Notes on Chapter 14.1 What is an Animal?

Multicellular Makeup Made of eukaryotic cells Lack cell walls; only surrounded by cell membranes Multicellular – made of many cells that work together

Organization in Animals Specific cells specialize to perform specific functions Same cells that work together form tissues Tissues that work together to perform a specific function form organs A group of organs that work together to perform a specific function make up an organ system

Body Plans Symmetry Asymmetrical – body not organized around a center Ex. Sponge Radial – body is organized around a center, like spokes on a wheel Ex. Starfish Bilateral – two sides of body mirror each other Ex. Tortoise Cephalization – central head region with sense organs concentrated Coelom – body cavity that surrounds and protects many organs

Getting Energy Animals cannot make own food – consume other organisms (consumer/ heterotroph) Many different types of food eaten by animals

Reproduction Some animals may reproduce asexually Ex. Budding in hydras – part of an organism develops into a new organism Ex. Fragmentation in sea stars – parts of an organism break off and develop into new individuals Most animals reproduce sexually – sperm + egg, fertilization

Development Fertilized egg divides into many cells to form an embryo As multicellular organism develops, cells become specialized during differentiation – process by which cells that will perform different functions develop different structures

Movement Nearly all animals move to search for food, shelter, and/or mates Some only move during larval stage (ex. Sponge larva) Muscle cells contract and relax to move organisms

Maintaining Body Temperature Endotherms – maintain body temperatures using energy released through chemical reactions Ex. Birds, mammals Ectotherms – rely on environment to maintain body temperature; may have developed behaviors to control tems. Ex. lizards