Exam 1 BIO 122 Flashcards
, Confirmation Bias
When someone finds/accepts evidence that supports their hypothesis (or opinion) and doesn’t test it or look at alternatives. Cherry picking data.
Who’s a scientist who is unaware of their confirmation bias?
Rats fed diet with genetically modified corn, the herbicide roundup, or both. Died earlier than control rats fed GMO free diet.
Used 200 rats, 20 control. 9/10 chance a rat would die from the treatment pool than the control pool.
Charles Walcott Lipalian geological interval.
Lipalian Interval was a time where animals gradually evolved from single celled organisms through progressively more complex forms into the animals found in the burgess shale, yet geological conditions prevented their fossilization.
Life is diverse, how can we describe it?
Taxonomy - use a hierarchical naming system to classify organisms based on similarity.
Cladistics/systematics/phylogenetics - Builds hypothetical trees to show evolutionary relationships between organisms - Phylogenies.
What does taxonomy do?
Places organisms into hierarchical groups.
Morphological Species Concept
Groups organisms based on their physical similarities.
What are all the hierarchical groups?
Domain, kingdom, phylum, class, order, family, genus, species.
Does classification via taxonomy reflect evolutionary history
Not necessarily
Binomial System
Genus species, devised by Carlos Linnaeus (1700s)
Why do evolutionary relationships not always resemble a branching tree?
Beacuse of endosymbiosis and horizontal gene transfer
What do phylogenies show?
Hypothesized evolutionary history and relationships.
Branching patterns show hypothesized speciation events from a common ancestor.
Parsimony
The phylogeny with the least amount of evolution needed is most likely correct. (Not always correct but a good starting point)
Why is it that the closer related two organisms are the more similar they should be?
Less time to accumulate differences since diverging from their common ancestor.
Occam’s Razor and how it relates to phylogenetics.
Among competing hypotheses, the one with the fewest assumptions is more likely to be correct.
Regarding phylogenetics, the assumption of parsimony requires one to construct a phylogeny with the fewest evolutionary events.
What do phylogenies show?
Relationships between taxa, the branching order shows speciation events relative to each other. Can show time, genetic difference, or morphological difference but most dont.
What is a node?
A branching point, shows the common ancestor of all the organisms branching after it.
What is a clade?
All the descendants from a node
How does one build a phylogeny?
Compile a list of characteristcs
Score each organism for the presence or absence of a characteristics
Shared Ancestral Characters
Characteristics that are shared by all of the organisms.
Shared Derived Characters
Characters that only a subset of organism’s posses.
Convergence vs Homology
Homologous meaning determining if the characteristics used were derived from a common ancestor.
Convergence meaning the same characteristic evolved independently.
Example of homologous vs convergence:
Forelimbs of birds and bats are homologous (their common ancestor had a humerus, radius, ulna, etc.)
However, their use as “wings” is convergent (their common ancestor had legs, not wings).
Paraphyletic vs Polyphyletic
l——— X
l —— Y
–l—l
l —— Z
l —— A
l—l
—— B
If you were to make a phylogeny with just X and Y it would be paraphyletic because it leaves out Z.
If you were to make a phylogeny with just Z and A it would be polyphyletic because it groups distantly related species together (and leaves out their close relatives).
Can phylogenies be constructed from morphological or molecular data or both?
Both or either or
Morphological data requires that researchers define characters and character states (open to human bias).
Molecular data can be gene sequence similarity, presence or absence of genes or gene families, sequence of siRNA.
Can phylogenies differ based on morphological to molecular data?
Yes, they can differ.
Lateral gene transfer/horizontal gene transfer
Molecular phylogenies reveal that DNA is sometimes passed between organisms, and not solely passed from one generation to the next.
What does lateral gene transfer allow?
One group to gain new traits from another group.
Is lateral gene transfer common among microorganisms and viruses?
somewhat
Is a phylogenic tree more or less parsimonious with the least amount of evolutionary events.
more
Lateral Gene transfer mechanisms:
Transformation, Transduction, Conjugation,
Transduction
Retroviruses occasionally incorporate host genes, and incorporate into host lineages.
Genetic material is transferred between bacteria by a bacteriophage, a virus that infects and carries bacterial DNA from one host cell to another.
Conjugation
Plasmids (fragments of DNA) can be passed between species of bacteria.
How did eukaryotes originate?
When archaea endosymbiosed aerobically respiring bacteria (branches of each domain merged and made a new domain).
What do archaea and eukarya share?
Characteristics related to packaging/organizing DNA, and gene expression.
Are bacteria and archaea all entirely single celled?
Do they have nuclei?
What are they called?
Yes, No, Prokaryotes.
Do prokaryotes reproduce rapidly?
yes
How do prokaryotes get energy?
Either from the sun or from a wide range of chemicals (photo vs chemo)
Oxidation of molecules vs light
How do prokaryotes get carbon?
Either from CO2 or other organisms (auto vs hetero)
How do bacteria get “virtually everywhere”?
In the absence of an essential nutrient, most bacteria can form an endospore which is dehydrated and metabolically inactive but can be revived centuries later to form new cells.
