chapter 7

• Organisms


  • Face environmental challenges that limit their ability to survive
  • Severe weather, famine, and competition for food and space are challenges that organisms may or may not be able to survive
• Organisms that survive/reproduce


  Pass along the DNA that helped them survive
• Theory


  A concise explanation that is supported by much evidence
• Evolution


  Involves 2 interrelated phenomena: Adaptation and Speciation
• Adaptation


  Modifications of a species' phenotype to help them succeed in their environment
• Speciation


  The formation of a new species from a pre-existing species
• Adaptation


  • A structural, behavioural, or physiological process that helps an organism survive and reproduce in its environment
• Structural Adaptations


  • Saiga: Odd-shaped nose; when it breathes, cool air is circulated in its large nasal cavity→ warms air
• Mimicry


  Harmless species resembles a harmful species in colouration or structure; predators who avoid the harmful species also avoid the harmless one
• Mimicry


  • Viceroy butterfly is tasty to predators, but the monarch butterfly is not (Share similar structure and coloration)
• Behavioral Adaptations


  Adaptations that help organisms survive through behaviours like hibernating, being nocturnal, and migrating
• Behavioral Adaptations


  • Hibernating–animals hibernate in cold months to conserve energy
  • Nocturnal animals – awake at night, conserve energy and avoid overheating during the day, protect from darkness
  • Migratory animals – animals migrate to areas with nutrients at different times of year
• Physiological Adaptations


  Adaptations that help organisms survive through physiological processes like producing venom, regulating body heat, and camouflage
• Physiological Adaptations


  • Venom: venomous animals make venom for defence; accompanied by warning colouration
  • Body heat: our bodies can change blood flow patterns to maintain a constant body temperature
  • Hibernation–species reduce metabolism to save energy; allows squirrels to survive in climates with harsh winters
  • Camouflage: allows an organism to blend in its environment to avoid predators/ attack prey
• Development of Adaptations


  Adaptations result from gradual, accumulated changes that assist survival/ reproduction
• Variations


  Structural, functional, or physiological differences between individuals–not all variations become adaptations (All species show variation)
• Environment


  • Variations can have positive, negative, or no effect on ability to survive/reproduce
  • Individuals with a helpful variation are more likely to survive–pass this variation to the next-gen
  • Interaction with environments is important to adaptation and variation because environments change: climates change, floods, human activities, etc...
• Natural selection


  Individuals who are best suited for an environment survive longer, reproduce more times, and pass on their genes
• Peppered Moth


  • Shows how proportions of some inherited characteristics in a population change in response to changes in the environment
  • The English peppered moth has 3 phenotypes: Greyish white with black spots (pepper), Black (melanic), Intermediate colour
• Pollution and Peppered Moths

  • Soot from factories darkened trees (air pollution), providing camouflage for melanic moths
  • Frequency of melanic alleles increased in population
  • Individual moths did not change from peppered to melanic
• Source of Variation


  From crossing over, independent assortment, sexual reproduction, and mutations
• Mutations


  • Permanent changes in DNA sequences
  • Can happen spontaneously when DNA is copied
  • Can be caused by UV, X-rays, chemicals, etc. (Mutagens–due to environmental agents)
• Mutations in DNA


  A cell may exhibit new characteristics: cell could die, malfunction, or multiply more than it should → cluster of cells that form a tumour
• Mutations in Gamete Cells

  • Mutation in a somatic cell: mutation disappears from the population when the organism dies
  • Mutation alters the DNA in a gamete: mutation may be passed on to succeeding generations as a new allele
• Selective Advantage


  • Genetic advantage that proves an organism's chance of survival (changing environment)
  • Many mutations may harm an individual
  • Some may provide an advantage: New function or Improved function
• Rapid Reproduction and Selective Advantage

  In populations that reproduce quickly, a new allele that resulted from a random mutation that was previously insignificant may provide a selective advantage to some individuals when the environment changes
• Staphylococcus aureus bacterium


  • Individual bacteria reproduce asexually very rapidly–helps adaptation to occur quickly: bacteria with an advantageous mutation may survive a changing environment and reproduce, whereas the bacteria without may not
• Antibiotic


  Drug used to treat infections caused by bacteria and other microorganisms
• Antibiotic treatment and Staphylococcus

  • Some individuals of the species have a new allele, from a random genetic mutation, that makes them resistant to the antibiotic
  • Only the individual bacteria with the new allele can survive and reproduce
  • Have the ability to pass on the DNA that resulted in resistance to that particular antibiotic to their daughter cells
• Individual members of the population do not change during their lifetime–population changes in its ability to resist certain antibiotics
• Natural Selection


  Process by which characteristics of a population change over many generations as organisms with heritable traits survive and reproduce, passing their traits to offspring
• Selective Pressure


  Abiotic (non-living) environmental conditions that select for certain characteristics of individuals and select against other characteristics
• Selective Pressure


  • In populations of Staphylococcus, individuals of the bacteria were selected for by their environment–survived the change in the environment
  • In a population of young trees—dense forest with low light, individual trees that survive in shade will reproduce (pass alleles to survive conditions)
• Natural Selection Is Situational


  • Natural selection does not anticipate change in the environment (situational)
  • Trait at 1 time in 1 situation with no relevance to survival may be the trait that, at a different time in a different situation, helps certain individuals in a population survive
• Fitness


  Contribution an individual makes to the gene pool of the next generation by producing offspring that survive long enough to reproduce (Survival of the Fittest)
• Artificial Selection


  Selective pressure exerted by humans on a population to improve or modify traits
• Artificial Selection and Peppered Moths

  Change occurred naturally in the population in response to changes in the environment due to the selective pressure exerted by natural selection
• Biotechnology


  Use of technology and organisms to produce useful products
• Artificial Selection and Food Crops


  • Food crops that we depend on for most of our diet are the result of selective breeding
  • Traits of the artificially selected varieties all differ from the wild plant, but they are members of the same species and can interbreed and produce viable offspring
  • We breed food crops to increase their nutritional value, harvest yield, and to be drought and pest-resistant
• Artificial selection limits: if plants are bred to grow quickly, they may not tolerate poor soil conditions