Transcript Chapter 15 Natural Selection and the Evidence of

Evidence of Evolution and
Natural Selection
Evidence of Evolution
• Short scale of human life makes it hard to
understand evolution
– Humans have only been on earth for
approximately 200,000 years.
– The earth is 4.6 Billion years old
Charles Darwin (English Scientist)
• First published modern evolutionary theory
– 1831 took a trip around the world
– Stopping everywhere he took different forms
of life
– Returned to England with many questions
Darwin’s Voyage
Evidence of Evolution
1) Adaptations
2) Homologous Structures
3) Analogous Structures
4) Vestigial Structures
5) DNA
6) Embryo’s
7) Camouflage
1) Adaptations are evidence of evolution
– Look at the picture below. What are some
adaptations of this bass?
Bald Eagle
Brown Bear
Structural Features
2) Homologous structures
– Structural features with a common
evolutionary origin
Homologous Structures
Salamander, Lizard, Turtle, and Opossum
3) Analogous Structures
– Similar in function but do not have a common
evolutionary origin
• Look on page 401
– Figure - 15.7
4) Vestigial structures
– No present day function but was probably
useful to an ancestor
Examples of Vestigial Structures
• Eyes on blind mole rats
• Tiny snake pelvic and limb bones
• Humans have a set of muscles for
wiggling ears
• Appendix in a human
The appendix is about 10 cm in length, but can range
from 2 to 20 cm. The diameter of the appendix is
usually less than 7–8 mm.
5) Embryo’s
– Earliest stage of growth and development in
both plants and animals
• Very similar embryo’s in Fish, Reptiles, Birds, and
Mammals (60271 on CD)
Vertebrate Embryos
Vertebrate Brains
• cerebrum - controls and integrates motor,
sensory, and higher mental functions, such as
thought, reason, emotion, and memory.
• Cerebellum - serving to coordinate voluntary
movements, posture, and balance in humans,
being in back of and below the cerebrum and
consisting of two lateral lobes and a central lobe.
• Brain Stem - sustaining the basic functions of
life, such as breathing and blood pressure.
6) Biochemistry
• CAT
TAC
DNA is made of the same building blocks
just in a different order
– DNA in a human could be
• AATGGGCCC
• TTACCCGGG
– DNA in a tree could be
• AAGTTTAGC
• TTCAAATCG
7) Camouflage
Some species just blend into their environment
• Offspring that survived had certain traits
that were helpful
• These organisms then passed down traits
to their offspring
• Which leads us to Natural Selection
Natural Selection
• Mechanism for change in
populations; occurs when organisms
with certain variations survive, reproduce,
and pass their variations to the next
generation
Evidence of Evolution
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Adaptations
Homologous Structures
Analogous Structures
Vestigial Structures
DNA
Embryo’s
Camouflage