“Land Biomes of the World”

Mrs. Hartge’s Science Class

• The global ecosystem is called the biosphere

– It is the sum of all the Earth's ecosystems

– The biosphere is the most complex level in ecology

The biosphere is the total of all of Earth's ecosystems

THE BIOSPHERE

Figure 34.2A

• The biosphere is self-contained

– except for energy obtained from the sun and heat lost to space

• Each habitat has a unique community of species

Figure 34.2B

Abiotic FactorsAbiotic factors are those non-living physical and chemical factors which affect the ability of organisms to survive and reproduce.   

Abiotic Factors

• Abiotic factors vary in the environment and determining the types and numbers of organisms that exist in that environment.

• light intensity

• temperature range

• type of soil or rock

• pH level (acidity or alkalinity)

• water availability

• dissolved gases

• level of pollutant

• The most important abiotic factors that determine the biosphere's structure and dynamics include

– solar energy

– water

– temperature

Physical and chemical factors influence life in the biosphere

• Disturbances such as fires, hurricanes, and volcanic eruptions are also abiotic factors

Figure 34.4

Biotic Factors

Biotic factors are all the living things or their materials that directly or indirectly affect an organism in its environment.   This would include organisms, their presence, parts, interaction, and wastes.  Factors such as parasitism, disease, and predation (one animal eating another) would also be classified as biotic factors.

• The presence and success of a species in a particular place depends upon its ability to adapt

• Natural selection adapts organisms to abiotic and biotic factors

– Biotic factors include predation and competition

Organisms are adapted to abiotic and biotic factors by natural selection

Figure 34.5

• Climate often determines the distribution of communities

• Earth's global climate patterns are largely determined by the input of solar energy and the planet's movement in space

Regional climate influences the distribution of biological communities

• Most climatic variations are due to the uneven heating of Earth's surface

– This is a result of the variation in solar radiation at different latitudes

Figure 34.6A

Low angle ofincoming sunlight

Sunlight directlyoverhead

Low angle ofincoming sunlight

Atmosphere

North Pole

60º N

30º N

Tropic ofCancer

0º (equator)

30º S

60º S

South Pole

Tropic ofCapricorn

• The seasons of the year result from the permanent tilt of the plant on its axis as it orbits the sun

Figure 34.6B

JUNE SOLSTICE(Northern

Hemisphere tiltstoward sun)

MARCH EQUINOX(equator facessun directly)

DECEMBERSOLSTICE(Northern

Hemisphere tiltsaway from sun)

SEPTEMBEREQUINOX

What is a Biome?

• Plants and animals don't live in isolation, but they live together with other plants and animals in an interdependent group called an ecological community. If you think about it for a moment, you will realize that all of the plants and animals in a particular ecological community must be adapted to the same climate so that they can all live in the same location.

• A distinct ecological community of plants and animals living together in a particular climate is called a "biome." Scientists have divided the broad spectrum of climates and ecological communities found on Earth into biomes in different ways - some with many divisions, some with only a few.

• Major terrestrial biomes

Figure 34.9

30º N

Equator

30º S

Tropical forest

Savanna

Desert

Polar and high-mountain ice

Chaparral

Temperate grassland

Temperate deciduous forest

Coniferous forest

Tundra (arctic and alpine)

• Several types of tropical forests occur in the warm, moist belt along the equator Tropical Rainforest

Tropical forests cluster near the equator

Figure 34.10

• Drier, tropical areas and some nontropical areas are characterized by the savanna Tropical Savannah

Savannas are grasslands with scattered trees

Figure 34.12

• Deserts are the driest of all terrestrial biomes

– They are characterized by low and unpredictable rainfall Desert

Deserts are defined by their dryness

Figure 34.13

– Desertification is a significant environmental problem

• Temperate grasslands are found in the interiors of the continents, where winters are cold

– Drought, fires, and grazing animals prevent trees from growing

– Farms have replaced most of North America's temperate grasslands

Temperate grasslands include the North American prairie

Figure 34.15

• Temperate deciduous forests grow where there is sufficient moisture to support the growth of large trees Deciduous Forest

– Nearly all of the original deciduous forests in North America have been drastically altered by agriculture and urban development

Deciduous trees dominate temperate forests

Figure 34.16

• The northern

coniferous forest, or taiga, is the largest terrestrial biome on Earth Taiga

Coniferous forests are often dominated by a few species of trees

Figure 34.17

• The taiga is characterized by long, cold winters and short, wet summers

• Coastal coniferous forests of the Pacific Northwest are actually temperate rain forests

• The arctic tundra lies between the taiga and the permanently frozen polar regions Arctic Tundra

– It is a treeless biome characterized by extreme cold, wind, and permafrost

– Permafrost is continuously frozen subsoil

Long, bitter-cold winters characterize the tundra

Figure 34.18