Natural Selection

• Mutation:

  • A random rare event
  • Change in the chemical letters that make up an organism’s DNA sequence
  • Occurs as a copying error when cells divide
• When the environment changes, species must adapt, leading to more frequent mutant traits in the environment
• Some traits are more advantageous in new environments, leading to organisms with advantageous traits passing them on to the next generation
• Organisms with disadvantageous traits decrease and may go extinct
• Rock pocket mice evolved to have dark-colored fur in certain habitats due to a change in the environment
• Dark-colored mice are more fit for the environment as visual predators can't see them, increasing their chances of survival
• Natural selection favors dark-colored mice due to their advantage of camouflage
• Dark-colored mice have a better chance of surviving and reproducing, causing the trait to increase in frequency
• Dr. Sean B. Carroll stated that "while mutation is random, natural selection is not"
• Mutation is a random copying error during cell division, while natural selection occurs when advantageous traits are favored due to environmental changes
• Trait

  A characteristic that an organism can pass on to its offspring through its genes.

  
• Heredity


  the transmission of traits from one generation to the next

  
• offspring


  Product of reproduction, a new organism produced by one or more parents

  
• DNA


  A complex molecule containing the genetic information that makes up the chromosomes.

  
• sexual reproduction


  A reproductive process that involves two parents that combine their genetic material to produce a new organism, which differs from both parents

  
• asexual reproduction


  A reproductive process that involves only one parent and produces offspring that are identical to the parent.

  
• Chromosomes


  threadlike structures made of DNA molecules that contain the genes

  
• Alleles

  Different forms of a gene

  
• Genes


  DNA segments that determine traits

  
• recessive allele


  An allele that is masked when a dominant allele is present

  
• dominant allele


  An allele whose trait always shows up in the organism when the allele is present.

  
• Heterozygous


  Hybrid. An organism that has two different alleles for a trait

  
• homozygous


  Purebred. An organism that has two identical alleles for a trait

  
• Genotype


  genetic makeup of an organism

  
• Phenotype


  An organism's physical appearance, or visible traits.

  
• Carrier


  A person who has one recessive allele for a trait, but does not have the trait.

  
• Natural selection is when variation within a species gives an advantage or disadvantage to the species, causing the animal with variation 1 to survive and variation 2 to go extinct
• Adaptations - traits that help an organism survive and reproduce in its environment
• Structural adaptations - physical characteristics that help the organism survive. E.g. body part, color, beak size, venom.
• Behavioral adaptations - behaviors that an organism does to help them survive. E.g. birdis flying south in the winter.
• successful reproduction - the likelihood of an organism producing offspring that are capable of surviving and reproducing themselves.