Animal Biology Study Guide for Exam III

Introduction to Animals

• Key Terms:

  • Heterotroph: Organisms that obtain food by consuming other organisms.
  • HOX Genes: Genes that control the body plan of an organism during embryonic development.
  • Parthenogenesis: A form of asexual reproduction where an egg develops without fertilization.
  • Sessile: Organisms that are attached to a surface and do not move.
  • Fragmentation: A type of asexual reproduction where an organism breaks into pieces, each capable of growing into a new organism.
  • Budding: A form of asexual reproduction where a new organism develops from an outgrowth or bud on the parent.
  • Cephalization: The concentration of sensory organs and nervous tissue at the anterior end of the organism.
  • Protoplasmic, Cellular, Tissue, Organ, Organ Systems: Levels of biological organization from simplest to most complex.
  • Germ Layers: Tissue layers (endoderm, mesoderm, ectoderm) that develop in the embryo.
  • Triploblastic: Organisms with three germ layers (ectoderm, mesoderm, endoderm).
  • Diploblastic: Organisms with two germ layers (ectoderm, endoderm).

• Shared Features of All Animals:

  • Key features include multicellularity, heterotrophy, and specific developmental stages.

• Differences Among Animals:

  • Classification based on cellular structure, tissue differentiation, and modes of reproduction (sexual/asexual).

Modes of Reproduction

• Sexual Reproduction: Involves the fusion of male and female gametes.
• Asexual Reproduction: Does not involve gamete fusion, e.g., fragmentation, budding.
• Parthenogenesis: A reproductive strategy seen in many invertebrates including some reptiles and fish.

Common Ancestor of All Animals

• Choanoflagellates: Single-celled organisms that are closely related to animals; support the colonial flagellate hypothesis.

Body Symmetry

• Radial Symmetry: Symmetry around a central axis (e.g., jellyfish).
• Bilateral Symmetry: Symmetrical on both sides, has a distinct front and back (e.g., humans).

Levels of Organization

• Classification ranges from protoplasmic (single cell) to organ systems (complex organisms with specialized functions).

Embryonic Development

• Germ Layers: Differentiation into tissues occurs based on whether the organism is diploblastic or triploblastic.
• Developmental Stages: Includes cleavage, blastulation, gastrulation, resulting in the formation of the body plan.

Body Cavities

• Coelomate: Organisms with a true coelom (body cavity).
• Acoelomate: Lack a body cavity between the digestive tract and outer body wall.
• Pseudocoelomate: Have a body cavity that is not fully lined by mesodermal tissue.

Sponges and Cnidaria

• Sponges (Porifera): Basic characteristics include being multicellular but lacking true tissues.

  • Terms to Understand: Choanocytes, mesohyl, spongocoel, ostia, osculum, sclerocytes, spicules.
  • Life Cycle: Includes external & internal budding.
  • Body Forms: Distinction between different structures like choanocytes (important for water flow and feeding).

• Cnidarians: Possess true tissues, exhibit both polyp and medusa forms.

  • Key Terms: Nematocysts (stinging cells), mesoglea (jelly-like substance), hydrostatic skeleton.
  • Life Cycle Stages: Planula (larval stage), polyp, medusa.

Lophotrochozoa (Part 1)

• Key Terms: Protostome, deuterostome, lophophore, trochophore.
• Morphology & Shared Features: Various groups exhibit features such as lophophore and trochophore larvae.

Worms

• Platyhelminthes: Examples include planarians and their physiology involving cephalization, regeneration, etc.
  • Trematoda (flukes): Life cycles involve multiple hosts.
  • Cestoda (tapeworms): Specialized anatomy for parasitism.

Lophotrochozoa (Part 2)

• General characteristics of mollusks include morphology regarding the visceral mass and body structure. Familiarity with bivalves, gastropods, and cephalopods is necessary.

Ecdysozoa: Nematodes, Tardigrades, Onychophora, Arthropods

• Key Terms: Cuticle, ecdysis (molting process), open circulatory system in arthropods.
• Distinguishing Features: Specific anatomical adaptations in Nematodes and Arthropods (e.g., chelicerae in Chelicerata, body plan in Crustacea).
• Life Cycle and Development: Understanding the concepts of complete and incomplete metamorphosis in insects, especially the development of flight in Endopterygota.