bio 115 final exam

• Natural selection explains how populations become well suited to their environments over time. The shape and coloration of leafy sea dragons (fishes closely related to seahorses) are heritable traits that help them to hide from predators.
• This chapter is about one of the great ideas in science: the theory of evolution by natural selection, formulated independently by Charles Darwin and Alfred Russel Wallace. The theory explains how populations—individuals of the same species that live in the same area at the same time—have come to be adapted to environments ranging from arctic tundra to tropical wet forest.
• In everyday English, the word "theory" suggests a thoughtful guess, but a scientific theory is an explanation for a broad class of observations that is widely supported by overwhelming evidence.
• Scientific theories


  Usually have two components: a pattern and a process
• Pattern component


  A statement that summarizes a series of observations about the natural world
• Process component


  A mechanism that produces that pattern or set of observations
• The advance of the theory of evolution by natural section represented a profound scientific revolution. The idea that Darwin and Wallace overturned—that species were supernaturally, not naturally, created—had dominated thinking about the nature of organisms in Western civilization for over 2000 years.

  
• Plato claimed that every organism was an example of a perfect essence, or type, created by God, and that these types were unchanging.
• Typological thinking


  The idea that organisms are examples of perfect essences or types
• Aristotle organized typological thinking into a linear scheme called the great chain of being, or scale of nature, where "scale" means a ladder or stairway.
• Great chain of being


  A linear scheme where species are organized into a sequence based on increased size and complexity
• Lamarck proposed the first formal theory of evolution—that species are not static but change through time.

  
• Lamarckian evolution


  The idea that species change through time via the inheritance of acquired characters
• Darwin and Wallace emphasized that the process responsible for change through time—natural selection—occurs because traits vary among the individuals in a population, and because individuals with certain traits leave more offspring than others do.
• Darwinian evolution


  The theory that species change through time via the process of natural selection
• The theory of evolution by natural selection was revolutionary because it overturned the idea that species are static and unchanging, replaced typological thinking with population thinking, and was scientific.

  
• The pattern component of the theory of evolution by natural selection makes two predictions: 1) Species change through time, and 2) Species are related by common ancestry.

  
• Hardy-Weinberg principle


  A mathematical null hypothesis for the study of evolutionary processes

  
• Hardy-Weinberg principle


  • If the frequencies of alleles A and a in a population are given by p and q, then the frequencies of genotypes AA, Aa, and aa will be given by p^2, 2pq, and q^2, respectively, for generation after generation
  • When alleles are merely transmitted via meiosis and random combinations of gametes, their frequencies do not change over time, meaning that evolution does not occur

  
• A fossil is any trace of an organism that lived in the past.
• Fossil record


  All the fossils that have been found on Earth and described in the scientific literature
• Allele frequencies do not change over time according to the Hardy-Weinberg principle

  
• Calculating genotype frequencies using Hardy-Weinberg principle


  1. Frequency of AA genotype = p^2

  2. Frequency of Aa genotype = 2pq

  3. Frequency of aa genotype = q^2

  
• Sedimentary rocks form from sand or mud or other materials deposited in layers at locations such as beaches or river mouths.
• Sedimentary rocks, along with rocks derived from episodic lava flows, form with younger layers deposited on top of older layers.
• Genotype frequencies in the offspring generation must add up to 1
• In the example, the frequency of allele A in the offspring is still 0.7 and the frequency of allele a is still 0.3

  
• Geologic time scale


  A sequence of named intervals called eons, eras, and periods that represented the major events in Earth history
• The values of p and q have not changed from one generation to the next according to the Hardy-Weinberg principle
• Radioactive decay furnished a way to assign absolute ages, in years, to the relative ages in the geologic time scale.
• Frequency of the AA genotype

  Frequency of the homozygous dominant genotype

  
• Sedimentary rocks reveal the vastness of geologic time
• Relative ages of sedimentary rocks


  Younger layers are deposited on top of older ones
• Frequency of the Aa genotype


  Frequency of the heterozygous genotype

  
• The deepest rock layer in the Grand Canyon is over a billion years old, and the top layer is 270 million years old
• Frequency of the aa genotype


  Frequency of the homozygous recessive genotype

  
• The geologic time scale was a relative one, the absolute age of Earth was still unknown
• The genotype frequencies in the offspring generation must add up to 1
• Radioactive decay


  The steady rate at which unstable "parent" atoms are converted into more stable "daughter" atoms
• In this numerical example, the genotype frequencies are 0.49 for AA, 0.42 for Aa, and 0.09 for aa