Transcript Evolution - My Teacher Pages

Chapter 15 Evolution
What You’ll Learn
You will analyze the
theory of evolution.
You will compare and
contrast the
processes of
evolution.
Darwin’s Theory of Natural Selection
• Section Objectives:
Summarize Darwin’s theory
of natural selection.
Explain the 4 principles of
natural selection
Show how natural selection
could change a population
What is Evolution?
• Evolution ~process of change through time
– explains how modern organisms have descended
from ancient organisms
Evolution!
Evolution!
Why do we accept this as a
Scientific Principle?
Evolution!
Evolution: process of change through time
• The change in characteristics of populations
through generations. Thus, existing life forms
have evolved from earlier life forms
• A unifying principle for biology.
• Provides an explanation for the difference in
structure, function, and behavior among
organisms
What do we know?
• There are many different creatures on Earth
• How do we know this?
OBSERVATION
Biodiversity
Diversity ofofLife
Lifeon
onEarth
Earth
WhatHow
accounts
did allfor
these
all this
creatures
biological
come
diversity?
about?
What do we know?
• All creatures have common characteristics
• How do we know this?
OBSERVATION
Unity of Life on Earth
cells
DNA
How could all of life have the same basic features?
What do we know?
• Creatures have changed over time
• How do we know this? OBSERVATION
Fossil Record
Evolution explains Unity & Diversity
• Only evolution explains both
– unity of life
• similarities between all living things
– diversity of life
• wide variety of different creatures on Earth
DNA
Darwin & Evolution
by
Natural Selection
Cactus
eater
Insect eaters
Seed eaters
Bud eater
2006-2007
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:
ancient Armadillo
Why should extinct
armadillos & modern
armadillos be found on
same continent?
Darwin found… birds
Darwin found:
Many different birds on
the Galapagos Islands.
Finch?
He thought he found
very
different kinds…
Sparrow?
QuickTime™ and a
Photo - JPEG decompressor
are needed to see this picture.
Woodpecker?
Warbler?
But Darwin found… a lot of finches
Darwin was amazed to
find out:
All 14 species of birds
were finches…
But there is only one
species of finch on the
mainland!
Large
Finch?ground
Finch?
finch
Small
ground finch
Sparrow?
Sparrow?
QuickTime™ and a
Photo - JPEG decompressor
are 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! beaks are inherited
 different
Darwin found:
The differences between
species of finches were
associated with the
different food they ate.
variations
serve as adaptations
that
help birds
Darwin
said:compete for
food
Ahaaaa!
 these birds survive &
A
flock
Large
Big seed
ground
eater of South
Small
ground
seed
eater
finch
Finch?
Sparrow?
reproduce
finch American finches were
 pass on the genes for those
stranded on the
more fit beaks
Galapagos…
 over time nature selected for
different species with
different beaks
QuickTime™ and a
Photo - JPEG decompressor
are needed to see this picture.
Warbler
Insect
eater
finch
Woodpecker?
Tree &
Leaf
finch
bud eater
Warbler?
Relationship between species (beaks) & food
DARWIN’S THEORY AND THE MODERN
SYNTHESIS
• Darwin also saw that humans choose
organisms with specific characteristics
Breeding organisms with specific traits in
order to produce offspring with identical traits
is called artificial selection.
• Darwin hypothesized that there was a force in nature
that worked like artificial selection.
Darwin proposed natural selection as the
mechanism of evolution
• Darwin hypothesized that there was a force in nature that worked like
artificial selection.
• Darwin saw natural selection as the basic mechanism of
evolution
• Darwin concluded that individuals best suited for a
particular environment are more likely to survive and
reproduce than those less well adapted
– As a result, the proportion of individuals with favorable
characteristics increases
– Populations gradually change in response to the
environment
• Organisms without these variations are less likely to survive and
reproduce.
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
Medium
ground
finch
Seed eaters
Vegetarian
tree finch
variation
Bud eater
natural selection for best
survival & reproduction
Large
ground
finch
What do we know?
• Populations are a mix of different individuals
• How do we know this?
Variation
OBSERVATION
How does that work?
Variation
Over-Production & Competition
Adaptation
Nature selects the ones that “fit” the environment
better … survive & reproduce
Natural Selection
What determines survival?
• Natural Selection
– traits that help individuals survive
•
•
•
•
survive predators
survive disease
compete for food
compete for territory
Adaptations
– traits that help individuals reproduce
• attracting a mate
• compete for nesting sites
• successfully raise young
Survival & Reproduction of the Fittest
Survival & Reproduction of the fittest
not the
…the
fittest!
strongest…
bravest…
fastest…
biggest…
Adaptations
the traits that help an organism fit the
environment better to
survive & reproduce
Survival & reproduction of the fittest bug…