evolution I Flashcards
(30 cards)
what is evolution?
โit is the accumulated, heritable changes within a population, over generations, giving rise to new species.
what is taxonomy?
โnaming of groups of organisms (taxa).
what is classification?
โarrangement of taxa into an ordered, hierarchical system according to their observed similarities.
what is phylogeny?
โphylogeny is the determination of ancestral relationships or organisms and their evolutionary history.
what are phylogenetic trees?
โphylogenetic relationships can be represented using phylogenetic trees.
โThe Phylogenetic Tree of Life illustrates that all Bacteria, Archaea and Eucaryota are derived from a distant, common ancestor called LUCA.
โA phylogenetic tree can also be based on morphological criteria.
how can organic material and rocks be dated?
โRock and organic material can be dated by measuring the decay of naturally occurring radioactive isotopes
where do fossils usually form and how are they dated?
โFossils usually form in sedimentary rock.
โFossil dates can be bracketed by the age of surrounding igneous rock.
how do fossils form?
1) There are surface erosions that occur, creating sediment.
2) When an organism dies, it settles onto the sediment, which then becomes sedimentary rock.
3) Thus, a fossil forms of that organism.
4) The soft sediment preserves the fine details in the bones, teeth, and leaves of plants.
how does the fossil record provide evidence for evolution? and what does it allow?
โ the fossil record allows for the order and age of organisms to be determined.
โsimpler life forms are present in older rock.
โWe also find fossilised organisms that no longer exist.
โproves that evolution takes place, for more complex organisms to have evolved from the simpler organisms, and for the extinct organisms to have died out due to their inability to survive in the environment.
what is radiometric dating? and what are radioisotopes used for?
โmeasuring the ratio of parent/daughter nuclides. โradioisotopes can be used to date rocks and fossils.
what are some requirements for radiometric dating?
โ the rate of radioactive decay is constant: not affected by temperature, pressure, chemicals, electrical or magnetic fields
โ the parent and daughter nuclides cannot leave or enter material after it is formed
โthere must be no intrusion of other, later rock
โ there must be no contamination
what is the cambrian explosion?
โrapid appearance (and disappearance) of complex organisms in the fossil record (about 525 million years ago).
what does homologous mean in relation to evolution?
โtwo structures are homologous when they are derived from a common ancestral version.
โthese structures are derived from a common ancestor so they form by a common mechanism. An example would be tetrapod limbs.
what does analogous mean in relation to evolution?
โ two structures are analogous when they have no common ancestor
โ the similar structures are produced by selection to meet similar function (convergent evolution)
โ they have different developmental mechanisms but some molecular components may be the same. An example would be insect wings and bird wings.
what is molecular analogy and give an example?
โ molecular convergence
โwhen proteins have the same function with no structural identity.
โAn example would be crystallins (lens proteins) There are many different transparent proteins in different species.
โthey all have other functions (in addition to being stable, transparent and refractive).
what is molecular homology?
โmolecular homology is determined from amino acid or nucleic acid sequence
what is a paralog and an ortholog?
โ two genes from the same organism (by duplication) are called PARALOGS
โtwo genes from different organisms (common ancestor) are called ORTHOLOGS
how is gene duplication a key driver in evolution?
โ when a gene is duplicated, the original gene can go back to executing itโs original function.
โThe duplicated gene is free to be modified.
โIt may perform functions complementary to the original geneโs function (acting as a backup).
โit can also evolve non-overlapping functions.
how did the influenza virus change so rapidly?
โdifferent flu strains infecting the same cell can swap parts of their genetic material.
give an example of evolution that has been observed
โ 12 colonies of E. Coli from a single clone
โ Subculture it every day, for 27 years
โ Freeze the culture samples every 500 generations (75 days)
โOver the completed experiment, 63,500 generations would have been observed
โtest the cultures for the ability to grow in citrate in the presence of oxygen
โThe ability to use citrate evolved after about 30,000 generations in one group in particular.
โearlier generations from this same ancestral E. Coli were repeatedly able to evolve the ability to utilise citrate at about the same time.
how were E.coli able to use citrate?
โThe ability of bacteria to utilise citrate is controlled by its citrate gene, controlled by the citrate promoter.
โgene is normally turned off in the presence of oxygen.
โ It is next to the RNK promoter, which controls the RNK gene.
โThis is turned on in the presence of oxygen.
โin cultures that were able to utilise citrate, the citrate gene and RNK promoter were duplicated right after each other.
โthis doesnโt affect the existing citrate gene, but the duplicated citrate has an RNK promoter before it which means it is under the control of the RNK promoter.
โcitrate gene now works in the presence of oxygen.
what are examples of little mistakes during DNA replication?
โ small duplications
โ small insertions
โ small deletions
โ base substitution
what are examples of big mistakes during DNA replication?
โ large DNA duplications โ chromosome rearrangements โ large deletions โ viral insertions โ insertion transposable elements
what is natural selection?
โ organisms better adapted to environment survive to produce more offspring
