Evolution

• Evolution occurs when the heritable characteristics of a species change over time.
• Evidence of evolution: Fossil record, Artificial selection resulting in selective breeding of animals, Homologous structures, Biogeography
• Fossils are the remains or impressions of organisms embedded in rock and preserved in petrified form.
• Evidence for Evolution in Fossils: Existence of fossils strongly suggest that different species of organisms have existed throughout the history of the Earth. The sequence in which fossils appear matches the sequence in which they would be expected to evolve. Many sequences of fossils exist which link together existing organisms with their likely ancestors.
• Selective breeding (also called artificial selection) is the

  process of humans choosing parents with desirable

  characteristics to breed together and produce offspring

  with more of those desirable characteristics.

  Selective breeding results in changes to the heritable

  characteristics of organisms, and is observable evolution.
• Homologous structures are body parts of organisms that

  have the same anatomical features, thus, indicating a

  common ancestor.

  The pentadactyl limb (five toes or fingers) in animals is

  an example of homologous structures.

  All animals with pentadactyl limbs have evolved from a

  common ancestor.
• Homologous structures are present in organisms that have

  descended from a common ancestor as a result of adaptive

  radiation.

  Populations of the common ancestor migrated to different locations

  with different challenges for survival.

  Populations evolved over time to be better adapted to their

  environments, resulting in modified (homologous) structures which

  are adapted to surviving in the new environments.

  Populations of a species gradually diverge into separate species by

  evolution as a result of adaptive radiation.
• Biogeography is the study of the geographic distribution of organisms. It is concerned not only with habitation patterns but also with the factors responsible for variations in distribution.
• Melanistic Insects

  Industrial melanism is an evolutionary effect prominent in several species of insects. The insects evolved to be darkly pigmented (due to the protein melanin) during the industrial revolution because of high levels of pollution which blackened the surfaces they were camouflaging on.

  Peppered moths are an example of insects which evolved during

  the industrial revolution.
• Natural Selection is the theory that explains the process whereby organisms better adapted to their environment tend to survive and produce more offspring.
• Key Terms for Evolution by Natural Selection Exam Questions

  • Selection pressure
  • Genetic variation
  • Mutation, meiosis and sexual reproduction
  • Competition
  • Favourable adaptations
  • Survive and Reproduce
  • Genes / Inherited characteristics passed to the next generation
  • Natural Selection
• A selection pressure is an evolutionary force that causes a particular trait to be more favorable under certain environmental conditions.

  Examples include:

  • Presence of antibiotics for bacteria
  • Predators and polluted environment for peppered moths
  • Drought and food available for Darwin’s finches
• Natural selection can only occur if there is genetic variation among members of the same species.

  Mutation, meiosis and sexual reproduction causes genetic variation between individuals in a species.
• Competition over: food, light, mates, space, water and air
• Adaptations are characteristics that make an individual

  suited to its environment and way of life.

  • Organisms with favorable adaptations are more likely to survive and reproduce.
  • Organisms with less favorable adaptations are less likely to survive and reproduce.
• Individuals that are better adapted tend to survive and produce more offspring while the less well adapted tend to die or produce fewer offspring.

  Individuals that reproduce pass on favourable characteristics (genes) to their offspring.

  Natural selection increases the frequency of characteristics that make individuals better adapted, and decreases the frequency of other characteristics, leading to changes within the species.
• Geospiza fortis is one of Darwin’s finches found on Daphne Major in the Galapagos islands.

  Rosemary and Peter Grant have studied the recent evolution of this species.

  They have measured the the beak size over generations.
• Natural Selection of the Beaks of the Geospiza fortis

  
• Natural Selection of the Peppered Moths

  
• • Natural classification classifies organisms to taxa using observable morphological features of organisms.
  • In a natural classification, the genus and accompanying higher taxa consist of all the species that have evolved from one common ancestral species.
  • Taxonomists sometimes reclassify groups of species when new evidence shows that a previous taxon contains species that have evolved from different ancestral species.
  • Natural classifications help in identification of species and allow the prediction of characteristics shared by species within a group.
• Taxonomy is the branch of science concerned with classification, especially of organisms into taxa

  A taxon is a taxonomic group of any rank, such as a species, family, or class.
• Taxon of Humans

  
• Taxon of California Redwoods

  
• Taxon order: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species
• Domains and their characteristics

  
• Chordate Classification: Body features that allow recognition, Endothermic or exothermic, Internal or external reproduction, Limbs
• Animal Classification: Symmetry, Segmentation, Mouth and anus, Body features that allow recognition
• A clade is a group of organisms (or viruses) that have

  evolved from a common ancestor.
• Evidence for which organisms are part of a clade can be

  obtained from the base sequences of a gene or the

  corresponding amino acid sequence of a protein.

  Clades can also be developed using observable

  characteristics of organisms.

  Gene and protein sequence differences accumulate

  gradually over time, so there is a positive correlation

  between the number of differences between two

  organisms and the time since they diverged from a

  common ancestor.
• Cladograms are tree diagrams that show the most probable sequence of divergence between clades.
• Nodes occur when two or more species diverge and represents a common ancestor.
• Molecular Clocks

  • Differences in the base sequence of DNA (and therefore proteins) are the result of mutations.
  • Mutations accumulate gradually over long periods of time.There is evidence that mutations occur at a constant rate, so

  they can be used as molecular clocks.
• A clade is a group of organisms that have evolved from a common ancestor.

  A branch on a cladogram that includes a single common ancestor and all of its descendants is a clade.
• Analogous structures are features of different species that are similar in function but not structure. They do not derive from a common ancestor and they evolved in response to a similar environmental challenge.
• Convergent evolution is the independent evolution of similar features in species of different lineages.
• Homologous structures have similar physical features in organisms that share a common ancestor, but the features may serve completely different functions. Homologous structures result from divergent evolution of organisms with a recent common ancestor.
• Divergent evolution is the accumulation of differences between closely related populations within a species, leading to speciation.
• Natural Classification vs Cladistics : Natural classification uses morphology (observable characteristics), Unrelated organisms with analogous structures may be classified within the same taxon, Cladistics analyzes gene or protein sequences resulting in better classification concerning evolutionary history of organisms.