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evidence for evolution Flashcards

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1
Q

comparative genomics

A

new genes are gained by mutation, others are lost by natural selection, genetic drift or other processes, code in DNA is different for different species, when speciation occurs new species would have very similar DNA however as new species gradually change through mutation, natural selection etc and they accumulate more and more differences in DNA

  • species more distantly related have more differences
  • species more closely related share greater portion of DNA
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2
Q

genome

A

complete set of DNA in each cell of an organism

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3
Q

comparative genomics (definition)

A

field of biological research where genome sequences of different species are compared, used to reveal diversity of gene composition in evolutionary lineages

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4
Q

endogenous retroviruses

A

viral sequence that has become part of an organism genome, store genetic info as RNA
chromosomes contain non-coding sequences of bases in DNA sequences (junk DNA) they serve no apparent function or purpose
- more closely related species have more common junk sequences
- less closely related species have less common junk sequences

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5
Q

endogenous retrovirus ( process of becoming an erv)

A
  • reverse transcription: upon entering cell retrovirus copies its RNA genome into DNA its then inserted into one of host cells chromosomes
  • retrovirus will only become endogenous if it inserts into cell whos chromosomes will be inherited by next generation (sperm or egg cell)
  • offspring if individual will have copy of erv at same place in same chromosome in every single one of cells
  • all subsequent generations will have copy of erv at same location
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6
Q

bioinformatics

A

use of computers to describe molecular components of things, use biochemical analysis to gain info on DNA and proteins and computers to store and analyse it

  • can assist evolutionary biologists to trace evolution of large number of organisms by measuring changes in DNA rather than through taxonomy or observations
  • annotation: identification of genes in DNA sequence, needs to be computerised, made possible because of start and stop codons
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7
Q

mitochondrial DNA

A
  • in form of small circular molecules 5-10 in each mitochondrion, has 37 genes all of which are essential for mitochondrion to function normally
  • 24 of these contain code for making transfer rna molecules which are involved in protein synthesis
  • other 13 have instructions for making some of enzymes necessary for reaction of cellular respiration
  • inherited from mother but also carried in sperm and provide energy for sperm to swim to egg, after sperm has penetrated egg at fertilisation mitochondria in sperm are rapidly destroyed
  • has higher mutation rate
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8
Q

how does mitochondrial DNA provide evidence for evolution

A

scientists are able to use similarity between mtDNA of any two individuals to estimate closeness of relationship through maternal ancestors, if mtDNA their last common maternal ancestor lived long ago, can be used to track evolution through gene flow, founder effect, track migration routes of ancient people

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9
Q

phylogenetic trees

A

represent evolutionary relationships between number of organisms derived from common ancestor

  • ancestral organism forms base of tree
  • organisms arisen from it are placed on ends of branches
  • closely related groups are positioned on branches close to one another
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10
Q

protein studies

A

by comparing type and sequence of amino acids in similar proteins from different species degree of similarity can be established, animals of same species have identical amino acid sequence in proteins
- degree of difference between proteins enables estimate to be made of amount of evolution taken place since two species developed from common ancestor

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11
Q

ubiquitous proteins

A

number of proteins that appear to be in all species from basic essential tasks that all organisms require for life, carry same function everywhere

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12
Q

cytochrome c

A

type of ubiquitous protein that shows how protein sequences can provide evidence for evolution, performs essential step in production of cellular energy, contains 104 amino acids:
- 37 of these have been found at same position in every sequenced cytochrome c molecule, strongly suggests these proteins descended from ancestral cytochrome c molecule found in primitive microbe (200 million years old)

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13
Q

cytochrome c: evidence for evolution

A

to compare cytochrome c they need to be aligned so maximum number of proteins containing same amino acids can be determined, the more similarity between two molecules the more recently they’ve evolved from common ancestor

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14
Q

fossil

A

any preserved trace left left by an organism that lived long ago e.g bones, shells, teeth, footprints, faeces

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15
Q

characteristics of fossilisation

A
  • hard parts (shell, bones, teeth) fossilise better than soft parts (skin, muscle)
  • bottom of sea is best place for fossilisation (anoxic, sediments, pressure)
  • must be buried, left un disturbed, compressed by sediments (die and get covered quickly
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16
Q

trace fossils

A

something such as footprint which has been left behind without any hard material

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17
Q

effect of soil type on fossilisation

A
  • if soil contains no oxygen complete preservation of soft tissues and bones of organism may occur
  • organisms buried in alkaline soils produce best fossils because minerals are not dissolved
  • in wet acidic soils minerals in bones are dissolved and no fossilisation occurs
18
Q

location of fossils

A

fossilisation of human ancestors are often found in edges of lakes/river systems/caves: because organism can buried rapidly (preventing decomposition), also build up sediments when flooding occurs or when water flow slows rapidly, many caves are in limestone which consists of calcium carbonate which may be deposited around dead organisms or cave may collapse covering it rapidly

19
Q

discovery of fossils

A
  • fossils may be found by chance at surface of ground and be uncovered by erosion
  • often discovered by slow excavation sites
20
Q

artefacts

A

objects that have been deliberately made by humans e.g stone tools, beads, carvings, charcoal

21
Q

relative dating

A

no age is given, only as comparison to other fossils, before or after or at same time

22
Q

index fossils

A

fossils with a wide distribution and limited time span, makes relative dating of strata more precise

23
Q

stratigraphy

A

study of layers or strata

24
Q

principle of superposition

A

assumes that in layers of sedimentary rock the layers at the top are younger than those beneath them
- any fossil of material on top layers will be younger than materials found lower down

25
Q

limitations of law of superposition

A

distortions of earths crust may occur (earthquakes, tsunami etc) and sequence of rock layers may be turned upside down

26
Q

correlation of rock strata

A

involved matching layers of rock from different areas can be done by examining rock itself and studying fossils it contains (rocks that contain same fossils may be assumed to be of same age

27
Q

incomplete fossil record

A
  • fossil record is incomplete as conditions for fossilisation do not always occur or occur at irregular periods of time: fossilisation is chance occurrence and there are gaps in fossil record because all organisms have not been preserved
  • very small portion of fossils that do exist have been discovered: buried too deep, inaccessible places, may not have been recognised as fossils when discovered, may have been destroyed by human activity (construction)
  • unusual to find fossils of entire organism or whole skeleton of organism , scientists must reconstruct what organism my have looked like: reconstructions are only approximations based on experience of scientist involved other scientists may disagree and can lead to controversy
28
Q

issues with fossil material dating

A
  • using carbon dating techniques material containing carbon must be present and can only be dated back to 60 000 years ago, to date older than this age of fossil is determined using potassium argon dating which relies on suitable e.g lava being present
29
Q

absolute dating

A

actual age of a specimen in years, approximate age of a particular organism/fossil

30
Q

isotopes

A

atoms fo same element with different numbers of neutrons, heavier of lighter than common form and is similar in chemical and physical properties

31
Q

decay of isotopes

A

some isotopes are unstable and change over a period of time to a more stable element, when an isotope decays it gives off radiation energy in the form of alpha, beta articles and gamma rays (unstable isotopes = radioactive)

32
Q

half life

A

time taken for half of original atoms to undergo decay (each radioisotope has its own rate of decay

33
Q

potassium argon dating

A

based on decay of radioactive potassium to form calcium and argon, K-40 is radioactive isotope and decays to form calcium-40 and argon-40 and occurs at an extremely slow but constant rate so determining amounts of potassium-40 and argon-40 in rock sample enables age of rock to be calculated
- as rock ages proportion of K-40 decreases while proportion of argon-40 increases

34
Q

limitations of potassium argon dating

A

not all rock types are suitable for this method and it can only date rocks older than 100 000 - 200 000yrs
- half-life of k-40 is 1250 billion years after 100000yrs only 0.0053 (very small amount) of k-40 would have decayed

35
Q

carbon-14 dating

A

based on decay of radioactive isotope of carbon 14 which is produced in upper atmosphere by action of cosmic radiation on nitrogen at same rate which it decays

  • when green plants use atmospheric carbon dioxide in photosynthesis one atom in every million of carbon atoms incorporated into plant tissue is carbon 14 (animal eats plant and c-14 becomes part of animals tissue and when it dies the c-14 in tissue continues to decay at fixed rate
  • by measuring amount of carbon 14 to carbon 12 age of sample can be estimated
36
Q

method of carbon 14 absolute dating

A
  • normal method of radioactive dating requires 3grams of organic material so decay of carbon14 can be measured, accelerator mass spectrometry radioactive carbon dating can be used to date samples as small as 0.001grams involved breaking up sample into constituent atoms so number of atoms so number of in each isotope of carbon 14 can be counted (cannot be used on samples older than 70 000 yrs
  • materials being dated must contain organic compounds from living things that contain carbon, amount of carbon14 in atmosphere varies so can be inaccurate
37
Q

comparative anatomy

A

similarities in structure suggests that species have common ancestor

38
Q

embryology

A

comparing very early stages of development or organisms

39
Q

how does embryology provide evidence for evolution

A

evolutionary change overtime by comparing early stages in development of organisms, in vertebrates comparing embryonic stages reveals similarities between different species at different times e.g presence of tail

40
Q

homologous structures

A

structures that are similar in structure (bone arrangement) but may be used in different ways (have different structures), convincing evidence they have evolved from common ancestor

41
Q

vestigial structures

A

structures that may have once have been important but have lost or changed function overtime (during evolution), to a point where they’re no longer fulfilling original function

42
Q

how do vestigial structures provide evidence for evolution

A

produced evolutionary history of species because they are remnant of structures found in ancestral species
- genome still codes for them indicates common ancestry e.g wisdom teeth or appendix (originally used in digestion of tough plant matter but is no longer needed bc of change in diet

Human Biology (8 decks)

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