Transcript Interactions Within Ecosystems

Interactions Within Ecosystems
Populations
• Made up of a group of organisms of the same
species that live together in one place at one
time and interbreed. (produce offspring)
• Understanding population growth is important
– Populations of different species interact
– Interactions can affect the number of individuals
in a population
Population Growth
• How do populations grow and shrink?
– Immigration
• Movement of individuals into a population
– Emigration
• Movement of individuals out of a population
• Growth Rate
– Affected when more individuals are born than die
• Population grows
– Exponential growth
• Numbers increase by a certain factor over a period of time
• J-shaped curve graph (pg 104 in text)
Exponential Growth
• Logistic Growth
– Exponential Growth illustrates what the
population would look like if there were no
outside influences
– Populations are affected by certain factors like
availability of habitat, predators, and disease
– Populations slow and stabilize
– Carrying capacity
• Largest population that an environment can support
• Logistic Growth
– Population growth that starts with a minimum
number of individuals and reaches a maximum
depending on the carrying capacity of the habitat
– S – shaped curve graph (pg 105)
• Population starts off small
• Growth rate increases due to the abundance of
resources
• Population reaches carrying capacity as resources
become scarce
• Competition for resources slows the growth rate of the
population
• birthrate = deathrate, no growth in population
Logistical Growth
Factors that Affect Population Size
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Abiotic Factors
Biotic Factors
Human Activities
Science and Technology
Predator – Prey Interactions
– Predation
– Coevolution
• Predator – Prey Interactions
– Predation
• Act of one organism killing another for food
– Coevolution
• Back and forth evolutionary adaptations as a result of
interactions
– Parasitism
• One organism feeds on the other (host)
– Herbivory
• Plants adapt to protect themselves from being eaten
• Herbivory
– Monarch caterpillar and
milkweed
– Milkweed is toxic to deter
herbivores but does not
harm caterpillar instead it
stores toxin to keep from
getting eaten itself
• Predation/Coevolution
– Zebra has stripes to confuse predator, also long
legs, stays in herds
– Lion hunts in packs, camouflage with landscape
• Symbiosis
• Species live in close association with each other
– Mutualism
• both species benefit
– Commensalism
• one species benefits other is neither harmed or helped
• Parasitism
– Tapeworm
• Mutualism
– Clownfish and Sea
Anemone
• Commensalism
– Orchid gets closer to the sun
Competition
• Competition determines the organism’s niche
– Role that the organism plays in the community
• Carving a Niche
– Affects other organisms in the community
– Niche vs Habitat
• Habitat is where an organism lives
• Niche is the role that the organism plays in that habitat
Ecosystem Resiliency
• Interactions between organisms and the number
of species (biodiversity) in an ecosystem add to
the resiliency of an ecosystem.
• Resiliency
– to withstand, resistant, tough, hardy, durable
• Keystone species
– Species that is critical to an ecosystem because the
species affects the survival and number of other
species in its community
– Examples (wolves in Yellowstone, Sea Otters off the
Pacific Coast)