Fundamentals of Evolution

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Fundamentals of Evolution

• A Summary of Evolution

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Fundamentals of Evolution

• A Summary of Evolution

Nothing in Biology Makes Sense Except in the
Light of Evolution
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EVOLUTION

• The frequency of an allele in a gene pool of a
  population depends on many factors and may be
  stable or unstable over time. As a basis for
  understanding this concept
• Students know why natural selection acts on the
  phenotype rather than the genotype of an
  organism.
• Students know why alleles that are lethal in a
  homozygous individual may be carried in a
  heterozygote and thus maintained in a gene pool.
• Students know new mutations are constantly being
  generated in a gene pool.
• Students know variation within a species
  increases the likelihood that at least some
  members of a species will survive under changed
  environmental conditions.
• Evolution is the result of genetic changes that
  occur in constantly changing environments. As a
  basis for understanding this concept
• Students know how natural selection determines
  the differential survival of groups of organisms.
  
• Students know a great diversity of species
  increases the chance that at least some organisms
  survive major changes in the environment.
• Students know the effects of genetic drift on the
  diversity of organisms in a population.
• Students know reproductive or geographic
  isolation affects speciation.
• Students know how to analyze fossil evidence with
  regard to biological diversity, episodic
  speciation, and mass extinction.
• Students know how to use comparative embryology,
  DNA or protein sequence comparisons, and other
  independent sources of data to create a branching
  diagram (cladogram) that shows probable
  evolutionary relationships.

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Evolution

• Definition A change in a population of a
  species over time

• Organisms evolve to adapt better to their
  environment

• According to Evolution, all living things
  (organisms) on the planet are related and have a
  common ancestor

• A unicellular prokaryote (bacteria) that lived
  near hydrothermal vents where the temperature is
  near 200 degrees Fahrenheit amidst poisonous
  hydrogen sulfide and deadly sulfuric acid

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Formation of EARTH

• First need to talk about formation of earth 4.6
  billions yrs ago!
• How do we know this stuff RADIOACTIVE DATING-
• Not relative dating-

• Solar system in beginning (5 billion yrs ago)
  was a swirling mass of gas and dust that
  collapsed inward leaving some debris outside
  (planets)

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Formation of Earth and water
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FORMATION OF LIFE(First organic molecules)

• Scientists believed early earth had perfect
  conditions ammonia (NH3), Water vapor, hydrogen
  gas, and methane gas (containing Carbon)
• Perfect boiling temperatures lead to first
  organic compounds amino acids
• Earth cooled and water vapor turned to liquid
  (oceans)
• Then complex reactions with UV light and
  lightning lead to more complex organic compounds
  that did not contain any genetic info (no DNA nor
  RNA)

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First replicating molecules

• RNA was the first genetic material to
  self-duplicate.
• DNA was the second and the one that most
  organisms use today

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First Prokaryotes (the early cells that are
still around today aka bacteria)

• Since no oxygen on earth before 1.7 bya, first
  cells must have been anaerobic--
• Most likely heterotrophs that depended on organic
  molecules. After consuming all organic
  molecules, there was a need for some organisms to
  evolve into autotrophs
• These first autotrophs resembled archaebacteria
  (aka extremophiles)--
• These early archaebacteria obtained their energy
  by chemosynthesis--

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Effects of Oxygen

• Oxygen began being produced about 1.7 billion yrs
  ago by photosynthetic organisms that resemble
  modern cyanobacteria (like simple unicellular
  green algae).
• Oxygen was probably deadly to most early
  organisms
• As O2 levels rose (for another 1billion years),
  ultraviolet radiation by the sun converted O2 to
  O3 ozone (poisonous to life) so life could still
  not exist on land yet
• Life continued to exist only in the ocean

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First cells by endosymbiosis
Then many of these cells began sticking together,
first in colonies, then permanently attached
first multicellular organisms early
invertebrates (look at timeline Handout in summer
reading packet) Then after more oxygen was
released by early plant forms and algae,
multicellular organisms diversified rapidly
(Cambrian explosion)
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EVIDENCE FOR EVOLUTION

• MACROMOLECULAR EVIDENCE 1 (Comparing the DNA,
  proteins and other molecules of life of other
  organisms)
• FOSSIL EVIDENCE 2
• BIOGEOGRAPHY
• EMBRYOLOGY
• COMPARATIVE ANATOMY
• VESTIGIAL STRUCTURES
• HOMOLOGOUS STRUCTURES
• ANALOGOUS STRUCTURES
• CLASSIFICATION

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1. FOSSIL EVIDENCE

• Allow scientists to see how organisms changed
  over time
• Shows when different forms of organisms appeared,
  lasted for periods of time, then disappeared only
  to be found by newer forms of life.

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Another look at sedimentary layers
Absolute age measuring radioactivity in certain
rocks
Relative age by comparing layers
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2. Macromolecular (Molecular biology) Evidence

• Since all organisms on the planet contain DNA, we
  can compare their DNA to see which organisms are
  more related and then construct a phylogenic tree
  or a cladogram

DNA EVIDENCE-
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DNA evidence
Here is the GENOTYPE (genetic information of an
organism). This Genotype will eventually lead to
an organisms PHENOTYPE (organisms physical or
behavioral appearance)
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2. Macromolecular (Molecular biology) Evidence
(continued)

• Amino acid evidence the building blocks of
  proteins!

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3. BIOGEOGRAPHY

• Study of Geographical distribution of fossils
• Same fossils on West Coast of Africa and East
  Coast of South America. HOW??---
• Scientists see a trend. Life forms arise in the
  same areas where similar, older forms once existed

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Homologous Structures
-Structures from different organisms that look
similar because the organisms descended from
common ancestors. These structures have evolved
to perform different functions
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ANALOGOUS STRUCTURES
Structures that are similar in form and function
but evolved independently. Although a bird and
insect are not recently related, they are
distantly related but for whatever reason, they
happened to evolve wings for flight.
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EMBRYOLOGICAL EVIDENCE
Embryos look similar ___________ ____________ but
look different __ ____________________________ Thi
s suggests that all these vertebrates have a
_____________ ______________. The fact that
they end up looking different, is a result of
evolution. Each organisms DNA (instructions)
has evolved a new message to become a different
type of organism
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VESTIGIAL STRUCTURES

• Definition-
• Examples-

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LAMARCK vs DARWIN

• Acquired traits (Lamarck)-
• Use and disuse
• Acquired Traits are passed down to offspring.
  NOT!- no genetic change only a phenotypic change

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DARWINS THEORY

• OVERPRODUCTION some must die because of
  ____________
• VARIATION increases the likelihood that at least
  some members of a species will survive under
  changed environmental conditions
• NATURAL SELECTION survival of the fittest
  (according to the environment!) not everyone
  survives the same!
• INHERITED (passed down) Successful individuals
  pass down these fit traits

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Genes and evolution Natural selection acts on
(tests) the phenotype
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PATTERNS OF EVOLUTION

• Co-evolution
• Hummingbirds beak and
• a long thin flower
• Convergent evolution
• similar environments push development of
• similar features anteaters tongue
• Divergent evolution
• Adaptive radiation - ___________
• Artificial selection- ____________

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SO HOW DO WE GET A NEW SPECIES????

• Called Speciation The formation of a new
  species occurs when members of a species are
  isolated reproductively (they cant reproduce
  with each other and so they adapt to their
  environment on their own)
• Two ways
• Geographic isolation
• Reproductive isolation

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FORMATION OF A NEW SPECIES (Branching on the tree
of life)

• BIOLOGICAL SPECIES CONCEPT Proposed by Ernst
  Mayr a species is a
• ____________________________________
• Limitations in this concept
• Extinct organisms?
• Asexual organisms?

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Population Genetics

• The smallest unit of evolution is the population.
• Population Collection of individuals from a
  single species that routinely interbreed.
• There is variation in a population (humans, fish,
  every life form)

A bell curve shows the variations on a population
and how they average out in the center. Extremes
at either end.
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The gene pool

• Gene pool
• all the genetic differences in a population

Lets pretend our classroom represents the gene
pool with all the differences in our population
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Things that can affect the gene pool

• Mutations add more variety to the gene pool
• Migration immigration () and emigration (-)
  both cause gene flow
• Genetic Drift When a random event causes your
  gene pool to change genetic drift is more
  dramatic in small populations not large
• Non random mating choosing to mate with
  organisms with similar characteristics not
  random but controlled

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Types of Natural Selection
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RATE OF SPECIATION

• GRADUAL VS PUNCTUATED

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Can organisms plan their evolution?

• Did giraffes grow longer necks on purpose to
  reach the trees?
• Did ancient primates decide to walk upright to
  become humans?
• If the world gets covered in water like in the
  movie Waterworld, will some of us grow gills?
• Will we look like aliens in the future?

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Evolution is random!!!

• Not something planned or on purpose
• Mutations and sexual reproduction create
  variation- if these variations happen to help you
  live in your environment then good for you! ?
• Youll get to survive better, reproduce more
  successfully, and pass those fit traits to
  others
• But what if the environment changes again? Well,
  we dont know if those traits will keep on
  helping you. Maybe they will, maybe they wont
• Just keep hoping that we keep creating
  variations- this will increase our chances of
  adapting
• What about the future of earth and global warming?