VCE Biology Unit 2 Area of Study 01 Adaptations of Organisms Chapter 13.2 Environmental factors and adaptations

VCE Biology Unit 2Area of Study 01

Adaptations of Organisms

Chapter 13.2Environmental factors and

adaptations

13.2 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.


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


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


Abiotic factor – Temperature


Abiotic factor – Light• Water allows light to reach photosynthetic

organisms.• The quality of light changes with depth (see

figure 13.3 page 247)• Turbidity also affects penetration of light: the

muddier the water the less light can penetrate. Few plants grow in muddy water

13.2 Living in waterAbiotic factor – Light


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





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.


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 (Fig 13.6(b) p. 248).

• The leaves have stomata only on the upper surface of the leaves.


Adaptations of plants living in water continued• Submerged sea grasses have their roots and shoots

under water (Fig 13.6(c) p. 248).– 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)


Xylem and Phloem - Transport systems in plants• Phloem transports sugars and other organic

compounds through plant• Xylem transports water and minerals• See Chapter 9 section 3 pages 161 – 167






Distribution of marine life on rocky shores pp. 248-249• 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.


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

13.2 Living in waterSorrento Back Beach

13.2 Living in waterSorrento Back Beach


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.


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.


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.


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


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


Spray Zone continued• Cynobacteria (blue-green algae)• Crustose• Orange or yellow lichens• SnailsSupratidal Zone• Completely out of range of sea water.



Adaptations to mangrovesType 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





Adaptations to mangrovesGetting rid of salt• Some mangroves actively pump salt out at

roots.• Some mangroves have salt-excreting glands on

leaves


Adaptations to mangrovesSpecialised 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


Adaptations to mangrovesSpecialised 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


Adaptations to mangrovesSeed 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

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VCE Biology Unit 2 Area of Study 01 Adaptations of Organisms Chapter 13.2 Environmental factors and adaptations