Chapter 40

biological form of an animal

__ favors, over many generations, the variations appearing in a population that best meet the animal's needs. The solutions to the challenges of survival vary among enviornments and species, but frequently result in a close match of __ meets __

because __ and __ are correlated, examiniing __ often provides clues to __- biological function.

An animal's size and shape are fundamental aspects of form that significantly affect the way an animal intereacts with its environment. Although we refer to size and shape as elements of a "__" and "__", this does not imply a process of conscious invention. The __ of an animal is teh result of a pattern of development programmed by the __, itself the product of millions of years of evolution.

__ that govern strength, diffusion, movement, and heat exchange limit the range of animal forms.
e.g. water
-- __ acts to shape us in a way that will benefit us in our environment.

__ also influence animal body plans with regard to maximum size. As body dimensions increase, thincker skeletons are required to maintain adequate strength. THe limitation affects internal skeletons, like insects or arthropods. In addition, as bodies increase in size, the muscles required for locomotion must represent an ever-larger fraction of the total body mass.

Animals need to exchange materials with their environment and this need imposes limitations on their body plans (as it does for all other multicellular organisms). __ occurs as substances dissolved in an aqueous medium move across the plasma membrane of each cell. The rates of exchange for nutrients, waste products, adn gases are proportiional to membrane __. In contrast, the amount of material that must be exchanged to sustain life is proportional to volume.

True or False:
The opportunity for exchange is strongly influenced by cell number. An animal composed of many cells, each with its own plasma membrane across which exchanege must occur. A multicellular organization works only if every cell has access to a suitable aqueous environment, either inside or outside of the animal's body.
True False

many animals with a simple internal organization have __ that enable direct exchange between the external environment and nearly all cells. Another common design that maximizes exposure to the surrounding medium is a flat body shape.

Most animals have a much more complex internal organization than that of a hydra or a tapeworm. Composed of compact masses of cells, these animals have outer surfaces that are relatively small compared with their volumes. As cell number increases, the ratio of the outer __ of the animla to its total __ steadily decreases.

Extensively branched or folded surfaces are the evolutionary adaptation that enables sufficient exchange with the environment. In almost all cases, these surfaces lie within the body, protecting delicate exchange tissues from __ or __ and allowing for streamlined body contours. In humnas, the __, __, and __ systems rely on exchange surfaces within the body that in each system have a total area more than 25 times that of the skin.

Internal body fluids link exchange surfaces to body cells. In all animals, the spaces between cells are filled with fluid, often called __ (Latin for "stand between"). Complex body plans also include a circulatory fluid, like blood. Exchange between the __ and __ enables cells throughout the body to obtain nutrients and get rid of wastes.

TRUE OR FALSE:
despite the greater challenges of exchange with the enviornment, complex body plans have distnict benefits over simple ones.
e.g.- external skeleton; sensory organs
True False

Cells form an animal's body thorugh their __ (arise through successive levels of structural and functional organization.) Cells are organized into __, groups of cells of similar appearance and a common function, which are then organized into functional units called __,w hich work together to provide an additional level of organization and coordination and make up an __.

__ oftn contain __ with distinct physiological roles. Sometimes, the roles are different enough that we consider the organ to belong to more than one __.

A view of the hierarchy fromt eh __ makes clear the multilayered basis of specialization.
e.g.: digestive system

TRUE OR FALSE:
The specialization characteristic of complex body plans is based on varied combos of a limited set of cells and tissue tiypes.
e.g.: lungs and blood vessels have distinct functions but are lined by tissues that are of teh same basic type and therefore share many properties.
True False

Animal tissues fall into four major categories: __, __, __, __

Occurring as sheelts of cells, __ covers the outside of the body and lines organs and cavities within the body. The close packing of __, often involving tight junctions, enables __ to function as a barrier against mechanical injury, pathogens, and fluid loss.

The ells of an __ , or __, also form active interfaces with the environment.

Epithelial cell shpae may be __ (like dice), __ (like bricks standing on end), or __ (like floor tiles). In addition, cells may be arranged in a __ (single cell layer), a __ (multiple tiers of cells), or a __ (a single layer of cells varying in height). Differnet cell shapes and arrangements correlate with distinct functions.

The most common functions of __ are to bind and support other tissues in the body. __ consists of a sparse population of cells scattered through an ECM. The matrix generally consists of a web of fibers embedded in a uniform foundation that may be liquid, jellylike, or solid. This variation in matrix structure is reflected in the six major types of this tissue in vertebrate: __, __, __, __, __, __.

Connective tissue fibers, which are made of protein, are of three kinds: __, __, and __. __ provide strength combined with flexibility. They are made of _-, probably the most abundant protein int eh animal kingdom. __ are nonelastic and do not tear easily when pulled lengthwise.

__ are easily stretched but are also resilient, snapping back to their origninal length when tension is released. Shaped as long threads, __ are made of a protein called __. __ are very thin and branched. Composed of collagen and continouous with __, tehy form a tightly woven fabric that joins connective tissue to adjacent tissues.

The connective tissue that holds many tissues and organs together and in place contains scattered cells of varying function. Of these cells, two types predominante: __ and __.

__ secrete the protein ingredients of the extracellular fibers

__ are cell sthat roa the maze of fibers, engulfing both foreign particles and the debris of dead cells by phagocytosis.

The tissue responsible for nearly all types of body movement is __. All __ cells consists of filaments containing the proteins __ and __, whcih together enable muscles to contract. __ is the most abundant tissue in many animals and muscle activity accounts for much of the energy-consuming cellular work in an active animal.
o WHat are the three types of this tissue?

THe function of __ is to sense stimuli and transmit signals in the form of nerve impulses from one part of the animal to another. __ contains __, or nerve cells, which have extensions called __ that are uniquely specialized to transmit nerve impulses. It also includes different forms of __, or __, which help norurish, insulate, and replenish neurons. In many animals, a concentration of __ forms a brain, an information-processing center. Neurons have a critical role in managing many of the anima's physiological functions.

An animal's __, __ and __ must act in conjunction with one another.

Coordinating activity across an anima's body in this way requires __.
o What are the two major systems for control and coordination?

Int eh __, signaling moleucles released into the bloodstream by _ cells reach all locations in the body. In the __, neurons transmit info between specific locatins.

The signaling molecules broadcast throughout th ebody by the endocrine system are called __. Different __ cause distinct effects, and only cells that have receptors for a particular hormone respond. Depending on which cells have receptors for that _he __ may have an effect in just a single location or in sites throughout the body. Cells, in turn, can express more than one receptor type. Thus, cells in teh ovaries and testes are regulated not only by sex __ but also by metabolic __. Such __ include __ which controls the level of glucose in the blood by binding to and regulating virtually every cell outside of the brain.

__ are relatively slow acting. However, they are long-lasting, because they remain in the bloodstream and target tissue for seconds, minutes or even hours.

In the __, a signal is not broadcast throughout the entire body. Instead, each signal, called a __, travels to a target cell along a dedicated communication line, consisting mainly of the neuron extensions called __. Four types of cells receive nerve impulses: other __, __, __ and __. Unlike the __, the __ conveys info by the pathway the signal takes.

Signaling in the __ usually involves more than one type of signal. Nerve impulses travel within __, sometimes over long distances, as changes in __. But in many cases, passing signals from one __ to another involves very short-range chemical signals. Overall, transmissin is extremely fast; nerve impulses take only a fraction of a second to reach the target and last only a fraction of a second.

because the two major communication systems of the body differ in __, __, __, and __, they are adapted to different functions. The __ is well suited for coordinating gradual changes that affect the entire body, such as growth and development, reproduction, metabolic proceses, and digestion. The __ is well suited for directing immediate and rapid responses to the environment, especially in controlling fast locomotion and behavior. Both systems contibute to maintaining a stable internal environment.