20.1 Organizing Life on Earth

20.1 Organizing Life on Earth

  • The organisim's relationships, such as from which organisms it may have evolved, or to which species it is most closely related, are described in a phylogeny.
    • Information on shared ancestry is provided by phylogenetic relationships.
  • Scientists use a tool to show the evolution of organisms.
    • Scientists consider the evolutionary past to be a hypothesis of the trees.
    • We can show the relationships among different organisms by constructing a tree of life.
  • We can read a tree like a map.
    • A common ancestor is represented at the base of many phylogenetic trees.
  • Plants and animals are compared with other organisms in a small branch in the diagram.
    • Some trees show relationships with other trees.
  • The relationship of the three domains of life--bacteria, Archaea, and Eukarya--is shown in both of these trees.
  • The branching in a tree shows evolutionary relationships.
    • Although sister taxa and polytomy share an Ancestor, it does not mean that the groups of organisms split or evolved from each other.
    • Organisms in two taxa may have split, but neither taxon gave rise to the other.
  • The root of a tree shows the origin of organisms on the tree.
    • A branch point is where the two lineages separated.
    • A taxon that evolved early and is unbranched is called a basal taxon.
    • Sister taxa are two lineages that stem from the same branch point.
    • A branch with more than one lineage is a polytomy.
  • The diagrams can be used to understand evolutionary history.
    • Through the evolutionary branches between the two points, we can trace the path from the origin of life to any individual species.
    • By tracing back towards the "trunk" of the tree, one can discover the ancestors of a single species.
    • The tree can be used to study entire groups of organisms.
  • The rotation at branch points does not change the information.
    • The information wouldn't change because the taxon's evolution from the branch point was independent of the other.
  • Data from fossils, from studying the body part structures, or from studying the molecule that an organisms uses, may be used by researchers.
    • By combining data from many sources, scientists can build a tree of life.
  • It is easy to assume that more closely related organisms look the same, but it is not always the case.
    • It is possible for the two groups to appear different than other groups that are not as closely related.
    • lizards and frog look similar to lizards and rabbits.
  • A ladder-like tree of vertebrates was roots by an organisms that lacked a column.
    • Scientists place organisms with different characters in different groups.
  • Unless otherwise stated, the branches do not account for length of time, only the evolutionary order.
    • Unless specified on the diagram, a branch's length doesn't typically mean more time passed or less time passed.
    • The order in which things took place is shown by the tree.
    • The tree shows that the oldest trait is the vertebral column, followed by hinged jaws and so forth.
    • A real tree does not grow in one direction after a new branch develops, but a phylogenetic tree does, and like a real tree, it does not grow in only one direction after a new branch develops.
    • It doesn't mean that a new branch was formed.
    • It is possible that groups that are not closely related, but evolve under similar conditions, are more similar to each other than to a close relative.
  • There are interactive exercises that allow you to explore the evolutionary relationships among species.
  • Think about the organization of a grocery store.
    • The produce, dairy, and meats departments are in one large space.
    • Each department divides into aisles, then each aisle is divided into categories and brands, and finally a single product.
    • This organization is called from larger to smaller, more specific categories.
  • The Linnaean system is named after Carl Linnaeus, a Swedish botanist, zoologist, and physician.
    • When one branch ends as a single species, the groups become more specific.
    • Scientists divide organisms into three large categories after the common beginning of all life.
    • The classification system uses a hierarchy to organize living organisms.
  • The wolf and dingo are included in the common dog, Canis lupus familiaris.
  • There are eight terms in the full name of an organisms.
    • For the dog, it is: Eukarya, Animalia, Chordata, Mammalia, and Canis.
    • The names are capitalized except for the species and the names are italicized.
    • Canis lupus is the scientific name for the dog.
    • Dogs are in order.
    • Canidae is the taxon at the family level, and so on.
    • The dog is a common name that people typically use for organs.
    • The "familiaris" is a subgroup of Canis lupus familiaris.
    • Subspecies are members of the same species that are capable of reproducing viable offspring, but they are separate due to geographic or behavioral isolation.
  • The levels move toward specificity with other organisms.
    • Plants and butterflies are included in the widest diversity of organisms that the dog shares.
    • The organisms are more closely related at each level.
  • The organisms become more similar at each sublevel.
    • Dogs and wolves are the same species because they can breed and produce viable offspring, but they are different enough to be classified as different subspecies.
  • There is a link to learning to explore the classifications of thousands of organisms.
    • About 10% of the species on the planet can be found on this reference site.