Transcript Water balance in organisms

Water balance in organisms
Kidneys
 Eliminate ammonia/urea
 Ensure water balance: dilution of
urine
Blood pressure
 Water level goes up, so does blood
pressure
 Governed by antidiuretic hormone
(ADH or vasopressin)
Vasopressin
 Produced in hypothalamus
 Dehydration = more vasopressin
 Vasopressin stops water moving from
blood into urine
 Also creates a thirsty sensation to
animal
Renin
 Hormone secreted in kidneys
 Response to low blood pressure
 Allows more water into blood,
increase blood pressure again
Water balance in organisms
Organism
Ways to balance water
Amoeba
-Enters cell by osmosis
-Excess water expelled by vacuoles
Fish
See table 10.4 on pg 328
-generally: salt water fish conserves water, fresh water expels water
Sea birds
-Must conserve water
-Concentrated uric acid (like urine)
-Excess salt excreted from salt glands above eyes, runs out nose
Reptiles
- Aquatic – do not need to conserve water
- Terrestrial usually need to conserve water
- Deactivation of water excreting part of kidney
-Water reabsorbed from cloaca
- May have salt secreting glands
Amphibians
-frogs: continuous uptake of water from surrounds via skin osmosis
-Produce a lot of dilute urine
Activities
Glossary: renin, vasopressin, diuretic
Quick Check pg 330
Water balance in plants
 90 – 95% of plant = water
Stomata: pores in leaf
 May be covered by cuticle, which is
water proof
 Stomata open to let water in or out
 As water leaves through stomata,
more water is pulled up the xylem to
replace it
Transpiration
 Loss of water vapour through stomata
http://www.sciencemag.org/sciext/vis200
5/show/transpiration.swf
 Transpiration stream is the stream of
water from roots to top of plant
Cuticle
 Thin cuticle means more
transpiration/water loss can occur
Sunken stomata
 Stomata sunk into pits
 Prevents water loss by creating a
barrier between the water in the leaf
and the outside air
 Fine hairs on leaves may do a similar
thing
Rolled up leaves
 Reduce surface area, and area for
water to be lost
Succulents
 Have large vacuoles to store excess
water
 Dry climates
 Thick cuticle
 Few stomata
Factors affecting transpiration
 Humidity – lots of water in air = less
transpiration
 Wind – less wind/air movement =
less transpiration
 Air temperature – low temperature =
less transpiration
 Stomata close if too much water is
lost
Activities
Glossary: transpiration stream,
stomata, cuticle
Quick Check questions pg 335
Biochallenge
Chapter review questions: 2, 3, 5, 6, 7,
9, 10, 13, 15