IB BIO - 5.5 Classification

• 5.5.1 

  • Outline the binomial system of nomenclature.

• The binomial system of nomenclature, developed by Carl Linnaeus in the 18th century, is a standardized method for naming species of organisms. It uses a two-part Latinized name, consisting of the genus name followed by the species name, to uniquely identify each species. Here's an outline of the binomial system:

  • 1. Genus and Species Names:

    •    - In the binomial system, each species is given a unique two-part name, known as the scientific name or binomial. The first part of the name represents the genus to which the species belongs, and the second part represents the species itself.

    •    - The genus name is always capitalized, while the species name is written in lowercase. Both parts are italicized or underlined when written, to indicate their scientific status.

  • 2. Hierarchy of Classification:

    •    - The binomial system is part of a hierarchical classification system that organizes organisms into increasingly inclusive categories based on their evolutionary relationships and shared characteristics.

    •    - The hierarchy of classification, from most inclusive to least inclusive, is as follows: Domain, Kingdom, Phylum (or Division for plants), Class, Order, Family, Genus, and Species.

    •    - Each species is assigned to a specific genus, which is then grouped with related genera into higher taxonomic categories such as family, order, and so on.

  • 3. Standardized Naming Conventions:

    •    - The binomial system provides a standardized framework for naming species, ensuring that each species has a unique and universally recognized scientific name.

    •    - Scientific names are based on Latin or Latinized forms of words to facilitate international communication and avoid confusion caused by differences in common names across languages and regions.

    •    - The use of standardized naming conventions allows scientists to accurately identify and communicate information about organisms, facilitating research, collaboration, and the sharing of knowledge across disciplines and geographic boundaries.

  • 4. Example:

    •    - An example of a scientific name using the binomial system is Homo sapiens, which refers to modern humans. In this example, "Homo" is the genus name, and "sapiens" is the species name. Together, they form the unique scientific name for the human species.

• Overall, the binomial system of nomenclature provides a systematic and standardized method for naming and classifying species of organisms, enabling scientists to organize and communicate information about the diversity of life on Earth in a clear, concise, and universally understood manner.

• 5.5.2 

  • List seven levels in the hierarchy of taxa—kingdom, phylum, class, order, family, genus and species—using an example from two different kingdoms for each level.

• 1. Kingdom:

  •    - Animalia: Example - Lion (Panthera leo)

  •    - Plantae: Example - Oak tree (Quercus robur)

• 2. Phylum:

  •    - Animalia: Example - Chordata (includes vertebrates like lions)

  •    - Plantae: Example - Magnoliophyta (includes flowering plants like oak trees)

• 3. Class:

  •    - Animalia: Example - Mammalia (includes mammals like lions)

  •    - Plantae: Example - Magnoliopsida (includes dicotyledonous plants like oak trees)

• 4. Order:

  •    - Animalia: Example - Carnivora (includes carnivorous mammals like lions)

  •    - Plantae: Example - Fagales (includes oak trees)

• 5. Family:

  •    - Animalia: Example - Felidae (includes cats like lions)

  •    - Plantae: Example - Fagaceae (includes oak trees)

• 6. Genus:

  •    - Animalia: Example - Panthera (includes big cats like lions)

  •    - Plantae: Example - Quercus (includes oak trees)

• 7. Species:

  •    - Animalia: Example - Panthera leo (lion)

  •    - Plantae: Example - Quercus robur (English oak)

• 5.5.3 

  • Distinguish between the following phyla of plants, using simple external recognition features: bryophyta, filicinophyta, coniferophyta and angiospermophyta.

• 1. Bryophyta (Bryophytes):

  •    - Bryophytes are non-vascular plants, meaning they lack specialized tissues for transporting water and nutrients. 

    •    - External recognition features:

      •      - Bryophytes include mosses, liverworts, and hornworts.

      •      - They are typically small, herbaceous plants with low-growing, carpet-like structures.

      •      - They lack true roots, stems, and leaves, although some mosses may have simple structures resembling leaves.

      •      - Bryophytes reproduce via spores, which are produced in structures like capsules or sporangia.

• 2. Filicinophyta (Ferns):

  •    - Ferns are vascular plants with well-developed vascular tissues for conducting water and nutrients.

    •    - External recognition features:

      •      - Ferns have true leaves (fronds) with complex leaf structures called pinnae or leaflets.

      •      - They reproduce via spores, which are produced in structures called sporangia located on the undersides of fronds.

      •      - Ferns typically have rhizomes, which are underground stems that anchor the plant and give rise to new fronds.

• 3. Coniferophyta (Conifers):

  •    - Conifers are gymnosperms, meaning they produce seeds that are not enclosed within fruits.

    •    - External recognition features:

      •      - Conifers are characterized by needle-like or scale-like leaves, which are usually evergreen.

      •      - They often have cones (strobili) for reproduction, with male cones producing pollen and female cones containing ovules that develop into seeds.

      •      - Conifers include familiar trees like pine, spruce, fir, cedar, and cypress.

• 4. Angiospermophyta (Angiosperms):

  •    - Angiosperms are flowering plants that produce seeds enclosed within fruits.

    •    - External recognition features:

      •      - Angiosperms are characterized by the presence of flowers, which are reproductive structures containing male and/or female reproductive organs.

      •      - They have true leaves with a wide variety of shapes and sizes.

      •      - Angiosperms produce seeds enclosed within fruits, which may be fleshy (e.g., apples, berries) or dry (e.g., beans, nuts).

      •      - Angiosperms represent the most diverse group of plants and include trees, shrubs, herbs, and grasses.

• 5.5.4 

  • Distinguish between the following phyla of animals, using simple external recognition features: porifera, cnidaria, platyhelminthes, annelida, mollusca and arthropoda.

• 1. Porifera (Sponges):

  •    - Porifera are simple, multicellular animals with porous bodies.

  •    - External recognition features:

  •      - Sponges have a porous body structure with numerous small openings called ostia and a larger opening called the osculum for water flow.

  •      - They lack true tissues and organs and have a simple body organization.

  •      - Sponges may have different shapes and sizes, ranging from encrusting forms to vase-like or branching structures.

• 2. Cnidaria (Cnidarians):

  •    - Cnidaria are radially symmetrical animals with specialized stinging cells called cnidocytes.

  •    - External recognition features:

    •      - Cnidarians have tentacles with stinging cells called cnidocytes, which they use for defense and capturing prey.

    •      - They typically have a sac-like body plan with a central gastrovascular cavity serving as both a digestive and a circulatory system.

    •      - Cnidarians may exhibit two body forms: the polyp form (e.g., sea anemones) with a cylindrical body and the medusa form (e.g., jellyfish) with a bell-shaped body.

• 3. Platyhelminthes (Flatworms):

  •    - Platyhelminthes are dorsoventrally flattened, unsegmented worms with bilateral symmetry.

  •    - External recognition features:

    •      - Flatworms have a flattened body shape with a distinct head region.

    •      - They lack a coelom (body cavity) and a circulatory system, and their digestive cavity has only one opening (incomplete digestive system).

    •      - Flatworms may be free-living (e.g., planarians) or parasitic (e.g., tapeworms), and they come in various sizes and colors.

• 4. Annelida (Annelids):

  •    - Annelida are segmented worms with a true coelom (body cavity) and bilateral symmetry.

  •    - External recognition features:

    •      - Annelids have a segmented body, with each segment containing a pair of bristle-like structures called setae for movement.

    •      - They typically have a distinct head with sensory structures and a mouth, as well as a well-developed circulatory system with blood vessels.

    •      - Annelids may inhabit various habitats, including terrestrial (e.g., earthworms), aquatic (e.g., leeches), and marine environments.

• 5. Mollusca (Mollusks):

  •    - Mollusca are soft-bodied animals with a muscular foot and a mantle that may secrete a calcareous shell.

  •    - External recognition features:

    •      - Mollusks have a muscular foot used for locomotion and a mantle that may secrete a protective shell made of calcium carbonate (not all mollusks have shells).

    •      - They typically have a distinct head with sensory structures and a radula, a rasping tongue-like structure used for feeding.

    •      - Mollusks exhibit diverse body forms, including snails, clams, octopuses, and squids, and they inhabit various aquatic and terrestrial habitats.

• 6. Arthropoda (Arthropods):

  •    - Arthropoda are characterized by their jointed appendages, segmented bodies, and exoskeleton made of chitin.

  •    - External recognition features:

    •      - Arthropods have jointed appendages, including legs, antennae, and mouthparts, which are used for locomotion, feeding, sensing the environment, and reproduction.

    •      - They have a segmented body divided into distinct regions, including a head, thorax, and abdomen (in most species).

    •      - Arthropods typically molt their exoskeleton to accommodate growth, and they exhibit a wide range of adaptations for various lifestyles, including flying, swimming, burrowing, and crawling.

• 5.5.5 

  • Apply and design a key for a group of up to eight organisms.