Animal Biology Study Guide for Exam III

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).

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.

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

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).

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

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.

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 (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.

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

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

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

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.