Chapter 3 Communities,
Biomes and Ecosystems
3.1 Community Ecology
1
Communities
• All the interacting populations in an
ecosystem
• A biological community is a group of
interacting populations that occupy the
same area at the same time.
• Abiotic and biotic factors interact and
result in condition that are suitable for life
for some organisms and unsuitable for
other organisms
2
Limiting Factors
• Environmental factors
(abiotic or biotic) that
restricts existence,
numbers,
reproduction or
distribution of
organisms
• Food, predators,
temperature, light…
3
Limiting Factors
• Factors that limit one organism may
indirectly limit others
What happens
when the number
of grasshoppers
is reduced?
4
Tolerance
• Ability of an organism to withstand
fluctuation in biotic and abiotic factors
5
Range of Tolerance
6
Ecological Succession
• Orderly, natural
changes and species
replacement that take
place in the
communities of an
ecosystem
• Primary Succession
– After volcano or
avalanche
– Start with rock (no soil)
• Secondary
Succession
– After forest fire or
abandoned farmland
– Start with soil
7
Primary Succession
8
Primary Succession
• Pioneer Species: first
species on bare
land/rock is lichen or
moss
• Breakdown of rock
and decay of moss
will build up the soil
so other plants can
survive
• Overtime additional
habitats develop
9
Primary Succession
• Producers are always present before
consumer
• Ends with climax community
– Stable, mature community which undergoes
little or no change in species
– Can take hundreds of years to develop a
climax community starting with rock
10
Secondary Succession
11
Secondary Succession
• Sequence of community changes that take
place after a community is disrupted by
natural disasters or human actions
• Occurs in places that previously contained
life
• On land that contains soil, so takes less
time than primary succession to reach
climax community
12
Primary or
Secondary
Succession?
13
Chapter 3 Communities,
Biomes and Ecosystems
3.2 Terrestrial Biomes
14
Effects of Latitude and Climate
• Weather is the condition of the
atmosphere at a specific place and time.
 One of the keys to understanding these
communities is to be aware of latitude and
climatic conditions.
15
Effects of Latitude and Climate
• The distance of any
point on the surface
of Earth north or
south from the
equator is latitude.
16
Effects of Latitude and Climate
• The average weather
conditions in an area,
including temperature
and precipitation,
describe the area’s
climate.
 The graph shows how
temperature and
precipitation influence
the communities.
17
Effects of Latitude and Climate
• Biomes are classified
by their plants,
temperature, and
precipitation.
18
Biomes
• Large group of ecosystems that share the
same type of climax community
• Identified by climax community of plants
rather than animals because plants don’t
migrate.
• Plants are a better indicator of long term
characteristics of a biome
19
Major Biomes of the World
20
Terrestrial Biomes
• From the North Pole
–
–
–
–
–
–
Tundra
Taiga
Temperate Forest
Grassland
Desert
Tropical Rain Forest
• Each have
characteristic abiotic
and biotic factors
21
Aquatic Ecosystems
• Temperature and
precipitation reflect its
associated terrestrial
biome
• Freshwater biomes
– Lakes, streams, rivers,
ponds
• Marine Biomes
– Oceans and seas
– Study by amount of
sunlight
– Specialty biomes:
estuary and intertidal
zone
Intertidal zone
22
Freshwater Ecosystems
 Only about 2.5 percent of the water on Earth is
freshwater.
23
Freshwater Ecosystems
 The characteristics of rivers and streams change
during the journey from the source to the mouth.
24
Freshwater Ecosystems
 Fast-moving rivers and streams prevent
much accumulation of organic materials
and sediment.
 Usually, there are fewer species living in
the rapid waters.
 In slow-moving water, insect larvae are the
primary food source for many fish,
including American eel, brown bullhead
catfish, and trout.
25
Freshwater Ecosystems
 The temperature of
lakes and ponds
varies depending on
the season.
26
Transitional Aquatic Ecosystems
• Areas of land such as
marshes, swamps,
and bogs that are
saturated with water
and that support
aquatic plants are
called wetlands
27
Marine Ecosystems
• The intertidal zone is
a narrow band where
the ocean meets land.
• Communities are
constantly changing
in this environment as
a result of
disturbance.
28
Open Ocean Systems
• The photic zone is
shallow enough that
sunlight is able to
penetrate.
• Below the photic zone
lies the aphotic zone—an
area where sunlight is
unable to penetrate.
• The benthic zone is an
area along the ocean
floor that consists of
sand, silt, and dead
organisms.
29