Organismal Relationships
Predator
An organism that eats another organism◦Bear eats fish◦Fox eats rabbit◦Lion eats zebra
Prey
An organism that is eaten by another organism◦Bear eats fish◦Fox eats rabbit◦Lion eats zebra
Practice!
What would happen if a family of lions (5 lions) moved into a savannah with 100000 zebras?
What would happen if the lions had babies and after a while there were 1000 lions?
Why are predator/prey relationships important?
The predator/prey interactions cause the populations to rise and fall in line with each other, since both animals' population sizes depend on factors from the other species so much.
Lynx-Hare Model
Symbiotic Relationships
A close relationship between two or more organisms of different species that may, but does not necessarily, benefit each one.◦Parasitism◦Mutualism◦Commensalism
Symbiotic Relationships
Predation(+/-) is where one organism eats another.
Parasitism(+/-) is where the parasite obtains food at the expense of the host.
Mutualism (+/+) is where both organisms benefit from the relationship.
Commensalism(+/o) is where one organism benefits while the other is neither harmed nor helped.
Population Density
The number of organisms in a population that live within a given area(length x width)
The amount of space for each organism
Population Density
EquationPopulation Density = #organisms/area
Which population is more crowded?
A deer population of 75 lives in a 150 square mile park.
A deer population of 20 lives in a 38 square mile park.
Population density of our room
We are going to figure out the population density of this classroom with all of us in it.
What makes populations change?
Moving in or out
Immigration: organisms move IN to a certain community◦Raise or lower?
Emigration: Organisms move OUT of a certain community◦Raise or lower?
Birth Rate/Death Rate
Birth Rate
The number of offspring that are born to a community within a timeframe◦Would this increase or decrease a population?
Death Rate
The number of organisms in a community that die within a certain timeframe◦Example: 5 deer in Sharon woods died this
year
Age Structure Diagram
Diagram shows:◦Number of males and females in a population◦Number of individuals at each age group
Type of Age Structure Diagrams
Rapid Growth◦High birth rates◦Deaths at each level-numbers decrease at each
age groupSlow Growth
◦Fewer births◦Organisms live longer generally
No Growth◦Very few births◦Organisms live very long
