Taxonomy and Classification Quiz

BIOL1262 Course Organisation

• Lecturers include Dr. Chinthapalli Rao (weeks 1, 2, & 6) and Dr. Denneko Luke (weeks 3, 4, & 5).
• Teaching Assistant: Mr. John
• Laboratory Technician: Mr. Hughlet Harvey
• Timetable: BIOL1262 & 1263 follow the same schedule as BIOL1017 & 1018 (from semester 1)

Taxonomy & Life Cycles (Lecture 1)

• 2024/2025 Lecture 1, by Dr. Chinthapalli Rao
• Life is structured in a hierarchical way, using a series of taxons
• Ecological Level includes categories such as biome, ecosystem, community, population, organism, organ system, organ, tissue, cell, and molecule

Taxonomy

• Earliest taxonomy systems were based on need and use of plants and animals
• Plants have been categorized by:
  • Growth form (herbs, shrubs, trees)
  • Life cycles (annuals, biennials, perennials)
  • Articles of diet (fruits, vegetables)
  • Medicinal uses (purgatives, doctrine of signatures)
  • Economic/social uses (crops, drugs, shade)
  • Reproductive features (sexual, asexual)

Terms associated with Taxonomy

• Taxonomy is the discipline of classifying organisms and giving them universally accepted names
• Taxonomy aims to accumulate knowledge about living organisms in an orderly manner
• Taxonomy includes four aspects:
  • Description: Describes the organism
  • Identification: Assigns features of the organism
  • Nomenclature: Names the organism
  • Classification: Places organisms into definite categories

Description

• Description provides detailed information about the characteristics and features of an organism to differentiate it from others.
• Characters are used to categorize organisms (e.g., petal colour, leaf texture, bark texture, leaf shape).

Identification

• Identification determines the identity of an organism based on its characteristics (often using keys or descriptions).
• If an unknown organism is new to science, it's described and named by the researcher.
• Dichotomous keys are commonly used to identify organisms.

Identification - Method

• Taxonomists utilize dichotomous keys to identify and describe organisms.
• Inferred characteristics include shared characteristics, trends, ancestral information, evolutionary relationships, and predictions about observed features.

Nomenclature

• The rules and regulations for naming taxa are formulated by scientists.
• The International Code of Nomenclature for Algae, Fungi, and Plants (ICN) provides a standardized system.
• Scientific names are written in Latin, often in the form of a binomial (e.g., genus name and species name).
• Scientific names are written in italics when printed but underlined separately with a single straight line in handwritten format.
• The genus name is capitalized, and the species name is lower case.

Nomenclature - Special Note

• The singular and plural forms of "species" are the same

Classification

• Classification is a general term referring to placing organisms into definite categories (ranks) to achieve an orderly study of organisms' relationships.
• Ranks are hierarchical, where each rank is inclusive. (e.g., Kingdom, Phylum, Class, Order, Family, Genus, Species)

More Taxonomic Terms

• Phylogeny refers to the evolutionary history and relationships among species or groups of organisms. It is also known as a "tree of life" or phylogenetic tree.
• Cladistics is a method for classifying organisms based on common ancestry emphasizing the order of branching in the evolutionary tree.
• Systematics is a more comprehensive field encompassing both taxonomy and phylogenetics (the study of evolutionary relationships)

Systematics: Modern Taxonomy

• The systematic approach to taxonomy has superseded the traditional phenotypic approach.
• Scientists primarily use evidence from evolutionary history (e.g., paleontology, comparative anatomy, comparative embryology, comparative biochemistry, molecular genetics, geographic distribution).

Progress of Taxonomic Systems

• This table shows how different taxonomists have categorized organisms over time, progressing from 2 kingdoms to 3-6 kingdoms and to 3 domains.

How is life rearranged and classified?

• Carl Woese and George Fox developed the three-domain model, which rearranged the classification of life to include Bacteria, Archaea, and Eukarya.

Life Cycles

• Life cycles are the series of changes in an organism's growth and development from its beginning to its mature state where offspring are produced.
• Reproduction can be either asexual or sexual.

Asexual Reproduction in Algae

• In unicellular algae such as Euglena, asexual reproduction occurs through mitosis (eukaryotic fission).
• Fragmentation is another method of asexual reproduction where the parent body breaks into many parts that grow into new organisms (e.g. Ulva, Sargassum, Spirogyra).
• Sporulation involves the production of spores in normal vegetative cells or specialized cells called sporangia (e.g. Chlamydomonas, Chlorella, Ulothrix)

Autocolony Formation

• In some algae (e.g. Volvox), daughter colonies develop within the parent colony.

Sexual Reproduction in the Algae

• Although most algae reproduce asexually, environmental disturbances can initiate sexual reproduction

Sexual Reproductive Cycles

• Sexual reproduction is categorized into three main types of cycles based on when meiosis takes place: zygotic meiosis, gametic meiosis, and sporic meiosis.
• These include freshwater Chlorophyta, marine Chlorophyta & Phaeophyta, and marine Chlorophyta, Phaeophyta & Rhodophyta

Zygotic Meiosis

• The dominant adult individual in this cycle is haploid
• The zygote divides immediately by meiosis to form four haploid cells
• Volvox, Chlamydomonas, Spirogyra

Zygotic Meiosis in Spirogyra

• A form of zygotic meiosis known as conjugation, happens in some freshwater green algae
• Two vegetative cells in adjacent filaments act as gametes fusing to form a zygote and completing meiosis

Gametic Meiosis

• Mature dominant adult is a diploid individual.
• The diploid individual undergoes meiosis, producing haploid gametes
• A diploid zygote will develop into a diploid individual
• Examples of gametic meiosis are Acetabularia

Sporic Meiosis

• The adult may be a haploid gametophyte or a diploid sporophyte.
• The gametophyte produces the gametes and the sporophyte produces the spores.
• This type of meiosis involves gametophytes and sporophytes alternating in the life cycle—a haplodiplontic cycle.
• Examples of organisms exhibiting sporic meiosis include different types of algae and land plants
• Two types of alternation of generations (isomorphic and heteromorphic) are observed

Sporic meiosis & Alternation of Generations

• Isomorphic alternation involves the sporophyte and gametophyte looking similar.
• Heteromorphic alternation involves the sporophyte and gametophyte looking different.
• These are observed in various algae such as Ulva (isomorphic) and Bryopsis (heteromorphic)

Viridiplantae - Origin

• Viridiplantae (plants) share features with Chlorophyta (green algae) including chlorophyll a and b, "plant" carotenoids, cell walls containing cellulose, starch in chloroplasts, phragmoplast formation, oogamy (egg-and-sperm fertilization), sporopollenin covering spores/pollen grains, and the development of alternation of generations.

Terminology - Revision

• Definitions for gametophyte, gametangium, gamete, sporophyte, sporangium, and spore are provided