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.