Chapter 34: Introduction to Animals

1. Chapter 34: Introduction to Animals 34-1 The Nature of Animals 34-2 Animal Bodies 34-3 Comparison of Invertebrates and Vertebrates

3. 34-1 The Nature of Animals I. The Nature of Animals (Kingdom Animalia) • Eleven major phyla based on phylogenetic relationships. (animals are for simplicity divided into invertebrates and vertebrates)

4. (1) Invertebrate • Animal lacking a backbone; 95% of ALL animals are invertebrates.

5. (2) Vertebrate • Animals with a backbone; represent ONLY 5% of all animal species.

8. II. Characteristics • Multicellular eukaryotes that are heterotrophic, no cell walls, locomotion.

9. (A) Multicellular Organization (enables adaptability) • Each animal cell depends on the presence and functioning of other cells (interdependency exist at the cellular level)

10. (1) Specialization • Is the adaptation of a cell for a particular function (i.e., there is a division of labor among animal cells)

11. Critical Thinking (1) From the perspective of a SINGLE cell, what may be one ADVANTAGE of cell specialization and one DISADVANTAGE of cell specialization?

12. (2) Cell Junctions (NOT found in unicellular organisms) • Connections between cells that hold the cells together as a unit (tissue).

14. (B) Heterotrophy • Nutrients are obtained from outside organic material and are ingested by all animals.

15. (1) Ingestion (Intracellular) • Digestion occurs WITHIN the animal’s body, allowing proteins, lipids, and carbohydrates to be extracted for cellular use (metabolic activity).

16. (C) Sexual Reproduction and Development • Most animals can reproduce sexually (unison of gametes), however some can reproduce asexually as well.

18. (1) Zygote (2N—a diploid cell, feature of sexual reproduction) • First cell of a new individual; undergoes mitotic divisions as development takes place, paving the way for cell specialization.

20. (2) Differentiation (a.k.a. the cellular pathway to specialization) • As new cells are yielded from a dividing zygote, genes become activated or deactivated leading to cell differentiation.

21. (D) Movement (e.g., locomotion is a common animal behavior) • Facilitated by the interrelationship of two types of tissue found ONLY in animals: (1) Nervous Tissue (2) Muscle Tissue.

22. Critical Thinking (2)Consider that an endoskeleton can support MORE weight than an exoskeleton, would a large-bodied animal with an exoskeleton be more likely to live in the water OR on land? Explain your reasoning.

23. (1) Neurons (Nervous Tissue Cells) • Conduct electrical signals working in a circuit between nervous tissue and muscles. (Detecting environmental stimuli can RESULT in movement)

24. III. Origin and Classification • The first animal ancestors were believed to be from the seas, and possibly arose from COLONIAL protists (of which were heterotrophic and eukaryotic). NOTE: Colonialism brought similar unicellular organisms together as a unit, possibly encouraging specialization of different cells.

27. 34-2 Animal Bodies I. Body Structure (morphology is BOTH external AND internal) • Those that LACK true tissues and an organized body shape (sponges) to highly organized tissues and a consistent body shape (the other ten phyla)

28. Critical Thinking (3)Observe the body of the animal pictured below. (a) What kind of symmetry does the animal display? (b) Is the animal cephalized? (c) How many germ layers are present? (d) How many openings does its digestive system possess? (e) Does the animal posses neurons?

29. (1) Symmetry • Refers to a consistent OVERALL pattern of structure in an animal body plan. (e.g., Sponges of Phylum Porifera display NO symmetry)

31. (A) Patterns of Symmetry (e.g., sponges excluded) • Symmetry shows ONE of TWO patterns depending on body plan.

32. (1) Radial Symmetry (e.g., Sea anemone, jellyfish, and hydra) • Similar parts BRANCH OUT in all directions from a central line; NO head region.

33. (2) Bilateral Symmetry (e.g., Moth, planarian, human) • Two SIMILAR halves on either side of a central plane; includes BOTH anterior/posterior ends AND a head region.

36. (3) Dorsal-Ventral & Anterior-Posterior (i.e., anatomical POSITIONS) • Top (dorsal), Bottom (ventral), Head (anterior), and Tail (posterior)

41. (4) Cephalization (evolution of a “head region” in an animal) • Concentration of sensory and brain structures in the ANTERIOR end of the animal (i.e., a “cephalized” animal has a head)

42. (B) Germ Layers (present in developing animal zygote; i.e., embryo) • Fundamental tissues found in embryos of ALL animals—give rise to EVERY body feature—tissues and organs. • Sponges are the ONLY animals with have NO GERM LAYERS. • Cnidarian and Ctenophore embryos have TWO GERM LAYERS. • ALL other animals have evolved THREE GERM LAYERS.

45. (C) Body Cavities (most animals have SOME type of body cavity) • A body cavity is a fluid-filled SPACE that forms between the digestive tract AND the outer wall of the body during development. • NOTE: TWO functions: • Provides a firm base against which muscles can contract. • Acts as a reservoir and transport medium for body chemicals.

48. II. Animal Diversity • There are features zoologists consider: (1) Presence/Absence of Tissue Layers, (2) Body Cavity Type, and (3) Presence/Absence of Backbone.

49. (A) Invertebrates (10 invertebrate PHYLA of Kingdom Animalia) • Highest VARIATION among the ANIMALS, including body symmetry, tissue organization, and cell specialization.

50. (B) Chordates (last phyla of Kingdom Animala, includes Vertebrates) • Characterized by PRESENCE of a notochord, dorsal nerve cord, pharyngeal pouches, and a postanal tail.