Transcript Species Change Over Time

Species Change Over Time
What is evolution?
• Definition:
• The gradual change in a species over
time
• Takes a Looooong time
• Results from a change in the GENETIC
material of an organism
• Not acted on at the individual level
• Passed on from one generation to the
next
Early Ideas of Evolution
• Lamarck
• When an individual
organism acquires a new
trait IN ITS LIFETIME it
passes that trait to its
offspring
• Ex. A giraffe wanted to reach
a higher tree so it stretched
its neck. This longer neck
was passed onto the next
generation
• No Evidence!
What replaced Lamarcks idea?
• Charles Darwin
• Developed his idea aboard the Beagle
• Studied rock formations and collected
fossils
• Compared animals
• Galapagos Islands
• Located off the South American coast
• Came up with natural selection
Galapagos Islands
South America
Darwin = populations on islands evolved from mainland species
Darwin versus Lamarck
What is natural selection?
• The process through which members of a species are best
suited to their environment survive and reproduce at a
higher rate than other less suited members of the species
• Species adapt to their environment
• Adaptation
• A characteristic, a behavior, or an inherited trait
• Fitness
• How well you are equipped to survive the environment you live
in
Simpler view of Natural Selection
• Survival of the fittest
• The most “fit” animals will be selected for and will survive.
• Ex. Giraffes were all born with different heights. The ones with longer necks
were more “fit” and they were able to get additional food, survive, and pass
on those traits.
Example
• Depending on the food source and environment, different birds
survived and changed to best fit each island
Natural Selection
• Often based on
• Overproduction
• Variation
• Adaptation
• Selection
Overproduction
• When a plant or an animal
reproduces it usually creates more
offspring than the environment
can support
• Ex. Salmon lay 100’s of eggs but
only a few will survive
Variation
• Within a species there are natural
differences in traits
• Occur due to mutations
• Change in genetic material/DNA
• Genetic variations are passed from
one generation to the next
Adaptation
• Mutation that makes an individual
better able to survive
• Gives organism an advantage
Selection
• Individual organisms with a
particular adaptation will survive
long enough to reproduce
• Adaptation becomes more
common in next generation
New Species Evolve from Earlier Species
• Speciation
• Evolution of a new species from
an existing species
• May occur when the
environment changes
dramatically or gradually
• Ex. Finch (mentioned
previously); Cichlid (fish); Polar
Bear
What can contribute to speciation?
• Isolation by geographical or other
barriers
• Species can also be isolated if they
feed on different things or reproduce
at different times of year
Examples of Natural Selection:
The Evolution of The Polar Bear
Our story begins with the Polar Bear’s
closest living relative – the Brown Bear
The Evolution of The Polar Bear
Around 300,000 years ago a small group of
Brown Bears became reproductively
isolated from the rest of the population
The Evolution of The Polar Bear
This small founding population of
Brown Bears were able to survive
and reproduce living in the Arctic
Tundra. After MANY
generations, a random genetic
mutation occurred . . .
The Evolution of The Polar Bear
Because of the genetic mutation, a litter of
Brown Bears exhibited WHITE coloration
The Evolution of The Polar Bear
How do you think the white fur color affected these bears
chances of surviving long enough to have cubs of their
own?
REMEMBER: Natural Selection Rests on 4 Premises:
Overproduction, Variation, Adaptation, Selection
The organism “most fit” for the environment will
survive to reproduce
Not every organism will be able to reproduce. The ones most fit will
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Remember traits have a genetic basis, or are inherited
from parents
Advantageous traits, which allows organisms to have more
offspring, will become more common in the population over time.
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What
Happened?
Through Reproductive Isolation and Natural Selection . . .
One Species Evolved Into Another New Species By
Adapting To Its New Environment
How long do you think this took?