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Biotic
Interactions8.11A DESCRIBE PRODUCER/CONSUMER,
PREDATOR/PREY AND PARASITE/HOST RELATIONSHIPS
AS THEY OCCUR IN FOOD WEBS WITHIN MARINE,
FRESHWATER AND TERRESTRIAL ECOSYSTEMS
Biotic
These are the living organisms in any
given ecosystem
Animals – vertebrate or invertebrates
Plants – flowering and non-flowering
Fungi – mushrooms, molds
Micro-organisms – bacteria, protists
(see ex.)
Abiotic
biotic and abiotic factors interact in ecosystems.
organisms are dependent on the abiotic and biotic factors in their environment.
Abiotic factor examples: Sun, heat, light, temperature, rocks, soil, wind, precipitation, air, water, clouds
The factors together:
Biotic Interactions In
Ecosystems
There are several types of interactions (also known as “feeding relationships”) among organisms in ecosystems.
Other interactions are caused by competition for food and resources
Producer/consumer
Relationships
Roles within Ecosystems
Producer/autotroph – organism that
makes its own food, such as a plant
or photosynthetic alga.
Recall that in order to make their
own food, autotrophs use the sun’s
energy to convert water and carbon
dioxide in to food , a sugar - glucose.
This is the process of photosynthesis,
Roles within Ecosystems
Consumer/heterotroph - an organism that
feeds on other organisms
There are different tiers or “levels” of
consumers
Include organisms that feed only on
autotrophs, organisms that feed solely on
other heterotrophs, and organisms that
feed on both auto and heterotrophs.
Roles within Ecosystems
Primary consumer (first level consumer)
– animals that get their energy from
eating plants
These are always herbivores, but can
also be omnivores
Roles within Ecosystems
Secondary consumer (second level
consumers) – animals that get their
energy from eating other animals
Always carnivores, but also some
omnivores
Roles within Ecosystems
Tertiary consumer (top level consumers) – animals
that get their energy from eating other animals
Top carnivore (may also be omnivore like bears)
Note – there can be higher levels than tertiary, but
these are few and far between due to energy
transfer that occurs within an ecosystem
Roles within Ecosystems
Decomposer – simple organism, such as
bacteria or fungus, that breaks down dead
organisms and waste, returning important
nutrients to the environment
How do these various roles
come about? Biotic factors include food chains and webs
where some organisms might share food sources setting up competition
Many organisms are adapted to survive in ecosystems by resource partitioning – they feed at different times of day or at different levels in the same tree
Carrying capacity – the number of animals that can obtain food, shelter, and water from the environment in a given area; the ability of an environment to support its animal population
CompetitionCompetition - occurs when
organisms try to make use of the same limited resources
Competition occurs between:
Members of the same species
Among species with similar niches
They are competing for abiotic or biotic resources
How do these examples to the right compete?
How does a “niche” come
about?
A niche is - an organism’s particular role, or
how it fits into an ecosystem
A niche is created when species compete
Many organisms are adapted to overcome
competition by resource partitioning:
They feed at different times of day
Or at different levels of the same tree
Words to Know
Resource partitioning- helps competing
species share a resource and develop
a niche for themselves in an
ecosystem.
For example:
Species of birds will feed at different
times of day
Or at different levels of the same tree
Warbler example:
Carrying Capacity:
Carrying capacity is the largest number of
individuals of a population that a given
environment can support. Living within the
limits of an ecosystem depends on three
factors:
the amount of resources available in the
ecosystem,
the size of the population, and
the amount of resources each individual is
consuming (using).
Carrying Capacity: An example of a situation in which the carrying
capacity of an environment is exceeded is the
example of deer in North America.
After the widespread elimination of wolves – the
natural predator of North American deer – the deer
reproduced until their need for food plant species
exceeded the environment’s ability to regenerate
their food plants. In many areas, this resulted in large
numbers of deer starving until the deer population
was severely reduced.
Predator/Prey
Relationships
Predation
Predation - An interaction in which one
organism hunts and kills another for food
Hunter – predator
Gets eaten - prey
Predator Adaptations
Predators have adaptations that help them
catch and kill their prey.
Cheetahs can run very fast to catch prey
Jellyfish have poisonous tentacles to
paralyze prey
Owls have big eyes to see at night
Prey Adaptations
Prey have adaptations to help
them avoid predators
Camouflage
Protective coverings
Warning coloring
Mimicry
False coloring
Effects on Predation on
Population Size
Predation can have a major effect on
population size
If predators are very effective, the
result is a decrease in the prey
population
In turn, a decrease in the prey
population will result in a decrease in
the predator population
Parasite/Host
Relationships
Symbiosis
A close relationship between
two different species that
benefits at least one of the
species
Benefits of Symbiosis:
Food
Transportation
Cleaning
Protection/Shelter
Reproduction
There are three types of
symbiotic relationships:
Mutualism
Both species benefit
Remora fish clean
sharks of external
parasites and in
return receive free
rides and food.
Giraffes and
oxpecker birds
Commensalism
One species benefits and the other is unaffected –
Ex. Clown fish are protected from predators by sea anemones’ poisonous tentacles. The relationship does not affect the sea anemone negatively or positively.
Barnacles and whales
Parasitism
One gains considerably
at the expense of the
other
Host – the organism that
the parasite lives on or
in – it will be harmed
Parasite – the organism
that benefits
Reef Symbiosis