Animal Diversity Chapter 32

Common Characteristics of Animals

• Animals can move and capture prey, and are multicellular, eukaryotes, and heterotrophic, with no cell walls.
• They are thought to have evolved from flagellated protists, with choanoflagellates being the closest living relatives.

Animal Body Plan

• Radial symmetry vs. bilateral symmetry: most animals have bilateral symmetry, allowing for faster movement and formation of a head with sensory organs and a central nervous system.

Embryo Development

• Animal zygotes undergo cleavage, a series of cell divisions without growth between divisions, forming a blastula.
• The blastula is often a hollow ball of cells.

Animal Tissues

• Only a few groups, such as sponges, have no tissue.
• Most animals have germ layers that give rise to tissues and organs, including:
  • Diploblastic: ectoderm and endoderm.
  • Triploblastic: ectoderm, endoderm, and mesoderm.
• Body cavity types:
  • Coelom: a cavity surrounded by tissues derived from mesoderm.
  • Hemocoel: filled with hemolymph.
  • Some animals have no cavity at all, such as flatworms.

Protostome vs. Deuterostome Development

• In protostome development, the blastopore becomes the mouth.
• In deuterostome development, the blastopore becomes the anus.

Invertebrate Animals

• Invertebrates are animals without a backbone.
• Examples of invertebrate phyla include:
  • Porifera (sponges): simplest animals, filter feeders, no tissue.
  • Cnidarians: true tissues, gastrovascular cavity, polyps and medusa life forms, nematocysts, radial symmetry.
  • Lophotrochozoans: have a lophophore for feeding or a trochophore larval stage.
  • Flatworms (platyhelminthes): flat body form for large surface area.
  • Molluscs: muscular foot, visceral mass, mantle.
  • Annelids: segmented worms, coelom.
  • Ecdysozoans: cuticle, molting.
  • Nematodes: have hemocoel.
  • Arthropods: segmented body, exoskeleton, jointed appendages, open circulatory system.

Vertebrate Animals

• Common characteristics of chordates: bilateral, deuterostome development, mostly vertebrates with two groups of invertebrates.
• Four characteristics of chordate embryos:
  • Notochord.
  • Dorsal nerve cord.
  • Pharyngeal pouches (slits).
  • Post-anal tail.
• Examples of vertebrate groups:
  • Hagfishes and lampreys: lacking jaws.
  • Shark and ray: oil in the liver to maintain buoyancy.
  • Ray-finned and lobe-fin fish: swim bladder for buoyancy.
  • Amphibians: need water and land, metamorphosis.
  • Reptiles: scales, shelled and amniotic eggs, ectothermic.
  • Birds: endothermic, direct descendants of dinosaurs.
  • Mammals: mammary glands, hair, endothermy.

Animal Form and Function

• Tissues: groups of cells with a similar appearance and function.
• Four types of tissues:
  • Epithelial tissue: covers the outside of the body and lines organs and cavities.
  • Connective tissue: holds tissues and organs together in place.
  • Muscle tissue: responsible for movement and contractions.
  • Nervous tissue: responsible for communication and coordination.
• Functions of specific tissues:
  • Fibroblasts: secrete fiber proteins.
  • Macrophages: engulf foreign particles.