Download Population Interactions

Do Now, 4.4
Food Web Labs,
Please
OBJECTIVE:
1. Describe interspecific
interactions, including:
predation, herbivores,
competition,
symbiosis, parasitism,
mutualism,
commensalism, and
mimicry.
TASK:
1. Using the food web
shown, describe what
might happen if the
squid population were to
decrease greatly. Which
populations would
benefit, and which would
be harmed?
Population Interactions
Predators and their Prey
• Predator survival depends on capturing
food.
• Prey survival depends on hiding, escape,
or other defenses.
• Since only successful organisms survive
and reproduce, the genetic material of the
best (or luckiest) organisms gets passed
onto the next generation. This is called
natural selection.
Plants and Herbivores
• Animals that eat plants = herbivores.
Some plants
produce
poisonous or
bad-tasting
secondary
compounds as
a defense
against
herbivores…
but not the
grass this cow
is munching!
Competition
• Resources (like food / energy) are limited.
When two populations share the same
niche, they will compete for use of that
resource.
• Do human populations compete for
resources?
• What resources?
Competitive Exclusion:
One species is removed
from the community because
it could not get enough of the
resource
Resource Partitioning:
Several species use part of
the available resource,
reducing competition.
Symbiosis
• Symbiosis is the close association
between two or more different species or
organisms.
• Three main types
– Parasitism
– Mutualism
– Commensalism
Parasites and Parasitism
• A parasite feeds on its host.
• Similar to predator / prey, but the prey isn’t
usually killed.
• Endoparasites are internal, Ectoparasites
aren’t.
Ectoparasite: Deer tick
Endoparasite: Trichonella
Mutualism
• A cooperative
relationship where both
organisms benefit
Commensalism
One organism benefits, the other is unaffected
Mimicry
• Batesian mimicry: A harmless organism
resembles a poisonous or distasteful one.
Or…
More Mimicry
• Müllerian mimicry: Several poisonous or
distasteful species look similar