Transcript Evolution Chapter 14

Game
 If you got lost on an island who would you
rather be stuck on the island with?
 The island is completely remote and you
will be the only two on the island.
 Goal is to survive!
Left or Right?
Bear Grylls
Left or Right?
Left or Right?
Left or Right?
Your mom or dad?
If you are on fire, what do you do?
Is this evolution?
Evolution
Chapter 14
What do you think about when you hear
the word evolution?
 Evolution:
 All the changes that have been transformed life over an
immense time. Or gradual change over time.
 Adaptation:
 Inherited characteristic that improves an organism’s ability to
survive and reproduce in an environment.
Story
 In 1831, a young man at 22 years old volunteered to set sail
on a voyage to visit different countries.
 The ship was meant to charter the South American coastline
for the British navy.
 This man did not want to fight or be in the navy.
 He wanted to observe nature.
 Who am I talking about?
 Charles Darwin
14.1 Darwin developed a theory of
evolution
 There were two theories about life before Darwin.
 1. Species were all fixed, or permanent. (Creationism)
 2. The Earth is only 10,000 years old and still not changing.
 Which do you agree with, are they correct?
True or False
 Kangaroos powerful hind legs were the result of ancestors
strengthening their legs by jumping and then passing the
acquired leg strength to their offspring.
 False
 Giraffes physically stretched their necks to be able to reach
tall trees for food.
 False
 In the 1700s, French naturalist Georges Buffon came up with
the idea that Earth is much older than a few thousand years.
 In the 1800s, Jean Baptiste Lamarck proposed that life
evolves.
 He thought that by using certain body parts, organisms
develop certain characteristics, and these characteristics
would be passed to offspring.
Darwin’s voyage
 English naturalists
 In 1831-1836 traveled to South America from England on the
HMS Beagle.
 Big stop was the Galapagos islands.
 Founding father for evolution.
5 year voyage
Darwin’s observations
 Large # of species
 Organisms are well adapted to their environments
 Organisms do not necessarily appear in same
ecosystems / locations
 Collected fossils
 Galapagos Islands
 Each island had different climate and vegetation
 Observed different but similar species on the
different islands
 EX: tortoises, finches, marine iguanas
Giant Tortoises of the Galapagos
Pinta Island
Hood Island
Isabela Island
Darwin’s Finches
 Depending on the location, Darwin noticed variations in
tortoises and finches.
 Some tortoises had long necks (eat tall shrubs) while other
had short necks ( eat food off the ground).
 Some finches had long beaks ( eat bugs), while others had
short beaks (eat nuts).
Ideas from geology
 Geologist Charles Lyell proposed that geological processes
such as erosion could explain the physical features of todays
Earth.
 Darwin learned that the slow process of mountains
suggested that the Earth is very old.
 These slow and gradual changes occurred over long periods
of time.
Erosion
 In 1844 after doing further research and support from other
scientists, Darwin wrote a 200 page essay that outlined his
ideas, but did not release it to public.
 After gathering more research in 1859 he released his book
The Origin of Species.
 Why did Darwin wait so long to release his book?
 Didn’t want to slander his fathers name, going against the
church.
Darwin’s two main points 1.
 Believed that organisms today descended from ancestral
species.
 Descent with modification:
 Early organisms spread out into different environments and
over millions of years the organisms changed or adapted.
Hare- two different environments
 The jackrabbit with dark fur blends in to the desert, while the
jackrabbit with light fur blends in to the snow.
Darwin’s two main points 2
 Natural selection:
 Process by which individuals with inherited characteristics
well-suited for its environment will leave more offspring.
14.2 Evolution has left much evidence
 What are some evidence for evolution?
 Fossil Record
 Geographic Distribution
 Similarities in Structure
 Similarities in Development
 Molecular Biology
Fossils
 Fossils:
 Preserved remains or markings left by organisms that lived in the
past.
 Fossil record:
 Chronological collection of life’s remains in the rock layers,
recorded during the passage of time.
 Extinct:
 Species no longer exists
 Paleontologist found fossils from 3.8 billion years ago!
FOSSIL RECORD
Modern Whale
Transitional
Forms
Common Ancestor
Geographic distribution
 Some species now living on different continents may have
descended from common ancestors.
Geographic Distribution Spotted Owl
Similarities in Structure
 Homologous structures:
 Similar structures in species sharing a common ancestor, but
with different function.
 Analogous structures:
 Different structure but similar function.
 Vestigial structure:
 Remnants of important structures from ancestral species, but
serve no current function.
Similarities in Development
 Many embryos of vertebrates look very similar during certain
stages of development.
Which is more closely related?
Molecular Biology
 DNA/Protein in closely related species are more similar.



Humans /chimps – Only 1 amino
acid difference (Closely related)
Humans /dogs – 11 amino acid
differences
Humans /rattlesnakes – Approx.
20 amino acid differences
(Distant relatives)
14.3 Darwin proposed natural selection as
the mechanism of evolution
 Population:
 Group of individuals of the same species.
 Suppose we take a single species and colonized them on
different islands.
 What will happen over time?
 Each organism will change depending on the environment.
Darwin’s Finches
 Darwin asked how did these different beaks arise?
 His idea…
Darwin’s Idea of Natural Selection
 All species tend to produce excessive numbers of offspring, called
overproduction.
 As we produce more offspring, resources become limited.
 This leads to a struggle of existence.
 The best adapted organisms will survive and reproduce. This is
called survival of the fittest.
 What makes organisms different is called variation.
 Variation:
 Differences among members of the same species.
Natural Selection Giraffes
 Artificial selection:
 Selective breeding of domesticated plants and animals to
produce offspring with genetic traits that humans value.
 Ex.
 Farmers want plants to produce more grain.
 People have been dog breeding certain types of dogs.
Natural selection in action
 What do you spray on your grass to kill insects?
 Pesticides
 With the first spray of pesticide on your yard you can kill 99%
of the insects.
 If you use that same pesticide are you going to kill the same
amount the next time you spray?
 Most likely not.
 Why?
 The insects who resisted the first spray now reproduced with
more offspring that are resistant to the pesticide.
14.4 Microevolution is a change in a
population’s gene pool
 Gene pool:
 Consists of all alleles (alternative forms of genes) in all the
individuals that make up a population.
Changes in gene pools
 Microevolution:
 Evolution on the smallest scale.
 Frequency of alleles:
 How often certain alleles occur in a gene pool. Generation to
generation change in frequencies of alleles.
 Hardy-Weinberg equilibrium:
 Condition that occurs when the frequency of alleles in a
particular gene pool remain constant over time.
Changes in gene pools
 Remember alleles are letters. Depending on these letters
certain traits will be expressed.
 Applying the Hardy-Weinberg
Equilibrium allows us to see if the
alleles in a population are changing.
Genetic Drift
 Genetic drift:
 A change in gene pool of a population due to chance.
 All populations are subject to genetic drift.
 The smaller the population is, the more impact of genetic drift has
on the population.
 When you flip a coin 10 times how many heads would you expect?
 5
 But if you flipped a coin 10 times and heads came up 7 times, would
that be reasonable?
 Probably
 What if you flipped a coin 1000 times and heads came up 700
times? Would that be reasonable?
 Probably not.
 As sample size increases, the likely percentage should level
out, ie heads 50% and tails 50%.
 Within a small population you are more likely to see genetic
drift.
Bottleneck effect
 Disasters such as earthquakes, floods, droughts, and fires
may drastically reduce the size of a population and lower the
genetic variation. Reducing the size of a population, also
reduces the size of its gene pool.
 Just because some organisms are better suited for the
environment does not mean that can survive a natural
disaster. Due to chance.
Bottleneck Effect
Founder Effect
 When a few individuals colonize an isolated island, the
smaller the colony the less its genetic makeup will represent
the gene pool of the larger population from which the
colonists came. Due to chance.
Gene flow and mutation
 Gene flow:
 The exchange of genes with another population.
 Occurs when fertile individuals or their sex cells migrate
between populations.
Gene flow example
 Suppose only white flowers live in a field.
 Wind takes the pollen of the white flowers
and lands on a population of red flowers.
Now the genes of each flower
are being mixed.
Mutation
 Recall a mutation is a change in an organisms DNA.
 Albinism can happen in many species.
 When can albinism be helpful in an environment?
 If it snows the organism can
blend in.
 What could happen to the
population of the albino organism?
Review
 Genetic drift, gene flow, and mutations can cause
microevolution or change in allele frequencies but it is by
chance that these changes would be adaptations.
 Fitness:
 Contribution that an individual makes to the gene pool of he
next generation compared to the contributions of other
individuals.
If you are the biggest, strongest animal in
your specie, are you always going to be fit?
 Remember even if the biggest, strongest, lion in the jungle
has zero fitness if it is sterile.
A return to the Galapagos
 What is happening with this picture regarding finches beak
length and passing of time?
 Depending on the season, when it’s wet season food is
plentiful for all finches, but when it’s dry season the finches
with long beaks are more prevalent.
14.5 Evolutionary biology is important in
health science
 In some African populations, sickle cell disease affects 1 out
of 25 individuals.
 Sickle cell is a disease of the abnormal shape of red blood
cells which weakens the body, causes pain, and damage to
organs.
 Caused by a recessive allele, so if your genotype is aa you
have sickle cell, if your genotype is Aa you do not have sickle
cell, but you are a carrier.
 If you are a carrier Aa, you are immune to malaria.
 Areas in Africa where malaria is common, the benefits
outweigh the risks of having sickle cell allele in a population.
 Example.
 In some places 4% of the population is homozygous for sickle
cell, however 32% of the population is heterozygous and
protected from malaria.
Evolution of antibiotic resistance in
bacteria
 What does the word antibiotic mean?
 Anti= opposite bio= life
 Antibiotic= killing life.
 Antibiotic:
 Medicines that kill or slow the growth of bacteria.
 When you take an antibiotic, some bacteria stays alive and
becomes immune. Those bacteria will reproduce and now
resistant to the original antibiotic.
 Example
 Tuberculosis.
 Doctors now do not want to
prescribe antibiotic because
bacteria is becoming resistant.