VCE Biology Unit 2
Area of Study 01
Adaptations of Organisms
Environmental factors and
adaptations
Living in water
Good place to live.
• O2 and CO2 and N are dissolved from
atmosphere.
– O2 also released from as by-product of photosynthesis
and CO2 released as a by-product of respiration.
• Mineral nutrients (phosphates, nitrates,
chlorides, sulfates and carbonates) dissolved
from land.
– Run off from fertilised lands brings increased amounts
of nutrients to the water.
Living in water
Abiotic factor – pH
• pH – determined by amount of CO2 dissolved
in water, which forms carbonic acid (H2CO3).
• pH of inland waters 6 – 9.
• Too much CO2 in water (low pH) will kill off
fish
• Acid water (like acid soils) deficient in mineral
nutrients
Living in water
Abiotic factor – Temperature
• Water retains heat very well. Water absorbs and
releases heat with little change in temperature.
• Aquatic habitats usually not affected by drastic
temperature fluctuations.
• Deep water lakes have temperature layering (fig
13.2, page 246). As water warms up it becomes
lighter. This creates different temperature
environments
Living in water
Abiotic factor – Temperature
Living in water
Abiotic factor – Light
• Water allows light to reach photosynthetic
organisms.
• The quality of light changes with depth
• Turbidity also affects penetration of light: the
muddier the water the less light can
penetrate. Few plants grow in muddy water
Living in water
Abiotic factor – Light
Living in water
Adaptations of billabong animals
• Pygmy perch (Nannoperca sp.) small native
fish that lives in slow moving water
• Factor affecting Pygmy perch is competition
from introduced species (carp, trout,
mosquito fish [Gambusia affinis holbrooki])
• Waterboatmen also found in slow moving
water. They have long paddle like feet to help
them move across the surface of the water
Living in water
Pygmy perch
Living in water
Mosquito fish
Living in water
Waterboatman
Living in water
Adaptations of plants living in water
• Hydrophyte (water loving) plants – water low
levels of [O2] and light compared to air.
• Aquatic vascular plants include rooted
emergence plants e.g. reeds (Fig 13.6(a) p.
248), and crop plants e.g. rice.
Living in water
Adaptations of plants living in water continued
• Water lilies have roots anchored in mud with
their leaves (filled with air spaces) floating on
the surface.
• The leaves have stomata only on the upper
surface of the leaves.
Living in water
Adaptations of plants living in water continued
• Submerged sea grasses have their roots and
shoots under water.
–
–
–
–
Leaves are flat with increased surface area
Few stomata
Very thin cuticle
Gases diffuse between water and plant across the
entire leaf surface
– Spongy tissue in leaves and stems ‘traps’ O2 from
photosynthesis to be used for respiration in the roots.
– Small amount of transport tissue (xylem)
Living in water
Xylem and Phloem - Transport systems in plants
• Phloem transports sugars and other organic
compounds through plant
• Xylem transports water and minerals
Living in water
Living in water
Living in water
Living in water
Living in water
Distribution of marine life on rocky shores
• Environmental factors change with position on
shore
• Zonation determined by tide
• Rising tide submerges organisms in sea water
• Falling tide exposes organisms to air
• From low to high tide marks – graduation of
increasing exposure to drying wind, sunlight, high
temperatures during and low temperatures
during night.
Living in water
Zones
• Supratidal – above high tide
• Spray – between average high tide and
extreme high tide
• Intertidal – between average low and high
tides
• Subtidal – below average low tide
Living in water
Sorrento Back Beach
Living in water
Sorrento Back Beach
Living in water
Subtidal Zone
• Least stressful zone
• e.g. algae – most abundant brown kelp
(strongly attached to rocks by holdfasts)
• Long floating fronds for photosynthesis, some
have air-filled bladders
• Small red algae (epiphytes) live on brown kelp.
Living in water
Intertidal (Littoral) Zone
• Brown algae (Hormosira banksii) (also known
as sea grapes or Neptune’s necklace)
• Protected from drying winds and high
temperatures by a covering of sticky mucilage
and water-filled bladders.
• Green and red algae live amongst brown
algae.
Living in water
Intertidal (Littoral) Zone
• Herbivorous and carnivorous molluscs live
amongst algae.
• Retreat into hard shells for protection.
• Barnacles do not move; when exposed to air
they close their hard shells, when exposed to
sea water they open up and filter water for
nutrients.
Living in water
Intertidal (Littoral) Zone
• Rock pools provide places of refuge for sea
stars, some fish, crabs, etc.
• Water temperature varies greatly depending
on depth, length of time of exposure to air
Living in water
Spray Zone
• Receives spray and splashes of water
• Intense exposure to sunlight, evaporating
water and concentrating salt
• Extreme variations in temperature (day night)
• Few organisms live here
• Tolerant of dry conditions
Living in water
Spray Zone continued
• Cynobacteria (blue-green algae)
• Crustose
• Orange or yellow lichens
• Snails
Supratidal Zone
• Completely out of range of sea water.
Living in water
Living in water
Adaptations to mangroves
Type of plant that can live in intertidal (littoral)
zone on muddy soil
• Fluctuating salinity levels (tides and
freshwater from streams/rivers)
• Lack of O2 at roots
• Aquatic environment for seed dispersal
Living in water
Living in water
Living in water
Living in water
Adaptations to mangroves
Getting rid of salt
• Some mangroves actively pump salt out at
roots.
• Some mangroves have salt-excreting glands on
leaves
Living in water
Adaptations to mangroves
Specialised roots
• O2 normally enter roots through lenticels
• Mangroves have evolved aerial roots, all of which
have lenticels
• These include peg roots, pneumatophores and
silt roots
• Pneumatophores increase surface area exposed
to air for O2 uptake at low tide
Living in water
Adaptations to mangroves
Specialised roots continued
• Cable roots spread laterally
• Cable roots and pneumatophores provide
stability for plant
• Cable roots have fine hair-like roots that
absorb nutrients and water
Living in water
Adaptations to mangroves
Seed dispersal
• Seed are buoyant and adapted for dispersal by water.
• Some mangroves are viviparous (seeds germinate and
young plants whilst attached to parental plant).
• Young plants drop off with developing root system.
• Can quickly establish in muddy substrate and not get
washed away by waves