Transcript Evolution Power Point

What is Evolution?
EVOLUTION:
the process of change over time
Evolution is the idea that new species
develop from earlier species by
accumulated changes.
Charles Darwin
The Father of Evolution
A scientist that traveled the world making
observations and collecting evidence
about the way life changes.
Darwin’s Travels
 He sailed from England as a crew
member on the H.M.S. Beagle
 Wherever the ship anchored, Darwin
went ashore to collect plant and animal
specimens that he added to his research
collection.
Darwin’s Travels cont..
 Darwin selected the
Galapagos Islands for
study because each
island had different
climates and a variety
of animal and plant
life.
 Darwin observed that
the characteristics of
many animals and
plants differed greatly
among the different
islands.
The Origin of Species
 Darwin’s book
presented evidence
that evolution has been
taking place for
millions of years and
continues in all living
things
Darwin's Hypothesis:
“Survival of the fittest” (not necessarily the
strongest): Those with more adaptive traits
tend to survive longer and/or produce the
most offspring.
Artificial
Selection
 Selections by humans
for breeding useful
traits from the natural
variations among
different organisms
Natural
Selection
 Individuals better
suited to their
environment survive
and reproduce most
successfully
Artificial Selection
How did humans in relatively short time produce dogs that are so
radically different from the wolf and each other?
 Sometimes, dogs are born
with unusual traits—short,
stubby legs, for example.
 In nature, this trait might
be harmful but under the
care of humans, this trait
may be desirable, so
humans will keep the dog
alive and use it to produce
more dogs with short
stubby legs.
Natural selection is based on 4 facts:
1.Organisms produce more
offspring than can survive.
2.There is variation among offspring.
3.There are limited resources
(not enough food, water, space,
etc. for everyone).
4.The organisms best fit to their environment
will survive and the others will not.
Evidence of Evolution
 Fossils are
preserved remnants
or impressions left
by an organism that
lived in the past.
 The deeper down
the fossil is, the
older it is.
FOSSIL RECORDS
 The fossil record provides evidence about the
history of life on Earth.
 It also shows how different groups of organisms,
including species, have changed over time.
Homologous Structures
Structures that have different shape and functions in different
organisms but develop from the same embryonic tissues.
 Examples: The limbs of the modern HUMAN, BIRD,
PORPOISE and ELEPHANTS are homologous structures
because they possess the same bones but these bones
perform different jobs.
Adaptations:
Inherited characteristic that increase
an organism’s chance of survival
 Why are most animals in the artic white?

So they blend in with the snow and avoid being seen
 Why do sharks have such sharp
teeth?

It allows them to catch their prey
 Why do elephants have such big ears?

To let heat escape their bodies so they can
stay cool
Vestigial Organs
organ that serves no useful function
over generations, they reduce in size
Whale
Human
Appendix
DARWIN’S Theory Of Evolution
1. Differences between species may be the result of
natural selection.
2. Organisms produce more offspring than can
survive, and many that do survive do not
reproduce.
3. Because more organisms are produced than can
survive, they compete for limited resources.
4. Individual’s best suited to their environment
survive and reproduce most successfully.
5. Species change over time.
Gene Pool
 All genes,
including all the
different alleles
presents in a
population
Genetic Variations
 Two main sources of genetic variation are
mutations and the genetic shuffling that
results from sexual reproduction
5 Conditions for maintaining
genetic equilibrium:
1. Random mating
2. Population must be very large
3. There can be no movement into or out of
the population
4. No mutations
5. No natural selection
Results of Evolution -- Speciation!!
 Speciation is the process that creates new species!
 A species is a group of organisms that can naturally
interbreed and produce fertile offspring.
 The Liger--the offspring of a tiger and a lion.
 Tigers and lions are still considered separate species, because
although they can produce
offspring, the offspring
is not fertile.
ENDOSYMBIOTIC THEORY
 Theory that eukaryotic cells
formed from a symbiosis among
several different prokaryotic
organisms.
A group of single celled organisms came
together to make a multicellular organism.
Types of Evolution
 Convergent Evolution process by which
unrelated organisms independently evolve
similarities when adapting to similar
environments.
Ex.. Sharks, Penguins & Dolphins
Types of Evolution
 Coevolution process by which two species
evolve in response to changes in each other.
Ex.. Humming Birds & Flowers
Extinction!
 Extinction occurs
when there
are no members
of a species
left alive.