Transcript Evolution Unit PowerPoint - All Topics

GEOGRAPHICAL ISOLATION AND
NATURAL SELECTION MAY LEAD
TO NEW SPECIES
First, What is a species?
 group of individual organisms that are
capable of interbreeding to produce fertile
offspring in nature.
Male (Purple) and female purple
martin (Progne subis )
What Exactly IS Evolution….
How About What it is NOT!
 It’s one of the most misunderstood, poorly taught aspect of
biology
 It is NOT a belief but a theory based on FACTS; we see it occurring
today (pesticide resistance, bacteria immunity to antibiotics,
yeast mutate quickly creating new species)
 Does NOT reject religion, faith or the existence of a ”higher
power”.
 I know scientists that study evolution of various organisms that sing in their
church choir!
 Although it encompass the origin of life, it’s focus is how life
changed, and is changing, after origin; how species branch from
common ancestry
 Individuals do not evolve, populations due. Remember genetic
diversity?
 Human activity can influence it
Evolution. What is it?
 Small or large genetic change at a population
level inherited over several generations.
 Has to occur at the genetic level
 Changes in allele frequency in a population over
time changes due to mutation and are passed
along
 Changes are seen in phenotypes (physical
traits)
 Descent with modification
 Suggests common ancestor
More Misconceptions
 It only occurs over long periods of time
 Over the past 50 years, we've observed squirrels
evolve new breeding times in response to
climate change, a fish species evolve resistance
to toxins dumped into the Hudson River, and a
host of microbes evolve resistance to new drugs
we've developed. Many different factors can
foster rapid evolution — small population size,
short generation time, big shifts in
environmental conditions — and the evidence
makes it clear that this has happened many
times.
Natural Selection…………
 In a nutshell, organisms with favorable
phenotypes that allow for adaptation in a
particular environment will survive, reproduce,
pass their alleles along to their off spring
 The term “survival of the fittest” doesn’t mean
only the best survive, just suitable
 Environment DOES NOT NECESSARILY MEAN
THE WEATHER!!!! It simply indicates those that
can withstand selective pressures such as:
 Selective pressures from competition for mates, for
food, for shelter, escaping predators, acclimation to
climate.
 Others may include physical features such as variation
in beak size (Darwin’s finches!)
Natural Selection
 It does NOT produce the perfect organism!!
There are still fish that swim too slow and get
eaten, not to mention the human genetic
diseases out there!!
 However, there is genetic variation in
populations of organisms (Remember genetic
recombination in Meiosis? Mutations?
 Natural selection LEADS to evolution; it isn’t
evolution!
Natural Selection Isn’t Random! It “Selects”
for, or against, phenotypes as environmental
occur. For example, if a new predator is
introduced to an area, prey organisms must be
quick to get away!
Natural Selection Does Not
Occur During an Individual
Organism’s Lifetime
Early theories explained changes as if they occur in an
individual, like the example below….NOT TRUE
Example of Natural Selection
• In this fish population, individuals have
variations. For example, they may differ in
color, size, and speed.
• *Individuals with
certain useful
variations, (in this
case speed) survive in
their environment,
passing those
variations to the next
generation.
* Over time, offspring
with certain
variations make up
most of the
population and look
different from their
ancestors.
Peppered Moth Video
 You Tube Title:
 Peppered Moth
 by Mark Drollinger
 http://www.youtube.com/watch?v=sVVldxxb
Wig
 (2 minutes!!)
Fitness??
**The word fitness describes how well a particular
phenotype persists in the next generation relative to how
individuals that do not have he phenotype. This does NOT
mean the organism is the strongest…just the suited
**For example, if brown beetles consistently leave more
offspring than green beetles because of their color (possibly
less noticeable to predators) you’d say that the brown beetles
had a higher fitness. Se say the brown phenotype is selected
for.
The brown beetles have a greater fitness relative to the green beetles.
Darwin’s Finches, Natural
Selection and Fitness
Charles Darwin
~Proposed changes in characteristics of a
population of organisms occur over time
_Suggested that is humans can
manipulate species to get desired traits,
why can’t something similar occur in
nature?
~”Descent with modification” that occur in
populations, not characteristics an
individual develops in its lifetime (such
as the prior slide)
~Studied organisms on the Galapagos
Islands…..he found some extremely
interesting organisms!!
Galapagos Turtles
Galapagos Turtle
Galapagos
Finches
Marine Iguana
Blue-Footed Booby
Blue-Footed Booby Dance
Red-Footed Booby
Darwin Develops Theory of
Natural Selection
• Darwin hypothesized that there was a
force in nature that worked like artificial
selection where breeders bred organisms
for a particular trait (Cattle, dogs, etc.)
• Suggests a Common Ancestor
Selective Breeding/Artificial
Selection
Darwin and the Galapagos
Finches Video
 YouTube Title:
 Galapagos: the finches (4/7)
 http://www.youtube.com/watch?v=l25MBq8T
77w
 (2 minutes long!!)
What’s Up
With The
Finches? What
do You Notice
About Their
Beaks? How
Would You
Explain This
Observation?
Competition for Food!? hmmm
 These finches were isolated thus competition
for food could have been the driving force
(selective pressure) of adaptation to new
types of food
A subspecies of this species is also known as
the vampire finch as it will occasionally drink
the blood of blue-footed booby nestlings!!!!!
Geographic Isolation
 Individuals population of the same species become
separated
 Mountain formation, river formation, human activity
such as deforestation and urbanization just to name a
few.
 After separation, natural selection occurs and
eventually become two distinct species that
can no longer interbreed to produce viable
offspring
Speciation and Geographical Isolation
~Geographical isolation is just what the name implies. A species of
organisms becomes separated by a physical barrier such as a
stream that develops into a river, mountain formation, lava flow,
after deforestation, even when cities are built (urbanization)!
~~ Since they are divided into difference environments, natural
selection occurs within each of the two populations forming two
distinct species. If they can no longer interbreed and produce
fertile offspring, we can say that speciation has occurred.
Another
Example of
Geographical
Isolation
and
Speciation
Geographic Isolation After
Deforestation
*We’ll use this population of
tree frogs as an example. As
of now, they live in a
subtropical area.
Geographic Isolation After
Deforestation
• After deforestation,
erosion occurs and a stream
is formed. This causes the
frog population to become
divided. Remember that
there is already genetic
variation in the frog
population!
Geographic Isolation After
Deforestation
• Notice the difference in
phenotypes between the two frog
populations. Those that were caught
on the side that had trees cut down
are now in a new ecological
environment….remember natural
selection??? These could be two
different species of frogs that can
no longer interbreed.
Natural selection
not only affects finches,
but insects, bacteria and
viruses as well!!
In Bacteria!!
~~They multiply like crazy
(exponentially!! ). You can visibly
see a colony after incubating over
night!
~~Mutations occur quickly as well;
~~ Along with overuse, and
misuse, of antibiotics many
strains have developed immunity
Antibiotics Are Medications Used to
Kill, or at Least Slow Down, Bacterial
Infections, Like Strep Throat
Antibiotic Resistance
Viruses
 Although viruses aren’t living, they have a single nucleic
acid chain (either DNA or RNA) surrounded by a protein
coat and capable of replication but only within the cells
of living organisms
Your Immunity  Ability to
Fight Off Infections and
Diseases
 Diseases can be caused by bacteria, viruses,
some protists and some fungi
 These are called pathogens
 Two basic types of acquired immunity
 Active
 Passive
Vaccines Help Guard Against
Antiviral Medications
 Antiviral resistance means that a virus has
changed in such a way that the antiviral drug
is less effective in treating or preventing
illnesses caused by viruses, such as the flu
 The drug Tamiflu shortens the duration and
severity of the flu
 Nucleic acids of the virus may change in a
way that results in the virus becoming
resistant to antiviral drugs
Other Forms of Resistance
Pesticide Resistance
To Summarize……
 Disease agents like bacteria, viruses and
chemicals can influence natural selection in
populations of a species
 Geographical isolation can lead to speciation
 Natural selection influences changes in
populations over time
Evidence of Evolution
Homologous Structures
 If a bat, a human, an alligator, and a penguin all
evolved from a common ancestor, then they
should share common anatomical traits
Vestigial Structures
 Body parts that seaming have little or no
function
 At one time in evolutionary history, they were
needed
 Such as the pelvis of a whale, pelvic girdle in some
snakes, wisdom teeth
 Leftovers from evolution
 It used to be thought our appendix was vestigial,
however, it is thought that when beneficial bacteria
in our gut is depleted, the appendix allows them to
be restored;
Fossils
 Fossils
 Formed when organism dies is in silt, mud, sand,
tar or clay soon after death
 Sometimes an insect will die in tree sap (amber)
 Not all dead organisms will fossilize
 The conditions have to be right!!
Example – Evolution of the
Camel
Dinosaur National Monument: Fossilized dinosaur skeleton in sandstone
Fossil of a fish: perch
Dinosaur tracks (‘trace fossils’)
Barosaurus (27 m tall herbivore from late Jurassic (140 mya)
Leaf impression:
Some fossils are imprints, some actually retain original organic matter
Petrified trees: Minerals dissolved in water seep into tissues of dead organisms, replace
its organic material, and turn it to stone
Scorpion in hardened resin from a tree (whole organism preserved
Horseshoe crabs (Limulus polyphemus)
“Living fossils” that have changed little in hundreds of millions of years.
Mammoth tusks (whole organism may be preserved in ice)
Biochemical (Molecular)
Evidence
 Organisms that are more related have fewer
differences in their amino acid sequences.
(Cytochrome C below)