Download How Natural Selection Works

How Natural Selection Happens
How Natural Selection Works
• How does the “fittest” organism happen?
How do we get organisms with the best traits?
1. Lots of offspring
2. Differences or variations occur in those offspring (due
to sexual reproduction or mutations)
3. Some variations are helpful, this results in a better
chance of survival, reproduction, and passing on of
those good variations.
4. Over time, individuals with new variations may
become a new species. This is evolution.
Giraffes with long necks exist because…
1.
Mom and Dad giraffe had lots of
offspring
2.
Those offspring were each
different.
Some had helpful variations
(longer necks) which meant better
survival (more food) and more
likely to reproduce.
Long neck genes get passed on to
future offspring, eventually a new
species of giraffe occurs.
3.
4.
•
•
•
•
Mom and Dad bug had
lots of offspring
Those offspring were
each different.
Some had helpful
variations (grey) which
meant better survival
(not eaten) and more
likely to reproduce.
Grey genes get passed
on to future offspring,
eventually a new species
of bug occurs.
http://www.nysci.org/explore/ontour/charlieandkiwi/Charliesand-Kiwis-Evolutionary-Adventure-Video
Adaptations are variations that make an
organism better suited for its environment.
• Adaptations can be physical (on their body) or
behavioral.
Adaptations can help an organism….
Attract a mate
https://www.youtube.com/embed/REP4S0uqEOc
Warn predators
Hide from predators (camouflage)
https://www.youtube.com/watch?v=k8RlGbpuhgc
Imitate a more
dangerous animal
(mimicry)
mimicry
Geographic
Isolation can allow
some variations to
appear in a species
that might have
been otherwise
stayed hidden
Geographic Isolation
Geographically Isolated Animal Examples
Flightless birds and mouse lemurs
Speed of Evolution
• Gradualism- a continuous series of mutations and
variations over time will result in a new species.
• Punctuated Equilibrium- rapid evolution that occurs
when the mutation of a few genes results in the
appearance of a new species over a relatively short
time.
+
The 0.1% of bacteria that
survives, reproduces and
now is resistant to the
spray
http://www.youtube.com/watch?v=BwuL4J_jEyc&feature=related
How many germs will survive?
20,000 single celled organisms, which are
genetically different from the dead, will still
survive and continue to reproduce.
So what? Why does evolution
matter?
https://www.youtube.com/watch?v=JGnNc8JAdWs
http://www.nytimes.com/2013/04/17/bu
siness/report-on-us-meat-sounds-alarmon-superbugs.html?_r=0
http://www.nytimes.com/2013/04/12/world/
asia/report-published-on-3-who-died-fromh7n9-bird-flu.html?_r=0
The End of Evolution….or is it?
https://www.youtube.com/watch?v=zGqae7vuUWo&feature=PlayList&p=60D07D9950E069A4&playnext_from=PL&playnext=1&i
ndex=16