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

Receive less

water than

savannas

Lower

temperatures

than savannas

Temperate Grasslands

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

Coniferous

forests

Winters are

cold

Precipitation is

in the form of

snow

Taigas

Ground

freezing

winters

Thawing of

upper soil

layers in

summer

results in

soggy soil

Permafrost –

deep soil is

permanently

frozen

Tundra

Ponds, lakes,

streams and

rivers

Fresh Water Biomes

Estuaries,

intertidal zones,

continental

shelves, coral

reefs, and

pelagic ocean

Marine Biomes

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

Secondary SuccessionSecondary

succession of lakes and ponds – begins with a body of water, progresses to a marsh-like state, then a meadow and finally to a climax community of native vegetation.