Biomes and Ecosystems
 Abiotic and Biotic interactions within terrestrial
and aquatic systems
Week 4
Bio 20 Cyber High
Roles in Ecosystems
 Each organism has its own place within
an ecosystem.
 Ecological niche – an organism’s role
in an ecosystem, consisting of its place
in the food web, its habitat, its breeding
area and time of day at which it is most
active.
Roles in Ecosystems
 Each species in an ecosystem tends to
have a different niche, a different role to
play. This helps to reduce competition
between species.
 E.g. Even if two species eat the same
food they are not in competition because
they may:
 Live in different places
 Eat at different times
Roles in Ecosystems
 E.g. Owls and hawks feed on many of the
same organisms, but occupy distinctly
different niches.
 Owls hunt down prey with in forests
 Hawk hunt down prey in grassland and open fields
 Owls are active during dusk and at night
 Hawk hunt by daylight
 Competition is further reduced because owls and
hawks nest in different areas.
Competition for
Niches
 When a new species enter an
ecosystem, it causes a disturbance
because it comes into competition for a
niche with one or more of the species
already in the ecosystem.
 Exotic species – species that are not
native to an ecosystem
 The introduction of new species
happens naturally. Animals are mobile
and can move from one ecosystem to
another.
Introduction of Exotic
species
 The introduction of new species by humans to
an ecosystem is one of the main causes of
species depletion and extinction, second only to
habitat loss.
 Problems with introducing Exotic Species:
 No natural population controls ( predators or diseases)
 Native species may not be able to compete for space, food
or reproductive sites.
 Prey organisms may not have defense mechanisms.
Introduction of Exotic
species
 The actual number of introduced species that have
established themselves in Canada is well over 300
species.
Supporting Biodiversity
in Terrestrial
Ecosystems
Limiting Factors in
Terrestrial
Ecosystems
 Terrestrial ecosystems are ecosystems that are
found anywhere on Earth that is not covered by
water.
 Despite their many differences in each
terrestrial region biotic and abiotic factors are
interdependent.
 These factors can limit the size of populations
and can also determine the number of species
that survive in each ecosystem.
Limiting Factors
 Abiotic Factors that can limit
Terrestrial ecosystems:
1. Soil
2. Available Water
3. Temperature
4. Sunlight
Soil
The quality and amount of
soil are critical factors in
determining the size and
health of the plant
community and the
biodiversity of an ecosystem.
Soil
Soil
 Soil pH
 Humans have been contributing to higher levels
of acidity in many soils by burning fossil fuels.
 Burning of fossil fuels release sulphur dioxide
and nitrogen oxides into the air which fall to
earth as acid deposition.
Acid deposition – the process by which
sulphur dioxide and nitrogen oxides in the
atmosphere form acidic compounds and fall
to Earth’s surface. (Acid rain is an example
of acid deposition)
Available Water
 The amount of available water in an
ecosystem help determine the size and
health of populations and the
biodiversity of an ecosystem.
Temperature
 Temperature affects both biotic and
abiotic factors.
 Temperature can vary significantly
throughout the year in an ecosystem.
Sunlight
 The amount of sunlight determines what
plants will grow in an ecosystem.
 In ecosystems around the equator
receive more or less the same amount of
daily sunlight.
 Regions at more southern or northern
latitudes experience changes in the
amount of sunlight during different times
of the year.
Taiga
 In a forest, the amount of sunlight varies
from the top of the canopy to the forest
floor.
 In Taiga biomes, the mature trees are
mostly conifers like spruce and pine
 These trees can only support certain
types of birds that have tough beaks for
cracking open cones and nuts
Taiga
 Year-round, these trees block the
sunlight from reaching the forest floor
 This determines the types of plants that
can grow below the canopy
 In the Taiga, we see shade loving plants
like shrubs, mosses and ferns
 These plants then determine which
primary consumers exist in this
ecosystem
Deer and moose
Taiga
 Due to the low growth on the forest
floor, nesting animals are only successful
if they are suitably camouflaged
Deciduous Forests
 Have higher temperatures and
precipitation than Taiga
 Also have more humus
 Decaying plant and animal matter
 These conditions lead to a richer soil and
support growth of deciduous trees
Deciduous Forests
 Spring: sun can reach all the way to
forest floor
 Summer: Canopy is full, so very little
sun gets to the understorey.
 This is ok, because the understorey had the
chance to grow in the spring and is already
mature
 Resulting in support for a diverse range
of organisms
Deciduous Forests
 Lots of leaf litter
 Many different insects
 Full understorey
 Moose and deer
 Leafy canopy
 Variety of birds and climbing mammals
Limiting Factors in
Aquatic Ecosystems
Limiting factors of
Aquatic Ecosystems

Like terrestrial ecosystems, aquatic
ecosystems are limited by abiotic
factors:
1. Chemical environment
2. Light levels
3. Temperature
Chemical
environment
1. The type of
water:
 Freshwater
 Saltwater
Chemical
environment
2. The amount of oxygen dissolved in the
water.
 The amount of dissolved oxygen depends
on:
 Temperature (warmer water holds less)
 Pressure (more oxygen dissolved at sea
level than mountain streams)
 And the amount of salt and other
substances dissolved in the water (more
salt, less oxygen)
Chemical
environment
3. Any other dissolved substance
E.g., Naturally occurring
minerals, and organic
pollutants.
Light Levels and
Temperature
 Light and temperature in an aquatic
ecosystem may vary over the course of the
year (seasonal changes), But these factors are
also affected by the depth of the water.
 Depending on the depth of the body of water the
amount of light available, the temperature and
oxygen levels can all vary. This will have a
significant impact on what organisms you can find.
Zones within Aquatic
Ecosystems
Littoral
Limnetic
Profundal
Littoral Zone
 the area extending out from the
lakeshore to the point where you can no
longer find plants rooted.
 Most productive part of the lake.
 High amount of sunlight.
Limnetic zone
 the area of a lake or pond in which there
is open water and sufficient light for
photosynthesis to occur.
 Most common form of organism in the
zone is plankton (small autotrophic and
heterotrophic microorganisms.
Profundal zone
 the region of a lake beneath the limnetic
zone, in which there is insufficient light
for photosynthesis to occur.
 Most of the time only sources of nutrients in the
zone are dead plants and animals that fall from
the limnetic zone.
 Low oxygen due to bacteria decomposing dead
organic matter.
 No sunlight, no photosynthesis.
Changes in Lake
Ecosystems
Lake Ecosystems
1.Oligotrophic
 Lakes are typically deep and
cold.
 Nutrient levels are low limiting
size of producer populations.
 Limited numbers of only a few
kinds of organisms.
 Water usually very clear.
Lake Ecosystems
2.Eutrophic
 Lakes are generally shallow and
warmer.
 Very good supply of nutrients.
 Many species of photosynthetic
organisms.
 Water is often murky.
Eutrophication
 In general oligotrophic lakes gradually
become eutrophic over time and
eventually filling in and becoming dry
land.
 This process is call eutrophication.
Eutrophication
Eutrophication
Eutrophication
Eutrophication
 Human sometimes accelerate
eutrophication by adding nutrients to
lakes:
Human wastes
Fertilizers
Household and Industrial products
Thermal energy