What are some characteristics of an animal?
Heterotrophs, Multicellular, Eukaryotes that can move
What is the needed relationship between surface area and volume in animals?
Larger in order to better exchange with the external environment
(Volume grows faster)
What is Basic Metabolic Rate? What does it measure?
Metabolic rate at rest, empty stomach, normal temperature
Measure the amount of energy (ATP) used at rest
Which has a higher metabolic rate, a rat or an elephant?
A rat would have a higher metabolic rate because it has a higher SA: V ratio
Larger animals have a lower SA: V ratio which means less gas exchange.
List Three Ways animals have adapted to increase Surface Area. Give an example for each one.
- Flattening: Gill Lamellae
- Folding: Lumen and Villi in Intestine
- Branching: Capillaries
What is Homeostasis?
the maintenance of a stable internal environment in response to environmental changes.
What factors are maintained Through Homeostasis?
Give some reason as to why?
- Temperature (enzymes)
- pH (proteins)
- Water and Electrolyte Balance
- Oxygen Levels
- Nutrient absorption
- Blood pressure
What are the three steps involved in maintaining homeostasis? What takes place in each step?
- Sensor: Detects stimuli from the internal or external environment
- Integrator: Evaluates if an action is needed in response to the change. Instructs the Effector.
- Effector: Mechanism that helps restore the desired condition back to normal.
In general, what is the goal of the three steps involved in maintaining homeostasis?
To return to the Setpoint, which is the normal value
What are the sensors and integrators when the body experiences a change in temperature?
Sensor: temperature receptors (skin, spinal cord, hypothalamus) record temperature
Integrator: Integrator: compares sensor input with a set point then instructs effectors (hypothalamus)
What are some actions, the body takes when it gets too cold? (3)
- Blood vessels near the surface constrict to lower blood flow and heat loss from the skin’s surface
- The body shivers, which generates heat in the muscles
- Chemical signals are sent to cells, which increase cellular respiration and heat production
What are some actions, the body takes when it gets too hot? (3)
- Blood vessels near the surface dilute to increase blood flow and allow more heat to escape through the skin’s surface
- Sweat glands create water on the body’s surface which evaporates and causes heat loss
- Respiratory centers stimulated to increase heat loss (panting)
What are some ways animals conduct thermoregulation? (4)
- Endotherms: Generate their own heat. Enough to warm tissues.
- Exotherms: Absorb heat from the environment
- Homeotherms: Maintain a constant body temperature
- Poikilotherms: Change body temperature in response to the environment.
What Strategies do Endotherms use?
Endotherms can warm themselves because their basal metabolic rates are extremely high
- Heat given off by a high rate of chemical reactions is enough to warm the body
- Mammals and birds retain this heat because they have elaborate insulating structures such as feathers or fur
What strategies do Ectotherms use?
Ectotherms gain heat directly from the environment and only generate a small amount of heat as a by-product of metabolism
- Most heat gain is by radiation or conduction
Compare Endotherms and Ectotherms.
- Endothermy and ectothermy are best understood as contrasting adaptive strategies
- Endotherms have higher metabolic rates and thus can be more active at all times
- But it costs a lot of energy to produce heat which is not available for other processes
- Ectotherms are able to thrive with much lower intakes of food and can use a greater proportion of their total energy intake to support reproduction
*But muscle activity and digestion slow when temperature drops, making them more vulnerable
Why do animals hibernate?
- increase insulation
- stock up on food
- find protected den
- slow down metabolic rate * reduce body temperature
- “sleep”
What are two types of Hibernators? Provide examples of each.
Facultative hibernators:
enter hibernation only when either cold-stressed, food-deprived, or both, (Ex. Bears)
Obligate hibernators:
animals that spontaneously, and annually, enter hibernation regardless of ambient temperature and access to food.
(Ex. bats, ground squirrels, and hedgehogs)
How do animals survive freezing? Why?
List 2 strategies.
If the liquid in an animal freezes, ice crystals damage cells and tissues
- Freeze avoidance: keep bodily fluids liquid below 0°C
- Freeze tolerance: keep ice formation outside of cells
How does Freeze avoidance work?
See Image
How does Freeze tolerance work?
See Image
How do Japanese bees combat agasinst wasps?
Hornets can tolerate no more than 44 °C but the bees survive at 46 °C.
So the Japanese bees crowd the hornet and vibrate vigorously to achieve a temp of 45°C.
How does Heat exchange work?
Often through blood vessels
Concurrent:
Parallel flow
Large gradients -> disappear quickly
Less effective
Countercurrent -> (minimized heat loss)
Antiparallel flow
Small gradients -> maintained
More effective
The camel is able to live in extremely hot environments. Identify anatomical and physiological adaptations of the camel to the extreme heat that help it control temperature homeostasis, as reviewed in class.
Camels have thick insulating layers of fur and fat, minimizing heat uptake by radiation or thermoconduction. To avoid overheating their blood and keeping especially the brain cool, the arteries leading to the brain are pre-cooled by a net of capillaries transporting cool blood in the opposite direction (countercurrent heat exchange). The blood flowing through the capillaries is cold because it has been cooled by passing the nasal cavity for a countercurrent heat exchange with the airways: dry, incoming air is moistened by the mucosa, and evaporation cools down the air and the tissues surrounding the airways. Upon exhaling, water is recaptured from the warm air, so that the water loss is minimized.
