Make your own free website on

Chapter 7


Hit Counter

7.1 The structure of water is based on hydrogen bonds

Unique substance


V-shaped arrangements

hydrogen bonding

lattice structure

Seawater behaves differently

7.2 Water has important and unique properties

Specific heat

value of one

ponds, lakes and seas - warm up and cools slowly

Latent heat


water 100 x greater than air

sperm whale

surface tension

supports small objects

water striders and water spiders


7.3 Osmosis and osmotic potential are essential to organisms

Osmosis - fluid movement across a membrane

Osmotic pressure - a balance of fluid by physical pressure the fluid exert on membranes

solute dilution by pure water

tugor - internal pressure ( plants )

Osmotic potential - solutes concentration

higher - the lower osmotic potential and the greater tendency to gain water

7.4 Water cycles between earth and the atmosphere

Water as a medium

Precipitation sets the cycle in motion

Water vapor falls

soil or bodies of water

on vegetation, plant litter, streets, buildings

How much gets into the ground?

Field capacity

Capillary water

Wilting point

Hydroscopic water

Surface runoff


7.5 Water moves through plants from soil to atmosphere

Terresterial plants - water in soil




water pressure - from highest to lowest

humidity and sucking water up a straw

gradient - roots and soil

varies - temperature, humidity, plant characteristics, the environment

regulator for water release and CO 2 intake - stomata

7.6 Plants reduce water loss in drought

Stomata partially closing

hottest part of day

afternoon when it is cooler

water balance deteriorates - stomata opens


Drought - stomata may stay closed

CO 2 diffusion into leaf

photosynthesis declines

lack of chlorophyll - leaves yellow

fold or roll leaves

conifers - warm winter temps., ice thaw, water lose ( transpiration ), ground frozen - can not replace water

7.7 Plants of arid regions possess other means of survival

Adaptations dealing with lower water availability

More photosynthate to production of roots

to reach water and max uptake

smaller leaf area reduces water loss through transpiration

angle of leaves

examples: desert shrub - ocotillo (Fouquieria splendens), paloverde ( Cercidium floridum ), Cacti - store water in their tissues , minimal root system CAM

leaf size, wax and resin

Phreatophytes - 60 to 80 m to water table

ex.: cottonwood, willows, salt cedar, mesquite

ephemeral cycle - seeds sprout when water is available

7.8 Plants respond to flooding in various ways

Too much water - stress

flooding and waterlogged soils

similar to drought

sufficient water and rapid gas exchange

roots and soil atmosphere

O 2 levels

aerobic, anaerobic

toxic to plants

anaerobic conditions - ethylene gas



7.9 Plants of saline habitats have physiologically dry environments

Salinity and absorption of water


osmotic pressure



salt-secreting glands

saline deserts

examples: salt marsh hay grass, salt marsh cordgrass, glasswort

7.10 Animals have ways of maintaining water balance

More complex than plants

excretory system

simple in some and complex in others

greater water to lesser water concentrations

fresh water organisms have higher saline concentration in bodies than in surrounding water

protozoan - contractile vacuoles

freshwater fish - absorbing and retaining salts in special cells

amphibians - through skin and gills

terrestrial animals - drinking, eating, metabolic in respiration, urine, feces, evaporation through skin, respiration

birds and reptiles - salt gland, cloaca

mammals - kidneys, urine

7.11 Animals of arid environments conserve water

Evade the drought

avoid the effects

leave the area - African animals ( oryx ) fig. 7.8 p. 82

southern desert of U.S. - spadefoot toad goes below ground

invertebrates, flatworm - develop hard cysts

diapause - stage of arrested development in their life cycle

burrows - nocturnal

kangaroos - highly concentrated urine and dry feces

camels - highly concentrated urine and dry feces

desert rabbit - degree of dehydration

7.12 Animals of a saline environments have special problems



Marine bont fish

Sharks and rays

Birds of the open sea - gulls, petrels

Marine mammals - porpoises

Vertebrates of Arctic and Antarctic have special problems - freezing saltwater

Back To:  349 Notebook