Module 21

Question 1

Osmotic homeostasis

Answer 1

a constant osmotic environment

Question 2

Osmotic regulation

Answer 2

maintenance of a constant osmotic environment
- Strategies that aim to maintain the solute and water concentrations of a cell or multicellular body within a range that allows cells to function

Question 3

Osmoconformers

Answer 3

animals, including most marine invertebrates, that allow their extracellular fluids to be the same concentration as their external environment
- Osmoconformers living in the open ocean are rarely exposed to fluctuations in water and ion concentration
- They therefore will die when exposed to less salty environments

Question 4

Estuarine and intertidal invertebrates

Answer 4

Osmoregulate to some extent by maintaining their internal body fluids at a higher salt concentration than their environment

Question 5

Avenues for water loss and gain

Answer 5

Terrestrial animals face the osmoregulation challenge of loss of water through evaporation

Question 6

Osmoregulatory organs

Answer 6

Integument – skin
Respiratory surfaces and associated structure
Kidneys
Intestinal tract
Salt glands

Question 7

Integument

Answer 7

At a base level, the integument prevents water from entering or leaving the body
- The skin that separates the inside from the outside of an animal varies across vertebrate animals
- Key characteristic used to distinguish different vertebrate groups
- Small number of restricted areas where it does not cover the entire body – mouth, cloaca/anus, gill slits

Question 8

Integument in fish

Answer 8

The scales are covered by thin epidermis that secretes mucus
Mucous helps prevent the movement of water and solutes between scales and acts as a predatory defence

Question 9

Integument in non-avian reptiles

Answer 9

Scales form the major component of the epidermis
Very thin layer of cells that covers the scales – this is shed by lizards and snakes as they grow
Reptilian scales typically aid in reducing evaporative water loss by reflecting heat and light
Form a tight seal where each scale overlaps to prevent exchange of water and solutes

Question 10

Integument in amphibians

Answer 10

In juveniles and adults, the integument is thin and moist around the entire body
It is very prone to evaporative water loss
→ In adults:
The dorsal surface is thicker than the ventral surface and typically contains mucous producing cells
The mucous helps to reduce water loss across the dorsal surface and reduces the amount of UV radiation and heat that enters the body

Question 11

Ventral integument

Answer 11

Extremely thin and highly vascularised
Enables amphibians to use the ventral integument for water and solute exchange, as well as gas exchange
Amphibians can ‘breathe’ using their ventral integument alongside their gills or lungs

Question 12

Predominately terrestrial frogs

Answer 12

Able to osmoregulate by dramatically altering the blood flow and number of capillaries that supply their ventral integument

Question 13

Endothermic vertebrates

Answer 13

Both mammals and birds are endothermic
- Produce their own body heat
- Have developed intertwined strategies to simultaneously regulate body temperature and water and solutes

Question 14

Mammalian integument

Answer 14

Each layer of the integument comprises a number of differentiated cells and gland types that contribute to osmoregulation and body temperature
→ Hair and sweat glands:
Across mammals, the number of hair follicles varies between species as well as in between seasons and habitats within a species
Hair plays an important role in helping to regulate evaporative water loss
The thicker the fur, the more insulated the moist surface of the skin and the less water loss
Some mammals apply moisture to thinly haired parts of their body to benefit from the cooling effects of evaporative water loss – licking or via sweat glands

Question 15

Birds integument

Answer 15

Evolved feathers from their scaled ancestors
Feathers overlap to provide protection against evaporative water loss – like scales
Added benefit of being lightweight and quick-drying

Question 16

Nasal turbinates

Answer 16

Complex structures made of cartilage that are located adjacent to the nares
Provide a water recapture system, where the temperature of the air exiting the nares is adjusted – warmed or cooled – to adjust the amount of evaporated water contained within
Desert animals have more elaborate turbinate systems than mammals and birds living in more temperate or humid climates

Question 17

Nasal turbinates in birds and mammals

Answer 17

Both possess nasal turbinates – endothermic
Increased temperature in the lungs means there is increased evaporative water content of the air

Question 18

Osmoregulatory behaviour

Answer 18

Seeking microclimates to regulate evaporative water loss
Changes in microclimate are an effective way to reduce evaporative water loss

Question 19

How did nasal turbinates evolve

Answer 19

Nasal turbinates evolved independently in birds and mammals

Question 20

Nasal turbinates in different birds

Answer 20

Marine birds have more complex nasal turbinates than birds in forest habitats

Question 21

What is the main goal of nasal turbinates?

Answer 21

Nasal turbinates reduce water loss from respiratory surfaces