Ideas That Shaped Darwins Thinking

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Ideas That Shaped Darwins Thinking
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Huttons Theory of Geological Change

• Rocks, mountains, and valleys are shaped by a
  variety of natural forces such as rain, heat, and
  cold temperatures.
• These geological processes operate very slowly
  often over millions of years.

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Lyells Principles of Geology

• Scientists must explain past events in terms of
  processes that they can actually observe, since
  processes that shaped the Earth millions of years
  earlier continue in the present.

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Lamarcks Theory of Evolution

• Use and disuse organisms can alter the size and
  shape of particular organisms by using their
  bodies in new ways.

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Lamarcks Theory of Evolution

• Inheritance of Acquired Traits If an animal
  altered a body structure, it would pass that
  change on to its offspring.

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Example An experiment disproving Lamarcks
Theory

• If you conduct an experiment and cut the tails of
  dogs and allow them to mate, the offspring will
  have tails
• Disproves the inheritance
• of acquired characteristics

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Population Growth

• Thomas Malthus reasoned that if the human
  population continued to grow unchecked, sooner or
  later there would be insufficient living space
  and food for everyone.
• He also proposed that war, famine, and disease
  limited the growth of human populations.

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Population Growth
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Back to fossils

• Evidence for evolution-
• Comparative anatomy- the study of the structures
  of different organisms provided evidence for
  evolution
• Different organisms share similar structures

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Fossil Record
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Homologous structures-

• the structure resembles that of the ancestor,
  similar structure different function ex. Human
  arm, bird wing, and whale fin

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Vestigial Organs-

• Structures that have no function although they
  may be useful in another organism

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Evidence from Embryology

• Comparative embryology

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Comparative Biochemistry

• Hemoglobin in a chimpanzee strongly resembles
  human hemoglobin

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Genetic Evidence

• DNA can mutate
• Within any population there is change over time
• due to mutations, duplications, meiosis
  crossing over, fertilization, which lead to new
  combinations of alleles

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Ancient DNA has been isolated from a few well
preserved fossils
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Molecular clock

• The rate of mutation between two DNA sequences
  can be used as a clock to provide a relative
  measure of time since divergence from a common
  ancestor.
• Assumes that mutation rate is constant.
• Can be calibrated by comparison to the fossil
  record.

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Molecular Evolution comparing chromosomes

• Human chromosomes banding is highly conserved
  between humans and the other great apes.

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Molecular Evolution comparing protein sequences
Variation in proteins can be used to establish
how similar two species are genetically. Cytochro
me c protein is involved in energy production in
the mitochondria and is found in all
eukaryotes. 20/104 amino acids are identical in
all eukaryotes.
Human and chimp cytochrome c are identical in
amino acid sequence.
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Artificial Selection

• Selecting individuals with the most desirable
  traits breeding them so the traits would be
  passed on to the offspring

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Rapid Evolution

• The reaction of bacteria to penicillin
• The few individuals with a penicillin resistance
  gene survive and go on to reproduce
• This group of bacteria has evolved (adapted to
  the new environment)

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Darwin Presents His Case
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Macroevolution

• The origin of taxonomic groups higher than the
  species level.
• Example. Evolution of mammals

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Microevolution

• A change in a populations gene pool over a
  secession of generations.
• Evolutionary changes in species over relatively
  brief periods of geological time.

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The Gene Pool

• All of the genes in the population
• Genetic resource that is shared (in theory) by
  all members of population

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Missing Links

• If one species can evolve into another, there
  should be transitional forms
• When Darwin published his work, no such forms
  were known
• First fossil Archaeopteryx found in 1860

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Key Terms

• Species organisms that can interbreed and
  produce fertile offspring
• Natural variation differences among individuals
  of a species.

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Populations Evolve

• Biological evolution does not change individuals
• It changes a population
• Traits in a population vary among individuals
• Evolution is change in frequency of traits

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Variation in Phenotype

• Each kind of gene in gene pool may have two or
  more alleles
• Individuals inherit different allele combinations
• This leads to variation in phenotype
• Offspring inherit genes, NOT phenotypes

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• Sources of Natural Variation
• Mutation
• Meiosis I crossing over
• Meiosis I independent assortment
• Random fertilization
• Changes in chromosome structure

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Struggle for Existence

• members of each species compete regularly to
  obtain food, living space, and other necessities
  of life.
• Which will survive to produce offspring?
• Supported by Malthus

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Monday, April 21

• Do Now hand forward study guides
• 1. Finish notes
• 2. Natural Selection- Pepper Moth
• HW- Natural Selection worksheet

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Descent with Modification

• Proposed by Darwin based on 2 things
• The struggle for existence artificial selection
• Variations lead to different traits
• These differences give certain organisms an
  advantage to survive in an environment
• Reproduction leads to more organisms that are
  adapted to their environment

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Key Terms

• Descent with modification over long periods,
  natural selection produces organisms that have
  different structures, establish different niches,
  or occupy different habitats.
• Each living species has descended, with changes,
  from other species over time.

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Common descent
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Natural selectionSurvival of the fittest
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Natural selection, Adaptation, Competition,
Predation
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Natural Selection the mechanism of evolution

• The best adapted individuals in a population
  survive and produce more offspring
• The least adapted individuals produce fewer
  offspring
• A matter of variations and chance

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Natural Selection

• 1. Tendency for Overproduction
• 2. Not all offspring that are produced survive
• 3. Variation exists in populations
• 4. Variations most suitable for the environment
  will survive to reproduce
• 5. The whole population will change as
  adaptation occurs

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Adaptation

• any inherited characteristic that increases an
  organisms chance of survival.

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Interactions within an Environment

• 1. competition
• 2. predation

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Competition

• Definition the struggle between organisms to
  survive in a habitat with limited resources
• Competition occurs because both organisms occupy
  the same niche
• Example plants compete with each other for
  space, food and sunlight

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Predation an interaction where one organism
kills and eats another

• Predator the organism that does the killing
• Example a tiger shark
• Predator adaptations
• Ability to run fast
• Poisonous venom
• Sharp teeth, claws or stingers

• Prey the organism that is killed
• Example an albatross
• Prey adaptations
• Camouflage
• Protective coverings
• Warning colorings
• Mimicry
• False coloring

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Effects of predation on population size

• If the death rate exceeds the birth rate,
  population will decrease
• If predators are very effective, the population
  of prey will decrease
• Cold temperatures and disease will decrease a
  population
• If the number of predators decreases, the
  population of prey will increase

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Fitness

• the ability of an individual to survive and
  reproduce in its specific environment.

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Darwins Theory

• Because each organism is unique, each has
  different advantages and disadvantages in the
  struggle for existence.
• The individuals that have the most desirable
  traits are more fit

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Survival of the fittest

• The existence of individuals with the highest
  level of fitness.
• Organisms that are alive today, are well suited
  to their environments

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Protective ColorationThe Pepper moth

• All populations originally whitish
• In polluted areas, black moths increases from 1
  to 95 in 50 years

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Protective ColorationThe Pepper moth
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Kettlewells experiment

• Release marked white and black moths
• Capture moths after a period of time
• Is the proportion of recaptures different between
  the two forms?

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Natural selection
Microevolution change in allele frequency in a
population
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Classwork

• List 5 examples of competition, adaptation,
  natural selection
• List 5 examples of
• 1. Living things overproduce
• 2. There is a variation among offspring
• 3. There is a struggle to survive
• 4. Individuals that have desirable traits are
  more fit