Animal Diversity Chapter 32

Study Notes

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.

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.

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.

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.

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.

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.