Biomes & Succession
EK 4.C.4 The diversity of species within an
ecosystem may influence the stability of the
ecosystem
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.
Biomes
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
Tropical Rainforest
Grasslands with
scattered trees
Tropical regions –
high temperature
but receive much
less water than a
rainforest
Hi Temp & Lo
Water
Savannas
Warm summers,
cold winters, and
moderate
precipitation
Deciduous trees
shed their leaves
during the winter
Temperate Deciduous Forrest
Hot & dry
Growth of
annual plants
is limited to
short periods
following
rains
Plants and
animals
adapt to hot
dry
conditions
Deserts
Ground
freezing
winters
Thawing of
upper soil
layers in
summer
results in
soggy soil
Permafrost –
deep soil is
permanently
frozen
Tundra
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.
Ecological Succession
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 soilSoil pH – decrease due to the decomposition of organic
matterSoil water potential – ability to retain water varies based
on substrateLight availability – full sunlight to partly shady to total
shadeCrowding – increases with population growth
Ecological 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
Primary Succession
Primary Succession 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
Primary SuccessionSand 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
Secondary Succession
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.
Secondary SuccessionSuccession on abandoned cropland – begins
with the germination of r-selected species from seeds already in the soil; trees follow