Homestasis, osmoregulation, salt regulation

Question 1

What is a homeotherm?

Homeotherms Regulate Body Temperature
through Metabolic Processes

Answer 1

regulate body temperature through metabolic processes.

▪ Birds and mammals produce heat through aerobic cellular respiration
▪ Basal metabolic rate (MR when inactive), measured by the rate of respiration (i.e., oxygen consumption, VO2)
* therefore there is a limit to how small mammals can be. ( have a high metabloic demand)

Question 2

What advantages does mainting a high body temps in hometherms have?

Homeotherms Regulate Body Temperature
through Metabolic Processes

Answer 2

▪ Be active for long periods of time.
▪ live in a wider range of thermal environments - very cold and very warm.
▪ generate energy rapidly when needed.
▪ Homeotherms have high metabolic rates.

Question 3

How do hometherms maintian heat?

Homeotherms Regulate Body Temperature
through Metabolic Processes

Answer 3

1. Insulation (be able to explain)
2. Shivering
3. Brown Fat
4. Behaviour

Question 4

Insulation in maintaining heat:

How do hometherms maintian heat?

Homeotherms Regulate Body Temperature
through Metabolic Processes

Answer 4

▪ Fur - insulation value varies with thickness. Thickness is usually greater in larger animals. Fur thickness can change with the season. (wet fur has bo insulating power)
▪ Feathers - heat loss is reduced when fluffing feathers. Some arctic birds have feathered feert.
▪ Blubber / fat - aquatic mammals often have no hair, instead have a thick layer of fat beneath the skin
- Why blubber instead of fur?
- Arctic and Antarctic birds

Question 5

Shivering in maintianing heat:

How do hometherms maintian heat?

Homeotherms Regulate Body Temperature
through Metabolic Processes

Answer 5

Involuntary response to cold temperatures.

Question 6

Brown Fat in maintianing heat:

How do hometherms maintian heat?

Homeotherms Regulate Body Temperature
through Metabolic Processes

Answer 6

Has a very high concentration if mitrochondria - can generate far more heat than normal fat can.

modified fat.

Question 7

Behaviour in maintining heat:

How do hometherms maintian heat?

Homeotherms Regulate Body Temperature
through Metabolic Processes

Answer 7

Moves to sunny areas ect.

Question 8

How do hometherms lose heat?

Homeotherms Regulate Body Temperature
through Metabolic Processes

Answer 8

1. Insluation
2. Evaporative cooling

Question 9

Insulation in losing heat:

Homeotherms Regulate Body Temperature
through Metabolic Processes

Answer 9

▪ prevent heat from being absorbed
▪ light body colour reflects solar radiation

Question 10

Evaporative cooling in losing heat:

Homeotherms Regulate Body Temperature
through Metabolic Processes

Answer 10

▪ Moisture evaporates from the skin and heat is lost
- panting and sweating
- birds use gular fluttering
- wallow in water or wet mud (eg. elephants)

Question 11

How are Unique physiological mechanisms used maintain a thermal balance in extreme temperatures?

Answer 11

▪ Losing heat without losing too much water
▪ “Store” body heat during the day.
▪ “Lose” heat at night
▪ Ectotherms in cold climates endure long periods of temperatures < zero.
▪ Supercooling body fluids – Tb < 0 C but don’t not freeze - protects against freezing damage.
▪ Tolerate freezing of body fluids - Such animals usually quite inactive (e.g terapins in North America).

Countercurrent heat exchange - blood vessels that flow in opposite directions in close proximity.
▪ Can conserve heat or cool depending on the configuration

see diagram in lecture 8 slide 32

Carotid rete in bucks - sweats from nostrils = evaprative cooling.

Question 12

Endothermy and ectothermy involve trade-offs.

Question 13

What are heterotherms?

What kind of organisms?

Heterotherms Take on Characteristics of
Ectotherms and Endotherms

Answer 13

Take on characteristics of both endo/ectotherms.

Adults of most flying insects.
▪ Tb of stationary insects = Ta
▪ Insect flight muscles function between 30C and 44C
▪ Have a high metabolic rate when flying
▪ wings produce large amounts of heat Enhances or enables high activity

Question 14

Some endotherms can be heterothermic explain?

Heterotherms Take on Characteristics of
Ectotherms and Endotherms

Answer 14

▪ Hibernation & torpor
▪ Endotherms drop Tb to close to Ta

▪ Small animals enter torpor - dinural animals enter torpor at night (birds) and nocturnal animals enter torpor during the day (bats)

▪ Usually larger animals hibernate - for a long
period of time during the winter.

Question 15

How do animals osmoregulate?

Animals maintain a balance between the
uptake and loss of water

Answer 15

Cells contain 75 – 95% water, and needed for:
▪ Biochemical reactions
▪ Excreting metabolic wastes
▪ Dissipating heat (evaporation – sweat, panting)
▪ Water balance (between loss and gain) must be maintained

Question 16

How do terrestrial animals osmoregulate?

Animals maintain a balance between the
uptake and loss of water

Answer 16

▪ Water balance in terrestrial animals
▪ Water gain
▪ directly
▪ indirectly
▪ Water loss
▪ urine and faeces
▪ evaporation from the skin
▪ exhaling moist air

Question 17

How do animals maintain water balance via behaviour?

Animals maintain a balance between the
uptake and loss of water

Answer 17

▪ Evading drought - migrate leaving ares during the dry season
▪ Avoiding effects
▪ Aestivation - a period of dormacy
▪ Diapause - a stage if arrested development in a life cycle, emerges when conditions improve, insects.

Question 18

How do derest animals adapt?

Animals maintain a balance between the
uptake and loss of water

Answer 18

▪ small mammals are active only at night
▪ extract water from their food
▪ have very concentrated urine and dry faeces
▪ tolerate a level of dehydration

Question 19

How do freshwater animals maintain water balance?

Animals maintain a balance between the
uptake and loss of water

Answer 19

Split into 2 groups - osmoregulators and osmoconformers.

osmoregulators = drinks a little water, and absorbs water through its skin, excretes dilute urine - actively pump ions through its gills to maintain a constant water balance.

Question 20

How do marine animals maintain water balance?

Type and explain.

Animals maintain a balance between the
uptake and loss of water

Answer 20

▪ Marine animals are hypo-osmotic, osmoregulators and osmoconformers.

▪ marine bony fish
▪ cartilaginous fish (sharks and rays)
▪ keep urea in body tissues

hypo-osmotic = drinks alot of water, loses water through skin, excretes concentrated urine - excretes ions through gills.

Osmoregulators =
▪ birds and turtles
▪ drink seawater and excrete the salt through special salt glands
▪ marine mammals
▪ eliminate salt through their kidneys

osmoconformers = isosmotic – body
fluids have the same osmotic pressure as the
seawater
▪ Mainly invertebrates
▪ tunicates, jellyfish, many mollusks, sea anemones

Question 21

Ecological Issues & Applications: Increasing Global Temperature Is Affecting the Body Size of Animals

Answer 21

Bergmann’s Rule for endotherms
▪ body size for a species tends to increase with decreasing mean annual temperature
▪ Cline in body size correlating with latitude (spatial)
▪ Similar changes have also been seen over time (temporal)
▪ Why?

Long term changes
▪ High global temperatures during the Paleocene - Eocene Thermal Maximum (PETM) ~56 mya
▪ Increase of ~5 – 10oC
▪ High global temperatures during the Paleocene - Eocene Thermal Maximum (PETM)
▪ Size of horses in Wyoming changed
according to Ta

Recent temperature increases
▪ Mean body mass of red- billed gulls has decreased from 1958 through 2004

▪ Increase in body size with rising temperatures do occur
▪ Increasing temperature may reduce cost of
metabolism
▪ Temperature can influence food availability and nutrition - otters in sweden showed an increase in average body size from 1962-2008.

lecture 8 slide 46

Question 22

How might an increase in
temperature affect very
small homeotherms?

Ecological Issues & Applications: Increasing Global Temperature Is Affecting the Body Size of Animals

Answer 22

Limit on how small animals can get, if it gets any hotter it cannot get any smaller and most likely will get extinct.