Transcript Ever-changing Populations

What is this Evolution stuff?
EVER-CHANGING POPULATIONS
Evolution:
Change in allele frequencies in a population’s gene pool over time.
Evolution does not occur in individuals…
but in populations.
Population:
Interbreeding group of
individuals (one species)
in a given geographic area
Gene pool:
The collection of genes (alleles) of a population
Change in base sequence…
Heritable (receivable) change in a gene…
→Gives rise to new genes
→ Can be harmful
→ May be beneficial
Mutation:
Gene flow:
Genes being
added (immigration)
or taken away
(emigration)
from a gene pool
The Voyages of Charles Darwin
The
Galapagos
Islands are
about 525
miles from
South
America, at
the
equator.
Natural selection:
How an env. favors or disfavors certain
phenotypes: The fittest survive and reproduce.
Genes of less fit individuals are lost.
Natural Selection:
4 Principles
 1. Overproduction of offspring
 Most “fit” will survive
 Inc. competition for resources
Natural Selection:
4 Principles
 2. Variation
 Traits (phenotypes) differ
 Can affect ability to find / utilize food, H2O,
shelter, O2, to reproduce, etc.
Natural Selection:
4 Principles
 3. Adaptation
 Leads to h in freq. of particular structure,
physiological process, or behavior – allowing org.
to survive /reproduce better.
 Fitness used to describe reproductive success
Natural Selection:
4 Principles
 4. Descent with Modification
 Environment Changes –
Nat. Sel. yields pops. w/new phenotypes to adapt
 New pops. live differently from ancestors
Better adapted than it’s ancestors? With its sheer strength and
deadly, bacteria-ridden saliva, the Komodo dragon is the top
predator in its range.
More about the Komodo…

Komodo dragons have thrived in the harsh climate of Indonesia's Lesser
Sunda Islands for millions of years, although amazingly, their existence was
unknown to humans until about 100 years ago.

Reaching 10 feet (3 meters) in length and more than 300 pounds (136
kilograms), Komodo dragons are the heaviest lizards on Earth. They have
long, flat heads with rounded snouts, scaly skin, bowed legs, and huge,
muscular tails.

As the dominant predators on the handful of islands they inhabit, they will
eat almost anything, including carrion, deer, pigs, smaller dragons, and even
large water buffalo and humans. When hunting, Komodo dragons rely on
camouflage and patience, lying in wait for passing prey. When a victim
ambles by, the dragon springs, using its powerful legs, sharp claws and
serrated, shark-like teeth to eviscerate its prey.

Animals that escape the jaws of a Komodo will only feel lucky briefly.
Dragon saliva teems with over 50 strains of bacteria, and within 24 hours,
the stricken creature usually dies of blood poisoning. Dragons calmly follow
an escapee for miles as the bacteria takes effect, using their keen sense of
smell to hone in on the corpse. A dragon can eat a whopping 80 percent of
its body weight in a single feeding.
Natural Selection:
4 Principles (review)
 Overproduction of offspring
 Variation
 Adaptation
 Descent with modification
Types of Natural Selection
Stabilizing
Selection
 Env. will eliminate
individuals at extremes of
population.
 Example:
 small babies-less healthy
 large babies-trouble being
born
 avg. babies – more fitness

Giraffes: Long necks are better for getting a
mate, short necks are better for drinking water.
Medium-sized necks have been selected for.
Stabilizing Selection:
Types of Natural Selection
Stabilizing
Selection
Disruptive
Selection
 Environment favors
individuals at extremes – not
intermediates
 Can split population into
subgroups
 Example:
 birds live in area where
medium-size seeds are less
common – birds with
large/small beaks eating
large/small seeds are more fit
Disruptive Selection:
Types of Natural Selection
Stabilizing
Selection
Disruptive
Selection
Directional
Selection
 environment favors
individuals at one extreme
 Example
 Lighter colored moths more
easily seen, birds eat them
more freq.
Directional Selection:
Types of Natural Selection
Stabilizing
Directional
(review)
Disruptive
Species: group of individuals that share some
features and can interbreed
Speciation: Change in a species
> Can be very slow, or relatively rapid.
What causes Speciation?
Geographic
barriers like
rivers and
mountains
What causes Speciation?
Reproductive
barriers – like
different
anatomy or
incompatible
gametes
What causes Speciation?
Temporal
barriers –
reproduce at
different times
What causes Speciation?
Behavioral
barriers:
blocked by
courtship
rituals &
other habits

Three male king penguins follow a female in a courtship
ritual.
What causes Speciation?
Reproductive Barriers
Geographic Barriers
Temporal Barriers
Behavioral Barriers
(review)
Evolution ENSI Lesson
on Human Evolution
- Hominoid Chromosomes
Patterns of Evolution
 Macroevolution
 large scale changes over long periods of time.
 Some important patterns …
Mass extinctions
Large numbers
of species died
out
Typically due
to habitat
change that
was too rapid
to adapt to.
Mass extinctions
Large numbers
of species died
out
Website
Gradual extinction
 Cause: other organisms, climate change,
disasters
 Gradual ext. and speciation occur at approx.
same slow rate
Thylacine (Tasmanian Wolf)
A carnivorous marsupial.
The last one died in a zoo in 1933.
Adaptive radiation (divergent ev.)
A species changes into many different forms
Convergent evolution
Unrelated organisms evolve similarities
(analogous structures) when adapting to similar
environments;
ex: shark, seal, dolphin, fish =
streamlined bodies, fins for movement
Coevolution
Two species
evolve in
response to
changes in
each other
ex: certain
flowers attract
certain insects
to pollinate

Tangle-veined fly (Prosoeca ganglbaueri) visits a small
flowering herb called the mountain drumstick
(Zaluzianskya microsiphon) in the Drakensberg Mountains
of southern Africa.
Coevolution
 Island of
Mauritius
 Humans &
their livestock
inhabited
island in 1581
 Last Dodo seen
in 1681
Coevolution
Calvaria Tree
Only about 15
trees left on
island, each just
over 300 years
old.
Dodo would eat
seeds. Only
partially
digested seeds
would ever
germinate…
Homologous Structures
Similar body structures inherited
from common ancestry
Examples…
Homologous Structures
Homologous Structures
Gradualism
Evolution
proceeding
in small,
gradual but
continuous
steps
Punctuated
equilibrium
Long periods
of stable
evolution
suddenly have
periods of
rapid change
show in fossil
record
MiniQuiz Warm-up
 1. The forelimb of a man, a cow, a horse, a
whale, and a bird have the same bone
structure. Are these structures known as
A. analogous?
B. homologous?
C. vestigial?
MiniQuiz Warm-up
 2. One type of bird does not understand the
courtship ritual of another type bird. What
type barrier is this?
A. Temporal
B. Reproductive
C. Behavioral
D. Geographic
MiniQuiz Warm-up
 3. The size of horses has gotten larger and
larger over time. What type example of
speciation is this?
A. Stabilizing
B. Disruptive
C. Directional
Phylogeny
Descent with modification:
Evolutionary tree of elephant family, based on fossil evidence)
 The
evolutionary
history of a
species or a
group of
species over
geologic
time
Sequences Reflect Relationships
 After working with sequences for a while, one develops an
intuitive understanding that for a given gene, closely
related organisms have similar sequences and more
distantly related organisms have more dissimilar
sequences. These differences can be quantified.
 Given a set of gene sequences, it should be possible to
reconstruct the evolutionary relationships among genes
and among organisms.
Human Evolution Interactive
(click here)
Human Evolution Interactive (click here)
Classifying by ancestry
Phylogenetic
trees or
Cladograms
(a “clade” is
shown in
blue)
Classifying by ancestry
Phylogenetic
trees or
Cladograms