APBIO- CHPT 44 SEC B “REGULATION OF BODY TEMPERATURE”

(PRIOR KNOWLEDGE FOR GOLDFISH HOMEOSTASIS LAB)

OBJECTIVES 1B. Students will be able to list and

explain four physical processes that account for heat loss or heat gain.

2B. Students will be able to compare and contrast ectotherms and endotherms.

3- EXTRA. Students will be able to describe how goldfish breathe and the role of homeostasis.

HOMEOSTASIS (EXTRA INFORMATION) The maintenance of constant internal

conditions in an organism. It’s important because cells function best

within a certain range of conditions. Breakdowns in homeostasis can be life-

threatening. Maintained through negative feedback.

Negative feedback is a change in a system which causes a response that tends to return that system to its original state.

REGULATION OF BODY TEMPERATURE Most biochemical and physiological processes

are sensitive to changes in body temperature. Q10 effect- most enzyme-mediated reactions

increase by a factor of 2-3 for every 10 degrees Celsius temperature increases.

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

Thermoregulation- maintains body temperature so cells can function.

1B. FOUR PHYSICAL PROCESSES ACCOUNT FOR HEAT GAIN OR LOSS Conduction- direct transfer of thermal energy (heat)

between molecules of objects in direct contact with each other Water is 50-100 X more effective than air in conducting

heat Convection- transfer of heat by the movement of air or

liquid past a surface Radiation- emission of electromagnetic waves by all

objects warmer than absolute zero, including an animal’s body, the environment, and the sun.

Evaporation- removal of heat from the surface of a liquid that is losing some of its molecules as gas.

REFLECTION 1B. List and explain four physical

processes that account for heat loss or heat gain.

FIG 44.3- HEAT EXCHANGE BETWEEN AN ORGANISM AND ITS ENVIRONMENT

2B. ECTOTHERMS HAVE BODY TEMPERATURES CLOSE TO ENVIRONMENTAL TEMPERATURE; ENDOTHERMS CAN USE METABOLIC HEAT TO KEEP BODY TEMPERATURE WARMER THAN THEIR SURROUNDINGS.

Ectotherm- low metabolic rate, body temperatures determined by surrounding environment. i.e., invertebrates, fishes, amphibians

Endotherms- high metabolic rate, body temperature warmer than environment. i.e., mammals (humans), birds, some

fishes a few reptiles, insects

ENDOTHERMYADVANTAGES DISADVANTAGES

• Stable body temperature regardless of environment

• High levels of cellular respiration

• Increased endurance during vigorous activity

• Mechanism for cooling off body temperatures

• Ability to withstand heat loads

• Favored in terrestrial environments

• Energetically expensive• Increased consumption

of food required

4B. MOST ANIMALS ARE ECTOTHERMIC, BUT ENDOTHERMY IS WIDESPREAD

Mammals & Birds (endotherms) Maintain body temperatures within a

narrow range Must counteract constant heat loss Heat production increases moving or

shivering Metabolic heat production, insulation, and

vascular adjustments assist in thermoregulation

4B. MOST ANIMALS ARE ECTOTHERMIC, BUT ENDOTHERMY IS WIDESPREAD Fishes (ectotherm)

Conformers Internal temperatures within 1-2 degree

Celsius of the surrounding water temperature

Most metabolic heat produced is lost to the environment when blood passes through the gills.

REFLECTION 2B. Compare and contrast ectotherms

and endotherms.

GOLDFISH ANATOMY

GOLDFISH, CARASSIUS AURATUS Maximum length 23 inches (59 cm) & maximum weight

9.9 lbs (4.5 kg). The oldest recorded goldfish lived to 49 years, but most

household goldfish generally live only six to eight years, due to being kept in bowls.

How do goldfish breathe? Fish use gills to extract oxygen from water. Process starts with the mouth, which is how the fish takes in

water. When a fish opens and closes its mouth, it‘s actually pumping water back through the gills and is thus breathing.

Have an effective pumping system involving mouth and outer cover of the gills (operculum).

When mouth opens, operculum closes, drawing water into mouth. When the mouth closes, operculum opens, fresh water crosses gills.

GOLDFISH Once through mouth, water continues past gill

rakers (filter system for the gills, straining water to sift out floating food particles or foreign material).

Water then continues through gill arches and passes over gills.

Each gill has two rows of thin membrane gill filaments which stick out into water flow.

Each gill filament composed of many rows of lamellae (thin, disc-like membranes with capillary network).

Water flows across lamellae. Oxygen and carbon dioxide are exchanged directly across the capillary membrane.

Fish can extract up to 85% of available oxygen out of the water.

Since water contains only 2-5% of the available oxygen that air at sea level does, such a high efficiency is extremely important.

GOLDFISH ANALYSIS 1. What happens to the rate at which gills

move when the temperature changes? Why? Gills move faster at higher temperatures. The fish is taking in more water and thus more

oxygen. 2. How do gills help fish maintain

homeostasis? The rate at which the gills move affects the

amount of oxygen that enters the blood. In this way, the gills help to maintain the proper balance of gases in the fish’s blood.

REFLECTION 3- EXTRA. Describe how goldfish

breathe and the role of homeostasis.