Chapter 20 Unifying Concepts of Animal Structure and Function

1. Chapter 20 Unifying Concepts of Animal Structure and Function Overview: Hierarchy of Structural Organization Exchanges with the environment

2. Climbing the Walls • The function of any part of an animal results from its unique structure • Consider the gecko, a small lizard commonly found in the tropics • A gecko can walk up a wall and across ceilings • How does it do that?

3. They are arranged in rows • Each seta ends in many split ends called spatulae, which have rounded tips • The explanation relates to hairs, called setae, on the gecko’s toes

4. The ability to “stick” to surfaces results from attractions between molecules on the spatulae and molecules on the surface • The structure of the gecko’s feet leads to a unique function

5. THE HIERARCHY OF STRUCTURAL ORGANIZATION IN AN ANIMAL Structure fits function in the animal body • The correlation between structure and function is one of biology’s most fundamental concepts

6. Animal structure has a hierarchy • Structure and function are correlated at each level in the structural hierarchy of an animal’s body

7. Life is characterized by hierarchical levels of organization • In animals • Individual cells are grouped into tissues • Tissues combine to form organs • Organs are organized into organ systems • Organ systems make up the entire organism

8. Anatomy is the study of the structure of an organism • Physiology is the study of the function of an organism’s structural equipment • Biologists distinguish anatomy from physiology

9. Tissues • In most multicellular animals, cells are grouped into tissues • A tissue is a collection of many structurally similar cells that act cooperatively to perform a specific function

10. Tissues are groups of cells with a common structure and function • A tissue is a cooperative of many similar cells that perform a specific function • Animals have four major categories of tissue • Epithelial tissue • Connective tissue • Muscle tissue • Nervous tissue

11. Epithelial tissue covers and lines the body and its parts • Epithelial tissue occurs as sheets of closely packed cells • It covers surfaces and lines internal organs and cavities • Examples: epidermis, stomach lining • The structure of each type of epithelium fits its function

12. Connective tissue binds and supports other tissues • Connective tissue is characterized by sparse cells • The cells manufacture and secrete an extracellular matrix • The matrix is composed of fibers embedded in a liquid, solid, or gel

13. Connective tissues have a sparse population of cells scattered through an extracellular matrix • The matrix consists of a web of protein fibers embedded in a uniform foundation • The structure of connective tissue correlates with its function • It binds and supports other tissues

14. Loose connective tissue is the most widespread connective tissue • It binds epithelia to underlying tissues • It holds organs in place • Adipose tissue stores fat • It stockpiles energy • It pads and insulates the body

15. Red and white blood cells are suspended in plasma • Blood is a connective tissue with a matrix of liquid • Fibrous connective tissue has a dense matrix of collagen • It forms tendons and ligaments

16. It functions as a flexible, boneless skeleton • It forms the shock absorbing pads that cushion the vertebrae of the spinal column • The matrix of cartilage is strong but rubbery • Bone is a rigid connective tissue with a matrix of rubbery fibers hardened with deposits of calcium

17. Muscle Tissue • Muscle tissue consists of bundles of long, thin, cylindrical cells called muscle fibers • Each cell has specialized proteins that contract when the cell is stimulated by a nerve

18. Skeletal muscle is responsible for voluntary body movements • Cardiac muscle pumps blood • Smooth muscle moves the walls of internal organs such as the stomach

19. It is responsible for voluntary movements • The contractile apparatus forms a banded pattern in each cell or fiber • It is said to be striated, or striped • Skeletal muscle is attached to bones by tendons • Cardiac muscle is found only in heart tissue • Its contraction accounts for the heartbeat • Cardiac muscle cells are branched and joined to one another

20. It is found in the walls of various organs • It is involuntary • Smooth muscle is named for its lack of obvious striations

21. Nervous Tissue • Nervous tissues makes communication of sensory information possible • Sensory input is received and processed • Motor output is then relayed to make body parts respond • Nervous tissue is found in the brain and spinal cord • The basic unit of nervous tissue is the neuron, or nerve cell • Neurons can transmit electrical signals rapidly over long distances

22. Nervous tissue forms a communication network • The branching neurons of nervous tissue transmit nerve signals that help control body activities

23. Organs and Organ Systems • The next level in the structural hierarchy after tissue is the organ • An organ consists of two or more tissues packaged into one working unit that performs a specific function • Examples: heart, liver, stomach, brain, and lungs

24. The body is a cooperative of organ systems • The level of organization higher than an organ is an organ system • Each organ system has one or more functions • The organs of humans and most other animals are organized into organ systems • Organ systems are teams of organs that work together to perform a vital bodily function

25. The respiratory system gathers oxygen • The digestive system gathers food

26. The immune system protects the body from infection and cancer • The circulatory system, aided by the lymphatic system, transports the food and oxygen

27. The excretory system disposes of certain wastes

28. The endocrine and nervous systems control and coordinate body functions

29. The integumentary system covers and protects the body • The skeletal system supports and protects the body

30. The muscular system enables movement

31. The reproductive system perpetuates the species

32. Connection: New imaging technology reveals the inner body • New technologies enable us to see body organs without surgery • Computed tomography (CT)

33. Magnetic resonance imaging (MRI) • Positron-emission tomography (PET)

34. EXCHANGES WITH THE EXTERNAL ENVIRONMENT • Every organism is an open system • This means that organisms exchange chemicals and energy with their surroundings • Organisms must do this to survive

35. Animals are not closed systems • An animal must exchange materials and heat with its environment • This exchange must extend to the cellular level

36. Body Size and Shape • An animal’s size and shape affect how it exchanges energy and materials with its surroundings • All living cells must be bathed in water so that exchange of materials may occur (e.g. hydra)

37. Hydras can exchange materials with the environment though direct diffusion • Small animals with simple body construction have enough surface to meet their cells’ needs

38. The entire surface area of an amoeba is in contact with the environment • Exchange with the environment is easy for single-celled organisms

39. Every living cell must be bathed in fluid • Every cell must have access to essential nutrients from the outside environment • Complex animals have extensively folded or branched internal surfaces • These maximize surface area for exchange with the environment • Animals with complex body forms face the same basic problem

40. Larger, complex animals have specialized internal structures that increase surface area

41. The epithelium of the lungs has a very large total surface area for this purpose • Lungs exchange oxygen and carbon dioxide with the air

42. Animals regulate their internal environment • In response to changes in external conditions, animals regulate their internal environment • They must do this to achieve homeostasis, an internal steady state

43. Homeostasis • Homeostasis is the body’s tendency to maintain relatively constant conditions in the internal environment even when the external environment changes

44. Negative and Positive Feedback • Most mechanisms of homeostasis depend on a common principle called negative feedback • The results of some process inhibit that very process

45. Negative feedback mechanisms keep fluctuations in internal conditions within the narrow range compatible with life

46. The results of a process intensify that same process • Example: uterine contractions during childbirth • Less common is positive feedback