Transcript Intro to Natural Selection Sept 2008

Intro to Natural
Selection
Sept 2008
“Survival of the fittest”
Get set: What have you learned?
• Survival depends on:
– Being able to obtain adequate amount of food
and water.
– Being able to protect one’s self from
predation.
– Having characteristics to deal with the
environment (climate, soil, plants, other
animals.)
– Being able to reproduce to keep the species
alive.
What happened to the animals in
round 1 of the Staying Alive
simulation?
• Toothpickta could not obtain enough food when
•
climate changes affected their natural food
source.
Toothpickta became extinct.
What happened to the
animals in round 2 of the
Staying Alive simulation?
• Tweezarian had slight variations in their
pinchers.
• Variations (mutations) are random –
some are helpful, some are not.
• Those with the helpful variation thrive
and the tweezarian population eventually
all display the “improved” variation.
What happened to the
animals in round 3 of the
Staying Alive simulation?
• Non-native species can be invasive.
• Native plant/animals can be affected
when non-native species are
introduced.
• Over-feeding can cause a disaster for
the entire ecosystem.
A scientific Explanation
• A theory is based on a number
of observations or
experiments.
• A theory attempts to explain
natural phenomenon.
Natural Selection
• the process by which
individuals that are better
adapted to their
environment survive and
reproduce more
successfully than less welladapted individuals do.
Variations
happen by
chance
Some variations
are helpful; some
harmful
What does the
theory say ?
helpful
variations =
survival
Those who
survive, pass
traits to young
Charles Darwin
• An English naturalist
• studied animals on Galapagos
Island
• Wrote the famous book: On the
Origin of Species by Means of
Natural Selection.
• Had a major impact on scientific
community.
SPECIATION
• THE FORMATION OF NEW SPECIES
• AS NEW SPECIES DEVELOP,
POPULATIONS BECOME
REPRODUCTIVELY ISOLATED
• REPRODUCTIVE ISOLATION –
MEMBERS OF 2 POPULATIONS
CANNOT INTERBREED & PRODUCE
FERTILE OFFSPRING.
Table 23.1a
These squirrels live on opposite sides of the Grand
Canyon. This is an example of allopatric speciation.
Table 23.1b
Fig. 23.6
Four species of leopard frogs: differ in their
mating calls. Hybrids are inevitable.
Hawaiian Honeycreepers
An example of adaptive radiation –
these species all diverged from a
common ancestor (founder species)
FOUNDER SPECIES
SPECIATION IN DARWIN’S
FINCHES
• SPECIAITON IN THE GALAPAGOS
FINCHES OCCURRED BY:
- FOUNDING OF A NEW POPULATION,
- GEOGRAPHIC ISOLATION which led to - REPRODUCTIVE ISOLATION and
CHANGES IN THE NEW POPULATION’S
GENE POOL due to COMPETITION.
Can species combines
in new and different
ways today?
http://www.nps.gov/archive/chis/r
m/IslandFox/index.htm
Tigon
Result of male tiger
and female lion
mating in captivity.
Offspring are infertile.
Separated both
geographically and
ecologically.
Liger
Result of male lion and female
tiger mating in captivity.
Offspring are infertile.
Closure: Summarize What
you’ve learned:
• Name 4 parts of Natural
Selection.
• Explain how speciation can
occur.