Download Interactions Among Organisms

Monday, August 31st
Learning Goals
• Compare and contrast the major types of species
interactions
Agenda
• Ch. 3 Quiz
• Interactions Notes
• Study Guide
Interactions Among
Organisms
Homework
• Unit 1 Test Thursday!
Ecological Niche
• The role of a species in its community. It
includes:
− environmental conditions the species can tolerate
− what it needs to grow, survive, and reproduce
− how it interacts with its biotic and abiotic
environment
• An organism is capable of using much more of its
resources or living in a wider variety of habitats than it
actually does
− Fundamental niche: the environmental conditions a species
can tolerate and resources it is capable of using under ideal
conditions.
− Realized niche: the portion of the fundamental niche a species
uses in the presence of other species (competition & predation)
• SO, ecological niche is the total adaptations, use
of resources, and lifestyle to which it is suited.
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Niche: Fundamental vs. Realized
Competition
• Greater Yellowlegs
• A relationship in which multiple organisms seek
the same limited resources they need to survive
− Food, water, space, shelter, mates, sunlight
• Intraspecific competition: between members of
the same species
− High population density = increased competition
• Interspecific competition: between members of
2 or more different species
− Leads to competitive exclusion or resource
partitioning
Results of Competition
• Two species with identical
niches cannot coexist over time
− When two species compete for
exactly the same resources, one
will be more efficient than the
other at gathering those resources
• Competitive Exclusion: one
species completely excludes
another from using the resource
Results of Competition
• Resource Partitioning: when
species divide shared
resources by specializing in
different ways
– EX: one species is active at
night, another in the daytime
– EX: one species eats small
seeds, another eats large
seeds
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More Species Interactions
• One of the most
important species
interactions is who eats
whom
• Predation: process by
which individuals of one
species (predators)
capture, kill, and consume
individuals of another
species (prey)
Adaptations of Prey
• Predation pressure: prey
are at risk of immediate
death
– Prey develops elaborate
defenses against being
eaten
– EX: camouflage, mimicry,
warning coloration,
assembling in groups,
chemical defenses, built
in protection
Adaptations of Predators
• Natural selection leads to the evolution of adaptations
that make predators better hunters
• Individuals who are better at catching prey:
– Live longer, healthier lives
– Take better care of offspring
• EX: keen senses, speed, intelligence, ambush, claws,
teeth, venom
Adaptations of Plants Against
Herbivory
• Exploitation in which animals feed on the
tissues of plants
– Widely seen in insects
– May not kill the plant, but affects its growth
and survival
• Defenses against herbivory include
– Chemicals: toxic or distasteful parts
– Physical: thorns, spines, or irritating hairs
– Other animals: protect the plant
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Other Species Interactions
• Symbiosis: relationship between two
different species live closely together
Mutualism: both species benefit
− Water buffalo & tick bird, bee & flower,
clown fish & anemone
Commensalism: one species benefits while the
other is unaffected
− Barnacles on a whale, bird’s nest in a tree,
moss on a tree, remora on a shark
Parasitism: one species benefits while the other
is harmed
− Tick feeding on a dog, tapeworm & human,
flea & cat
Interactions help maintain
ecosystems
• Loss of mutualistic relationships
would ripple through the
biosphere until very few
organisms remained
− These relationships are
important to the survival of both
species involved
• When prey species disappear,
predators soon decline
− Predators keep prey populations
in check and maintain balance in
the ecosystem
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