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Biology > UNIT 4 - AOS 2 - CH 8 > Flashcards

UNIT 4 - AOS 2 - CH 8 Flashcards

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1
Q

Hierarchy of intervals for earths geological time

A

Eons -> Eras -> Periods -> Epoch -> Ages (largest to smallest)

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2
Q

Relative age

A

“The age of an object expressed in relative terms, so it is identified as older or younger than another fossil”

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3
Q

Absolute age

A

“The age of an object (rock / fossil) in actual yrs”

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4
Q

evidence seen from fossils

A
  • Until ~400 mya, plants and animals were almost all limited to life in oceans (bacteria, microbes, ferns)
  • Since ~ 400mya, plants and animals became established on land (insects, reptiles, mammals, flowering plants)
  • Diversity has ^ over time
  • Mass extinction = global enviro event = species in large # die and cant evolve = diversification (decrease variation)
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5
Q

Fossil

A

“Evidence of life on earth in the past”
MOULD = impressions of living thing is left in rock
CAST = Formed when mould is filled with minerals or sediments

  • Physical, trace & biosignatures
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6
Q

Physical fossils

A

“Remains of all or part of the structure of an org”

  • Fossil impressions (mould)
  • Mineralised fossils (cast)
  • Preserved org (completely preserved in substance)
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7
Q

Trace fossils

A

“Evidence of activities of org’s”
- Footprints, toothmarks, tracks, burrows

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8
Q

Biosignatures

A

“Chemical/physical traces that can be inferred to have resulted from the action of life forms”

  • Corrosion pits in rocks caused by chemosynthetic microbes
  • Detection in rocks of isotopic ratios produced by life processes of microbes.
  • Stable molecules that persist
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9
Q

Macroscopic vs microscopic fossils

A

Microscopic - can be studied with eye

Microfossils - need light or microscope

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10
Q

Process of fossilisation

A
  • remains buried rapidly with a lack of o2 (sediments on sea floor, volcanic ash)
  • Weight compresses original sediment to form rock
  • Overtime rock is eroded (through movement of tectonic plates or human intervention) until fossil is exposed
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11
Q

Fossil record

A

Shows that changes have occurred in types of living organisms on earth overtime

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12
Q

types of evidence from fossils

A
  • faunal succession
  • index fossils
  • transitional fossils
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13
Q

Faunal succession

A

“the principle that fossilised flora and fauna in sedimentary rock strata are arranged vertically in a specific order”

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14
Q

Index fossils

A

“fossils of geologically short lived species that have limited occurrence in fossil record. so are found in a restricted depth of rock strata and widely spread “

  • the presence of these in different regions of the world shows the rocks having the same age
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15
Q

Absolute dating

A

RADIOMETRIC DATING:
- Radioactive isotopes decay overtime to stable daughter products
- rate of decay is specific for each radioactive isotope
- measured by half-life = time taken for half the original radioactive isotope to decay

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16
Q

Transitional fossils

A

“ Show traits between an ancestral group and its descendants acting as evidence of an intermediate form “

17
Q

Ways of dating fossils

A

‘to determine how old a fossil is and where it fits into the geological time scale’

relative dating and absolute dating

18
Q

Relative dating

A

“determines the relative age of rock strata”

  1. Stratigraphic method
    (law of superposition and uses faunal selection) - deepest layer = oldest stratum
  2. use of index fossils
19
Q

types of radiometric dating

A

CARBON-14 (60,000 and below)

POTASSIUM-40 (500,000 yrs +)

URANIUM-235 ( 10 million yrs +)

RUBIDIUM-87 (most ancient)

20
Q

speciation and steps

A

“process of forming a new species “

  1. NATURAL SELECTION
    oops of same species living in diff locations under diff conditions can evolve in different directions
  2. DIFFERENT SELECTION PRESSURES
    pops can become increasingly different from each other in structure, physiology and behaviour
  3. Speciation
21
Q

Specific reasons species are recognised as different

A
  • unable to interbreed
  • offspring are not viable
22
Q

Methods of isolation (speciation)

A

Pre-zygotic (pre-mating)
“barriers to finding and securing a mate”

  • temporal isolation (active at different times of day)
  • geographic location
  • behavioural isolation (don’t recognise each others courtship rituals)
  • mechanical isolation (mating attempted but unsuccessful)

Post-zygotic (post mating)
“isolation due to chromosomal and chemical imbalances between different species”

  • Incompatibility of gametes (sperm can’t penetrate egg)
  • zygote mortality (fertilisation occurs but zygote fails to develop)
  • non-viable zygote (doesn’t develop past embryo)
  • sterility of hybrid( hybrid offspring survive but can’t produce offspring)
23
Q

How does speciation occur

A
  1. variation of characteristics present in pop
  2. the breeding pop becomes isolated
  3. diff characteristics arise through random genetic drift, mutation and enviro pressures = genetic divergence
  4. enviro changes and natural selection occurs (some characteristics are favoured)
  5. survivors reproduce and pass on favourable genes and features to offspring
  6. frequency of the genes of new characteristics appearing increases. the isolated pop is now quite diff = new species
24
Q

Allopathic speciation steps

A

ONE : single pop with variation is divided by physical barriers becoming geographically isolated. no gene flow between pops

TWO : Over generations, each isolated pop is subjected to diff environment selection pressures = diff phenotypes selected for natural selection

THREE : Genetic divergence continues and if fertile offspring can’t be produced = 2 different gene pools and species

25
Q

Genetic divergence

A

“ When 2 or more pops accumulate genetic differences, leading to eventually being reproductively isolated”

26
Q

Example of allopatric speciation

A

(geographically separated and absence of gene flow)

GALAPAGOS FINCHES

Wood pecker finch
- Isabella island (high elevation and mixture of trees )
- food : invertebrates living in tree crevices
- have longer and narrow beaks (selective advantage)

Large cactus finch
- Espanola island (low elevation and most plants and cacti)
- Food: cactus (pulp, flowers and fruit)
- larger and stronger beaks (selective advantage)

27
Q

Sympatric speciation

A

ONE: single pop divided by pre-zygotic isolation barriers other than geographical isolation (eg temporal/behavioural isolation) - some gene flow

TWO: over gene, genetic divergence occurs (isolated pops subjected to diff enviro selection pressures = diff phenotypes selected for natural selection)

THREE: genetic divergence continued and if fertile offspring can’t be produced = two diff species

28
Q

Sympatric speciation example

A

Biology (37 decks)

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