Populations and
Communities
Living Things and the
Environment
A little vocab…



Ecology - the study of
how organisms interact
with their environment
Organism - a living
thing
Habitat - the specific
environment that
provides the things an
organism needs to live,
grow, and reproduce
Living or Nonliving?
 Biotic
habitat
Factor - living parts of a
– Examples - flowers, worm, frog
 Abiotic
Factor - nonliving part of
a habitat
– Examples - water, sunlight, oxygen
The Line-Up




Species - group of organisms
that mate and reproduce
Population - all members of
one species in a particular
area
Community - all different
populations that live in an
area
Ecosystem - a community
including its surrounding
environment (abiotic factors)
Populations and
Communities
Studying Populations
Types of Observations
 Direct
Observation - counting all
individuals by ones
 Indirect
Observation - counting
the “signs” of an individual
Methods of Study


Sampling - taking
an estimate of a type
of organism in an
area
Mark-andRecapture Studies
- catch an organism,
mark it, then release
Population Fluctuation


Birth Rate - # of births in a population
during a specific time
Death Rate - # of deaths in a population
during a specific time
If birth rate is > than death rate, then
population is ____________
If birth rate is < than death rate, then
population is ____________
Population Fluctuation


Immigration - organisms moving into a
population
Emigration - organisms moving out of a
population
Population Growth Equation:
(B - D) + (I - E) = N
*If N is a positive #, the population is
increasing
Population Fluctuation
 Population
Density - # of
individuals in a specific area
Population Density Equation:
# individuals
Unit area
Population Factors

Limiting Factor - an environmental factor
that causes a population to decrease
– Examples: food and water, space and weather

Carrying Capacity (K) - the largest
population that an area can carry
Populations and
Communities
Interactions Among Living
Things
The Theory

Natural Selection –
individuals who have
the best characteristics
are more likely to
survive and produce
offspring
– Charles Darwin – (1809
– 1882) father of
evolutionary biology
A Place in the World
 Adaptations
– a physical
characteristic that helps an organism
live in an area
– Example: cacti in the desert
 Niche
– the role of an organism in
its habitat, or how it makes its living
– type of food I eat
– Who else eats you
– Whether you need to survive
The Fight
 Competition
– the struggle (fight)
between two organism to get the
same thing
Let’s Eat!
 Predation
– when one organism kills
another for food
– Predator – dominant organism
 Predator
Adaptations – help them catch
and kill their prey
– Prey – inferior organism
 Prey
Defense Strategies – certain
adaptations to prevent being killed by
predators
– Skunk, poison ivy, porcupines
Relationships

Mutualism – both species benefit
– Example – hippo and bird

Commensalism – one species benefits
and the other is neither helped nor
harmed
– Example – clown fish and sea anemone

Parasitism – one species is benefited and
the other is harmed. Doesn’t kill because
it needs the host to live
– Example – head lice, ringworm, tape worm,
ticks
Relationship
Species One Species Two
Mutualism
+
+
Commensalism
+
O
Parasitism
+
-
Populations and
Communities
Changes in Communities
Primary Succession
 Where
no soil or organisms exist
– Example: rocks after volcano erupts or
glaciers
 Pioneer
Species – the very first
organisms that inhabit an area
– How do they get there?
 wind,
water, other organisms carry them
– What are they?
 Lichens
and moss
Secondary Succession
A
series of changes in an area where
the ecosystem has been disturbed,
but the soil and organisms still exist
– Example – tornadoes, hurricanes, fires,
logging, and farming
– Faster rate of succession
Succession Diagram