Bio 102 General Biology II: Animal Kingdom Survey and Body Plans

BIO 102: General Biology II - Course Overview

  • Course Code: BIO 102
  • Course Title: General Biology II
  • Credit Units: 2 units
  • Course Lecturer: Prof. J. C. Ozougwu
Course Outline
  1. Viruses: Basic characteristics, structure, replication, human viral diseases, and classification.
  2. Bacteria: Characteristics, cell structure, types, reproduction (binary fission, conjugation), beneficial/harmful bacteria, and classification (e.g., Gram staining).
  3. Fungi: General features, structure (hyphae, mycelium, spores), nutrition (saprophytic, parasitic, symbiotic), reproduction, and classification.
  4. Plant Kingdom - Survey of Lower Plants:
    • Bryophytes (e.g., Funaria - moss): Characteristics, classification (Mosses, Liverworts, Hornworts), life processes, and adaptations.
    • Pteridophytes (e.g., Nephrolepis - fern): Characteristics, classification (Mosses, Liverworts, Hornworts - Note: The transcript replicates the Bryophyta classification for Pteridophytes), life processes, adaptations, and differences from Bryophytes.
  5. Plant Kingdom - Survey of Higher Plants:
    • Gymnosperms (e.g., Pinus - pine): Characteristics, classification, life processes, and adaptations.
    • Angiosperms (e.g., Hibiscus): Characteristics, classification, life processes, adaptations, pollination, and double fertilization.
  6. Survey of Animal Kingdom: Introduction to animal diversity, body plans, invertebrates, and vertebrates.
  7. Survey of Invertebrates: Study of basic characteristics, classification, life processes, and examples from Phyla Porifera through Echinodermata.
  8. Survey of Vertebrates (Subphylum Vertebrata, Phylum Chordata): Study of basic characteristics, classification, and life processes for Classes Agnatha through Mammalia.

Overview of Kingdom Animalia

  • General Characteristics:
    • All animals belong to the kingdom Animalia.
    • They are multicellular, eukaryotic, and heterotrophic organisms.
    • They lack photosynthetic pigments and obtain nutrients by ingesting other organisms.
    • Cellular Structure: Animal cells lack cell walls.
    • Complexity: Many members exhibit advanced tissue differentiation and complex organ systems.
    • Mobility: Most move about freely.
    • Responsiveness: Characterized by quick responses to stimuli due to specialized nervous tissue for coordination.
    • Growth: Growth is determinate, typically resulting in a definite size and shape.
Broad Classification
  • Invertebrata (Invertebrates): Animals without backbones.
  • Vertebrata (Vertebrates): Animals with backbones.

Animal Body Plan: Structural and Functional Design

  • Definition: A body plan is an animal’s architecture; the major features of its structural and functional design.
  • Four Defining Features:
    1. The number of tissue types found in embryos (evolution of tissues).
    2. The type of body symmetry and degree of cephalization.
    3. The presence or absence of a fluid-filled body cavity.
    4. The developmental patterns of the embryo (protostome vs. deuterostome).
1. Evolution of Tissues
  • Parazoans: Animals that lack true tissues. Sponges (Phylum Porifera) are the only members. Although they have several cell types, they are not organized into integrated structural and functional units.
  • Eumetazoans: All other animals that possess true tissues.
  • Germ Layers: Embryonic tissues organized in layers.
    • Diploblasts: Embryos have two tissue layers/germ layers (ectoderm and endoderm). Examples: Cnidaria and Ctenophora.
    • Triploblasts: Embryos have three tissue layers/germ layers: ectoderm, endoderm, and mesoderm (located between the other two). Examples: All other animals from leeches to humans.
2. Symmetry and Cephalization
  • Asymmetry: No planes of symmetry; the organism cannot be sectioned into similar sides. Most sponges are asymmetrical.
  • Radial Symmetry: At least two planes of symmetry. Common in organisms that need to capture prey or react to predators from multiple directions.
  • Bilateral Symmetry: Exactly one plane of symmetry, resulting in a long, narrow body with a distinct head end. This was a critical evolutionary step.
  • Cephalization: Triggered by bilateral symmetry; the evolution of a head or anterior region where sensory, feeding, and information processing structures are concentrated. It facilitates uni-directional movement.
3. Evolution of a Body Cavity (Coelom)
  • Coelom: An internal fluid-filled cavity.
  • Acoelomates: Triploblastic animals that lack a fluid-filled body cavity (e.g., Platyhelminthes and Acoelomorpha).
  • Coelomates: Animals possessing a coelom.
    • Pseudocoelom ("False Hollow"): A cavity that forms between the endoderm and mesoderm (e.g., roundworms and rotifers).
    • True Coelom: A cavity that forms within the mesoderm itself and is lined with cells from the mesoderm.
  • Note: Diploblasts have a central canal for digestion/circulation but lack a coelom.
4. Protostome and Deuterostome Patterns
  • Protostomes: Development proceeds with spiral cleavage. This group includes the vast majority of animals (e.g., arthropods).
  • Deuterostomes: Development proceeds with radial cleavage. This group includes chordates (mammals, fish, frogs, etc.) and echinoderms.

Phylum Porifera (Sponges)

  • General Characteristics:
    • Commonly called "pore-bearing" animals.
    • Simplest of all animals; lack true tissues.
    • Body develops from two cell layers.
    • Asymmetrical and free-living.
    • Sessile (attached to a substrate).
    • Filter feeders with intracellular digestion.
Morphological and Cellular Features
  • Porous Body Structure: Network of channels and chambers allowing water flow for feeding, respiration, and waste removal.
  • Skeletal Elements: Spicules (made of calcium carbonate or silica) and spongin (flexible proteinaceous material).
  • Mesohyl: A gelatinous extracellular matrix (acellular) between the outer and inner layers that provides structural support.
  • Specialized Cells:
    • Choanocytes (Collar Cells): Line internal channels; possess a flagellum surrounded by a collar; generate water currents and trap food particles.
    • Archaeocytes (Amoeboid Cells): Mobile cells in the mesohyl; responsible for digestion, nutrient transport, regeneration, and cell differentiation.
    • Pinacocytes: Epidermal cells forming the outer layer.
    • Porocytes: Form the pores (ostia) for water entry.
Water Flow and Structural Types
  1. Asconoid: Simplest and smallest; tube-like. Water entering through ostia goes directly to the central spongocoel (atrium) lined with choanocytes. Primitive and mostly freshwater.
  2. Syconoid: Intermediate complexity. Features radial canals lined with choanocytes. Water enters ostia -> radial canals -> apopyles -> spongocoel -> exit.
  3. Leuconoid: Most complex and diverse. Lacks a central spongocoel. Features numerous flagellated choanocyte chambers. Water moves through a complex system of canals and exits via multiple oscula.
Vital Functions and Ecological Adaptations
  • Respiration: Simple diffusion across high surface-area-to-volume bodies.
  • Excretion: Simple diffusion of metabolic wastes (e.g., ammonia) across cell membranes.
  • Circulation: Passive circulation via water canals; facilitated by choanocytes.
  • Reproduction: Asexual (fragmentation) and sexual (seasonal patterns).
  • Chemical Defenses: Production of toxins to deter predators.
  • Symbiotic Relationships: Partnerships with algae or bacteria for nutrients (e.g., nitrogen fixing).

Phylum Cnidaria (Coelenterata)

  • General Characteristics:
    • Predominantly marine; tissue-level organization.
    • Radial symmetry and diploblastic (ectoderm and endoderm separated by gelatinous mesoglea).
    • Single opening (hypostome) surrounded by sensory tentacles.
    • Gastrovascular Cavity (Coelenteron): Functions in both digestion and circulation.
Basic Body Forms
  1. Polyp: Cylindrical or vase-shaped; sessile. Reproduces asexually (budding). Dominant in corals and hydroids.
  2. Medusa: Bell-shaped or umbrella-shaped jellyfish form; free-swimming. Reproduces sexually (releases gametes). Dominant in jellyfish.
  • Metagenesis: The alternation between polyp and medusa stages.
Vital Functions and Specialized Features
  • Nematocysts: Specialized stinging cells (cnidocytes) containing toxins used for prey capture and defense.
  • Feeding: Carnivorous; extracellular digestion in the gastrovascular cavity.
  • Reproduction: Sexual and asexual (budding/fragmentation). Sexual reproduction produces a planula larva.
  • Regeneration: High capacity, especially in polyps.
  • Mutualism: Relationships with zooxanthellae (algae) or fish (e.g., anemones providing shelter).
  • Bioluminescence: Some species produce light for communication or defense.

Phylum Platyhelminthes (Flatworms)

  • General Characteristics:
    • Dorso-ventrally flattened; bilateral symmetry.
    • Triploblastic and acoelomate.
    • Organ-system grade of organization.
    • Incomplete digestive system (often no separate mouth/stomach structure).
Classification
  1. Turbellaria: Mostly free-living, freshwater flatworms (e.g., Planaria). High regenerative capacity.
  2. Trematoda: Parasitic flukes (e.g., Fasciola hepatica - liver fluke; Schistosoma - blood fluke). Complex life cycles.
  3. Monogenea: Ectoparasites on fish (e.g., Gyrodactylus).
  4. Cestoda: Intestinal parasites with segmented bodies (e.g., Taenia solium - tapeworm); absorb nutrients directly through the tegument.
Vital Functions and Adaptations
  • Respiration/Circulation: Solely via diffusion due to flattened body shape.
  • Excretion: Protonephridia containing flame cells for filtration and osmotic regulation.
  • Reproduction: Mostly hermaphroditic (internal fertilization); also asexual through fission and fragmentation.
  • Parasitic Adaptations: Hooks, suckers, and adhesive structures.
  • Ciliated Epidermis: Aids in locomotion and creating water currents.
  • Size Metadata: Example liver fluke structure measures approximately 3 mm3\,mm in specific contexts.
Questions & Discussion
  • Task for Students: Read up on the growth and development processes specifically among Poriferans.