1、Chapter 20 Unifying Concepts of Animal Structure and Function,Overview: Hierarchy of Structural Organization Exchanges with the environment,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 w
2、all and across ceilings How does it do that?,Climbing the Walls,The explanation relates to hairs, called setae, on the geckos toes,They are arranged in rows Each seta ends in many split ends called spatulae, which have rounded tips,The ability to “stick” to surfaces results from attractions between
3、molecules on the spatulae and molecules on the surface,The structure of the geckos feet leads to a unique function,The correlation between structure and function is one of biologys most fundamental concepts,Structure fits function in the animal body,THE HIERARCHY OF STRUCTURAL ORGANIZATION IN AN ANI
4、MAL,Structure and function are correlated at each level in the structural hierarchy of an animals body,Animal structure has a hierarchy,Life is characterized by hierarchical levels of organization,In animals Individual cells are grouped into tissues Tissues combine to form organs Organs are organize
5、d into organ systems Organ systems make up the entire organism,Biologists distinguish anatomy from physiology,Anatomy is the study of the structure of an organism Physiology is the study of the function of an organisms structural equipment,In most multicellular animals, cells are grouped into tissue
6、s,Tissues,A tissue is a collection of many structurally similar cells that act cooperatively to perform a specific 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
7、Nervous tissue,Tissues are groups of cells with a common structure and function,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,Epitheli
8、al tissue covers and lines the body and its parts,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,Connective tissue binds and supports other tissues,Connective tissues ha
9、ve 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,Loose connective tissue is the most widespread
10、 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,Blood is a connective tissue with a matrix of liquid,Red and white blood cells are suspended in plasma,Fibrous connective tissue has a de
11、nse matrix of collagen,It forms tendons and ligaments,The matrix of cartilage is strong but rubbery,It functions as a flexible, boneless skeleton It forms the shock absorbing pads that cushion the vertebrae of the spinal column,Bone is a rigid connective tissue with a matrix of rubbery fibers harden
12、ed with deposits of calcium,Muscle tissue consists of bundles of long, thin, cylindrical cells called muscle fibers,Muscle Tissue,Each cell has specialized proteins that contract when the cell is stimulated by a nerve,Skeletal muscle is responsible for voluntary body movements Cardiac muscle pumps b
13、lood Smooth muscle moves the walls of internal organs such as the stomach,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,Its contraction accounts fo
14、r the heartbeat Cardiac muscle cells are branched and joined to one another,Cardiac muscle is found only in heart tissue,Smooth muscle is named for its lack of obvious striations,It is found in the walls of various organs It is involuntary,Nervous tissues makes communication of sensory information p
15、ossible,Nervous Tissue,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 distance
16、s,The branching neurons of nervous tissue transmit nerve signals that help control body activities,Nervous tissue forms a communication network,The next level in the structural hierarchy after tissue is the organ,Organs and Organ Systems,An organ consists of two or more tissues packaged into one wor
17、king unit that performs a specific function Examples: heart, liver, stomach, brain, and lungs,The level of organization higher than an organ is an organ system Each organ system has one or more functions,The body is a cooperative of organ systems,The organs of humans and most other animals are organ
18、ized into organ systems,Organ systems are teams of organs that work together to perform a vital bodily function,The digestive system gathers food,The respiratory system gathers oxygen,The circulatory system, aided by the lymphatic system, transports the food and oxygen,The immune system protects the
19、 body from infection and cancer,The excretory system disposes of certain wastes,The endocrine and nervous systems control and coordinate body functions,The integumentary system covers and protects the body,The skeletal system supports and protects the body,The muscular system enables movement,The re
20、productive system perpetuates the species,New technologies enable us to see body organs without surgery Computed tomography (CT),Connection: New imaging technology reveals the inner body,Magnetic resonance imaging (MRI),Positron-emission tomography (PET),Every organism is an open system,EXCHANGES WI
21、TH THE EXTERNAL ENVIRONMENT,This means that organisms exchange chemicals and energy with their surroundings Organisms must do this to survive,Animals are not closed systems An animal must exchange materials and heat with its environment This exchange must extend to the cellular level,An animals size
22、 and shape affect how it exchanges energy and materials with its surroundings,Body Size and Shape,All living cells must be bathed in water so that exchange of materials may occur (e.g. hydra),Small animals with simple body construction have enough surface to meet their cells needs,Hydras can exchang
23、e materials with the environment though direct diffusion,Exchange with the environment is easy for single-celled organisms,The entire surface area of an amoeba is in contact with the environment,Animals with complex body forms face the same basic problem,Every living cell must be bathed in fluid Eve
24、ry 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,Larger, complex animals have specialized internal structures that increase surface area,Lun
25、gs exchange oxygen and carbon dioxide with the air,The epithelium of the lungs has a very large total surface area for this purpose,In response to changes in external conditions, animals regulate their internal environment They must do this to achieve homeostasis, an internal steady state,Animals re
26、gulate their internal environment,Homeostasis is the bodys tendency to maintain relatively constant conditions in the internal environment even when the external environment changes,Homeostasis,Most mechanisms of homeostasis depend on a common principle called negative feedback,Negative and Positive
27、 Feedback,The results of some process inhibit that very process,Negative feedback mechanisms keep fluctuations in internal conditions within the narrow range compatible with life,Less common is positive feedback,The results of a process intensify that same process Example: uterine contractions during childbirth,
