Evolution

• Adaptation


  A structural, behaviour or physiological process that helps an organism survive and reproduce in a particular environment
• Variation


  The visible or individual differences between individuals of the same species
• Variation in individuals can be an advantage or disadvantage or have no effect on the individuals
• Lamarck - "Inheritance of Acquired Characteristics"


  • Felt species increased in complexity over time, until they achieved a level of perfection
  • Felt characteristics that were acquired during an organism's lifetime could be passed on to its offspring
• Initially Lamarck's ideas were believed but later rejected after biologists learned about cells, genes and heredity
• Natural Selection


  A process that results when the characteristics of a population of organisms change because individuals with certain inherited traits survive specific local environmental conditions and through reproduction, pass on their traits to their offspring
• For natural section to occur, there must be variety of diversity within a species
• Populations change NOT individuals
• Natural selection does not anticipate change in the environment, instead natural selection is situational
• A trait at one time my have no relevance to survival but if the environment changes the trait might now be advantageous
• Mutation


  • Changes in the genetic material of an organism
  • Happen continuously in the DNA of any living organism and can occur spontaneously, when DNA is copied before a cell divides
  • When DNA mutates, a cell can exhibit new characteristics
  • Mutations can lead to good or bad changes
• Mutations Can Provide Selective Advantage


  Mutations can be harmful, good or even a mutation that causes a disadvantage in one environment can cause an advantage in another environment
• 5 Key Points to Remember About Natural Selection


  • Overproduction (more babies than can survive)
  • Competition
  • Variation – mutation
  • Survival of the fittest – most adapted
  • Origin of new species
• Lamarck


  • "Inheritance of Acquired Characteristics"
  • Felt species increased in complexity over time, until they achieved a level of perfection
  • Felt characteristics that were acquired during an organism's lifetime could be passed on to its offspring – called this the inheritance of acquired characteristics
• Lamarck's ideas were initially believed but later rejected after biologists learned about cells, genes and heredity
• Darwin


  "Theory of Natural Selection"
• Further Evidence of Evolution


  • Fossil Records
  • Transitional Fossils
  • Patterns of Distribution
  • Anatomy
  • Embryology
  • Molecular Biology
  • Genetics
  • Artificial Selection
• Fossil Records


  • Fossil record shows the history of life by showing the species that were alive in the past
  • Fossils found in young layers of rock (from recent times) are more similar to species that are alive today than fossils found in older, deeper rocks
  • Fossils appear in chronological order to the rock layers so probably ancestors to species can be found in older rocks
  • Not all organisms appear in the fossil record at the same time – fossil record shows that fish are the oldest vertebrate, amphibians came later, reptiles came later, mammals and birds came later than that
• The fossil record reinforces the idea that amphibians evolved from ancestral fish, reptiles evolved form ancestral amphibians, mammals and birds evolved from different groups of reptiles
• Transitional Fossils


  • Original fossils showed gaps that led people to be skeptical of idea of evolution
  • Later "transitional fossils" were discovered – these show intermediary links between groups of organisms
• Patterns of Distribution


  • Biogeography is the study of the past and present geographical distribution of organisms
  • Darwin and Wallace hypothesized that species evolve in one location and then spread out to other regions
• Evidence supporting patterns of distribution


  • Geographically close environments are more liked to be populated by related species than locations that are geographically separate but similar
  • Animals found on islands often closely resemble animals found on the closest continent
  • Fossils of the same species can be found on the coastline of neighbouring continents
  • Closely related species are almost never found in exactly the same location or habitat
• Homologous Structures


  Structures that have similar structural elements and origin but may have a different function. They are similar because they came from a common ancestor.
• Analogous Structures


  Body parts that perform similar functions, even though the organisms do not have a common evolutionary origin.
• Embryology


  • Embryos of different organisms exhibit similar stages of embryonic development, suggesting a common ancestry
  • Embryos of different organisms that are closely related show very similar stages of embryonic development.
• Molecular Biology


  • Evolutionary relationships among species are reflected in their DNA and proteins
  • All cells consist of membranes filled with water, genetic material, proteins, lipids and carbohydrates
  • Proteins called enzymes control biochemical reactions in all organisms
  • Proteins are synthesized from amino acids in all organisms
  • All cells can replicate DNA in all organisms
  • Scientists can determine how closely related two organism are by comparing their DNA
• Artificial Selection


  Another word for plant and animal breeding, in which people breed individuals with desired characteristics in order to get offspring with those same characteristics
• Convergent Evolution


  When one or more different species evolve similar characteristics due to a common environment
• Analogous structures


  Structures that are similar in function but different in origin
• Divergent Evolution


  When an ancestral species diverges into many different species
• Homologous structures


  Structures that are similar in origin but may have different functions
• Speciation


  The formation of new species
• Species


  A group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding
• Speciation


  1. Two populations are prevented from interbreeding

  2. Populations become isolated long enough

  3. Natural selection affects reproduction

  4. Populations become reproductively incompatible
• Ways populations stay separated


  • Geographical barriers
  • Biological barriers
• Geographical barriers


  • Physically separate populations
  • Examples: Mountains, islands, lava flow, rivers
  • Species do not have to be isolated forever but long enough to become reproductively incompatible
• Biological barriers


  • Keep species reproductively isolated even if their ranges overlap
  • Examples: Behaviour, pheromones, different habitats
• Allopatric speciation


  1. Physical barrier separates a single population

  2. Natural selection works on the separated groups independently

  3. Accumulated physical and/or behavioural differences lead to reproductive incompatibility
• Sympatric speciation


  Occurs when there are no physical barriers preventing mating, but a characteristic causes a preference for a certain aspect of the environment
• If speciation was only by transformation, the total number of species and diversity would not change over time