Section 2

  1. Define phylogeny.

Phylogeny is the study of the evolutionary history and relationships among organisms.


  1. What is shown on phylogenetic trees?

Phylogenetic trees illustrate evolutionary relationships among species, showing their common ancestors and divergence over time.


  1. On a phylogenetic tree, what is represented by:

    1. the location of the branch points

The point where two species diverge, representing a common ancestor.

  1. the positions of the species on the tree

How closely related species are to each other, with more closely related species being closer on the tree.

  1. The phylogenetic tree below shows evolution of the major groups from the earliest cell ancestor. Answer the following questions, based on this tree. 

    1. Which group is most closely related to animals?

Fungi are the closest relatives to animals 


  1. Which group is most closely related to plants?

Green algae are the closest relatives to plants


  1. Which group is most closely related to brown algae?

Cialates are the closest relatives to brown algae

  1. How is the process of science applied to a group of phylogenetic trees showing different possible relationships among groups of organisms?

Scientists test different phylogenetic hypotheses using genetic, morphological, and fossil evidence, rejecting trees that conflict with the best available data.


  1. Explain why humans use classification systems and the limitations of the systems we use.

Classification helps organize biodiversity into meaningful categories for study. However, it is limited by the artificial nature of categories and the fact that evolution is a continuous process, not always fitting neatly into human-made classifications.


  1. Explain how the process of classification works.

Organisms are grouped based on shared characteristics, with similarities in physical traits, genetics, and evolutionary history forming the basis for classification.


  1. What kinds of structures have been used in classification?

Structures such as bones, DNA sequences, embryonic development patterns, and biochemical pathways have all been used to classify organisms.


  1. What is the key evidence that all living things descended from the same common ancestors?

The universal genetic code, similarities in DNA sequences, and common biochemical pathways (e.g., ATP as an energy carrier) all suggest common ancestry.


  1. What assumption can be made about two different organisms that have the same type of cell or tissue in their bodies?

They likely share a common ancestor that had the same cell or tissue type.


  1. What is taxonomy?

Taxonomy is the science of naming, describing, and classifying organisms based on shared characteristics.


  1. List the levels of taxonomic classification, from largest to smallest.

  • Domain

  • Kingdom

  • Phylum

  • Class

  • Order

  • Family

  • Genus

  • Species

  1. What are the parts of a scientific name?

A scientific name consists of a genus name (capitalized) and a species name (lowercase), written in italics or underlined.


  1. What are the rules for writing out a scientific name by hand?  In print?

  • Handwritten: The name is underlined (e.g., Homo sapiens).

  • Printed: The name is italicized (e.g., Homo sapiens).

  1. Define a species, using the biological species concept.

A species is a group of organisms that can interbreed and produce fertile offspring under natural conditions.


  1. What two conditions are necessary for individuals to belong to the same species?

  • They must be capable of interbreeding.

  • Their offspring must be fertile.

  1. Describe the Three Domain classification system.  Describe the characteristics of the organisms in each Kingdom.

  • Domain Bacteria: Unicellular prokaryotes with peptidoglycan cell walls.

  • Domain Archaea: Unicellular prokaryotes that often live in extreme environments.

  • Domain Eukarya: Organisms with eukaryotic cells, including protists, fungi, plants, and animals.

  1. Which two Domains contain prokaryotes?

  • Bacteria

  • Archaea

  1. Which Domain is most closely related to Domain Eukarya?

Archaea


  1. The study of the history of evolution focuses on.

The relationships among organisms and how they evolved over time.


  1. The study of the process of evolution focuses on.

The mechanisms (e.g., natural selection, genetic drift) that drive evolutionary change.


  1. Define biodiversity.

The variety of life forms on Earth, including species diversity, genetic diversity, and ecosystem diversity.


  1. The earliest cells to evolve were. (Choose between eukaryotes and prokaryotes.)

Prokaryotes


  1. Why are cyanobacteria important in the history of the Earth?

They were the first organisms to perform oxygenic photosynthesis, leading to the oxygenation of Earth’s atmosphere.


  1. Describe the origin of eukaryotic cells, including the origin of the nucleus, mitochondria, and chloroplasts.

  • The nucleus likely evolved from membrane infolding.

  • Mitochondria originated from an ancestral prokaryote through endosymbiosis.

  • Chloroplasts evolved from photosynthetic bacteria that were engulfed by early eukaryotes.


  1. What are protists?

A diverse group of mostly unicellular eukaryotic organisms that do not fit into the categories of plants, animals, or fungi.


  1. Briefly describe the characteristics of:

    1. Plants

      1. Multicellular, autotrophic organisms that perform photosynthesis.

    2. Fungi

      1. Absorptive heterotrophs that secrete enzymes to digest food externally.

    3. Animals

      1. Multicellular, ingestive heterotrophs that consume other organisms for food.