1. Chapter 2

2. All animals are in the Kingdom Animalia. Some have fur, others have scales or feathers. Some fly, while others walk or swim. Animals are grouped by the functions and structure of their bodies: – Vertebrate – Invertebrate Animals fall into several classes: – Birds (Aves) – Fish (Osteichthyes) – Mammals (Mammalia) Chapter 2 Introduction to Livestock and Companion Animals2

3. The structural basis of animals begins with cells. Cell division is the process of a cell splitting into two cells. Cell specialization is the difference in cells that allows them to perform unique activities. Chapter 2 Introduction to Livestock and Companion Animals3  Groups of cells form tissues. A tissue is a cluster of cells that are alike in structure and activity.  An organ is a group of tissues with a similar function.  An organ system is a group of organs working together to carry out a specific activity.

4. Animals have several systems that make their living condition possible. The physiology of these organ systems involves essential functions: The muscular system acquires materials and energy. The skeletal system provides the framework for the body. The digestive system breaks food into smaller parts that are used by the body. The respiratory system governs gas exchange. Chapter 2 Introduction to Livestock and Companion Animals4

5. Nutrients, oxygen, and metabolic wastes are moved by the circulatory system. The excretory system rids the body of waste. The lymphatic system protects the body from disease. The nervous system coordinates body activities. The integumentary system, or skin, protects internal body tissues from outside dangers. The reproductive system produces offspring. Chapter 2 Introduction to Livestock and Companion Animals5

6. The Kingdom Animalia includes all agricultural animals. Organisms in the Kingdom Animalia are made of cells, can move about on their own, and get their food from other sources. Animals carry out life processes. When these processes stop, the animal is no longer in the living condition. A knowledge of anatomy and physiology helps animal producers understand their animals. Chapter 2 Introduction to Livestock and Companion Animals6