Transcript How do organisms sometimes change over time?

How do organisms
adapt and change
over time?
Charles Darwin (1809-1882)
Sailed around the world 1831-1836
Galapagos
Turtles
Darwin’s Travels
Revealed
• The diversity of living
species was far
greater than anyone
had previously known!
• These observations
led him to develop the
theory of evolution.
Natural Selection
• The process by which plants and animals
with favorable traits survive and
reproduce.
• Occur because of a mutation in the DNA
or the environment.
Ex. Organisms adapt to their
environment.
Natural Selection is NOT
Selective Breeding!
• Nature provides variation, humans select
variations that are useful.
Ex a farmer breeds only his best livestock
Natural
Selection
• The traits that help
an organism
survive in a
particular
environment are
“selected” in
natural selection.
Example of Natural Selection
Peppered Moths
• A study on different
colored moths
disappearing and
appearing in an area.
Darwin’s Finches
• The isolation of the birds
on an island caused the
finches to develop lots of
different kinds of beaks.
Summary of Natural Selection
1. Organisms differ; variation is inherited.
2. Organisms produce more offspring than
survive.
3. Organisms compete for resources.
4. Organisms with advantages survive to pass
those advantages to their children.
Examples of Beneficial Traits:
Mimicry
• Physically or
actively looking like
another organism.
Ex. A walking stick
insect.
Monarch Butterfly
Coral Snake
• "Red on yellow, kill a
fellow. Red on black,
won't hurt Jack."
How do organisms ensure
the survival of there
species?
Natural Selection Must Haves:
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Overproduction of offspring (children)
Inherited variation or differences
Struggle to survive
Successful reproduction
Possible Reasons for Natural
Selection
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Variation In Genes
Competition
Pollution/Mutations
Environmental Changes
Separation
Adaptation
Division
What is a theory?
• A way to explain something in nature.
• Usually accepted by the scientific
community.
• May or may not be true.
Different types of evolution?
• Micro-evolution
– Changing of an organism within its kind
– Basically the same thing as natural selection
• Macro-evolution
• Long-term change from one organism to
another
• Both involve change over a period of time.
• The BIG difference:
– Micro-evolution has been observed to happen.
– Macro-evolution has not.
Things used as evidence for
macro-evolution:
Fossil Records
• Are solid remains or imprints of once-living
organisms.
• Are formed from layers of sediment and minerals
replacing bone.
Relative Dating
• Can determine a
fossil’s relative age
• Performed by
estimating fossil age
compared with that
of other fossils
• Drawbacks –
provides no info
about age in years
Absolute Dating
• Can determine the
absolute age in
numbers
• Is performed by
radioactive dating –
based on the amount
of remaining
radioactive isotopes
remain
• Drawbacks - part of
the fossil is destroyed
during the test
Carbon-14 Dating
What do fossil records and
skeletal records show
Similarities!
Vestigial Structures
• Structures that do not appear to have a use.
Ex. The hind-limb bones deeply embedded inside
the whale.
Can you find the vestigial
structure?
Homologous Structures
• Similar structures in
different organisms.
Ex. Bones
See pg. 156
Homologous Body Structures
Embryonic Structures
• Embryos of vertebrates are not the same but look
similar.
(And, grow into different organisms.)
Pg. 157