Chapter 12 - changes in species over time (evo)

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26 Terms

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What is evolution?

Change in heritable traits of populations over generations.

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Darwin & Wallace’s theory of natural selection (4 points)?

  • Overproduction (more offspring produced than can possibly survive)

  • variation (traits vary among individuals)

  • differential fitness (different traits = diff rates of survival/repro)

  • heritability (traits can be passed from generation to geenration)

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geological time scale

  • chronological dating that relates geological strata (distinct layers of sedimentary rock/soil)

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evidence for evolution

  • Paleontology - the study of the fossil record

  • Structural morphology - the study of structural features of related organisms

  • Molecular homology  - the study of DNA similarities



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the fossil record

  • over time, changes have occurred in the types of organisms living on the planet (e.g.tribolites, dinosaurs, etc)

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What is the law of fossil succession?

Fossils appear in a predictable order in rock layers.

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transitional fossil?

  • fossils that show features of both older and newer species.

  • e.g. Archaeopteryx (between reptiles and birds).

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Four main fossil types?

Impression, mineralised, trace, mummified.

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impression fossil

A mark or imprint of an organism left in rock (like a leaf print).

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mineralised fossil

Organic material replaced by minerals, turning it into rock (like dinosaur bones).

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trace fossil

Evidence of an organism’s activity, like footprints or burrows.

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mummified fossil

  • Preserved soft parts of an organism, often in dry or cold conditions.

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how do fossils form?

Organism dies → buried into sediments (e.g. ash from volcanic eruption, sediments on seafloor,etc → minerals replace it → fossil forms.

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biosignatures/biomarkers

Physical or chemical signs in rocks or minerals from past life, e.g.,

  • Corrosion pits by microbes

  • Life-like isotopic ratios (C, S)

  • Stable molecules like steranes from cell membranes

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Relative dating

Tells which rock/fossil is older or younger, but not exact age.

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absolute dating

  • Gives the exact age in years using methods like carbon dating.

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what is relative age of rocks calculated by?

  • stratigraphy

  • younger strata of rock laid down over older strata of rocks

<ul><li><p>stratigraphy</p></li><li><p>younger strata of rock laid down over older strata of rocks</p></li></ul><p></p>
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What is C-14 dating used for?

Organic remains up to ~60,000 years.

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Definition of a species (biological concept)?

Can interbreed and produce fertile offspring.

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What is allopatric speciation?

New species form due to geographic isolation.

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Darwin’s finches are an example of what?

Adaptive radiation.

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What is convergent evolution?

Unrelated species evolve similar traits due to similar environments.

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What is sympatric speciation?

New species arise in the same area (often plants, polyploidy)

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Prezygotic vs postzygotic barriers?

Prezygotic = prevent fertilisation; Postzygotic = after fertilisation (e.g., sterile hybrids).

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Example of postzygotic isolation?

Mule (horse × donkey) is sterile.

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fertile vs viable

fertile - ability to reproduce

viable - ability to survive