evolution I

Question 1

what is evolution?

Answer 1

→it is the accumulated, heritable changes within a population, over generations, giving rise to new species.

Question 2

what is taxonomy?

Answer 2

→naming of groups of organisms (taxa).

Question 3

what is classification?

Answer 3

→arrangement of taxa into an ordered, hierarchical system according to their observed similarities.

Question 4

what is phylogeny?

Answer 4

→phylogeny is the determination of ancestral relationships or organisms and their evolutionary history.

Question 5

what are phylogenetic trees?

Answer 5

→phylogenetic relationships can be represented using phylogenetic trees.

→The Phylogenetic Tree of Life illustrates that all Bacteria, Archaea and Eucaryota are derived from a distant, common ancestor called LUCA.

→A phylogenetic tree can also be based on morphological criteria.

Question 6

how can organic material and rocks be dated?

Answer 6

→Rock and organic material can be dated by measuring the decay of naturally occurring radioactive isotopes

Question 7

where do fossils usually form and how are they dated?

Answer 7

→Fossils usually form in sedimentary rock.

→Fossil dates can be bracketed by the age of surrounding igneous rock.

Question 8

how do fossils form?

Answer 8

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.

Question 9

how does the fossil record provide evidence for evolution? and what does it allow?

Answer 9

→ the fossil record allows for the order and age of organisms to be determined.

→simpler life forms are present in older rock.

→We also find fossilised organisms that no longer exist.

→proves 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.

Question 10

what is radiometric dating? and what are radioisotopes used for?

Answer 10

→measuring the ratio of parent/daughter nuclides. →radioisotopes can be used to date rocks and fossils.

Question 11

what are some requirements for radiometric dating?

Answer 11

→ the rate of radioactive decay is constant: not affected by temperature, pressure, chemicals, electrical or magnetic fields
→ the parent and daughter nuclides cannot leave or enter material after it is formed
→there must be no intrusion of other, later rock
→ there must be no contamination

Question 12

what is the cambrian explosion?

Answer 12

→rapid appearance (and disappearance) of complex organisms in the fossil record (about 525 million years ago).

Question 13

what does homologous mean in relation to evolution?

Answer 13

→two structures are homologous when they are derived from a common ancestral version.

→these structures are derived from a common ancestor so they form by a common mechanism. An example would be tetrapod limbs.

Question 14

what does analogous mean in relation to evolution?

Answer 14

→ two structures are analogous when they have no common ancestor

→ the similar structures are produced by selection to meet similar function (convergent evolution)

→ they have different developmental mechanisms but some molecular components may be the same. An example would be insect wings and bird wings.

Question 15

what is molecular analogy and give an example?

Answer 15

→ molecular convergence

→when proteins have the same function with no structural identity.

→An example would be crystallins (lens proteins) There are many different transparent proteins in different species.

→they all have other functions (in addition to being stable, transparent and refractive).

Question 16

what is molecular homology?

Answer 16

→molecular homology is determined from amino acid or nucleic acid sequence

Question 17

what is a paralog and an ortholog?

Answer 17

→ two genes from the same organism (by duplication) are called PARALOGS

→two genes from different organisms (common ancestor) are called ORTHOLOGS

Question 18

how is gene duplication a key driver in evolution?

Answer 18

→ when a gene is duplicated, the original gene can go back to executing it’s original function.

→The duplicated gene is free to be modified.

→It may perform functions complementary to the original gene’s function (acting as a backup).

→it can also evolve non-overlapping functions.

Question 19

how did the influenza virus change so rapidly?

Answer 19

→different flu strains infecting the same cell can swap parts of their genetic material.

Question 20

give an example of evolution that has been observed

Answer 20

→ 12 colonies of E. Coli from a single clone
→ Subculture it every day, for 27 years
→ Freeze the culture samples every 500 generations (75 days)
→Over the completed experiment, 63,500 generations would have been observed
→test the cultures for the ability to grow in citrate in the presence of oxygen
→The ability to use citrate evolved after about 30,000 generations in one group in particular.

→earlier generations from this same ancestral E. Coli were repeatedly able to evolve the ability to utilise citrate at about the same time.

Question 21

how were E.coli able to use citrate?

Answer 21

→The ability of bacteria to utilise citrate is controlled by its citrate gene, controlled by the citrate promoter.

→gene is normally turned off in the presence of oxygen.

→ It is next to the RNK promoter, which controls the RNK gene.
→This is turned on in the presence of oxygen.

→in cultures that were able to utilise citrate, the citrate gene and RNK promoter were duplicated right after each other.

→this doesn’t 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.

→citrate gene now works in the presence of oxygen.

Question 22

what are examples of little mistakes during DNA replication?

Answer 22

→ small duplications
→ small insertions
→ small deletions
→ base substitution

Question 23

what are examples of big mistakes during DNA replication?

Answer 23

→ large DNA duplications
→ chromosome rearrangements
→ large deletions
→ viral insertions
→ insertion transposable elements

Question 24

what is natural selection?

Answer 24

→ organisms better adapted to environment survive to produce more offspring

Question 25

what is genetic drift?

Answer 25

→ variation in relative frequency of genotypes in small populations due to chance

Question 26

what is gene flow?

Answer 26

→ transfer of alleles from one population to another

Question 27

what is applied selection?

Answer 27

→ plants or animal breeding

→ antibiotics, drug, pesticide resistance

Question 28

what is a Hox gene?

Answer 28

→ Hox genes bind in DNA sequence specific fashion and regulate the expression of adjacent genes.

→ ( determine where certain genes are expressed
confer positional identity )

Question 29

how do populations evolve?

Answer 29

→ changes in gene frequency brought about by random genetic drift, gene flow and natural selection

Question 30

what is speciation?

Answer 30

→ gradual evolution of reproductive isolation amongst populations