Chapter 6: Water Relations

Neil Hadley and Thomas Schultz studied two types of tiger beetles, Cincidela oregona which live in moist conditions & cincidela obsoleta who's more active in summer. 1. How did they conduct their experiment? 2. What did they find out?

1. - Weigh beetles initially - Pumped dry air into chamber at a constant rate and kept temperature at 30 degree celsius for 3 hours - Weigh them again to estimate water loss 2. - C. Oregona lose water two times faster than C. Obsoleta. - C. Obsoleta is waterproofed & has more saturated hydrocarbon.

Randall Tracy & Glenn Walsberg studied 3 populations of merriam kangaroo rats. 1. What was their question? 2. What was their experiment? 3. What was the result?

1. Did they have different adaptations depending on the dryness of their original environment in Southwest (31.5 C), Central (29.1 C) , and north central (23.5 C) Arizona? 2. - Collected 3 populations of merriam kangaroo rats from Southwest (31.5 C), Central (29.1 C) , and north central (23.5 C) Arizona. - Kept them in laoratory under ontrol conditions 3. - Population from dryest conditions lose water at a lower rate. They have adaptations like producing concentrated urine and feces with less water content, condense and reclaiming water vapor in breath, restrict activity, and is waterproofed.

Animals in deserts strategies to balance water gain/loss: 1. How do beetles, Lepidochora brionidae, acquire water? 2. How do beetles, onymacris unguicularis, acquire water? 3. Kangaroo rats, Dipodomys Heteromyidae 4. Camels 5. Scorpions 6. Desert Cicada

1. Dig trenches on the face of sand dunes to condense and concentrate fog. The water runs down the trench where the beetle waits for a drink. 2. - Orient abdomen upward, fog will condense on the body and flow to its mouth. - Food 3. Don't drink water, they rely entire on metabolic water 4. Store large amount of water and conserve it through long periods (6-8 days). Also keep body temp high to lose less water. 5. - Slow down, conserve, and stay out of sun. - Can survive on low food and lose little water during respiration (low rate of metabolism) - waterproofed with hydrocarbon in cuticles - Water from prey 6. - Evaporative cooling through pores

Eric Toolson studied the natural history of the cicada, Diceroprocta. 1. What was his main question? 2. How did he conduct his experiment? 3. What are they results?

1. How could this species be active & regulate its water content and body temp in extremely hot temperatures? 2. EXPERIMENT: - Capture them and bring it back to lab to measure its body temp and water loss rate under different conditions. - Release them when finished 3. RESULT: - Evaporative cooling through pores (proved this by plugging pores and they died)

1. What determines how much water an animal will lose through evaporation? 2. Will evaporative coolers work well in humid conditions?

1. It depends on the temperature and water content of the air around them. - If the amount of water vapor in the air increase, the water concentration gradient from organism to air is reduce so the animal lose less water. - If the amount of water vapor in the air decrease, the water concentration gradient from organism to air is increase so the animal increase less water. - The amount of water in air increase when there are oceans, lakes, and rivers. 2. No, because as the amount of water vapor in air increase, the organism will lose less water.

Relative humidity 1. What is it? 2. What is the equation?

1. Measure of water content in air 2. Relative humidity = (water vapor density /saturation water vapor density) * 100

1. How do plants balance water gain/loss? 2. How to animals balance water gain/loss?

1. Plants have - Deep root system (taproot) to extract water from soil . - Water proofing with wax to reduce water loss - Thick leaves decrease transpiration - Shed leaves 2. Animals have - Water proofing with hydrocarbons to reduce water loss. Saturated hydrocarbon increase quality of waterproofing.

1. What is water vapor pressure? 2. What is saturation water vapor pressure? 3. Vapor pressure deficit? 4. What units are these values measured in?

1. The partial pressure due to water vapor. 2. Pressure exerted by water vapor in air that's saturated with water 3.Diference between actual water vapor pressure and the saturation water vapor pressure at a particular temperature. 4. kilopascals or PKa.

Water movement in aquatic environments: 1. Define diffusion 2. Define osmosis 3. What are the three environmental circumstances of aquatic animals? Please define them.

1. The tendency of substances will move down concentration gradients when the internal environment of organism differ from the external environment in terms of concentration of water and salt (high to low concentration of solutes) 2. Diffusion of water across a semipermeable membrane. 3. - Isosmotic: when organisms have the same concentration of water and solute as external environment so there will be no water movement. - Hypoosmotic: Organism with higher water content than external environment lose water to environment. - Hyperosmotic: Organism with higher solute content than external environment tend to gain water from environment.

Water movement between soil and plant: 1. In what direction do they move? 2. Define water potential 3. What is the equation for water potential for plants & soil? 4. In what conditions in terms of water potential will the water from soil move to plant? 5. Is pressure and matric a reduction?

1. Water move down a concentration gradient (from soil, into plant, into atmosphere) 2. Capacity of water to do work that is defined by its free energy content. It usually negative as in water flow towards a lower water potential like gravity) 3. Ψplant = Ψsolutes + Ψmatric + Ψpressure Ψsoil = Ψ=matric 4. When water potential of soil is higher than water potential of plant. 5. Yes

How much water do organisms have in their bodies?

50%-90%

What did Knut Schemidt-Nielson find out about kangaroo rats?

He showed that kangaroo rates mainly survive on metabolic water & just a little through food.

What is the equation that represent how animals balance their water acquisition against loss in order to regulate internal water? Please explain the meaning of each variable.

Wia = Wd + Wf + Wa - We - Ws Wd = water taken by drinking Wf = water taken in with food Wa = water absorbed from air We= water loss via evaporation Ws = water loss with secretions and excretions

What is the equation that represent how plants balance their water acquisition against loss in order to regulate internal water? Please explain the meaning of each variable.

Wip = Wr + Wa - Wt - Ws Wr = water taken from soil by roots Wa = water absorbed from air Wt = water loss by transpiration Ws = water loss with secretions and reproductive structures such as nectar, fruits, and seeds

aridity

dryness

Salinity

the amount of salt in water

Metabolic water

water released during cellular respiration

How does the saguaro cactus survive with low water availability in the desert?

- Trunk of the arm store large quantities of water - Use them during droughts - Can endure long periods w/o water because of this - Also gets water from roots at the oasis - Close stomata during the day - Orient trunk away from sun - Spines insulate against radiative heat gain

What is the equation for cellular respiration?

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 6CO2

transpiration

Evaporation of water from the leaves of a plant

What is matric forces?

Forces within small spaces such as the interior of the plant that makes the water adhere to walls of containers.

Concentration gradient influence what?

The movement of water between an organism and its environment.

How does water typically move in concentration gradients?

Water has a tendency to move down concentration gradients