Transcript Evolution - OCPS TeacherPress

Section 1
Evolution
Darwin’s Theory of Natural Selection
Darwin on the HMS Beagle
 Darwin’s role on the ship was as naturalist
and companion to the captain.
 His job was to collect biological and
geological specimens during the ship’s travel.
Section 1
Evolution
Darwin’s Theory of Natural Selection
Section 1
Evolution
Darwin’s Theory of Natural Selection
The Galápagos Islands
 Darwin began to collect mockingbirds, finches,
and other animals on the four islands.
 He noticed that the different islands seemed to
have their own, slightly different varieties of
animals.
 Almost every specimen that Darwin had collected
on the islands was new to European scientists.
 Populations from the mainland changed after
reaching the Galápagos.
Section 1
Evolution
Darwin’s Theory of Natural Selection
The Galápagos Islands
Section 1
Evolution
Darwin’s Theory of Natural Selection
Darwin Continued His Studies
 Darwin hypothesized that new species could
appear gradually through small changes in
ancestral species.
 Darwin inferred that if humans could change
species by artificial selection, then perhaps the
same process could work in nature.
 Like Persian cat would survive in nature?
Section 1
Evolution
Darwin’s Theory of Natural Selection
Persian Cat
Section 1
Evolution
Darwin’s Theory of Natural Selection
Natural Selection
 Individuals in a population show variations.
 Variations can be inherited.
 You don’t inherit an injury.
 Organisms have more offspring than can
survive on available resources.
 Variations that increase reproductive success
will have a greater chance of being passed on.
 Acts to select the individuals that are best
adapted for survival and reproduction
Section 1
Evolution
Darwin’s Theory of Natural Selection
Natural Selection
Section 1
Evolution
Section 1
Evolution
Section 2
Evolution
Evidence of Evolution
The Fossil Record
 Fossils provide a record of species that lived long
ago.
 Fossils show that ancient species share similarities
with species that now live on Earth.
 The ancient Glyptodont
have been compared to
modern day armadillos.
 No species today are found
in the fossil record over a
million years ago!!
Glyptodont
Section 2
Evolution
Evidence of Evolution
 Derived traits are newly evolved features,
such as feathers, that do not appear in the
fossils of common ancestors.
 Ancestral traits are more primitive features,
such as teeth and tails, that do appear in
ancestral forms.
 Anatomically similar structures inherited from
a common ancestor are called homologous
structures.
Section 2
Evolution
Evidence of Evolution
Homologous Structures
Section 2
Evolution
Evidence of Evolution
Vestigial Structures
 Structures that are the
reduced forms of functional
structures in other organisms.
 Appendix and hip bones in
whales
 Evolutionary theory
predicts that features of ancestors that no
longer have a function for that species will
become smaller over time until they are lost.
Section 2
Evolution
Evidence of Evolution
Vestigial Structures
Section 2
Evolution
Evidence of Evolution
 Analogous structures can be used for the
same purpose and can be superficially
similar in construction, but are not inherited
from a common ancestor.
 Show that functionally similar features can
evolve independently in similar
environments
 Examples include dorsal fins of dolphins vs.
sharks or wings of birds vs. insects
Analogous Structures
Section 2
Evolution
Evidence of Evolution
Comparative Embryology
 Vertebrate embryos exhibit homologous
structures during certain phases of
development but become totally different
structures in the adult forms.
 All vertebrates have a:
 post anal tail
 dorsal nerve cord (becomes the spinal cord)
 pharyngeal slits (gills)
 notochord (becomes the spine)
Section 2
Evolution
Evidence of Evolution
Comparative Embryology
Section 2
Evolution
Evidence of Evolution
Comparative Biochemistry
 Common ancestry
can be seen in the
complex metabolic
molecules that many
different organisms
share.
Section 2
Evolution
Evidence of Evolution
Comparative Biochemistry
 As species evolved,
one change after
another should have
become part of their
genetic instructions.
 Therefore, more and
more changes in a
gene’s nucleotide
sequence should build
up over time.
Section 2
Evolution
Evidence of Evolution
Geographic Distribution
 Evolution is intimately linked with climate and
geological forces.
 If environments never changed, then the traits
best suited to survive would continue and
mutations would not be beneficial
 Examples are alligators, swamps haven’t
changed in many years.
 As climates change, new mutations may now
be beneficial.
Section 2
Evolution
Evidence of Evolution
Types of Adaptation
 An adaptation is a trait shaped by natural
selection that increases an organism’s
reproductive success.
 Organisms cannot change “adapt” to
their environment.
 Either they have the genetic traits to
survive or they do not.
 Fitness is a measure of the relative
contribution an individual trait makes to the
next generation.
Section 2
Evolution
Evidence of Evolution
Camouflage
 Allows organisms to become almost invisible to
predators
Mimicry
 One species evolves to resemble another
species.
Section 3
Evolution
Shaping Evolutionary Theory
Mechanisms of Evolution
 Hardy-Weinberg principle states that when allelic
frequencies remain constant, a population is in
genetic equilibrium.
 In order for populations to remain constant, the five
components of Hardy-Weinberg must occur:
1. No natural selection
2. Mating is random
3. No mutations
4. Large population
5. No gene flow - migration
Section 3
Evolution
Shaping Evolutionary Theory
Genetic Drift
 A change in the allelic frequencies in a
population that is due to chance
 In larger populations, the alleles tend to remain
more stable
 In smaller populations, the effects of genetic
drift become more pronounced, and the
chance of losing an allele becomes greater.
 Genetic drift reduces genetic variation!!!
Section 3
Evolution
Shaping Evolutionary Theory
Genetic Drift - Founder Effect
 Occurs when a small sample of a population
settles in a location separated from the rest
of the population.
 Alleles that were uncommon in the original
population might be common in the new
population.
Section 3
Evolution
Shaping Evolutionary Theory
Genetic Drift - Founder Effect
 For example, one of the founding members of
a small group Germans that began an Amish
community in Pennsylvania had an allele for
polydactylism (more than 5 fingers or toes)
 After 200 years of isolation, the 8000
Amish have a much higher % of
polydactylism than the rest of the world
Section 3
Evolution
Shaping Evolutionary Theory
Founder Effect
Section 3
Evolution
Shaping Evolutionary Theory
Genetic Drift - Bottleneck
 Occurs when a population declines to a very
low number and then rebounds.
 Certain traits may
become more
prevalent while
others may die out
because of the
traits that survived.
 Caused by floods
or hurricanes
Section 3
Evolution
Shaping Evolutionary Theory
Gene Flow
 Increases genetic variation within a population
and reduces differences between populations
 Caused by migrations
Nonrandom Mating
 Promotes inbreeding and could lead to a
change in allelic proportions favoring
individuals that are homozygous for particular
traits
Section 3
Evolution
Shaping Evolutionary Theory
 Sexual selection operates in populations
where males and females differ significantly
in appearance.
 Qualities of sexual attractiveness appear to
be the opposite of qualities that might
enhance survival.
 Sexual selection will effect natural selection
by increasing certain traits in a population
such as big pretty feathers on peacocks
Section 3
Evolution
Shaping Evolutionary Theory
Superior Male
Higher Quality Offspring