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Chapter 40 Basic Principles of Animal Form and Function

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Aaron Torres

on 2 April 2014

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Transcript of Chapter 40 Basic Principles of Animal Form and Function

Chapter 40 Basic Principles of Animal Form and Function
Overview: Diverse Forms, Common Challenges
Animals inhabit almost every part of the biosphere.
Despite their great diversity, all animals must solve a common set of problems.
All animals must obtain oxygen, nourish themselves, excrete wastes, and move.

Anatomy is the study of the structure of an organism.
Physiology is the study of the functions an organism performs.
Natural selection can fit structure to function by selecting, over many generations, the best of the available variations in a population.

bioenergetics—how organisms obtain, process, and use energy resources—
Physical laws and the environment constrain animal size and shape
An animal’s size and shape, features often called “body plans” or “designs,” are fundamental aspects of form and function that significantly affect the way an animal interacts with its environment.

Physical requirements constrain what natural selection can “invent.”

Tunas, sharks, penguins, dolphins, seals, and whales are all fast swimmers.
All have the same basic uniform shape, tapered at both ends.
This shape minimizes drag in water, which is about a thousand times denser than air.

The similar forms of speedy fishes, birds, and marine mammals are a consequence of convergent evolution in the face of the universal laws of hydrodynamics.

Convergence occurs because natural selection shapes similar adaptations when diverse organisms face the same environmental challenge, such as the resistance of water to fast travel.

Body size and shape affect interactions with the environment.

Many Animals regulate their internal environment within relatively narrow limits
*Interstitial fluid - The internal environment of vertebrates
~ Exchanges nutrients and wastes with blood contained in capillaries
*Homeostasis- A steady state of internal balance
~ Homeostasis is NOT a constant state of stability, but a dynamic one

Regulating and Conforming

* Regulating animals maintain stability by using internal mechanisms to moderate responses to external fluctuations.
* Conformers are animals that allow their internal conditions to vary with external changes.
* No animal is rigidly regulator or conformer
~ Animals are able to maintain homeostasis by regulating some conditions and allowing others to fluctuate

Regulator: Large mouth bass
Conformer: Spider Crab

An animal’s size and shape have a direct effect on how the animal exchanges energy and materials with its surroundings.
As a requirement for maintaining the fluid integrity of the plasma membrane of its cells, an animal’s body must be arranged so that all of its living cells are bathed in an aqueous medium.
Exchange with the environment occurs as dissolved substances diffuse and are transported across the plasma membranes between the cells and their aqueous surroundings.

For example, a single-celled protists living in water has a sufficient surface area of plasma membrane to service its entire volume of cytoplasm.

Surface-to-volume ratio is one of the physical constraints on the size of single-celled protists.

Multicellular animals are composed of microscopic cells, each with its own plasma membrane that acts as a loading and unloading platform for a modest volume of cytoplasm.
This only works if all the cells of the animal have access to a suitable aqueous environment.

For example, a hydra, built as a sac, has a body wall only two cell layers thick.
Because its gastrovascular cavity opens to the exterior, both outer and inner layers of cells are bathed in water.
Ectotherms and Endotherms
* Ectotherms: Gain most of their heat from the environment
~ Fish, amphibians, lizards, snakes
*Endotherms: Use metabolic heat to regulate their body temperature
~ Mammals,birds, insects
* Being endothermic allows for vast amounts of heat to be generated for vigorous activities. However, endotherms use much more energy maintaining a stable internal temperature.
* These terms should not be related to cold or warm-blooded animals because these terms are misleading.
* Ectothermy and endothermy are not mutually exclusive

Mechanisms of Homeostasis
* The three parts of a homeostatic control center are : The receptor, the control center, and the effector
~ Receptors: Detect a change, Control Center: Processes information from the receptor
Effector: Directs an appropriate response
* Negative Feedback: Prohibits further change in the same direction
* Positive Feedback: Amplifies change in the same direction

By: Ralph Aime, Gabrielle Chin, Kerrol Hermit, Breanna Higgins, Aaron Torres
Size and Shape
Which is which??
Animal form and function are correlated at all levels of organization
Life is characterized by hierarchical levels of organization, each with emergent properties.

Tissues are groups of cells with a common structure and function.
Different types of tissues have different structures that are suited to their functions.

The term tissue is from a Latin word meaning “weave.”

Tissues are classified into four main categories: epithelial tissue, connective tissue, nervous tissue, and muscle tissue.

Types of Tissues
Epithelial tissue covers the outside of the body and lines organs and cavities within the body.

The epithelium functions as a barrier protecting against mechanical injury, invasive microorganisms, and fluid loss.
Connective tissue functions mainly to bind and support other tissues.

There are three kinds of connective tissue fibers, which are all proteins: collagenous fibers, elastic fibers, and reticular fibers.

Collagenous fibers are made of collagen, the most abundant protein in the animal kingdom.

Collagenous fibers are nonelastic and do not tear easily when pulled lengthwise.

Elastic fibers are long threads of elastin.
Elastin fiber provides a rubbery quality that complements the nonelastic strength of collagenous fibers.

Reticular fibers are very thin and branched.
Composed of collagen and continuous with collagenous fibers, they form a tightly woven fabric that joins connective tissue to adjacent tissues.

The major types of connective tissues in vertebrates are loose connective tissue, adipose tissue, fibrous connective tissue, cartilage, bone, and blood.
Cartilage has an abundance of collagenous fibers embedded in a rubbery matrix made of a substance called chondroitin sulfate, a protein-carbohydrate complex.
Animals use the chemical energy in food to sustain form and function
All organisms require chemical energy for growth, physiological processes, maintenance and repair, regulation, and reproduction.

The flow of energy through an animal—its bioenergetics—ultimately limits the animal’s behavior, growth, and reproduction and determines how much food it needs.
Studying an animal’s bioenergetics tells us a great deal about the animal’s adaptations.

There are two basic bioenergetic “strategies” used by animals.
Endothermy is a high-energy strategy that permits intense, long-duration activity of a wide range of environmental temperatures.

The ectothermic strategy requires much less energy than is needed by endotherms, because of the energy cost of heating (or cooling) an endothermic body.

However, ectotherms are generally incapable of intense activity over long periods.
In general, endotherms have higher metabolic rates than ectotherms.
Body size influences metabolic rate.

Metabolic Rate
Every animal has a range of metabolic rates.
Minimal rates power the basic functions that support life, such as cell maintenance, breathing, and heartbeat.
In ectotherms, body temperature changes with temperature of the surroundings, and so does metabolic rate.
Therefore, the minimal metabolic rate of an ectotherm must be determined at a specific temperature.
Different species of animals use the energy and materials in food in different ways, depending on their environment, behavior, size, and basic energy strategy of endothermy or ectothermy.

A physiological state in which activity is low and metabolism decreases

An adaptation that enables animals to save energy while avoiding difficult and dangerous conditions


long-term torpor that is An adaptation to winter cold and food scarcity during which the animal’s body temperature declines

Body temperature declines
Periodic arousals may for body functions that require a high temperature

Estivation, or summer torpor

Slow metabolism and inactivity

Enables animals to survive long periods of high temperatures and scarce water supplies

Daily torpor

Is exhibited by many small mammals and birds and seems to be adapted to their feeding patterns

Nocturnally feeding animals enter torpor during the daylight hours.
Torpor and Energy Conservation
A major thermoregulatory adaptation in mammals and birds is insulation: hair, feathers, or fat layers.
Insulation reduces the flow of heat between an animal and its environment and lowers the energy cost of keeping warm.
In mammals, the insulating material is associated with the integumentary system, the outer covering of the body.
Skin is a key organ of the integumentary system.
Marine mammals have a very thick layer of insulating blubber just under their skin.
Vasodilation is triggered by nerve signals that relax the muscles of the vessel walls.
In endotherms, vasodilation usually warms the skin, increasing the transfer of body heat to a cool environment.
The reverse process, vasoconstriction, reduces blood flow and heat transfer by decreasing the diameter of superficial vessels.
Another circulatory adaptation is an arrangement of blood vessels called a countercurrent heat exchanger, which reduces heat loss.
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