Download Chapter 18, section 2 Interactions of living things How does the

Chapter 18, section 2
Interactions of living things
How does the
natural
environment
control population
size/density?
How do humans
affect carrying
capacity?
How can a limiting
factor and
predation make
organisms better
adapted to survive?
What are some
different examples
of symbiotic
relationships?
How can organisms
share the same
habitat but have
different niches?
1. Population size refers to the number of organisms in one particular
location. Many times it is hard to get an exact match so usually the number
is estimated by studying a small area. Birth, death, predators, disease,
famine, moving, etc… are all examples of ways population sizes can change.
2. Population density- the number of individuals in a population that occupy
a definite area. The more organisms live in an area the higher the density.
3. Population spacing- Evenly spaced have a fairly constants amount of
distance between organisms. Random spacing means the location of one
organism does not depend on the location of another. Clumped spacing
occurs when resources such as food or space cause organisms to group
together.
4. Limiting Factors- a population of any particular organism cannot grow
indefinitely. All ecosystems have a limited amount of food, water, living
space, mates, nesting sites, and other resources. Limiting factors can be
biotic or abiotic. Because of limiting factors competition exist between
organisms. This struggle among organisms to obtain the same resources
needed to survive and reproduce. As the density increases so does the
competition among individuals for those resources.
5. Carrying capacity: is the largest number of individuals of a species that an
environment can support and maintain for a long period of time. If a
population gets bigger than its CC then some individuals are left without
resources and will die or would be forced to move.
6. Biotic Potential: the ability for a population to grow indefinitely. A place
where no limiting factor or carrying capacity exists. Usually only happens
when a non-native species has been introduced to an area.
7. Symbiosis: is any close interaction between different species. 3 types.
Mutualism: 2 different species of organisms benefit from their relationship.
Commensalism: 1 species benefits while the other is not affected
Parasitism: 1 species benefits and the other organism is harmed. (tick on a
dog)
8. Predation: common method of controlling population size is through
predation. The act of hunting, killing, and feeding on another organism. Both
then number of prey or predator can be a limiting factor in an ecosystem.
Typically old or ill prey are easier to capture and this causes the prey to
adapt and become stronger of time.
9. Habitat and Niches
The role or job of an organism in an ecosystem is called a niche. What a
species eats, how it gets its food, and how it interacts with other organisms.
The place where an organism lives is called its habitat.