Biomes & Succession
 The biosphere is divided into regions called BIOMES
that exhibit common environmental characteristics.
 Each biome is occupied by unique communities or
ecosystems of plants and animals that share
adaptations which promote survival within a biome.
Tropical
Rainforest
High temperatures and
heavy rainfall
Tall trees with wide
canopy that allows
little light to reach
forest floor
Epiphytes – vines that
grow on trees to reach
the sun
Savannas
Grasslands with
scattered trees
Tropical regions – high
temperature but
receive much less
water than a rainforest
Hi Temp & Lo Water
Temperate
Grasslands
Receive less water
than savannas
Lower
temperatures
than savannas
Temperate
Deciduous
Forrest
Warm summers, cold
winters, and moderate
precipitation
Deciduous trees shed
their leaves during the
winter
Deserts
Hot & dry
Growth of
annual plants is
limited to short
periods
following rains
Plants and
animals adapt
to hot dry
conditions
Taigas
Coniferous
forests
Winters are cold
Precipitation is in
the form of snow
Tundra
Ground freezing
winters
Thawing of
upper soil layers
in summer
results in soggy
soil
Permafrost –
deep soil is
permanently
frozen
Fresh Water
Biomes
Ponds, lakes,
streams and
rivers
Marine
Biomes
Estuaries,
intertidal zones,
continental
shelves, coral reefs,
and pelagic ocean
 The change in composition of species over time.
 Describes how one community with certain species is
gradually and predictable replaced by another
community consisting of different species.
 As succession progresses, species diversity and total
biomass increase.
 Climax Community – final successional stage of
constant species composition is attained which
remains unchanged until destroyed by some
catastrophic event.
 Physical and biological conditions influence the pace of
succession – in both cases, the conditions which make a
habitat attractive to resident species may no longer exist,
making the habitat more favorable to a new species.
Changes include:
 Substrate texture – change from solid rock, to sand, to fertile




soil
Soil pH – decrease due to the decomposition of organic
matter
Soil water potential – ability to retain water varies based on
substrate
Light availability – full sunlight to partly shady to total shade
Crowding – increases with population growth
Primary Succession
Occurs on
substrates that
never previously
supported living
things.
Occurs on volcanic
islands, on lava
flows, on rock left
behind by
retreating glaciers
The first organisms
to colonize a newly
exposed habitat are
called pioneer
species
 Rock & Lava
 1st pioneer species is
typically lichens; hyphae
of fungal component holds
onto rock and absorbs
moisture; lichen secretes
acid which breaks down
rock into soil; as soil
accumulates more and
more species can move in
 R-selected species will be
replaced by K-selected
species
 Sand Dunes – begins
with the appearance of
grasses adapted to taking
root in shifting sands;
grasses stabilize sand to
allow for new species to
follow
 Dunes of Lake Michigan
are an example
Process begins in habitats where communities were entirely of
partially destroyed by some kind of damaging event – this event
does not destroy the soil which allows secondary succession to
proceed at a faster rate.
 Succession on abandoned cropland – begins with the
germination of r-selected species from seeds already in
the soil; trees follow
 Secondary succession of
lakes and ponds – begins
with a body of water,
progresses to a marshlike state, then a meadow
and finally to a climax
community of native
vegetation.