Download APES Lesson 30B - Species Interactions (2014-15) - science-b

AP Environmental
Science
Mr. Grant
Lesson 30
Species Interactions
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Mastery Check
How do predation, parasitism, and herbivory
differ?
Predation is the relationship in which one organism, a
predator, consumes another, its prey. Parasitism is a
relationship in which one organism, the parasite,
depends on another, the host, for nourishment or
some other benefit while simultaneously harming the
host (but generally not killing it). Herbivory is the
consumption of a plant or a portion of a plant by an
animal, the herbivore.
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Objectives:
• Define the term resource partitioning.
• Compare and contrast the major types of species
interactions.
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Define the term resource partitioning.
Resource partitioning: The process by which species
adapt to competition by evolving to use slightly different,
or to use their shared resources in different ways, thus
minimizing interference with one another.
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Compare and contrast the major types of
species interactions.
• Species interactions shape and define communities
• Natural species interactions:
- Competition = relationship in which both species are
harmed
- Exploitative = one species benefits and the other is
harmed
- Predation, parasitism, and herbivory
- Mutualism = relationship in which both species
benefit
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Competition results when individuals or species vie for
limited resources.
Like what?
Food, space, water, shelter, mates, sunlight
It can occur within or among species and can result in
coexistence or exclusion.
Explain…
Within species… Intraspecific competition
High population density leads to increased competition
Among species… Interspecific competition
It also can lead to realized niches, resource partitioning,
and character displacement.
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 What is the difference between a fundamental
niche and realized niche?
 Fundamental niche = the full niche of a species
 Realized niche = the portion of the fundamental
niche that is actually filled
 Due to competition or other species’ interactions
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Someone explain this…
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 Character displacement = competing species
diverge in their physical characteristics due to the
evolution of traits best suited to the resources they
use
Competition
is reduced
when two
species
become
more
different
What are other
examples of
character
displacement?
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In predation, an individual of one species kills and
consumes an individual of another. Predation is the
basis of food webs and can influence population
dynamics and community composition.
Predator–prey interactions can sometimes drive cyclical
population dynamics… someone explain this.
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• Natural selection leads to evolution of adaptations that make
predators better hunters
• Individuals who are better at catching prey:
- Live longer, healthier lives
- Take better care of offspring
• Prey face strong selection pressures: they are at risk of immediate
death
- Prey have evolved elaborate defenses against being eaten
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In parasitism, an individual of one species derives
benefit by harming (but usually not killing) an
individual of another.
Some parasites are freeliving
Infrequent contact with
their hosts
Ticks, sea lampreys
Some live within the host
Tapeworms
Others cause disease
These are pathogens
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• Parasitoids = insects that parasitize other insects
- Lay eggs in larva or adults of other species
- Kill the host
• Coevolution = process in which hosts and parasites
become locked in a duel of escalating adaptations
- Has been called an evolutionary arms race
- Each evolves new responses to the other
- It may not be evolutionarily beneficial to the parasite
to kill its host
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Herbivory is an explorative interaction in which an
animal feeds on a plant.
- May not kill the plant, but
affects its growth and
survival
• Defenses against herbivory
include:
- Chemicals: toxic or
distasteful
- Thorns, spines, or irritating
hairs
- Other animals: protect the
plant
• Like in parasitism, herbivore–
plant interaction can result in
coevolution.
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In mutualism, species benefit from one another.
What are other
examples of
mutualism?
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In some mutualistic and parasitic interactions, the
participants are symbiotic, whereas in others they are
free living.
Symbiosis = mutualism in which the organisms live in close physical
contact
Each partner provides a service the other needs (food, protection,
housing, etc.)
Microbes within digestive tracts
Mycorrhizae: plant roots and fungi
Coral and algae (zooxanthellae)
Pollination = interaction in which bees, bats, birds, and others transfer
pollen from one flower to another, fertilizing its eggs
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Stop Presentation Here.
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Central Case Study: Black and White and Spread
All Over: Zebra Mussels Invade the Great Lakes
• In 1988, zebra mussels were accidentally introduced to Lake St.
Clair in discharged ballast water
• By 2010, they had invaded 30 states
- No natural predators, competitors, or parasites
• They cause millions of dollars of damage to property each year
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Predators kill and consume prey
• Zebra mussels eat phytoplankton and zooplankton
- Both populations decrease in lakes with zebra mussels
• Zebra mussels don’t eat cyanobacteria
- Cyanobacteria increase in lakes with zebra mussels
• Predators may also be prey
- Zebra mussels are being eaten by diving ducks,
muskrats, crayfish, flounder, sturgeon, eels, carp, and
freshwater drum
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Competition can occur when resources are
limited
 Competitive exclusion = one species completely excludes
another species from using a resource
 Zebra mussels displaced native mussels in the Great
Lakes
 Species coexistence = neither species fully excludes the
other from resources, so both live side by side
 This produces a stable point of equilibrium, with stable
population sizes
 Species minimize competition by using only a part of the
available resource (niche)
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