Transcript PPT

Evolution Part 2
Origins of Biological
Diversity
Artificial vs. Natural Selection
Artificial Selection – selective breeding of
domesticated plants and animals to produce
offspring with traits valuable to humans.
• Humans choose which traits are more common.
• Example – Dog Breeding (for temperament)
Natural Selection – Nature “selects” and favors
traits more suitable for their particular
environment.
• Result?  Evolutionary adaptation to the
environment.
Darwin’s Finches – The Making of New Species
• 13 species of Finches are unique to the Galapagos
Islands!
• All 13 species resemble the mainland species
• All 13 different species of finches have different
beaks…result of Natural Selection!
• Why might they have different beaks?
Mainland
Why might Darwin’s Finches beaks
look different?
• Hint: Galapagos is made of many different
islands…each with different environments!
Darwin’s Observations:
4 Steps Leading to Natural Selection
1. Overproduction of Offspring – species produce
more offspring than the environment can support
2. Leads to a “Struggle for Existence”
3. Many Variations within a population!
–
(def.) Differences among members of the same species
4. Individuals with ‘best suited’ traits survive &
have reproductive success = pass on their advantageous
traits.
Pesticides
Natural Selection in Action!
Using pesticides against insects can cause
resistance over time!
Evolution (Part 2)
Microevolution &
Speciation
Objectives
• Describe populations in terms of gene pools,
gene frequencies, and genetic variations
• Identify types of genetic drift as random
changes in population’s gene pools.
• Describe various ways speciation occurs.
Population & Natural Selection
Population – a group of individuals of the same species
living at the same place at the same time
**Individuals don’t evolve…Populations Do!**
Example – Population of Deer in Berks County
Changes in Gene Pools
…Microevolution!
• Microevolution is evolution on the smallest scale.
– A generation – to – generation change in the
frequencies of alleles within a population.
– A population is the smallest level at which evolution
can occur.
• Populations NOT undergoing change or evolving
are said to be in Hardy-Weiberg Equilibrium.
– Doesn’t really exist (almost impossible)
Microevolution is a Change within a
Population’s Gene Pool
•Gene Pool – all of the alleles (forms
of genes) in all the individuals of a
population.
– Where genetic variation (the raw material
of evolution) is stored.
•Allele Frequencies – how often an
allele for a particular trait appears in a
population.
Changes in Gene Pools are due to…
Genetic Drift
Genetic Drift – a change in the gene pool of a
population due to chance
1. Bottleneck Effect
2. Founder Effect
3. Gene Flow
4. Mutations
Bottleneck Effect
(type of genetic drift)
• Disasters (earthquakes, floods,
droughts, and fires) can
drastically change the size
and gene pool of a
population.
• By chance, some alleles might be
more frequently represented in
survivors.
• Decreases genetic variation in
populations.
Founder Effect
(type of genetic drift)
• Occurs when a few individuals colonize an isolated
new habitat (island, lake, etc.)
• The smaller the “founding colony” = the smaller
the gene pool
• Reduces genetic variation
Gene Flow, Mutations, & Fitness
Gene Flow - Exchange of genes with another population
– Occurs when individuals migrate between populations
Mutation - A random change in an organism’s DNA
__________________________________________
Fitness – The contribution that an individual makes to the
gene pool of the next generation compared the
contributions of others.
Speciation
• (part 2 pp)
Come up with a definition for
“species”
Hint: try to think about what makes these
species different from one another.
15.1
Diversity of Life is Based on the Origin
of New Species
Biological Species
Concept
– Defines a species as a
population or group of
populations whose
members have the ability
to breed with one another
and produce fertile
offspring
Micro vs. Macroevolution
• Microevolution – smallest scale (populations
evolved by gene pools changing by chance)
• Macroevolution – Dramatic! LONG!
– Speciation
• The origin of different species (biological diversity)
– Extinction of Species
– Evolution of new features
• Wings, webbed feet, etc.
What separates species & where do new
species come from???
Reproductive Isolation- When a reproductive
barrier keeps similar or closely related species from
interbreeding!
–
–
–
–
Timing
Behavior
Incompatibility
Infertile Offspring
Geographic Isolation & Speciation
If Earth’s changes cause a population to
become separated, the “splinter”
populations may break off and follow
their own evolutionary path and
eventually become 2 or more different
species.
Timing
• Breeding opportunities occur
at different times of the
year…
Behavior
Example: Spring vs. Fall
Frigate birds
Mating Dance
Birds of Paradise
• Different “dances”,
communications, etc. initiate
breeding.
Ellen - Mating
Rituals
World's 10 Most
Bizarre Animal
Mating Rituals
Incompatibility
• Male and female reproductive organs are not able to
come together.
• Male sperm & female eggs biologically/genetically can
not become fertilized!
• Offspring (babies) are produced but are unable to
reproduce. (genes can’t “live on”)
Infertile Offspring
• Off
Speciation – gives rise to new
species!
• Speciation: An Illustrated Introduction - YouTube
The Fossil Record Provides Evidence to Life’s
History
• Fossils form when organisms are buried in
sedimentary rock or other material and
remains are preserved.
– Petrified (turned to stone)
– Impressions (footprints, dung etc.)
– Entire organisms preserved in ice (wooly
mammoth)
– Amber (tree sap preserves insects)
Punctuated Equilibrium
In the fossil record we notice that:
•Species can appear abruptly
•Species can remain unchanged for long periods of time
•Species can disappear as quickly as they showed up
Punctuated Equilibrium – Long periods of little change
(equilibrium) are broken (punctuated) by shorter times of
rapid change/speciation.
Wooly Mammoth & Other Fossil Videos
Mammoth in Siberia
Geologic Time Scale
Organizes Earth’s history into 4 distinct
Eras:
1.
2.
3.
4.
Precambrian (oldest)
Paleozoic
Mesozoic
Cenozoic (most recent)
• Boundaries between eras are characterized
by major changes & mass extinctions
• T-Rex (extinct 65 million
years ago)
• Irish Deer (extinct 7,700
years ago)
• Thylacine Tasmanian
Tiger (extinct 1936)
• Quagga: ½ horse ½
zebra (extinct 1883)
Dating Fossils
Scientists can only study fossils if they know their
age!
By using the layered “rock strata” scientists can
determine the general age of each fossil based on
which layer it was found in. (Example- Wallpaper)
Youngest
Oldest
Radiometric Dating
• Method used to determine the age of
rocks and fossils based on the amount
of radioactive isotopes in the object.
• An isotopes half-life is the time (years)
it takes for 50% (half) of an original
sample to decay.
• Isotope Half-Lives are unaffected by
temp., pressure, etc.
 Uranium-238 (half-life = 4.5 billion
yrs.)
 Carbon-14 (5,730 yrs.)
 Plutonium 239 (24,000 yrs.)
video:
How Does Radiocarbon Dating
Work? - Instant Egghead #28
- YouTube
Quick Demonstration
• How long does it take to for half of this
same to decay (be lost)??
• WATCH THE CLOCK!!!
Activity: Understanding Half-Life
• You will be given a 8 pieces of paper and a “trash” cup.
• You will be asked to remove ½ of the paper you have in
your hand every 30 seconds.
•
When you remove ½ the paper…put it into the trash
cup and assume it is gone forever!
• After each time you remove paper…write down how
many pieces of paper remain in your hand and the time
elapsed on the data table.
• Do not talk…just follow directions!!!!