Biomes and Communities

Environmental factors that affect an organism’s ability to survive in its environment are called limiting factors. Ex. Strong winds, cold temperatures, lack of moisture

Tolerance is the ability of an organism to withstand fluctuations in biotic and abiotic environmental factors. Some organisms have a greater range of tolerance.

Succession is the orderly, natural change and species replacement that takes place in the communities of an ecosystem.

Primary succession is the colonization by communities of organisms in an area where life has not existed before. Ex. Rocks exposed by an avalanche

Example of succession Mt. St. Helens

Secondary succession is the sequence of community changes that takes place after a community is disrupted by natural disasters or human actions.

Ex. of Secondary Succession

A climax community is a stable, mature community that undergoes little or no change in species.

A biome is a large group of ecosystems that share the same type of climax community. They can be either aquatic(water) biomes or terrestrial(land) biomes.

Aquatic biomes are either marine or freshwater. Marine biomes contain the largest amount of biomass(living material) on earth.

Marine biomes have a photic(light) zone or aphotic(no light) zone. Photic zones are shallow and exist along the coastlines of all landmasses. Aphotic zones are deep and dark(90% of the ocean is more than 1km deep.

An estuary is a coastal body of water, partially surrounded by land, in which fresh and saltwater mix. Estuaries may extend miles inland and salinity changes with the tide.

The intertidal zone is the portion of the shoreline that lies between the high and low tides. Intertidal ecosystems have the high levels of sunlight, nutrients and oxygen.

Plankton are small organisms that drift and float in the photic zone. They include autotrophs, diatoms, eggs and the juvenile stages of many marine animals.

As you move north or south the sun strikes the earth differently. This causes a change in wind, cloud cover, temperature, humidity and precipitation.

Earth’s Biomes

Tundra is a treeless land with long summer days and short periods of winter sunlight. Temperatures never get above freezing for long and only the top layer thaws at all. The rest is in permafrost.

The taiga is south of the tundra is also called the boreal or northern coniferous forest. The climate is harsh but are somewhat warmer and wetter. The soil is acidic due to the abundance of pine trees.

A desert is an arid region with sparse to almost non-existent plant life. Desert plants have many adaptations that allow them to live on small amounts of rainfall. Most animals are herbivores that remain undercover during the day.

Grasslands are large communities covered with rich soil, grasses and similar plants. They principally occur where there is insufficient rainfall to support forests. Soil contains considerable humus from dead plants.

Temperate or deciduous forests are dominated by broad-leafed hardwood trees. The soil has a top layer that is rich in humus and a deeper layer of clay.

Rain forests can be temperate or tropical . Tropical rain forests have warm temperatures, wet weather and lush plant growth. Rain forests are home to more species than any other biome on earth.