Astrobiology Chapter 7: Tree of Life Flashcards
What are the two hypotheses for alien life?
A: Alien life deviated from branch, we would have common ancestor
B: An independent origin of life would belong on a completely different tree of life
What did Carolus Linnaeus do?
System of taxonomy based on resemblences
What is the Linnean System?
Generate two-part scientific name called binomial
First part is genus- level of hierarchy of species
Second part is specific epithet- unique for each species with genus
What is homology?
Similarity due to shared ancestor
What is analogy?
Similarity caused by evolutionary pressures resulting from exposure to similar conditions or adaptation pressures, meaning organisms do not share common ancestor
What is Cladistics?
The part of taxonomy that groups organisms by common descent
What is Clade?
A group of species that includes an ancestral species in all of its descendants
What are evolutionary relationships traditionally based off of?
Morphology
What are modern phylogenetic trees based on?
Genetic information, Molecular Systematics
What are the three domains?
Bacteria, Archaea, Eucarya
What is the Phylogenetic Tree of Life?
A powerful reference as we seek to understand life across the universe
Framework for exploring the evolution and interconnectedness of terrestrial life
Fundamental reference database for evaluation of possible life beyond Earth
What does a phylogenetic tree of life show?
A variety of groups of organisms associated with each other
What is Ribosomal RNA
Responsible for reading the order of amino acids and linking amino acids together
Creates peptide bonds between amino acids in polypeptide chain
What is the purpose of building trees using DNA?
Find part of DNA that doesn’t change much over time
The closer two organisms are as relatives, the smaller the number of changes that would have occurred
What causes mutations to generate changes in the genetic code?
Errors in DNA replication
Exposure to agents that damage DNA
What are the three types of mutations?
Transversion- purine mutates into pyrimidine
Transition- purine into other purine
Insertions/Deletions
What does more deviation in DNA sequences mean?
Greater evolutionary distance
Why are phylogenetic trees useful?
For classification and ordering
To test scientific hypothesis
How can we use trees to test where humans originated?
Changes in rRNA are too few in the last 3 million years of human evolutions
Mitochondrial DNA changes faster to resolve changes in human lineage
What are the complication in building the universal tree with horizontal gene transfer?
The movement of genetic material between organisms like endosymbiosis is common in prokaryotes and complicates the tree of life
What is transformation?
Prokaryotes take up naked DNA from environment
What is transduction?
DNA transfer into a microbe through an agent such as a bacteriophage
What is conjuction?
Genetic information transferred between microorganisms
Donor cells transfers info through pilus
What is LUCA?
The last universal common ancestor
What does it imply if the genes are found in all three domains?
The duplication occurred before the domains diverged
What did Carl Woese infer?
The tree of life is rooted in bacteria with a later divergence between archaea and eukaryotes
What did early analysis of the tree of life show?
Deepest branching organisms were heat-loving
What was LUCA?
An anaerobe that lived from gasses
It used the most simple and ancient method of CO2 fixation called the aceytal-CoA pathway
It had a reverse gyrase, an enzyme typical of thermophiles
What do the genes that trace to LUCA, ancient biochemical pathways, and aqueous reactions of CO2 with iron and water seem to converge on?
Similar sets of simple, exergonic chemical reactions occur spontaneously at hydrothermal vents. LUCA was rooted in rocks.
What are phylogenetics?
The study of evolutionary relationships among groups of organisms
