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Biology. Evolution : A History & a Process. Terms:. A species is a group of organisms, or population, that can be interbreed & produce fertile offspring . Variations are the differences found within species . Ex: eye color and hair color.

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Evolution: A History & a Process

  • A speciesis a group of organisms, or population, that can be interbreed & produce fertile offspring.
  • Variationsare the differences found within species. Ex: eye color and hair color.
    • These can be determined by the environment, genetics or both.
    • If inherited, it is the result of a random mutation or recombination.


Adaptationsare inherited traits that increase a population’s chances of survival and reproduction in a particular environment.

  • A nicheis a habitat and the role a population plays in that habitat.
    • This includes where an organism lives, what & how it eats, how offspring are raised, where predators are, and space, light, moisture, & temperature.

concept 14 1 darwin s theory of evolution
Concept 14.1 Darwin’s Theory of Evolution
  • Darwin wroteThe Origin of Species
  • Describes his idea of evolution:Natural Selection
  • Theory based on observations made when traveling on theBeagle around the S. American coastline, specifically the Galapagos Islands.
  • Based theory on current thoughts of the time
influences on darwin
Influences on Darwin

Evolutionmeans change over time; process by which populations change in response to their environment

  • Georges Buffon suggested the Earth was older than originally believed (few thousand years).
  • Jean-Baptiste Lamarck (1809) theorized that fossils are extinct forms of living organisms found today (in other words, evolution occurred- the organisms today exist b/c of the fossils; they are the ancestors). His theory includes 3 points.
lamarck s idea of evolution
Lamarck’s Idea of Evolution:
  • Organisms were striving toward constant improvement.
  • Body parts that were used in life continued to develop whereas unused body parts waste away. This is the idea ofuse and disuse.

3. Once the structure is modified by use and disuse (#2), the modification is inherited by the offspring. This is called theinheritance of acquired characteristics. Think of Dobermans.

Charles Darwinstudied finches and many other organisms on the Galapagos Islands. He studied many factors which influenced his theory of evolution by natural selection.
    • Charles Lyell’s hypothesis about geological change:it occurs extremely slowly & gradually but it can influence plant and animal life over long periods of time.
    • Thomas Malthus’s (an economist) idea of supply and demand and populations:Darwin believed this principle could be applied to the competition of food, water & space and the ability to survive allowed for reproduction.

darwin s theory of evolution by natural selection
Darwin’s Theory of Evolution by Natural Selection:
  • Darwin wrote a book, On the Origin of Species by Means of Natural Selection, which explains his theory.

His Theory involves: Descent with Modification:

  • Organisms descended from ancestral species & Descendants accumulated different modifications (or adaptations)

2. Natural Selection is the mechanism for evolution

descent with modification natural selection
Descent with Modification & Natural Selection

This means:

  • Variations occur within a population (they are ALREADY there).
    • These are inherited.
    • Understand, all of Darwin’s knowledge was based on observations. He knew nothing of genetics.
  • Some variations are favorable.


Not all of the young produced in each generation survive.

    • This may be the result of disease, lack of food, or they may be the victims of predation.
  • Individuals that DO survive and have favorable variations WILL reproduce(and pass on those favorable variations to the next generation). THEREFORE, the next generation will have a larger number of offspring with the favorable variations.


Darwin stated ALL organisms were related.

  • He used a tree analogy.

evidence of evolution
Evidence of Evolution
  • Fossilsare preserved remains, or imprints, of ancient organisms found in rocks or sediments.
  • Paleontologistsare scientists who study fossils.
  • Biodiversityis the variety & abundance of species that makeup a biological community.
  • 99% of all types of organisms that ever lived are now extinct (no longer exists).
  • Geographic distribution (patterns of life) has provided evidence as well.
  • Homologous structuresare traits such as the human arm and whale fin that are similar in different species b/c the 2 species share a common ancestor.
    • In this case, the arm and fin have evolved from the forelimb of a vertebrate ancestor.
  • Analogous structuresare characteristics that are similar in function but are different in structure in distantly related organisms.
    • Ex: wings of bats and wings of insects.

  • Vestigial structuresare structures that are often small or reduced in size and no longer used but inherited and still present in organisms.
    • Ex: pythons have leg and hip bones, humans have an appendix, manatees have leg bones.

  • Embryologyis the study of early developmental stages of organisms.
    • Scientists use this, along with biochemistry, to study and understand evolution.

other evidence
Other Evidence
  • Developmental: stages of embryonic devo are similar
  • Molecular: similar DNA sequences

Selective breeding to produce a desired trait isartificial selection (think dog breeding).
  • Example of Natural Selection in Action: Pesticide resistance
  • Pesticidesare poisons (kill insects that destroy crops & homes)
  • Some insects are resistant to pesticides (have genes); they survive & reproduce (passing on this trait).
  • Understand, insects do not BECOME resistant; they already had the genes for resistance!
ns sca
  • Sickle Cell Anemia (SCA) is a genetic disease affecting the shape of RBCs, creating symptoms of fatigue, body pain, organ damage & sometimes death.
  • There is a high frequency of SCA in Africa and even higher frequency of heterozygous individuals



  • Heterozygous SCA have resistance to malaria (plasmodium, organism that causes malaria, does not reproduce well w/in sickle-shaped RBCs); this is called the heterozygote advantage.

antibiotic resistance
Antibiotic Resistance
  • Antibiotics are medications that kill (or inhibit the reproduction of) bacteria
  • Some bacteria are resistant to antibiotics (again, this is b/c they contain genes for the resistance).
  • Antibiotic resistanceallows the bacteria that survive the 1st round of antibiotics to reproduce & pass on the gene(s) for resistance.
  • This is becoming a health concern.