Download Part 6 - glenbrook s hs

Ex: Vestigial Structures
• These are some of the most
interesting homologous
structures which have
marginal, if any, use or
importance to the
organism. They are
historical remnants of
structures which had
important functions in
ancestors.
• Ex: the whales of today
lack hind limbs, but have
vestiges of pelvic and leg
bones of their four-footed
terrestrial ancestors.
• Vestigial organs are
evidence of evolution shows linkage to a past
ancestor.
• 4. Comparative
Embryology - comparison
of structures that appear
during development of
different organisms
• A sign that vertebrates
evolved from a common
ancestor: all of them have
have an embryonic stage
in which gill pouches
appear on sides of throat
• At this stage, embryos of
fish, frogs, snakes, birds &
apes look more alike than
different.
• As development
progresses, the vertebrates
take on more distinctive
features.
• 5. Molecular Biology- there is a common genetic code shared by all
species. This genetic language has been passed along through all
branches of evolution since an early form of life.
• Ex: DNA bases same, RNA, amino acids, use ATP for energy.
• Ex: In above chart- chimps & humans are less than 2% different in DNA
sequences
• Darwin Review:
• 1. Overproduction of
offspring; competition for
limited resources and struggle
for existence
• 2. Individual variation
1.Overproduction of spores
• 3. Differential reproductive
success (natural selection).
Environment (nature)
determines who is fit. Those
most fit survive & reproduce.
Favored traits accumulate in
2.Variation in beetles
population over generations =
adaptive evolution.
Large ground finch
Woodpecker finch
Small tree finch
Natural Selection in Action
• Ex: Evolution of finches on Galapagos Islands: the islands were
colonized by finches that strayed from the South American mainland,
then diversified on the different islands.Adaptive evolution/radiation.
• Ex: Pesticides - do not create resistant individuals, but selects for
resistant insects that were already present in the population