Download - Objective 6 Notes
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OBJECTIVE 6 NOTESEvolution, Natural Selection & Adaptations
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1. Vocaba) Evolution
• A genetic change in a population over time• Note: individuals do not evolve, only populations show change
b) Theory• A well supported explanation of a scientific phenomenon
c) Fitness• The ability of an organism to survive and reproduce in a given
environment
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2. Charles Darwin• From 1831-1836, a young naturalist called
Charles Darwin toured the world in HMS Beagle.
• Where food was limited, competition meant that only the fittest would survive.
• This would lead to the natural selection of the best adapted individuals
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3. Assumptions of the Evolutionary Theory
• The earth is billions of years old
• Time + small changes = large changes
• Mutations can be beneficial
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3. Natural Selection• The process by which individuals that are better suited to
their environment survive and reproduce most successfully
• Also called:• Survival of the Fittest
• Artificial Selection
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3. Natural Selection• Types
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4. Mechanisms of Evolution • Genetic Variation
• Mutations• Meiosis (crossing over)
• Natural Selection• Reproductive Isolation
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5. Evidence of Evolution• Fossil Records• Homologous Structures• Analogous Structures• Vestigial Structures• DNA
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Fossil Record• Fossils are preserved evidence of dead organisms• Assumes that it takes a long time for sediment to
accumulate• Assumes that the dead organism had offspring• Assumes that there are millions of years separating each
sediment layer.
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Homologous Structures• Structures that have a similar structure (anatomy) from one
organism to another.
• Example: limbs– Human leg v. Whale
flipper• Both contain bones
called femur, tibia, fibula, etc.
• Similar structure but different functions
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Analagous Structures• Structures that have a similar function (physiology) but
different structure between organisms.
• Example: Wings• Butterfly wing v. Bird wing• Both enable flight, but are very different structures
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Vestigial Structures• Defined as a structure that serves no useful function in an
organism.• Most common citations of this are not accurate:
• Coccycx: without it humans cannot pass solid waste.• Appendix: might have immune/lyphatic functions• Tonsils: have immune and lyphatic functions• Eyebrow/lash: keeps sweat/dust/particles out of eyes• Body Hair: mechanoreceptors at base, traps heat, offers protection
from sun rays