All species are interdependent on each other in some way. Predator-prey relationships keep both populations in check by controlling their sizes. Symbiotic relationships can be mutualistic, commensalistic, or parasitic depending on whether both, one, or neither species benefit. On Sable Island, the horse population is closely tied to the seal population through a nutrient cycle, as seals fertilize grass that horses then eat. Interspecies competition occurs when two species compete for the same resources and can sometimes lead to extinction of one species, but species can coexist by differentiating their niches or partitioning resources.

1. z
Relationships
Interdependence
- all species are dependent on other
species

2. z1) Predator - Prey
the interactions between two species where one
species is the hunted food source for the other.
The organism that feeds is called the predator and the
organism that is fed upon is the prey.
Both populations benefit – size of populations are
controlled

3. z1) Predator - Prey
the size of both populations are kept in check:
• reduced prey populations prevent the stripping of the
food source preventing starvation of surviving
members
• the weak members tend to be captured, leaving the
strong to produce similar offspring

4. z1) Predator - Prey
the size of both populations are kept in check:

5. z
Relationships
Symbiosis: Whenever different living things
live closely together where the relationship
may benefit one or both living things

6. z2) Symbiotic Relationships
Mutualism: Both species benefit ex: flowers & bees
Commensalism: Only one species benefits and neither
are harmed ex: barnacle & whale
Parasitism: Only one species benefits and the other is
harmed ex: ticks & deer

7. zSable Island
The species of wild horses on Sable island are genetically unique in
the world. They also have a unique relationship with the seals of the
island:
Seals get food from the ocean, and fertilize the grasses of Sable
island.
The horses eat the grass.
Horse population is closely tied to the seal population: more seals ->
more fertilizer -> more nutritious grass -> more horses.

8. zSable Island
Horse population is closely tied to the seal population: more seals ->
more fertilizer -> more nutritious grass -> more horses.

9. z3) Interspecies Competition
When two different species are competing for the same
resource.
The competitive exclusion principle states that if two
species with identical niches compete, then one will
inevitably drive the other to extinction.

10. z3) Interspecies Competition
When two different species are competing for the same
resource.
When two species differentiate their niches, they tend
to compete less strongly, and are thus more likely to
coexist.
Species can differentiate their niches in many ways,
such as by consuming different foods, or using different
parts of the environment.

11. z3) Interspecies Competition
Niche: How an organism satisfies its needs; how it "fits"
into the ecosystem.
An organism's niche can be described by any or all of the
following:
• habitat
• energy source
• water source
Species occupying the same niche are in competition.

12. z3) Interspecies Competition

13. z3) Interspecies Competition
Bio-invasion is an example of competition resulting from two species
occupying the same niche. Often the result is the extinction or
extirpation of the native species.
Purple loosestrife, a European invader introduced to Canada in the 1800s, degrades wetlands. It
can decimate and choke out native plants that make up the habitats where fish, birds and
animals feed, seek shelter and rear their young. A single plant can produce over 300,000 seeds.
The plant grows in ditches, irrigation canals, marshes and even standing water. In some
locations, purple loosestrife has also begun invading dry habitats like pastures and cropland.

14. z3) Interspecies Competition
Resource Partitioning: Species in competition coexisting by sharing a
resource by dividing it (partitioning).
Ex: 5 species of Warbles (small songbird) all feed off spruce
bud worms but in different parts of the spruce ​tree.