AP Bio Chapter 40

What is a homeotherm?

A homeotherm is an animal that maintains a relatively stable internal temperature.

What effect do hormones have?

A hormone may have an effect in a single location or in sites throughout the body.

What does a smaller animal demand more of?

A smaller animal's higher metabolic rate demands a faster rate of oxygen delivery.

How must endotherms counteract constant heat loss?

Because endotherms generally maintain their body temperatures above environmental temperatures, they must counteract constant heat loss by varying heat production.

What does homeostasis limit?

Homeostasis limits—but does not eliminate—changes in the internal environment.

How do hormones act?

Hormones are relatively slow-acting and long-lasting.

What is acclimatization ?

In birds and mammals, acclimatization often includes adjusting the amount of insulation.

What do larger animals have more of?

Larger animals have more body mass and therefore require more chemical energy.

What three cells can receive nerve impulses?

Only three types of cells receive nerve impulses: other neurons, muscle cells, and endocrine cells.

How can organisms be classified?

Organisms can be classified by how they obtain chemical energy.

What does the endocrine system broadcast

The endocrine system broadcasts chemical signals called hormones throughout the body.

What is the essence ofthermoregulation?

The essence of thermoregulation is maintaining rates of heat gain that equal rates of heat loss.

What does the hypothalamus contain?

The hypothalamus contains a group of nerve cells that functions as a thermostat.

How much of her energy budget does a human female use?

A 60-kg human female spends a large fraction of her energy budget for BMR and relatively little for activity and body temperature regulation.

What is a major thermoregulatory?

A major thermoregulatory adaptation in mammals and birds is insulation: hair, feathers, or fat layers.

What is a more indirect way of measuring metabolic rate?

A more indirect way to measure metabolic rate is to determine the amount of oxygen consumed or carbon dioxide produced by an animal's cellular respiration.

What deters the stimulus that triggers a response?

A receptor, or sensor, detects the stimulus and triggers a response, a physiological activity that helps return the variable to the set point.

What do acclimatization responses entail?

Acclimatization responses in ectotherms often include adjustments at the cellular level. o Cells may increase the production of certain enzymes or produce enzyme variants with different temperature optima. o Membranes change the proportions of saturated and unsaturated lipids to remain fluid at different temperatures. o Some ectotherms produce "antifreeze" compounds, or cryoprotectants, to prevent ice formation in body cells.

When does additional fluctuation occur? What does homeostasis depend on?

Additional fluctuation occurs if a variable has a normal range rather than a single set point. Homeostasis depends on feedback circuits.

What happens after energetic needs are sufficed?

After the energetic needs of staying alive are met, any remaining food molecules can be used in biosynthesis.

How do amphibians control their body temperature?

All amphibians are ectothermic organisms that control body temperature mainly by behavior— by moving to a location where solar heat is available or by seeking shade.

What does each species have with optimal temperature change

Although different species of animals are adapted to different environmental temperatures, each species has an optimal temperature range.

What do complex animals have that allows them to exchange nutrients in their environment?

Although exchange with the environment is a problem for animals whose cells are mostly internal, complex forms have distinct benefits. -sensory organs can provide detailed information about the animal's surroundings; specialized filtration systems can adjust the composition of the internal fluids that bathe animal body cells; and internal digestive organs can break down food gradually, controlling the release of stored energy.

What is a related response that happens in ectotherms?

Although only endotherms develop fever, ectotherms exhibit a related response. o The desert iguana responds to bacterial infection by seeking a warmer environment.

Why are two layered sacs and a flat body not a solution?

Although two-layered sacs and flat shapes are designs that put a large surface area in contact with the environment, these solutions do not permit much complexity in internal organization.

what does an animal as a conformer allow particular values to dO?

An animal is a conformer for a particular environmental variable if it allows its internal condition to vary as external conditions fluctuate.

What is an animal a regulator for?

An animal is a regulator for a particular environmental variable if it uses internal control mechanisms to moderate internal change while external conditions fluctuate. o Forexample,ariverotterisaregulatorfortemperature,keepingitsbodyatatemperature that is largely independent of the water in which it swims.

What does an animal maintain while regulating internal conditions?

An animal may maintain homeostasis while regulating some internal conditions and allowing others to conform to the environment.

What is poikilotherm?

An animal with a body temperature that varies with its environment is called a poikilotherm.

What is an animal's size and shape and aspect of and what does it represent?

An animal's size and shape are fundamental aspects of form that significantly affect the way an animal interacts with its environment. - animals are not concours of their body plan and formation - the body plan of an animals is a pattern of development from evolution millions of years ago

What does an animals' size have an effect on the animal?

An animal's size and shape have a direct effect on how the animal exchanges materials with its surroundings.

How do animal bodies achieve homeosttasis?

Animal bodies achieve homeostasis by maintaining a variable, such as body temperature or solute concentration, at or near a particular value or set point.

What are the two main systems for control and coordination? What happens in the endocrine system? What happens in the nervous systeM?

Animal bodies have two major systems for control and coordination: the endocrine system and the nervous system. o In the endocrine system ,signa ls released into the blood stream by endocrine cells reach all locations in the body. o In the nervous system, neurons transmit information between specific locations.

How do animals accomplish thermoregulation?

Animals accomplish thermoregulation through mechanisms that reduce heat exchange overall or mechanisms that favor heat exchange in a particular direction.

How do animals exchange heat with their external environment?

Animals exchange heat with their external environment through four physical processes: conduction, convection, radiation, and evaporation.

What kind of tissues do animals require?

Animals require coordination of tissues, organs, and organ systems

Wha are another's?

Animals that are mainly endothermic are called endotherms, while those that are mainly ectothermic are called ectotherms. o Endothermy and ectothermy are not mutually exclusive thermoregulatory strategies. o A bird is an endotherm but may warm itself in the sun on a cold morning, just as a lizard does.

What is countercurrent exchange?

Another circulatory adaptation is countercurrent exchange, the transfer of heat or solutes in adjacent fluids that flow in opposite directions.

What is another way t maximize exposure?

Another way to maximize exposure to the surrounding medium is to have a flat body. - example a parasitic tapeworm can be several meters long but because they are so thin the cells are bathed in intestinal fluid of the worm's vertebrate host

How does heat transfer between veins and artery?

Arteries and veins are near one another. As warm blood passes through the arteries, heat transfers to the colder venous blood returning from the extremities. Heat transfer occurs along the entire length of the exchanger.

How must an animals integrity of plasma membrane be arranged?

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.

What happens ad body dimensions increase?

As body dimensions increase, a thicker skeleton is required to maintain adequate strength. In addition, as bodies increase in size, the muscles required for locomotion represent an increasing fraction of the total body mass.

At what size does mobility become limited and why?

At a certain size, mobility becomes limited. o By considering the fraction of body mass in leg muscles and the effective force such muscles generate, scientists can estimate the maximum running speed for a wide range of body plans. o For instance, the dinosaur Tyrannosaurus rex, more than 6 meters tall, was unable to run fast.

How can the metabolic rate be measured?

Because nearly all the chemical energy used in cellular respiration eventually appears as heat, metabolic rate can be measured by monitoring an animal's heat loss.

Why are the communication systems adapted to different functions? What is the nervous system well suited for?

Because the two major communication systems of the body differ in signal type, transmission, speed, and duration, they are adapted to different functions. o The endocrine system is well suited for coordinating gradual changes that affect the entire body, such as growth and development, reproduction, metabolic processes, and digestion. o The nervous system is well suited for directing immediate and rapid responses to the environment, especially in controlling fast locomotion and behavior.

Why do ectotherms require less ffood?

Because their heat source is primarily the external environment rather than internal metabolism, ectotherms require much less food than endotherms of equivalent size. o Ectotherms usually tolerate larger fluctuations in their internal temperatures.

What does biosynthesis include?

Biosynthesis includes body growth and repair; synthesis of storage material such as fat; and production of reproductive structures, including gametes.

What do cells express?

Cells can express more than one receptor type. o cells in the ovaries and testes are regulated by not only sex hormones by by metabolic hormones such as insulin which controls level of glucose in blood by binding to and regulations every cell outside of the brain

How can mammals get to produce heat?

Certain mammalian hormones can cause mitochondria to increase their metabolic activity and produce heat instead of ATP. o This non shivering thermogenesis takes place throughout the body.

What do collagenous fibers provide?

Collagenous fibers provides strength with flexibility. o Collagenous fibers are made of collagen, the most abundant protein in the animal kingdom. o Collagenous fibers are nonelastic and donot tear easily when pulledlengthwise.

What are connective functions?

Connective tissue functions mainly to bind and support other tissues. Connective tissues have a sparse population of cells scattered through an extracellular matrix.

What is the coordination od activity?

Coordination of activity across the body requires communication.

Despite their great diversity what must all animals obtain?

Despite their great diversity, all animals must solve a common set of problems. o All animals must obtain oxygen nourish themeselves fight offf infection and produce offspring

What do different hormones cause?

Different hormones cause distinct effects, and only cells that have receptors for a particular hormone respond.

Where do ectothermic animals gain most of their heat?

Ectothermic animals, such as snakes and most fishes, gain most of their heat from the external environment.

Why do animals develop a fever?

In response to certain bacterial and viral infections, mammals and birds develop fever, an elevated body temperature.

What is ectothermy?

Ectothermy is an extremely effective and successful strategy in most of Earth's environments, as evidenced by the abundance and diversity of ectothermic animals.

What does elevated blood flow in the skin result from?

Elevated blood flow in the skin results from vasodilation, an increase in the diameter of superficial blood vessels near the body surface.

How can endothermic animals maintain body temperatures?

Endothermic animals can maintain stable body temperatures in the face of temperature fluctuations in the external environment. o Many endotherms—but few ectotherms—are active at below-freezing temperatures. o In a cold environment, an endotherm can generate enough heat to keep its body substantially warmer than its surroundings. o In a hot environment ,an endotherm has mechanisms to cool its body.

What do endothermic animals use to regulate heat?

Endothermic animals, such as birds and mammals, use metabolic heat to regulate their body temperature.

What are epithelia classified as?

Epithelia are classified by the number of cell layers and the shape of the cells on the free surface. o A simple epithelium has a single layer of cells, and a stratified epithelium has multiple tiers of cells. o A pseudo stratified epithelium is single-layered but appears stratified because the cells varying length.

What serves as stiimulus?

Fluctuations in the variable above or below the set point serve as the stimulus.

How may endotherms increase their heat?

For example, endotherms may increase their heat production through muscle activity such as moving or shivering.

What are three important concepts in bioengernetics?

For example, the typical annual energy "budgets" of four vertebrates reinforce three important concepts in bioenergetics. 1. A small animal has a much greater energy demand per kilogram than does a large animal of the same class. 2. An ectotherm requires much less energy per kilogram than does an endotherm of equivalent size. 3. Size and energy strategy have a great influence on how the total annual energy expenditurei s distributed among energetic needs.

What is hibernation?

Hibernation is long-term torpor that is an adaptation to winter cold and food scarcity.

What kind of feedback does homeostasis rely on?

Homeostasis in animals relies largely on negative feedback, a response that reduces or "damps" the stimulus.

What is homeostasis?

Homeostasis is a general process by which organisms maintain a "steady state" or internal balance. Through homeostasis, animals maintain a relatively constant internal environment, even when the external environment varies.

How do honeybees expand?

Honeybees expend considerable energy to keep warm during long periods of cold weather. This is the main function of the honey stored in the hive. Honeybees also cool the hive in hot weather by transporting water to it and fanning it with their wings to promote evaporation and convection.

How do honeybees maintain a constant temperature?

Honeybees use a thermoregulatory mechanism that depends on social behavior. o In cold weather, honey bees increase their heat production and huddle together to retain heat. o The honey bees maintain a relatively constant temperature by changing the density of the huddling, and moving individuals between the cooler outer edges of the cluster and the warmer center.

Why is the hypothesis for the inverse relationship wrong?

However, this hypothesis fails to explain the inverse relationship between metabolism and mass in ectotherms, which do not use metabolic heat to maintain body temperature.

What is the environmental temperature above the body temperature?

If the environmental temperature is above body temperature, evaporation is the only way to keep body temperature from rising.

What happens if the hypothalamus detect a decrease in temperatures?

If the hypothalamus detects a decrease in the temperature of the blood below the set point, it inhibits heat loss mechanisms and activates heat-saving mechanisms such as vasoconstriction of superficial vessels and erection of fur, while stimulating heat-generating mechanisms such as shivering and nonshivering thermogenesis.

What happens if the thermostat detects a rise in temperature?

If the thermostat in the brain detects a rise in the temperature of the blood above the set point, it shuts down heat retention mechanisms and promotes body cooling by vasodilation, sweating, or panting.

What are the different mechanisms in the integumentary system?

In mammals, several of these mechanisms involve the integumentary system, including the skin, hair, and nail

What does heat transfer involve?

In many birds and mammals, heat transfer involves an antiparallel arrangement of blood vessels called a countercurrent heat exchanger.

What are organs and what d they contain?

In most animals, combinations of various tissues make up functional units called organs, and groups of organs work together as organ systems. o For example, the skin is an organ of the integumentary system ,which protects against infection and helps regulate body temperature. o Organs may contain tissues that have different physiological roles. Organs such as the pancreas may belong to more than one organ system.

What is the average daily rate of BMR AND SMR?

In most terrestrial animals, the average daily rate of energy consumption is 2 to 4 times BMR (for endotherms) or SMR (for ectotherms).

What is some species and how does blood travel?

In some species, blood can either go through the heat exchanger or bypass it. o The relative amount of blood that flows through the two paths varies ,adjusting the rate of heat loss as the animal's physiological state or environment changes. o In some insects ,the counter current mechanism can be"shutdown"to allow heat to be shed during hot weather.

What does the nervous system do?

In the nervous system, nerve impulses travel to a target cell along a dedicated communication line, consisting mainly of neuron extensions called axons.

What does insulation reduce?

Insulation reduces the flow of heat between an animal and its environment and lowers the energy cost of keeping warm.

What do internal body fluids link?

Internal body fluids link exchange surfaces with body cells. o- in vertebrates interstitial fluid fills the space within cells - complex body plan has a circulatory fluid like blood - exchange between the interstitial fluid enable cells throughout the body to obtain nutrients

What are the sources of heat for thermoregulation?

Internal metabolism and the external environment are the sources of heat for thermoregulation.

What is cold blooded misconception?

It is a common misconception that ectotherms are "cold-blooded" and endotherms are "warm- blooded." - Ectotherms donot necessarily have low body temperatures. o While sitting in the sun, many ectothermic lizards have higher body temperatures than mammals.

How can animals adjust to a new range of environmental temperatures?

Many animals can adjust to a new range of environmental temperatures by a physiological response called acclimatization.

How do ectotherms maintain a constant body temperature?

Many ectotherms can maintain a constant body temperature by simple behaviors, such as hibernating or migrating to a more suitable climate

How do many endothermic insect use countercurrent exchange?

Many endothermic insects (bumblebees, honeybees, and some moths) have a countercurrent exchanger that maintains a high temperature in the thorax, where the flight muscles are located.

What is the difference between endotherms and ectotherms?

Many endotherms and ectotherms can alter the amount of blood flow between the body core and the skin.

What is daily torpor?

Many small mammals and birds exhibit a daily torpor that is adapted to their feeding patterns.

How can marine mammals live in water?

Marine mammals swim in water colder than their body core temperature, and many species spend at least part of the year in near-freezing polar seas.

What is the minimal metabolic rates?

Minimal metabolic rates power the basic functions that support life, such as cell maintenance, breathing, and heartbeat.

What are most animals like?

Most animals are more complex and are made up of compact masses of cells, producing outer surfaces that are relatively small compared to the animal's volume.

What are most fuel molecules used for?

Most fuel molecules are used to generate ATP by the catabolic processes of cellular respiration and fermentation.

What do most animals have extinsevily branched?

Most organisms have extensively folded or branched internal surfaces specialized for exchange with the environment. - humans the digestive respiratory and circulatory systems have exchange surfaces

What are multicellular animals composed of?

Multicellular animals are composed of microscopic cells, each with its own plasma membrane across which exchange must occur.

How much muscle is in the animals? What are the three types of muscle

Muscle is the most abundant tissue in most animals, and muscle contraction accounts for most of the energy-consuming cellular work in active animals. The three types of muscle tissue in the vertebrate body are skeletal muscle, cardiac muscle, and smooth muscle.

What is muscle tissue respobsible for?

Muscle tissue is responsible for body movement. All muscle cells consist of filaments containing the proteins actin and myosin.

What has natural selection fit us with?

Natural selection has fit anatomical structure to function by selecting, over many generations, the best of the available variations in a population that meets the animal's needs.

Where are nerve cells concentrated?

Nerve cells that control thermoregulation (and other aspects of homeostasis) are concentrated in a brain region called the hypothalamus.

What is nervous tissue?

Nervous tissue senses stimuli and transmits signals in the form of nerve impulses from one part of the animal to another.

What do nervous tissue include? Where is nervous tissue concentrated in many animals?

Nervous tissues also include glial cells, or glia, which nourish, insulate, and replenish neurons. In many animals, nervous tissue is concentrated in a brain, an information-processing center.

What is the rate of nervous transmission?

Nervous transmission is extremely fast and short-lived. Nerve impulses take only a fraction of a second to reach the target and last only a fraction of a second.

Where do epithelial tissues occur?

Occurring in sheets of tightly packed cells, epithelial tissue covers the outside of the body and lines organs and cavities within the body.

What is one hypothesis for the inverse relationship between metabolic rate and mass?

One hypothesis for the inverse relationship between metabolic rate and mass is that the smaller the size of an endotherm, the greater the energy cost of maintaining a stable body temperature.

What is the rate of food consumption?

Over long periods, the rate of food consumption, the energy content of food, and the chemical energy lost in waste products can be used to estimate metabolic rate.

What do physical laws govern in Biology?

Physical laws that govern strength, diffusion, movement, and heat exchange limit the range of animal forms.

What does regulating and conforming represent?

Regulating and conforming represent extremes on a continuum of how animals deal with environmental fluctuations.

How do reptile thermoregulate/

Reptiles other than birds also thermoregulate behaviorally. o When cool, they seek warm places ,orient themselves toward a heat source, and expand the body surface exposed to the heat source.

What are reticular fibers and what are they composed of ?

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

What do the laws of hydrodynamics govern?

Similarly, the laws of hydrodynamics constrain the shapes that are possible for aquatic organisms that swim very fast. o water is more dense than air and any body bump of body surface limits a swimmer

What are the two layers of skin?

Skin consists of two layers, the epidermis and the dermis, underlain by a tissue layer called the hypodermis.

What are some adaptations for evaporate cooling?

Some animals have adaptations to augment evaporative cooling. o Panting is important in birds and many mammals.

What kind of fish use countercurrent heat exchange? How

Some bony fishes, sharks, and insects also use countercurrent heat exchange. - Such fishes include large, powerful fishes such as blue fin tuna, sword fish, and great white sharks. o By keeping the main swimming muscles several degrees warmer than the surface tissues, this adaptation allows vigorous, sustained activity.

How do terrestrial animals lose water by evaporation?

Terrestrial animals lose water by evaporation across the skin and when they breathe. Water absorbs considerable heat when it evaporates; this heat is carried away from the body surface with the water vapor.

What is the amount of energy an animal uses in a unit?

The amount of energy an animal uses in a unit of time is called its metabolic rate—the sum of all the energy-requiring biochemical reactions that occur during a given time interval.

What are the function of epithelial cells?

The cells of an epithelium are closely joined, and in many epithelia, the cells are riveted together by tight junctions. The epithelium functions as a barrier protecting against mechanical injury, invasive microorganisms, and fluid loss.

What do epithelial cells also form?

The cells of epithelial tissue also form active interfaces with the environment.

What does the energy of ATP power?

The chemical energy of ATP powers cellular work, enabling cells, organs, and organ systems to perform the many functions that keep an animal alive.

What is the connective tissue?

The connective tissue that holds many tissues and organs together contains scattered cells of varying functions. o Fibroblasts secrete the protein ingredients of the extra cellular fibers. o Macrophages are amoeboid cells that roam the maze of fibers, engulfing bacteria and the debris of dead cells by phagocytosis.

What does matrix generally consist of ?

The matrix generally consists of a web of fibers embedded in a uniform foundation that may be liquid, jellylike, or solid.

What does the desert locust do to remain at the same temperature?

The desert locust must reach a certain temperature to become active, and on cold days it orients in a direction that maximizes the absorption of sunlight.

What is the flow of energy through an animal ?

The flow of energy through an animal—its bioenergetics—determines how much food it needs and is related to the animal's size, activity, and environment.

What is the functional unit of a nervous tissue?

The functional unit of nervous tissue is the neuron, or nerve cell, which includes extensions called axons that are uniquely specialized to transmit nerve impulses.

What does the layer of fur or feather depend on?

The insulating power of a layer of fur or feathers depends mostly on how much air the layer traps.

What is the basal metabolic rate?

The metabolic rate of a nongrowing endotherm at rest, with an empty stomach and experiencing no stress, is called the basal metabolic rate (BMR).

What is the standard metabolic rate?

The metabolic rate of a resting, fasting, nonstressed ectotherm is called its standard metabolic rate (SMR).

How does the nervous system convey information?

The nervous system conveys information by the pathway the signal takes. o nerve impulses travel within axons sometimes over long distance as changes in voltage? - passing signals from one neuron to another involve very short range chemical signals

When does the range of omeostasis change?

The normal range of homeostasis may change by acclimatization, a process by which an animal adjusts to changes in its external environment.

What do the properties of membranes change ?

The properties of membranes also change with temperature, becoming increasingly fluid or rigid as temperatures rise or fall.

What are the rates of exchange of nutrients proportional to?

The rates of exchange of nutrients, wastes, and gases are proportional to the membrane surface area, while the amount of material that must be exchanged is proportional to the volume. - surface to volume is a physical constraint

What are the rates of most enzyme mediated reactions?

The rates of most enzyme-mediated reactions increase by a factor of 2 or 3 for every 10°C temperature increase, until proteins start to lose activity. o For example ,the oxygen carrier hemoglobin becomes less effective at binding oxygen as temperature increases.

What is vasoconstriction?

The reverse process, vasoconstriction, reduces blood flow and heat transfer by decreasing the diameter of superficial vessels.

What are the shape of cells exposed as ?

The shape of cells on the exposed surface may be cuboidal (like dice), columnar (like bricks on end), or squamous (flat like floor tiles).

What is a consequence of convergent evolution?

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 when diverse adaptations face the environmental challenge such as resistance to water

What is the skin temperature of a marine mammal ?

The skin temperature of a marine mammal is close to water temperature. However, blubber insulation is so effective that marine mammals can maintain body core temperatures of 36-38°C without requiring more food energy than an equivalent-sized land mammal.

What is the variation in matrix structure is reflected ?

The variation in matrix structure is reflected in the six major types of connective tissue in vertebrates: loose connective tissue, cartilage, fibrous connective tissue, adipose tissue, blood, and bone.

What are the three kinds of connective tissue?

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

Is there a fixed relationship between the source of body heat and the stability of body temperature?

There is no fixed relationship between the source of body heat and the stability of body temperature.

What does thermoregulation help in?

Thermoregulation helps keep body temperature within the optimal range, enabling cells to function effectively as external temperature fluctuates.

When is thermoregulation important?

Thermoregulation is critical to survival because most biochemical and physiological processes are very sensitive to changes in body temperature.

What is thermoregulation?

Thermoregulation is the process by which animals maintain their internal temperature within a tolerable range.

When can the exchange across the plasma membrane occur?

This exchange works only if all the cells of the animal have access to a suitable aqueous environment, inside or outside the body.

What can a complex animal maintain?

Through exchange, a complex animal can maintain a stable internal environment while living in a variable external environment. o A complex body form is especially well suited to life on land, where the external environment may be variable.

How can mammals increase their metabolic heat production to 5 or 10 times?

Through shivering and nonshivering thermogenesis, mammals and birds may increase their metabolic heat production to five or ten times the minimal levels characteristic during warm weather.

What are the different tissues?

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

What do several fast swimming animals have in common and why?

Tunas, sharks, penguins, dolphins, and seals are all fast swimmers, and all have the same basic fusiform shape, tapered at both ends. - their shape minimizes the drag in water

What does positive feedback involve what is an example?

Unlike negative feedback, positive feedback involves a change in some variable that triggers mechanisms that amplify rather than reverse the change. Forexample,duringchildbirth,thepressureofthebaby'sheadagainstreceptorsnearthe opening of the mother's uterus stimulates uterine contractions.

What aspects are the internal environment is at a set point?

While some aspects of the internal environment are maintained at a set point or within a normal group, regulated change is essential to normal body functions. - For example, many animal shave a lower body temperature when asleep than when awake. o Some regulated changes are associated with a particular stage of life, such as the changes in hormone levels that occur with puberty.

What are elastic fibers that are easily stretched but also resilient?

elastic fibers are long threads of elastin that are easily stretched but also resilient . o Elastin fiber has a rubbery quality that complements then on elastic strength of collagenous fibers.

What does examining anatomy allow us to do?

examining anatomy ( Biological form) often provides clues to physiology (biological function)