Community Interactions
Community Interactions
• Community:
Many different
species interacting
in the same
environment.
• Three types of
interactions:
– Competition
– Predation
– Symbiosis
Competition
• Defined: Competing for resources
– Water, nutrients, light, food, space
– Occurs due to a limited number of resources
• Intraspecific competition: When organisms of the same species
compete for resources.
•• Interspecific
When No
organisms
of differing
species
Competitive competition:
exclusion principle:
two species
can occupy
compete
resources.
the same for
niche
in the same habitat at the same time.
– Example: What happens to the neighborhood coffee shop when a
Starbucks is built next to it?
Predation
• Defined: when an organism captures and feeds on
another organism.
• Predator = hunter
• Prey = hunted
Symbiosis
• Defined: a relationship between two or more species
that live in direct contact with one another.
• Three types
– Mutualism
– Commensalism
– Parasitism
Mutualism
Fungus
Fish
obtains
receives
protection
nutrients
Crocodile
and
from
a home
the
has
algae
parasites
removed
•
•
•
•
Anemone
Algae
feedslives
on
amongst
undigested
the
Bird
food
fungal
from
cells
the
receives
fish
food
Defined: both species benefit from a relationship.
Ex: Lichens (fungus and Algae)
Ex: Clown fish and anemones
Ex: Cleaner birds and crocodiles
Commensalism
• Defined: One member of a symbiotic relationship benefits and the
other is neither helped nor harmed
• Ex: Cattle and Birds
– Birds eat insects stirred up by the cattle
• Ex: Barnacles and whales
– Barnacles grow on whale
Ø
Human Our eyelashes
are home to tiny mites
that feast on oil
secretions and dead
skin. Without harming
us, up to 20 mites may
be living in one eyelash
follicle.
Commensalism
Ø Organism is not affected
+
+
Organism benefits
Demodicids Eyelash
mites find all they need to
survive in the tiny follicles
of eyelashes. Magnified
here 225 times, these
creatures measure 0.4
mm in length and can be
seen only with a
microscope.
Parasitism
• Defined: One creature benefits
and one creature (the host) is
harmed
• Endoparasitism:
A parasite that inhabits the
inside of an organism.
– Ex: Tapeworm feeds within a
human’s intestines absorbing
his/her nutrients
• Ectoparasitism:
A parasite that inhabits the
outside of an organism.
– Ex: A leech feeds on the blood of
an organism from a host’s skin.
Identify these relationships
1)
2)
3)
4)
5)
6)
7)
Review
What is a community?
Name the 3 types if community interactions.
When do organisms usually compete?
How do predators and prey interact?
Name the 3 types of symbiosis.
What is the competitive exclusion principle?
How does mutualism, commensalism, and
parasitism differ?
8) How is predation and parasitism differ?