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