Biomes and Ecosystems

Broad categories of living systems Defined mainly by climate vary in biodiversity, productivity, and structure

communities shaped by temperature ranges and availability of moisture (precipitation)

Abundant rainfall; warm and hot temperatures all year soil: thin, acidic, nutrient-poor - 90% of nutrients in organisms species: very high number Types of Tropical Rainforest: - tropical moist forests - tropical seasonal forests

Distinct wet and dry seasons Drought-deciduous trees and shrubs - lose leaves and cease growing with low water availability More agriculturally productive than moist forests Highly endangered - more humans living near

Savanna: grassland with sparse tree cover Rainy season: less abundant; less dependable Dry season: risk of fires - plant adaptations: deep, persistent roots Threat: grazing from livestock

Temperature: extreme hot and extreme cold Precipitation: low and sporadic Plant adaptations: drought-deciduous Animal adaptations: nocturnal; concentrated excrement

Enough rain to support grass: not enough for a forest like plants in the savanna - deep, persisten roots - produces thick, organic-rich soils Main threats: agriculture and overgrazing

aka broad-leaf forests Trees lose leaves in winter Dense canopy in summer; diverse understory in spring Greatest Threat: rapid deforestation

aka evergreen forests often occur with limited moisture in pacific coast: known as temperature rainforests (cool, rainy, often enshrouded in fog) pines, spruce, fir, and other species of trees

Dominated by conifers with some deciduous trees - low species diversity due to allelopathy extreme cold and short summer - limit growth rate of trees

Below freezing temperatures most of the year occurs at high latitudes or on mountaintops Low productivity - short growing season - frost any month of the year Low diversity Not directly threatened - indirectly affected by climate change and air pollution

Extensive nights (winter) and 24-h sunshine (summer) - important for migratory birds

on or near mountaintops; conditions and vegetation similar to arctic tundra - alpine tundra plants: deep pigmentation, leathery leaves - protect against UV

Depend on tiny, free-floating phytoplankton; ocean currents and upwelling currents: transport nutrients; vertical stratification due to temperature and light decreasing with depth

Described by depth and proximity to the shore relatively low productivity but have thriving communities Features that support communities in the open ocean: - sea mounts (undersea mountain chains and islands) - ocean currents - free floating mats of brown algae

Unkowng until 1977 - alvin (deep-sea submarine) Communities based on microbes that capture chemical energy - taken from sulfur compounds released from vents Magma under oceanic crust provide heat to vents

Vary with depth, light, and temperature - like the open ocean high productivity and density - nutrients washing from land - shallow, clear, warm waters supporting photosynthesis

Very high productivity and biodiversity Occurs where waters are shallow and clear - enough for sunlight Calcium-rich skeletons - shelter algae and other species Coral Polyps - colonial animals symbiotic with photosynthetic algae Vulnerable to human activities and ocean warming

Occur in shallow, warm, sandy coastlines support rich communities of grazers same vulnerabilities as coral reefs Vulnerable to human activities and ocean warming

Depressions in rocky shoreline subjected to violent wave action - prevents plant growth and sediment accumulation High tide: flooded Low tide: minimal water with hot desiccating sunshine Specialized animals and plants

Bays where rivers empty into the sea; fresh water mixes with salt water calm, warm, and nutrient-rich Rivers: provide nutrients and sediments Biologically diverse and productive; spawning for marine fish and shellfish

Shallow wetlands regularly or occasionally flooded with seawater; occurs in estuaries

Distinct Vertical zones; Littoral zone: emergent plants create functional links between layers Benthic zone: lowest oxygen due to little mixing; lowest light

Shallow ecosystems; saturated or submerged part of the year described by vegetation; adapted in saturated conditions support rich biodiversity; essential for breeding and migratory birds Reduce flooding; replenish groundwater supplies; filters run-off