Ecology: study of the relationship of living things and their
Review: A population is a group of organisms of the same species that
live in the same area or are interbreeding and sharing genetic
Limiting factors: carrying capacity
For many populations, the number of individuals in an
area is determined by the environment.
environment can support only a limited number of
individuals. Population size hovers around this number
which is kn
Mortality patterns affect age structure of a population.
Age structure is the number of individuals of different
ages in the population. A cohort is the individuals in a
population of the same age.
A plot of cohort
survivorship for the po
. THE REGULATION OF POPULATION SIZE
Two influences on population size are limiting factors and
Specific limiting factors affect the size and density of a
The most important factors are the
C. LIFE HISTORY PATTERNS
This is a variable property of populations.
There are two extreme alternatives: r- selected (prodigal)
and k- selected (prudent).
Early or Late Reproduction
Breeding early or late can affect population growth.
A short life expe
Consequences of Life-History Patterns
Opportunistic organisms appear to lead risky lives, but
these populations can recuperate their numbers quickly
following a population crash because a population can
be built from only a few organisms.
The Ecological Niche
Thee total environment and way of life of all the
members of a species in a community, or a specific
role of a species within a community is termed its
niche. The niche includes physical factors, such
as temperatures and moisture;
Character displacement is a phenomenon in which
species that live together in the same environment
tend to diverge in those characteristics that
Winner Takes All
Competition may not only wipe out individual
Predation and Species Diversity
The number and types of species can be affected by
predators. Predators can eliminate species in an
area, but can also maintain species diversity.
Predation often keeps a species that would normally
dominate an area in c
COMMUNITY COMPOSITION AND THE QUESTION OF
community? What factors underlie the changes in
community composition that are revealed by close
observation to occur with the passage of time?
1. Island Biogra