BIO 461 - Exam 3 - Cold Environments PowerPoint

Question 1

Thermoregulation - 3 types of behavior

Answer 1

1. Microhabitat: the nice thing about thermoregulation (predator avoidance) is complexity. If you live in a complex environment, you can go into a microhabitat and get heat, but still be protected. Constant flat land has a higher risk of predation and the risk of how to thermoregulate. Snow is a good insulator. What is a very poor insulator and good conductor? Air. Snow has a lot of trapped air. Six inches of snow melted is an inch of water.
2. Aggregations: form large huddles (well defended). Emperor penguin temperature on the outside of the huddle is above 0 °C and inside is above 20 °C (68 °F) on a -17 °C Day. They rotate through the huddle so they do not get too hot. Many penguins reduce the surface-to-volume ratio; most of their surface is covered by something and not exposed to the environment and increase thermal inertia. Can apply to groups of animals, not just one.
3. Migration: Birds cheat. They spend the summer in the Arctic and the winter in Antarctic. Take advantage of two short growing seasons. You must be a big terrestrial animal or have the ability to fly to migrate.

Question 2

Basking: How is an animal with that much blubber able to absorb heat?

Answer 2

Vasodilate. They also stick their flipper straight up.

Question 3

Thermoregulation - Shape

What is Bergmann’s rule?

Answer 3

Bergmann’s rule: within a species, body mass increases with latitude and colder climates.

1. More cells = more metabolic heat production & greater thermal inertia.
2. Lower S:V = slower heat loss.

Question 4

Thermal inertia vs S:V ratio

Answer 4

Thermal inertia and S:V ratio work together but are two different things: thermal inertia is how much heat you have in your body (the more heat you have, the longer it will take to change temperatures), regardless of how much heat you lose. S:V ratio (regardless of how much heat you have) is the rate at which you lose it.

Question 5

What about ectotherms, dealing with Thermal inertia & S:V ratio?

Answer 5

They are not producing heat. Being bigger does not mean more heat production. Thermal inertia is bad for an ectotherm; they get cold at night and bask in the day. If you have a lot of thermal inertia, it will take you longer to heat up; longer time that lizard cannot sprint away. They want rapid heat exchange for an ectotherm. In an ectotherm, the smaller one is from the high latitudes (can heat up faster with less heat).

Question 6

Thermoregulation - Shape

What is Allen’s rule?

Why?

Answer 6

Endotherms from colder climates usually have shorter limbs & appendages than the equivalent animals from warmer climates. You will need to know this for the final exam!

Reduced surface area → reduced heat loss

Question 7

Thermoregulation – Insulation

Cariboo

Answer 7

Cariboo hairs are not solid hairs; has air filled pockets that serve as insulation (dive suit). Each hair traps air underneath and inside of itself. Their coat is extremely effective at keeping heat in. Outside could be -10 °C and their fur is 38 °C.

Blubber layer becomes thinner in the summer, even though the total mass of the animal does not change (adjustable seasonably). They also use vasoconstriction and vasodilation.

Question 8

Why might a Cariboo have to adjust its temperature acutely?

Answer 8

A Cariboo standing there then sprinting away from wolves is going to generate a lot of heat quickly. They can dilate the vessels and bring blood to the surface to release the heat.

They have a thin coat on the leg and abdomen. It is a risk of heat loss. They need an area where you are mainly relying on fat (not a good insulator) to release heat when exerting a lot of energy. Every fluffy animal is going to have an area where they are thinner to release heat when needed.

Question 9

How at rest is the Cariboo not losing heat; when it is running it is losing heat?

Answer 9

Countercurrent heat exchange. When they run, they can bypass the countercurrent heat exchange; two returning veins that go right through the plexus, adjacent to the artery to gain heat, or an alternate vein that goes around the artery that does not heat up on the way in, does not take the heat from the arteries. You need warm blood flow and poor insulation to give off excess heat.
You can have long, skinny legs and not worry about Allen’s rule because functionally, in terms of where their heat is being kept, it is in the blood.

Question 10

Thermoregulation - peripheral heterothermy

Vasoconstriction at very low temperatures: ____________________________________________.

Answer 10

reduces heat loss but decreases flow supply.

Question 11

Why is the snout cooler than the core?

Answer 11

Poorly insulted that gives off a lot of heat, and has countercurrent heat exchange. It can trap water and not lose moisture. Core temperature can be different than their extremities; enables them to have both short hairs to release heat when necessary or to conserve water when they are breathing.

Question 12

How does counter-current heat exchange makes the blood cool in the feet?

Answer 12

You will not lose heat from the feet because there is nothing in the feet to lose. As the air gets colder, there is no air going into the feet, and so they cannot lose it. They do lose heat from the feet at 0 °C, when tissues freeze. Muscles are higher that control the legs. As temperatures outside reach 0 °C, you cannot have a countercurrent heat exchange removing all the heat in the feet, or else the feet get below 0 °C. If they do that, it is a problem. They do allow some heat to go out the feet (enough to be above 0 °C). Core temperature will drop from losing heat. They are a homeotherm. As they release heat, their metabolic rate goes up to accommodate the core from losing heat. A negative is it takes more energy (there is not a lot of food in the environment).

Question 13

How does a Cariboo not starve to death or keep their limbs from freezing?

Answer 13

To not starve to death but keep the feet from freezing, they lay on their limbs to decrease their surface area. The heat they send to the limbs goes back to the body. The snout is the only poorly insulted part of their body. They cannot lay all day; predators will hunt them and they need to look for food.

Question 14

Thermoregulation - What is the thermal neutral zone?

Answer 14

Range of ambient temperatures at which metabolism & body temperature is unchanged.

Question 15

How can an animal alter their thermal neutral zone?

Answer 15

They can change their shape (and go lay down), fluff themselves up (piloerection to thicken their insulation), vasoconstriction, countercurrent heat exchange, are cost-free (does not have to burn extra calories).

Thermal neutral zone is different between lemmings (12°), snow buntings (8°), and arctic gulls (-32 °C) (slide 12).
∙ Borrows of lemmings never get below 10-12°, even if the cold outside is -20°.
∙ The snow buntings cheat and migrate to warmer places; summer they are in the arctic and the winter they are in southern Canada.
∙ Arctic gulls must tolerate it (well insulated plumage, countercurrent heat exchange, and pilo-erect) since they do not migrate (feed off fish). Staying near the water has more heat than being inland.

Question 16

Endotherm water balance

Answer 16

When you breathe, you moisten the air and then you exhale it out. You are losing water to get oxygen for metabolism and get rid of nitrogenous waste. You need to find some way of getting that water back. They cool the turbanes, and as the warm air leaves the lung, it is going to cool off when it enters the snout. When it condenses out, it is going to onto the turbanes, which can be used to remoisten the next breath, and bring it back into blood circulation. We also talked about countercurrent exchange in the opah, blood coming from the gills cools off before it gets to the gills (or else the heat would be lost to the water) – the warm vessel coming back from the core passes the cold vessel coming from the gills.

Question 17

Graph – how they save water.

Answer 17

We have water content in the air (higher up, the more water in the air). There is the temperature (how much water is in the air if it is 100% saturated). Cool temperatures can hold a little bit of water. As you warm up the temperatures, the air can hold more and more water (a significant amount). Normally, when the air is out in the environment, it is going to be 15 degrees (relatively cool) with 20% humidity.
Warmer temperatures hold more water. The animal must expend a lot of water and heat before send the air into the alveoli and lungs. It is cold, dry air (a lot of times in the winter). How much water is in the air? It is where the temperature crosses the 20% humidity line.

When it gets to the lungs, you are going to heat it and wet it. You will heat it up to 35 (much more than it was at 15) at 100% humidity to be fully saturated to not damage the respiratory membranes. You are going to have to add a lot of water to have this much water in the air you breathe. From here up (water content) is water that had to be added by the animal as it inhaled it. You are adding a lot of water to that air.
When you exhale, you lose all that air if it goes out just as warm, which will hold the same amount of water and lose it to the environment. But, if you cool it in the snout to 18 degrees (countercurrent heat exchange and short hair – insulation) the snout is going to get cold, and therefore (at 18 degrees), you are still going to be 100% saturated, but 100% saturated at 18 vs 35 degrees, the air can only hold, instead of what it was holding when it was in the respiratory membrane in the lung, is not going to hold that much. All that water had to leave and condense in the turbanes. The water gets saved and stays in the body to be added to the next breath. The difference that you are going to lose is the difference between the water when you inhaled it and the water that is leaving. Two-thirds of the water you added is saved by having a cooler snout (poorly insulated) and counter-current heat exchange.

Before air leaves the nostrils, they are going to be 20° and 100% humidity. Instead of losing all the water you gave, it is condensed in the nasal passages. The only thing the animal loses is a quarter of the water.

Question 18

What is another way to reduce the amount of water lost from breathing?

Answer 18

Counter-current heat exchange. Each breath is moistened – if you breath less frequently, you will not lose as much water over the course of an hour. They cut their breathing frequency by 2/3rd. They extract 6% of the oxygen from each breath (3x the amount) so they can breathe 1/3 of the time. It moves more slowly across the respiratory membrane because the concentration gradient is not going to be as big.

Question 19

Why is global warming bad for polar wildlife?

Answer 19

Increased icing (thaw-freeze) events, preventing access to lichens. If there are areas where the seals can pop up not through ice, it is cheaper for them, since the do not have to dig breathing holes, giving the polar bear fewer feeding grounds. The polar bears also must swim further to get to other ice sheets. Polar bears are considered the most impacted animal from climate change.
Fluctuating populations: if you are a species that relies on one thing (polar bears on seals; snow owls on lemmings) If the lemming population crashes, the owl population crashes. They do not have enough energy to reproduce. If the owl population crashes, the lemming population increases, which increases owl population, which decreases lemming population, etc. The years the snow owl produces nests are when lemming populations are high.

Question 20

Explain the Emperor penguin (Aptenodytes forsteri).

Answer 20

∙ Most well adapted animal for the cold.
∙ Largest penguin of all the penguins of the world (Bergmann’s Law – the colder the environment, the larger the animal). Being large is good for two reasons: it decreases surface area to volume (slower loss of heat), more cells (more energy source to produce heat), and thermal inertia.
∙ The relative length of their bill and flippers are 25% smaller than most other penguins (Allen’s law – appendages provide more surface area – shorter when it is cold).
∙ Huddle increases temperature as you get into the middle. It does not increase the surface area of the individual penguin; it creates enormous body heat of many penguins. Their function surface area is much lower.
∙ Scaley, unfeathered feet that uses countercurrent heat exchange and ha the potential for heat loss. Thick plumage with high density that covers some of their feet.
∙ Vascular adaptations – keep warm blood from going to the feet.
∙ They use nasal heat and water recovery through countercurrent heat recovery and moisture of the breath.
∙ Thermal neutral zone can drop down to -10 °C. The environment can be below -10 °C, but they can use huddling to be above that temperature. They do not want to bump up metabolic rate, which would mean burn more calories.
∙ March inland a great distance to the base of a cliff (protection from winds) to lay eggs. Females then go back to the ocean for 3 months while the father raises the child. The male has no food, so he must use his energy stores. They place the egg on his feet to keep the egg warm – bypass countercurrent heat exchange to keep the feet warm. He lays on the feet to keep from losing too much heat (insulate the egg).
∙ Some species produce crop milk (pigeons do this too). Emperor penguins produce crop milk. There is no other source of food for the chicklet. Mom can then produce cop milk when she returns and the father goes to hunt. They switch off every 3 weeks.
∙ Must march inland so that the snow melt does not impact their ability to grow. It is a shorter distance than what their parents had to overcome. Parents go to another island to molt. There are no predators on the ice to worry about.

Question 21

Why do Cariboo not follow Allen’s law?

Answer 21

They must be able to run, and cover great distances to forage. Longer legs mean more efficient movement. They get by the high surface area and not lose heat by counter-current heat exchange.
Animals are bigger as you get to colder places: advantages – lower surface-to-volume ratio, greater heat production (more cells) and higher thermal inertia (hold more heat). All support Bergman’s Law.