.
Describe what is special about the Rhizobium genus, state what bacterial group it is a part of, and describe some additional characteristics of that group.
Rhizobium is a group of nitrogen-fixing bacteria that live in plant roots. It is a proteobacteria.
Proteobacteria is the largest bacterial group in terms of species number, and endosymbiosis of a member of this group led to the evolution of mitochondria in eukaryotes.
Compare and contrast proviruses and endogenous retroviruses.
Proviruses are the result of a retrovirus embedding their genetic information into the host's genome, causing the host's body to continuously create viral particles.
Endogenous retroviruses are fragments of DNA from retroviruses that become nonfunctional -- basically nonfunctional, dead, or broken proviruses that serve as evidence of ancestors having been infected by retroviruses.
State what the two Rhizarian groups are and describe the characteristics of each.
Foraminiferans have external shells and mostly live on the seafloor. Dead foraminiferans are a big component of limestone rock layers.
Radiolarians are zooplankton that float in water, with shells covered in holes that thin, pointy extensions of the cell come through.
All Rhizarians are unicellular, most are aquatic, and all have shells of some sort.