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Anatomy & Physiology I - Unit 4:
Evolution and Natural Selection
Tree of Life ~2000
Tree pattern suggests evolution
- the hierarchy of life is a family tree in which
populations change with time.
- in general, similarities between species are due
to relatedness.
Evidence for
evolution
Fossils
Evidence for Evolution:
Structural Similarities
Evidence for Evolution:
Developmental Similarities
Gill pouch
Tail
Chick
Human
Homology: similarities caused by common descent
But how do species evolve?
Darwin figured
out how.
It’s a process
similar to how
humans breed
animals
Charles Darwin
1809 - 1882
Animal breeding
aka “Artificial
Selection”
How do you get this?
Evolution in action:
Giraffe neck length
Happy Giraffes
Hungry Giraffes
Surviving Giraffes
With Evolution You Get:
Taller giraffes over time
Evolution:
A change in a population over time
Natural selection
An environmental influence that
gives some individuals in a
population a reproductive or survival
advantage over others.
Principal cause of evolution.
Requirements for Evolution
• Variability
• Heritability
• Differential survival or reproduction
Tall Giraffes
Mutation: random genetic changes
Speciation: separation by natural events
that causes new species to develop
Discussion Question:
Are humans still evolving?
Common
Misperception:
Individuals
evolve
“And now there go the Wilsons!... Seems
Like everyone’s evolving except us!”
Acquired characteristics
are not inherited!
as in…..
Timmy & Gobbles
Evolution is slow
Great Calendar
1 month
1 day
1 second
Jan
Earth
forms
Feb
Mar
383 million years
13 million years
143 years
Apr
First
fossils
May
Jun
Jul
Aug
Sep
Oct
First
algae
Nov
Dec
First
land
plants
December
1
Land
animals
5
10
15
20
25
30
Dinosaurs
extinct
December 31
11:48 pm
Modern humans
leave Africa
noon
1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12
11:58:23 pm
Native
Americans
reach
Americas
Classroom Assignment:
Building the Perfect Beast
- I want you to think about how the human
body has evolved over time, and how it
might have evolved better.
- Today you are in charge of the world, and
you have to think about ways to make the
human species better adapted to the
environment.
Building the Perfect Beast
• Pick any ten attributes or parts of the
human body
• Note the defect of that part, or how it might
be made better
• Describe your changes, piece by piece, oh
master of the universe…
• Draw me a picture of your perfect beast