Evolution

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Evolution

• Changes in types of organisms over a period of
  time

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Fossils

• A fossil is some remnant of an organism that
  proves its existence
• Imprints of bacteria, leaves or footprints
• Insects, pollen, or flower parts in amber
• Tools or pottery shards
• Bones of organisms in sedimentary rock
• Cave drawings

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Determining fossil age

• Relative dating
• Oldest fossils are in the deepest sedimentary
  rock layers
• Younger layers hold newer, more complex fossils

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• Absolute dating
• Can be used to determine a precise age in years
• Use the decay rate of radio-isotopes like carbon
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• The oldest known fossils are approximately 3
  billion years old

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Comparative studies

• Researchers use comparative studies to establish
  evolutionary relationships between organisms

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Comparative anatomy

• Comparing specific body structures
• Analogous structures have a similar function but
  the structure is different
• Ex the wing of an insect and the wing of a bird

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• Homologous structures are similar in structure
  but may have different functions
• Ex) human hand, cat paw, whale flipper, bat wing

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• Vestigial structures are reduced in size and have
  no known function
• They resemble structures in other organisms
• Ex) the human appendix or the pelvis bone in a
  whale

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Comparative embryology

• The comparison of embryonic development
• Early development is similar in many species
• The closer the relationship between species the
  more similar is development

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Comparative cytology

• Observing similarities in cell structures
• All cells have some common organelles that
  perform identical functions
• Plasma membrane, cytoplasm, and ribosomes

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Comparative Biochemistry

• Similarities involving proteins, enzymes and
  nucleic acids
• All organisms share genetic codes
• Transcription and translation
• All organisms carry on cell respiration in the
  same way
• All autotrophs carry on photosynthesis in the
  same way

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Theories of Evolution
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J.B. Lamarck

• Use and disuse
• Organisms can change their body structure over
  the course of a lifetime
• ATROPHY structure decreases in mass with disuse
• HYPERTROPHY structure increases in mass with
  use

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• Lamarck believed that ACQUIRED TRAITS could then
  be passed to the offspring
• Example) the neck of the giraffe

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August Weissman

• Disproved Lamarcks theory of use and disuse
• He cut off the tails of mice then mated them
• All of the offspring had long tails
• This experiment was repeated for 22 generations
• All of the mice were born with long tails!

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Charles Darwin

• Theory of Natural Selection
• Darwin served as a geologist, botanist,
  zoologist, and general man of science aboard the
  H.M.S. Beagle from 1831-1836

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• Overproduction organisms produce more offspring
  than can possibly survive
• Struggle for existence there are only limited
  resources available
• Not all offspring will survive
• Natural selection those organisms with
  advantages in a given environment are most likely
  to survive and reproduce
• Those who survive and reproduce are the FITTEST

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• Variation offspring tend to be different from
  their parents and each other
• Speciation after many generations are involved
  in natural selection
• A population may be so different from the
  original population that it can be classified as
  a different species
• SPECIES organisms who can mate and produce
  fertile offspring

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Speciation

• Involves isolation
• Anything which prevents two groups within a
  species from interbreeding

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Geographic isolation

• A population is divided by a natural barrier
• mountains
• Deserts
• Body of water
• Landslide cause by an earthquake
• Geographic isolation can instigate a speciation
  eventbut genetic changes are necessary to
  complete the process

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Reproductive isolation

• Differing selection pressures on the new
  environments can complete the differentiation of
  the new species.

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• the differences between the isolated groups
  become so great that they can no longer interbreed

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Microevolution

• Small, gradual changes which are detectable
  within a few generations

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• Industrial Melanism changes in the colors of a
  population as a result of human industrial
  activity

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Macroevolution

• Long term changes that make a new species

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General patterns for evolution

• Divergent evolution different groups evolve
  from one ancestor

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• Convergent evolution two or more different
  groups evolve so that they resemble one another
  strongly

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• Adaptive radiation organisms spread into new
  environments and become adapted through natural
  selection

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Adaptations

• an anatomical structure, physiological process or
  behavioral trait of an organism that has evolved
  over a period of time by the process of natural
  selection
• it increases the expected long-term reproductive
  success of the organism

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• Organisms that are adapted to their environment
  are able to
• obtain air, water, food and nutrients
• cope with physical conditions such as
  temperature, light and heat
• defend themselves from their natural enemies
• reproduce
• respond to changes around them

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• Camouflage and mimicry are adaptations some
  animals use as protection from predators.
• An animal that uses camouflage looks like things
  in its environment. It might look like a leaf, a
  twig, or a rock.

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http//oncampus.richmond.edu/academics/education/p
rojects/webunits/adaptations/mimicry.html

• Animals that use mimicry use colors and markings
  to look like another animal.
• Example) the Monarch Butterfly and the Viceroy

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Symbiosis

• Two species live in close association with each
  other
• In symbiosis, at least one member of the pair
  benefits from the relationship. The other member
  may be
• injured parasitism
• relatively unaffected commensalism
• may also benefit mutualism

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• Mutualism () ()
• Both organisms benefit

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• Moray eel and cleaner fish
• The eel gets clean
• The fish gets food
• Both organisms benefit

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• Parasitism () (-)
• the parasite benefits while the host is harmed

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• (1) The hookworm latches on the walls of the
  colon with its sharp teeth where it feeds on
  blood.
• (2) The tapeworm is the longest parasite. A
  mature adult can lay a million eggs a day.
• (3) Tapeworm eggs embedded in the colon.
• (4) The roundworm can grow to be 20 inches (50
  cm) long and lay 200,000 eggs per day.
• (5) Pinworms migrate outside the colon during the
  night to lay their eggs around the anus. This
  causes the nightly itching of many unsuspecting
  victims.

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• Commensalism () (0)
• One organism benefits while the other is neither
  helped or harmed

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Heterotroph Hypothesis

• 1920-30s
• Formulated by a small group of scientists
• Suggests a probable sequence in which organisms
  appeared

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• Life on Earth began about 3.5 billion years ago.
• The atmosphere was very different from what it is
  today.
• The early Earth atmosphere contained mostly
  hydrogen, water, ammonia, and methane.
• There was very little oxygen

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• There were abundant energy sources for chemical
  reactions to occur
• Heat
• UV radiation
• Electrical activity

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Primordial soup
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• Gases in the atmosphere reacted with each other
  to form simple organic molecules
• Example ) Amino acids, nucleotides

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Atoms combined to form molecules
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Amino acids were formed
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Stanley Miller

• Miller built an apparatus to test these ideas in
  1953
• A mixture of gases thought to resemble the
  Earths primitive atmosphere was passed through
  an electric spark

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• After one week the contents were analyzed
• Miller found that it contained organic molecules
• Urea
• Amino acids
• Lactic acid
• Acetic acid

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• The Heterotroph Hypothesis SUGGESTS
• The first organisms were anaerobic
• No O2 was available in Earths primitive
  atmosphere

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• The first organisms used the organic molecules in
  the water for food
• They released CO2 as a waste product
• These organisms were ANAEROBIC HETEROTROPHS

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• Organisms that were able to use the CO2 evolved
  next
• These organisms were ANAEROBIC AUTOTROPHS
• They used the CO2 for photosynthesis
• O2 was released as a waste product

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• Organisms that were able to use O2 evolved next
• These were AEROBIC AUTOTROPHS and AEROBIC
  HETEROTROPHS

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Rate of Evolution

• Gradualism evolution occurs slowly and
  continuously over time

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• Punctuated equilibrium evolution can occur
  quickly
• It can be followed by long periods of little or
  no change at all

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Population Genetics

• The study of the genes in an entire population at
  one time
• Population all of the members of one species in
  a specific area
• Gene pool all of the alleles within a
  population
• Gene frequency the of all alleles for one
  trait that are dominant or recessive

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• The Hardy-Weinberg Law based on genetic
  equilibrium
• The condition where gene frequencies do not
  change from one generation to the next

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• The Hardy Weinberg Equation
• p q 1
• Where p dominant allele
• q recessive allele
• p2 2pq q2 1
• Where p2 homozygous dominant
• 2pq heterozygous
• q2 homozygous recessive

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• Example
• 30 of a population of banana-nose hoseringers
  show the recessive phenotype of yellow
  banana-nose as opposed to the dominant phenotype
  of green banana-nose

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• p q 1
• Where p dominant allele
• q recessive allele
• 30 show the recessive phenotype

p .3 1 p .7
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• What of the banana-nose hoseringers are
  heterozygous for nose color?
• p2 2pq q2 1

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• (.7)2 2 (.7)(.3) (.3)2 1
• .49 .42 .09 1
• 42 are heterozygous

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• For the Hardy-Weinberg law to be true five
  conditions must be met

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• 1) Large Populations
• In small populations alleles of low frequency
  might be lost by the death of a few individuals

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• 2) No Migration
• Individuals may not migrate into or out of the
  population

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• 3) No Mutations
• These will change the frequency of the alleles in
  the population

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• 4) No Natural Selection
• Each member of the population must survive long
  enough to have offspring

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• 5) Random Mating
• Each member of the population must have an equal
  chance to reproduce

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• The Hardy-Weinberg law does NOT apply to
  situations in the real world!

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• Mutations occur spontaneously
• Reproduction is NOT random
• Natural selection DOES occur

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• The failure of Hardy-Weinberg Law is a sign that
  evolution is occurring!
• There are changes in allele frequencies
• External factors cause the changes in frequency