Download 7th Evolution Darwin.key

Evolution
Darwin’s Journey
and Observations
Who was Charles Darwin?
• English naturalist
• Took a 5 year voyage
on the HMS Beagle
• Voyage’s intent was to
explore the coast of
South America
• Darwin took many
specimens and made
many important
scientific observations
Where did the HMS Beagle go?
The Galapagos Islands
Galapagos Tortoises
• Much larger than tortoises found elsewhere
• Tortoise sizes and shell shapes vary on different
islands
• Islands with a lot of food à large tortoises with
dome-shaped shells
• Islands with less food à smaller tortoises with
saddle-shaped shells
• Why are there different shapes?
– Height, size, food, and weather!
Saddlebacked tortoise
Domed tortoise
Blue-footed Booby
Sea gull with bright blue feet
The foot color comes from pigments in their diet – the more
well-nourished, the bluer they are.
Mating Dance
• Male parades feet in
front of female, do a
crazy dance, and then
give the female one
last look at his feet
• Females continuously
evaluate male foot
color in mate
• Evidence for sexual
selection
Marine Iguana
• The only aquatic
iguana found
anywhere in the world!
• Hypothesized that the
marine iguana and
land iguana came
from a common
ancestor
What ideas influenced Darwin?
• Jean Baptiste
Lamarck’s Theory of
Acquired
Characteristics
• Use & Disuse theory
• Ex: Giraffes
– Believed that giraffes
stretched necks to
reach food, then passed
that on to offspring
What does Lamarck’s theory mean?
• If I dye my hair red, will my babies have
red hair?
• If I work out and pump iron all day, every
day, will my future children be more
muscular?
• If I spend hours in a tanning bed, will my
children inherit darker skin?
NOPE.
You can’t change your genes!
The Theory : Natural Selection
• The most fit organism survives and
reproduces
• There is a struggle for existence known as
competition – for food, shelter, and mates
• Living things reproduce in greater numbers
than will survive
• All members of a population show
variation- we are all unique!
Common Descent
CAT ANCESTOR
LEOPARD
MOUNTAIN LION
JAGUAR
HOUSECAT
• Different species share a common ancestor
• If you go back far enough, all life might have a
common ancestor
• Divergent evolution
• What do you think the process of the creation of
new species from a common ancestor might look
like?
Steps to a new species from a
common ancestor
• 1. Environmental changes
• 2. Some individuals survive and some die
• 3. Those that live move and inhabit a new
area
• 4. Those that live become reproductively
isolated from the common ancestor
• 5. New species!
What EVIDENCE do we have to
support evolution?
• Fossil record
– Remains of organisms
– Fill in the gaps!
• Comparative anatomy
– Similarities in body structure
– Homology and vestigial structures
• Comparative biochemistry
– DNA sequencing
– Amino acid sequences
Fossils
• What are fossils?
• How does a jellyfish
leave a fossil?
• Fossils: a remnant of
a dead organism
• These can take many
forms – bones,
imprints, footprints,
etc.
• Paleontology – the
study of fossils
Homologous Structures
•
•
•
•
Different organisms show a unity in body plan
Inside: bone structure similar
Outside: really different uses!
Indicate common ancestry
Vestigial structures
Do humans have tails?
• Remnants of an
organism’s
evolutionary past
• Something an
ancestor would
have used, but the
current animal no
longer needs
Human tailbone!
Whale legs!
Snake legs!
Comparative Embryology
• Um…yikes.
• Embryology – the study of the formation
and early growth of organisms.
• Embryo development
• Think early pregnancy / in-egg
development
Comparative Embryology
• Organisms with a common ancestor will
share similar embryo development
Where’s the human?
Molecular homology
• A fancy way of saying that evolutionary
relationships can be seen by looking at
similarities in DNA
• All living things have a genetic code
based on DNA
• DNA structure : sequences of base pairs
• Closely related organisms will have
similar DNA sequences
Biogeography
• Two organisms that are NOT closely related
can develop similar characteristics due to
their niche
• Structures are similar, but there’s little/no
evolutionary relationship
• These are called analogous structures
– Example: a bird and a bat
• Both have wings for flight, but little or no evolutionary
relationship
• Convergent evolution
Homology or Analogy?
Endemic Species
• Located in only one
area of the world and
found nowhere else!
• The Galapagos
tortoises, blue footed
booby, and marine
iguana are all
examples
• Madagascar lemur
– Madagascar split from
Africa 165 million years
ago!