Unit 1 Practice Questions Flashcards
Why is the origin of cyanobacteria considered a critical step in evolution?
Because cyanobacteria created oxygen that led to the big oxygenation event at the end of Archaean. Oxygen development in proper amounts (20%) was the basis for the evolution of eukaryotes, and also helped in formation of ozone shield. Without ozone shield evolution could proceed only beneath the ocean floor because UV radiation was highly toxic, but when ozone developed from accumulated oxygen protection was there.
What caused the formation of banded iron formations?
Banded iron formation formed when cyanobacteria created oxygen via oxygenic photosynthesis, and oxygen reacted with available and abundant iron (Fe2+), forming insoluble iron (Fe (OH)3).
What lines of evidence indicate that microbial life was present on Earth 3.5 billion years ago?
Radioactive isotopes of macronutrients like sulfur and carbon in rocks.
What evidence supports the idea that the mitochondrion and chloroplast were once free-living members of the domain Bacteria? Give 4
i) Ribosomes in mitochondria and chloroplasts are similar to bacterial, 70S and have 16S r RNA
ii) Antibiotics that target ribosomal biosynthesis in prokaryotes affect mitochondrial and chloroplasts ribosomes
iii)Mitochondria and ribosomes have their own genome independent of nuclear genome
iv)there are many resemblance between bacterial cells and eukaryotic organelles
What major events in the evolution of microbial life had to occur before the origin of the acquisition of chloroplasts and mitochondria by eukaryotic cells?
Development of macromolecules and self-replicating structure that resulted in LUCA which branched to two amin lineages Bacteria and Archaea.
In what ways are modern eukaryotes a combination of attributes of Bacteria and Archaea?
Eukaryotes resemble archaeal structure in terms of transcription and translation machinery.
What kinds of evidence support the three-domain concept of life?
Phylogeny described through 16S r RNA (SSU r RNA) used to create phylogenetic tree.
List three reasons that SSU rRNA genes are suitable for phylogenetic analyses.
16S r RNA is suitable because it is universally distributed, slowly changed (conservative), and has proper length that can provide information on organisms relations and origin.
What are the different processes that give rise to genetic variation?
Mutations (neutral, beneficial, detrimental), recombination and Horizontal Gene Transfer (HGT).
What is the difference between selection and genetic drift and how do they promote evolutionary change?
Selection is mechanism of evolution that promotes and favorize specific treats based on the fitness that that treat provides for the organism, while genetic drift promotes certain trait through generations by chance (individuals are randomly selected).
What is the difference between the core and pan genomes of a given species?
Core genome represents genes that are shared between species, while pan genome is the set of genome acquired through various processes, such as HGT.
What kind of recombination might have the greatest impact on the core genome?
Homolog recombination (the one that requires presence of specific genetic elements around the sequence).
- What is the age of planet Earth? What is the age of the earliest known microfossil?
4.5bya
4 bya for fossil
What is a stromatolite and when can they be found in Earth’s history?
Stromatolites are microbial formations that are knowns as microbial fossils, and they can be ancient (originating from anoxygenic phototrophs, 3.2 BYA) or modern from cyanobacteria (2.8 BYA).
What is the endosymbiotic hypothesis for the origin of mitochondria and chloroplasts?
Endosymbiosis assumes the existence of chemoorganotrophic host that engulfed oxygen consuming bacetria (mitochondria) followed by alter engulfment of oxygen producing bacterium (chloroplasts).
