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Chapter 1

Chapter 1

2 Pages
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Department
Anthropology
Course Code
ANTB14H3
Professor
Michael Schillaci

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How Human Evolved
Week 1
Chapter 1: Adaptation By Natural Selection
Organisms more than just suited to their environments: they are complex machines, made up of
many exquisitely constructed components, or adaptations, that interact to help the organisms
survive and reproduce
Human eye is good example of adaptation
oAllow us to move confidently through environment
oTo locate critical resources like food and mates
oTo avoid dangers like predators and cliffs
oLight enters eye through transparent opening, passes through iris, regulates amount of
light entering eye and allows eye to function in wide range of lighting conditions
Lens in human
oCamera like
oShaped like squashed football and has same index of refraction throughout
oLight is bent when it passes from air through cornea
Lens in fish
oSphere located at center of curvature of retina, index of refraction of lens increases
smoothly from surface of lens to center
oSpherical gradient lens provides sharp image over full 180 visual field, very short focal
length and high light gathering power
oLight is not bent when it passes from water through cornea of aquatic animals
Darwins Postulates
1.Struggle for existence: ability of population to expand is finite, but ability of any environment to
support population is always finite
oPopulation grow until they are checked by dwindling supply of resources in environment.
2.Variation in fitness: organisms within population vary, this variation affects ability of individuals
to survive and reproduce
oSome individuals will possess traits that enable them to survive and reproduce more successfully
(producing more offspring) than others in the same environment
3.Variation in inheritance: variation is transmitted from parents to offspring
oIf advantageous traits are inherited by offspring, then these traits will become more common in
succeeding generations natural selection
Example of adaptation by natural selection- Darwins finches.
oMorphology: an organisms size, shape, and composition
Selection produces adaptations that benefit individuals
May or may not benefit population or species
Selection often leads to changes in behaviour or morphology that increases the reproductive
success of individuals but decrease the average reproductive success of group, population and
species
Two categories of variation:
Continuous and discontinuous
Discontinuous did not play an important role in evolution
Continuous is essential for evolution of complex adaptations
www.notesolution.com

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Description
How Human Evolved Week 1 Chapter 1: Adaptation By Natural Selection Organisms more than just suited to their environments: they are complex machines, made up of many exquisitely constructed components, or adaptations, that interact to help the organisms survive and reproduce Human eye is good example of adaptation o Allow us to move confidently through environment o To locate critical resources like food and mates o To avoid dangers like predators and cliffs o Light enters eye through transparent opening, passes through iris, regulates amount of light entering eye and allows eye to function in wide range of lighting conditions Lens in human o Camera like o Shaped like squashed football and has same index of refraction throughout o Light is bent when it passes from air through cornea Lens in fish o Sphere located at center of curvature of retina, index of refraction of lens increases smoothly from surface of lens to center o Spherical gradient lens provides sharp image over full 180 visual field, very short focal length and high light gathering power o Light is not bent when it passes from water through cornea of aquatic animals Darwins Postulates 1. Struggle for existence: ability of population to expand is f
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