Week 33 – Types of Biological Relationships

Over the past few weeks, we have acquired a significant amount of evidence for evolution:

  • Natural selection (the common ancestry of brown bears and polar bears; dinosaurs and chickens)
  • Artificial selection (humans selecting for desired traits, such as dog breeding)

As we continue learning about evolution, we must expand our view to consider the concept of co-evolution:

  • Co-evolution is the idea that organisms do not evolve in a vacuum.  Evolution takes place concurrently in nature: populations of organisms influence each other’s evolution.
  • The term co-evolution is used to describe cases where two (or more) species reciprocally affect each other’s evolution.
  • Plants and insects represent a classic case of co-evolution — one that is often, but not always, mutualistic (keep reading – the definition of mutualism is further down). Many plants and their pollinators are so reliant on one another and their relationships are so exclusive that biologists have good reason to think that the “match” between the two is the result of a co-evolutionary process.
  • For more about co-evolution, visit the evolution.Berkeley.edu website!

Important Vocabulary:

  • Host: an organism that harbors a parasite, or a mutual or commensal symbiont, typically providing nourishment (food) and shelter.
  • Bacteria: microscopic living organisms, usually one-celled, that can be found everywhere. They can be dangerous, such as when they cause infection, or beneficial, as in the process of fermentation (to make foods like kimchi, fish sauce, Tabasco sauce, and salami) and that of decomposition.
  • Virus: Any of various simple submicroscopic parasites of plants, animals, and bacteria that often cause disease and that consist essentially of a core of RNA or DNA surrounded by a protein coat. Unable to replicate without a host cell, viruses are typically not considered living organisms.
  • Infection: Invasion and multiplication of an infectious agent in body tissues of the host and may lead to clinical symptoms or local cellular injury as a result of competition in metabolism, production of toxins, intracellular replication, or antigen antibody response.
  • Symbiosis: the interaction between two different organisms living in close physical association.
  • Symbiotic Relationships:
    • Mutualism: symbiosis that is beneficial to both organisms involved.
    • Commensalism: an association between two organisms in which one benefits and the other derives neither benefit nor harm.
    • Parasitism: a non-mutual symbiotic relationship between species, where one species, the parasite, benefits at the expense of the other, the host.

Your assignment:

  1. Create a Google Doc titled Week 33 – Your Name (Example: Week 33 – Olive Swart)
  2. Create a section in your Week 33 Google Doc titled “Biological Relationships Vocabulary”.
  3. Make a numbered list of each of the 11 words from this lesson highlighted in red bold text.
  4. For each word in your list, research your own examples of these biological processes, type of organisms, or relationships between organisms and write up your work in your Week 33 Google Doc.  Include source citations as appropriate.  Need some help getting started? Click here for examples of symbiotic relationships.

Return to the Week 33 – Co-Evolution post and continue our work for the week.

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