Download UNIT 1: INTRODUCTION TO BIOLOGY

IX. BIOTIC RELATIONSHIPS
A. Competition = the struggle between organisms for food
water, space, shelter, etc.
1. Interspecific competition = competition between
members of different
species
examples: humans vs. tigers
2. Intraspecific competition = competition between
members of the same
species
examples: humans vs. humans
B.
Predation = one organism kills and feeds on another
organism
1. Predator = an animal that kills another animal for food
examples: lions, sharks, humans, & ants
2. Prey = an animal that is killed by another animal as food
examples: antelope, rabbits, cows, & fish
C. Symbiosis = two dissimilar organisms live together in a
close relationship
1. Parasitism = one organism (parasite) obtains nutrition
from another organism (host) in a way that
is harmful (+/-)
examples: leeches, ticks, tapeworms, mistletoe
2. Commensalism = a relationship that is neither helpful
nor harmful to the host (+/0)
examples: epiphytes on trees & mites on eyelashes
3. Mutualism = the relationship is beneficial to both
organisms (+/+)
examples: bacteria in the intestines