Ecological Succession

Ch. 4 continued

How do ecosystems change over time?

• Always changing in response to natural and human disturbances– Older inhabitants die out, new organisms

move in

• Ecological succession – predictable changes in a community over time– Caused by slow changes in physical

environment– Caused by sudden natural disturbance

What is primary succession?

• Succession on land where no soil previously existed– Hardened volcanic lava

or ash– Rocks exposed from

glacier melt

• Pioneer species – 1st to populate an area– i.e. Lichens– Creates soil

c. Steps of Primary Succession

1. Formation of Soil- rocks broken down by

lichen- pioneer species (1st in area)

weathering- wind, rain, frost

2. Colonization- of plants and animals

Grasses & small plants

Shrubs

Pine trees

Deciduous trees- oak, hickory, maple, elm

3. As plants move in, they create shade. This causes smaller plants to die off. As they die, their bodies decompose and create more soil. This allows larger plants to take over.

4. As plants become established, animals will move in. Herbivores first followed by their predators.

5. This process can take 100’s of years.

*** A final stable complex community will form- CLIMAX COMMUNITY.

What is secondary succession?

• Follows a community changing disturbance– Wild fires, humans clearing land

• Climax Communities – ending point of succession – mature stable community– Still goes through change over time

Secondary Succession after a fire

Secondary Succession of

a

Lake

Succession in Marine Ecosystems

• Begins with the death a large animal like a whale• Carcass sinks to barren ocean floor• Scavengers and decomposers feast on dead meat• Meat is gone now and population of scavengers is

smaller• Decomposed nutrients in sediment attract many

sediment dwellers like worms• Lastly, heterotrophic bacteria decompose oil in

remaining bones• This releases chemical compounds which serve as

energy for chemosynthetic bacteria which serve as food for a diverse marine community

Biomes

• particular physical environment with unique set of abiotic factors, especially climate, and a characteristic ecological community

• Major biomes: tropical rainforest, tropical dry forest, tropical savanna, desert, temperate forest, temperate grassland, temperate woodland and shrubland, NW coniferous forest, boreal forest, and tundra

Other land areas

• Don’t fit neatly within a biome

• Mountain ranges – abiotic and biotic factors vary with elevation

• Polar Ice Caps -

Describe some aquatic ecosystems.

• Determined by depth, flow, temperature, and chemistry of overlying water

• Inhabitants specially adapted to each ecosystem

• Freshwater ecosystems– Flowing water – rivers,

streams, creeks– Standing water – lakes,

ponds

More aquatic ecosystems

• Estuaries – wetlands where rivers meet the sea, fresh and salt water – made of mostly detritivores– Salt marshes – east

coast– Mangrove swamps –

everglades in Fla.

– Both of these are valuable nurseries for fish, shellfish, and vegetation

Marine Ecosystems• Light zones

– Photic – well lit upper layer where organisms are able to carry out photosynthesis

– Aphotic – permanently dark zone beneath the photic zone, chemosynthetic autotrophs live here

• Zones based on depth and distance from shore– Intertidal zone– Coastal ocean– Open ocean– Benthic zone – ocean floor– Coral reefs – unique, diverse and

productive environment