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BIO U3/4 > AOS 4 > Flashcards

AOS 4 Flashcards

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Biology 101 flashcards
1
Q

what is mass extinction

A

when a larger-than-normal number of groups become extinct on regional and global scale
* evolutionary opportunity for other species to thrive and diversify

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2
Q

evidence for evolution

A
  • fossils
  • biogeographical distribution
  • comparative
    • anatomy - structural morphology
    • embryology - developmental biology
    • molecular homology - DNA and amino acid sequences
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3
Q

conditions that favour fossilisation

A
  • rapidly buried
  • protected from scavengers
  • prevented from decomposition by low oxygen levels and low tempratures
  • organisms having hard structures (won’t decompose as rapidly)
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4
Q

process of fossilisation

A
  • an organism dies and is rapidly buried
  • protected from scavengers
  • prevented from decomposition by low oxygen levels + low temperatures
  • continued deposits of sediments bury it more and more deeply
  • over time the molecules in the organism (usually the hard parts) are replaced by minerals from groundwater
  • gradually, the weight of the overlying sediments compresses the original sediment layer so that it becomes rock
  • over time the rock is eroded, uplifted through the movement of tectonic plates or excavated
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5
Q

timeline of life on earth

A
  • prokaryotes
  • first unicellular eukaryotes
  • first multicellular eukaryotes
  • first vertebraes (jawless fish)
  • first insects
  • first land plants
  • first amphibians
  • first ferns
  • first reptiles
  • first conifers
  • first dinosaurs
  • birds
  • first mammals
  • first flowering plants
  • primates
  • humans
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6
Q

mineralised/petrified fossils

A

organic material of a structure replaced by minerals

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7
Q

mold fossils

A
  • form when a mineralised/petrified fossil dissolves and leave an impression of the original
  • these can be filled in to make cast fossils
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8
Q

trace fossils

A
  • form when traces of activity are buried before they are erased and turn into rock
    • eg footprints, teeth marks, scats (faeces)
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9
Q

purpose of fossil record

A
  • the fossil record reveals that over time changes have occurred in the types of organisms living on this planet
  • provides evidence in support of the prediction that ancestral species will appear before the species that descend from them
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10
Q

fossil/faunal succession

A
  • based on the premise that strata accumalates in chronological order
  • fossils in lower strata are older than fossils closer to the surface
  • fossils in lower strata are less complex than strata closer to surface
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11
Q

relative dating

A
  • sedimentary rocks form in layers (strata)
  • newer layers are at the top and the older layers are at the bottom
  • can determine relative age from that (as in newer or older - not the specific time)
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12
Q

index fossils

A
  • index fossils can be used to determine the relative ages of rock strata anywhere in the world
  • presence of index fossils in rock strata in widely separated regions of the world can identify these rocks as having the same age.
  • must be
    • abundant
    • distributed worldwide
    • existed for only a short period of time
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13
Q

transitional fossils

A
  • can tell us about major changes - evidence of evolution
  • is the fossilised remains of a life form that exhibits traits common to both an ancestral group and its derived descendant group
  • e.g: archaopteryx - dinosaur and modern birds (claws on wings + feathers)
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14
Q

absolute dating techniques

A
  • radiometric dating is the most common way to find the actual age of a fossil (rock)
  • measure the relative amounts (decay) of radioactive materials (parent) and their daughter products
  • the radioactive isotopes (parents) spontaneously decay or break down over time to form stable daughter products
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15
Q

relative vs absolute dating

A

relative age provides a comparative age whereas absolute age provides a more precise numerical age

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16
Q

half-life

A

half life → the time taken for half of the original radioactive isotope to decay

17
Q

carbon dating

A
  • carbon 14 will decay into nitrogen 14 (half-life of 5700 years)
  • living things take in C14 when they eat living things stop taking in C14 when they die
  • by comparing the amount of C14 and N14, the time since death can be determined
  • limitation: can’t be used to date fossils older than around 50000 - 60000 years, there are very small amounts of carbon 14 left in the organic matter
18
Q

speciation

A

the formation of a new species

19
Q

process of speciation

A
  • variation of characteristics is present in the population
  • breeding population becomes isolated
  • different selective pressures applied to isolated populations, random genetic drift, mutations
  • b/c of natural selection, some characteristics are favoured over others
  • those best suited to the environment survive
  • survivors reproduce and pass on favourable genes + traits to offspring
  • frequency of genes for new traits increases
  • overtime, differences and mutations accumulate resulting in speciation
20
Q

definition of species

A

organisms that can breed and produce fertile and viable offspring

21
Q

allopatric speciation

A
  • Initially a population (or populations) of the same species becomes isolated by a geographical barrier.
  • Over time the isolated population(s) is exposed to different selective pressures and accumulates
  • sufficient differences to the original population so that it forms a new species.
22
Q

galapagos finches

A
  • 13 volcanic islands w/ a variety of habitats - arid regions and mountainous regions
  • after finches had arrived on an island they would become geographically isolated
  • differing environmental selection pressures on each of the islands based on food availability (main environmental pressure)
    • caused change in beak shape bc of diff food source
    • no gene flow
23
Q

sympatric speciation

A
  • members of a populations living in the same area diverge to become 2 species
  • no geographical barrier - both species continue to inhabit the same geographic region
  • non-geographical barrier isolates populations from each other (active day/night) - some gene flow
  • isolated populations are subject to different selection pressures → different phenotypes are favoured
  • over generations, genetic divergence occurs
    • responds to diff environmental pressures → different phenotypes and isolated populations change
  • when the population come together again - can no longer interbreed - two separate species (2 distinct gene pools and different species)
24
Q

lord howe island palms

A
  • there was variation in the lord howe island population
  • shift in nutrient content in the soils which caused a shift in flowering times
  • those that flowered at the same time would interbreed
  • over time there was accumulation in the differences and mutations in the palms
  • speciation occurs and the two species can no longer interbreed
25
Q

why is sympatric speciation rare?

A
  • gene flow can still occur in sympatric speciation
  • genetic drift has less of an impact
  • less likely to be isolated as it requires reproductive isolation
  • natural selection would need to be strong to favour specific traits that then lead to a divergence and a new species evolving
26
Q

what is a common ancestor

A
  • is a species that existed earlier in the fossil record
  • subsequently evolved into two or more different species
  • an ancestor shared by later species: one from which two or more species evolved
27
Q

pre-zygotic/post zygotic isolation

A
  • pre-zygotic: barriers that prevent an organism from finding and securing a mate
  • post-zygotic: barriers that prevent fertile offspring from developing after mating
28
Q

relatedness

A

species that are more closely related are those that have most recently shared a common ancestor

29
Q

what is structural morphology

A
  • the process of comparing similarities in body structures to infer relatedness
  • fossil record
30
Q

structural morphology - homologous structures

A
  • homologous structures are those structures that have been derived from a common ancestor
    • would show similarities in structure
    • even though they may have different functions
  • evolution commonly occurs by modification of pre-existing structures - not by the production of TOTALLY new structures
  • eg. mammalian forelimbs
31
Q

structural morphology - vestigial structure

A
  • structures that are non-functional remnants of structures that were functional in ancestral species
  • eg. tailbone in humans
32
Q

what is molecular homology

A

involves comparing the similarities in DNA and protein sequences to infer relatedness

33
Q

amino acids for molecular homology

A
  • species that are more closely related are expected to have fewer differences in the amino acid sequences of their corresponding proteins than species that are more distantly related
34
Q

challenges with amino acid sequencing

A
  • multiple triplets can code for a particular amino acid
  • genetic code is redundant
  • some mutations (silent mutations) aren’t visible in amino acid sequencing
  • also sometimes two mutations that occur in the same codon will only cause one amino acid change.

BIO U3/4 (8 decks)

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