Download Agenda Biology 2-6 and 2-7

Starter #46 and Objectives
Table of Content: Darwin’s Theory of
Evolution by Natural Selection
• Starter: What do you think of when you
think of the word Evolution?
• Objectives:
–Explain the process of Evolution by
Natural Selection
Homework and Reminder
Homework:
None but there is a writing
assignment I’ll tell you at the end
of class
Reminder:
Cell phone should be off and out of sight!
Evolution
•Evolution is the change in the allele
frequency and heritable characteristics
of a population over many successive
generations over time.
Charles Darwin
• Proposed a way how
evolution works
– How did creatures change over
time?
– by natural selection
• Collected a lot of evidence to
support his ideas
– 1809-1882
– British naturalist
Voyage of the HMS Beagle
• Invited to travel around the world
– 1831-1836 (22 years old!)
– makes many observations of nature
• main mission of the Beagle was to chart
South American coastline
Robert Fitzroy
Voyage of the HMS Beagle
• Stopped in Galapagos Islands
– 500 miles off coast of Ecuador
Galapagos
Recently formed volcanic
islands. Most of animals on the
Galápagos live nowhere else in
world, but they look like species
living on South American
mainland.
800 km west of Ecuador
Darwin found…many unique species
Many of Darwin’s observations made
him wonder… Why?
Darwin asked:
Why were these creatures found only
on the Galapagos Islands?
Darwin found…clues in the
fossils
Darwin found:
Evidence that creatures
have changed over time
present day Armadillos
Darwin asked:
Glyptodonts
ancient Armadillo
Why should extinct
armadillos & modern
armadillos be found on
same continent?
Darwin found… more
fossils
Darwin found:
Evidence that creatures
have changed over time
present day Sloth
(extinct) Giant ground sloth
Darwin asked:
Why should
extinct sloths &
modern sloths be
found on the same
continent?
Darwin found:
Different shells on tortoises on different islands
Darwin asked:
Is there a relationship
between the environment
& what an animal
looks like?
Darwin found… birds
Darwin found:
Many different birds
on the Galapagos
Islands.
He thought he found Finch?
very different kinds…
Sparrow?
QuickTime™ and a
Photo - JPEG decompressor
are needed to see this picture.
Woodpecker?
Warbler?
But Darwin found… a lot of
Darwin was amazed tofinches
find out:
All 14 species of birds
were finches…
But there is only one
species of finch on the
mainland!
Large
ground
Small
ground
Finch?
Sparrow?
Finch?
Sparrow?
QuickTime™ and a
- JPEG decompressor
finch arePhoto
finch
needed to see this picture.
Darwin asked:
If the Galapagos
finches came from the
mainland, why are they
so different now?
Warbler finch
Woodpecker?
Woodpecker?
Tree
finch
Warbler?
Warbler?
The finches
cinched
it!
 different
beaks are
Darwin found:
inherited variations
The differences
 serve as adaptations
between species of
that help
birds said:
compete
Darwin
finches were
for
food
associated with the
Ahaaaa!
these birds survive &
different food they  Big
Aeater
flock of South
Large
seed
ground
Small
Small
seed
ground
eater
Finch?
Sparrow?
reproduce
ate.
finch
finch
American finches


QuickTime™ and a
Photo - JPEG decompressor
are needed to see this picture.
pass on the genes for
were stranded on the
those more fit beaks
Galapagos…
over time nature selected
for different species with
different beaks
Warbler
Insect eater
finch
Woodpecker?
Leaf
Tree
& bud
finch
eater
Warbler?
Relationship between species (beaks) & food
Darwin’s finches
• Darwin’s conclusions
– variations in beaks
• differences in beaks in the original flock
• adaptations to foods available on islands
– natural selection for most fit
• over many generations, the finches were
selected for specific beaks & behaviors
– offspring inherit successful traits
• accumulation of winning traits:
both beaks & behaviors
– separate into different species
From 1 species to 14
species…
Warbler finch
Cactus finch
Woodpecker finch
Sharp-beaked finch
Small
insectivorous
tree finch
Large
insectivorous
tree finch
Small
ground
finch
Cactus
eater
Insect eaters
Seed eaters
Vegetarian
tree finch
variation
Bud eater
Medium
ground
finch
Large
ground
finch
natural selection for best
survival & reproduction
Earlier ideas on Evolution
• LaMarck
– evolution by acquired
traits
• creatures developed
traits during their lifetime
• give those traits to their
offspring
– example
• in reaching higher
leaves giraffes stretch
their necks & give the
acquired longer neck to
offspring
– not accepted as valid
Darwin’s view of Evolution
• Darwin
– giraffes that already
have long necks
survive better
– leave more offspring
who inherit their long
necks
•variation
•selection &
survival
•reproduction &
inheritance of
more fit traits
Natural Selection
Darwin developed the idea of:
natural selection – organisms with
favorable traits are more likely to
survive and reproduce;
“survival of the fittest”
Natural Selection
fitness –
combination of physical traits and
behaviors that allow an organism to
be
more successful in its environment
adaptation –
any inherited characteristic that
increases an organism’s fitness for
survival
Natural Selection
Lamarck –
thought acquired traits could be
passed on to future generations
ex: giraffe neck length
• Darwin published this
•
work to explain the
variety of species
that exist on the
planet
He proposed the
“Theory of Evolution
by Natural Selection”
1. Variation exists among individuals in a species.
2. Individuals will compete for resources (food,
mates, and space)
3. Competition would lead to the death of some
individuals while others would survive
4. Individuals that had advantageous variations are
more likely to survive and reproduce.
This process came to be
known as Natural Selection
The favorable variations are
called Adaptations
Photo courtesy of
digitalART2, flickr
creative
commons
•Say in a species of blob….there exists
blobs of all shapes and sizes (variation)
Blobs eat the little purple organisms that live
underground and on the surface.
During a particularly hot year, food became less
abundant (competition), blobs that had the ability
to dig into the soil to get food had a better chance
of survival.
Many blobs died that year…….
The ones that survived mated and passed their
genes to the next generation. (reproduction)
The next generation had move blobs with the pointed
noses. That is NATURAL SELECTION.
1.Variation
2.Competition
3.Survival
4.Reproduction
Asking Questions
is a good adaptation!
2006-2007