Download E-5 Notes

Science 8: Unit E: Fresh
and Saltwater Systems
Topic 5 – Living in Water
Biodiversity in Aquatic Ecosystems
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Biodiversity – variety of different kinds of
species in an ecosystem.
Large bodies of water have different layers or
zones with each having its own biodiversity.
Some organisms live in only one zone, while
others live in all three.
Zones in Lakes and Ponds
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Upper Zone – area of a lake from the shore down to
where the aquatic plants stop growing. Species you will
find here include water lilieis, small fish, clams, insects,
frogs.
Middle Zone – open water area that still has light
reaching the bottom. Species you will find here include
phytoplankton, fish.
Deep Zone – No light reaches the bottom, so no plant
growth here. Food for organisms living here comes
from dead organisms/waste from higher zones. Species
you will find here include deep water fish (larger fish).
Zones in Rivers and Streams
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Streams usually alternate
between areas where
water is calm (pools) and
areas where water is
moving rapidly (riffles).
Organisms often attach
themselves to rocks as
their habitat.
Zones in Oceans
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I. Estuary – Where freshwater washes into the saltwater
(at river mouths) forming brackish water. Makes for
very diverse ecosystems.
II. Inter-tidal Zone – shoreline of ocean. Animals here
must be able to withstand pounding of waves.
III. Continental Shelf – Warmer water in area with full
light penetration. Contains phytoplankton and many
fish and plants.
IV. Oceanic Zone – little light penetrates here so no
plant growth.
Aquatic Adaptations
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Adaptation – physical or
behavioral characteristic
of a species that
increases the species’
chances of survival in
their ecosystem.
Many aquatic organisms
have adapted to being
able to filter their food
from the water.
Aquatic Adaptations Cont’d
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There are five key ecosystem factors that aquatic
species must adapt to, or die out.
I. Temperature – Species must be adapted to the
temperature of the surrounding water. Certain
species actually have a form of antifreeze in
their blood to keep it from freezing in cold
waters.
II. Lights Levels – Most species need light.
Some animals in the ocean floor can produce
their own light (bioluminescence).
Aquatic Adaptations Cont’d
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III. Pressure – Skeletal and muscular tissues are
adapted for pressures/forces a species must deal
with in their habitat zone. They will die if
moved.
IV. Salinity – Because of osmosis animals have
been adapted to specific concentrations of salt
in the water.
V. Water Movement – Animals are adapted to
deal with water movement and for moving
through water. (streamlined shape of shark)
Aquatic Plants
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Two types: those that float freely:
phytoplankton, and those that attach themselves
to ocean/lake floor.
Stomata are specialized cells in plants that open
and close to allow in carbon dioxide for
photosynthesis (making sugar) or oxygen
(consuming their sugar)
Plants need phosphate and nitrate nutrients.
They get these in the oceans from detritus.
Temperature Mixing
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When temperatures cool in the fall, the surface
water becomes denser, sinking to the bottom,
allowing nutrients to resurface. This increases
the phytoplankton growth. Cold water holds
dissolved gases better than warm water –
meaning higher oxygen levels in the surface
waters in the fall.
The level of nutrients and salts in oceans is in a
steady balance. Not only does it get added to the
water as described earlier, but it is also taken out
of the water.
Nutrient Pollution
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Too many nutrients can cause problems in
aquatic environments. An increase in algae
growth (algal bloom) covers the surface of the
water, blocking out the light. As the algae dies,
they are decomposed by bacteria, which use up
all the oxygen.
This cycle continues until a balance is achieved
again.
Population Changes
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Population – a group of organisms of the same
species living in the same ecosystem.
There are three types of population changes:
I. Seasonal Change: Populations swell in the
summer and disappear in winter. The
disappearance of a population may mean
survivors are dormant, or hibernating in the
winter months.
Breeding cycles can also cause seasonal changes
in populations.
Population Changes Cont’d
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II. Short-Term Changes: take place over a relatively
short period of time and don't last very long. They
happen irregularly and may be part of a natural event,
or caused by human activities.
III. Long-Term Changes: result from natural events or
human activities. A landslide can change the course of a
river or stream. Addition of a new species (zebra
mussels introduced by accident) to an area (the Great
Lakes) may result in overpopulation of that species
because there are no natural enemies.
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Humans and Aquatic Species
Over-fishing, dumping of toxic
chemicals and fertilizers into
aquatic ecosystems, as well as the
use of pesticides have all
negatively affected populations
of aquatic species.
Biomagnification – Residues
from human produced chemicals
can find their way into ground
water and bodies of water. As
the chemicals move up the food
chain, they become more and
more concentrated in the tissues
of the organisms.