A3.1 - SL PT 1

  • Diversity of Organisms

    • Focus on species diversity, part of the core content.
    • Variation is a key characteristic of living organisms.
    • Example: Even within the same species (e.g., humans), individuals differ in appearance and traits.
    • Identical twins show variation in genetic expression despite having identical DNA.

  • Species Definition

    • Defining a species is complex.
    • Traditional creationist view: species were created and remain unchanged.
    • Evidence shows species can change over time, indicating that reliance on physical characteristics (morphology) for definition can be misleading.

  • Binomial Nomenclature

    • Each species has a unique two-part name (binomial name).
    • "Bi" means two, "nome" means name; thus, binomial = two names.
    • Purpose: To have a universal naming system to avoid confusion across languages.
    • Example: Common name (white clover) vs. scientific name (Trifolium rapens).
    • Rules for writing binomial names:
    • First part: Genus (capitalized)
    • Second part: Species (not capitalized)
    • Example: Trifolium rapens
    • Typed names in italics; handwritten names should be underlined.
    • Abbreviation: Once fully written, future references can use the first initial of the genus followed by the full species name.

  • Biological Species Concept

    • A species is defined as a group of individuals that can interbreed and produce fertile offspring.
    • Importance of the term "fertile": offspring must be capable of reproduction.
    • Example: Zorse (zebra + horse) can interbreed but is sterile, indicating that zebras and horses are distinct species.

  • Population vs. Species

    • Population: A group of the same species living in the same area and capable of interbreeding.
    • Divergence occurs when species don't interbreed.
    • If separated populations can produce fertile offspring when reunited, they are considered the same species.
    • Environmental differences can lead to evolutionary divergence over time, complicating species definition.
    • Challenges exist in determining the exact point when two species can no longer interbreed (grey areas in defining species).

  • Conclusion

    • There is no perfect system for defining species due to such complexities and transitional scenarios in nature.