A3.1 - Diversity Of Organisms

Biological Species Concept

  • Definition: The biological species concept defines a species as a group of organisms that can interbreed and produce fertile offspring.

  • Skepticism: There are limitations and criticisms of this concept, including:

    • Hybridization: Some species can hybridize, complicating strict species definitions as hybrids are not always infertile.

    • Asexual reproduction: It doesn't account for species that reproduce asexually. Examples include parthenogenesis, where organisms can synthesise a baby while being virgins, and binary fission where a single organism divides into two identical offspring. As well as vegetative propagation where plants can reproduce asexually by producing new individuals from their structures such as stems, roots, or leaves.

    • Cryptic species: Similar-looking species that do not interbreed but are distinct genetically.

    • Organisms made up of DNA from multiple organisms (horizontal gene transfer)

Gene Transfer

  • Vertical Gene Transfer: The process of transferring genetic material from parent to offspring (through generations), typically through reproduction.

  • Horizontal Gene Transfer: The transfer of genetic material between organisms in a manner other than through parent-offspring relationships (within the same generation). This process is significant in prokaryotes and can lead to rapid genetic changes.

Xenologs refer to genes that have been transferred between organisms of different species, typically through horizontal gene transfer.

Hybrids

  • Hybrids are organisms that result from the crossing of two different species. They can exhibit varying traits from both species and may have fertility issues.

  • Female Horse (64 Chromosones) + Male Donkey (62 Chromosones) = Mule (63 Chromosones)

Dichotomous Key

  • Definition: A tool that uses a series of questions with two possible answers to help identify organisms.

  • Limitations: While it aids classification, it may not be as precise or comprehensive as more modern methods, such as DNA barcoding.

DNA Barcoding

  • Definition: A method for identifying species using a short genetic sequence from a standardized region of the genome. Barcode Identification Number.

  • Advantages over Dichotomous Keys:

    • Greater accuracy in species identification.

    • Ability to store vast amounts of information in databases.

    • More efficient for classifying and cataloging biodiversity.

    • Analogous to shopping for items in a detailed, organized database.

Environmental DNA (eDNA)

  • Definition: Genetic material obtained directly from environmental samples (e.g., soil, water) without capturing the organism.

  • Advantages:

    • Can detect multiple species in a single sample, saving time and effort compared to individual organism sampling.

    • Non-invasive method that can provide insights into entire ecosystems.

  • Disadvantages:

    • DNA degradation over time can complicate results.

    • Potential contamination of samples may lead to faulty conclusions.

    • Does not account for whether the species is alive or dead.

    • Does not inform of how many of the species there is.

Bioindicator Species

  • Definition: Species that are used to assess the health of an ecosystem. They can indicate the presence of certain environmental conditions or changes.

  • Importance: Understanding bioindicators helps in conservation and environmental monitoring.

  • When present = pollution absent

  • When absent = pollution present

Conclusion

  • Essential for HL Studies: Understanding these concepts forms the foundation for further exploration into biodiversity, genetics, and environmental science. Review and understand the key terms: Biological Species Concept, DNA Barcoding, eDNA, and Bioindicator Species.