Download V. Relationships in the Ecosystem

V. Relationships in the
Ecosystem
A. Predators and prey
1. Predators are active hunters
2. The organism which is eaten is the
prey
3. Population sizes are very closely
linked
a. Increase and decrease with each
other
b. Directly proportional
4. Populations go through cycles as well
a. Lynx and hares have a 10 year
cycle
b. Mice and birds have a 4 year
cycle
c. Larger animals live longer and
reproduce more slowly
d. Prey items determine the cycle
of the predator
B. Parasitism
1. Parasitism- relationship in which one
organism feeds on the tissues or body
fluids of another
a. Organism that is fed on is the
host
b. Harmful or fatal to the host
c. Not good to kill the host though
2. Most parasites are entirely dependent
on host
3. Populations of parasites are closely
related to the host populations
a. Crowded makes it easy to get
from host to host
b. Density dependent
C. Symbiosis
1. Symbiosis is the a relationship where
two species live closely together
2. Parasites are symbiotic
3. Commensalism: one species benefits
and the other is entirely unaffected
a. Clown fish and the anemone
4. Mutualism: both species benefit