Comparing Invertebrates Chapter 29: Biology II
Evolutionary Trends • Specialized Cells, Tissues and Organs • Body Symmetry • Cephalization • Segmentation • Coelom Formation • Early Development
Feeding and Digestion • Intracellular Digestion: process by which food is digested inside cells; performed by simple animals • Extracellular Digestion: process by which food is broken down outside the cells in a digestive tract
Respiration • Respiratory organs have large SA that are in contact with the air or water • For diffusion to occur, the respiratory surfaces must be moist • Aquatic invertebrates: skin, gills • Terrestrial invertebrates: book lungs
Circulation • Most complex animals move blood through their bodies using one or more hearts and either: • Open circulatory system: system in which blood is not always contained within a network of blood vessels • Closed circulatory system: system in which blood is contained within a network of blood vessels
Excretion • Most animals have an excretory system that rids the body of metabolic wastes while controlling the amount of water in the tissues • Aquatic invertebrates: ammonia diffuses out through tiny pores in the skin • Terrestrial invertebrates: urea eliminated through urine
Response • Invertebrates show 3 trends in the evolution of the nervous system: • Centralization • Cephalization • Specialization
Movement and Support • Hydrostatic skeleton: layers of circular and longitudinal muscles, together with the water in the gastrovascular cavity, that enable movement • Exoskeleton: external skeleton; tough external covering that protects and supports the body of many invertebrates • Endoskeleton: structural support located inside the body of an animal
Reproduction • Most invertebrates reproduce sexually during at least part of their life cycle • Many invertebrates may also reproduce asexually, depending on environmental conditions
Reproduction • External Fertilization: process in which eggs are fertilized outside the female’s body • Internal Fertilization: process in which eggs are fertilized inside the female’s body