Biomes

Climate and Climatographs

Climate

• Climate: Average conditions, including temperature and precipitation, over long periods of time in a given area
• Weather: Day-to-day conditions in Earth’s atmosphere
• Climatographs: Diagrams that summarize an area’s average monthly temperature and precipitation
• Each biome has a set of characteristic organisms adapted to its particular climate conditions.

Net Primary Productivity

NPP

• Gross primary production: The rate at which primary producers undergo photosynthesis
• Net primary production: The amount of organic matter (biomass) that remains after primary producers use some to carry out cellular respiration
• Ecosystems vary in their net primary productivity, the rate at which primary producers convert energy to biomass.
• Warm, wet biomes generally have higher net primary productivity than cold, dry biomes.

Tropical Dry Forest

Tropical Dry Forest

• Warm year-round, but rainfall highly seasonal
• Most trees are deciduous—they lose their leaves and cease photosynthesis part of the year.
• Plants and animals exhibit adaptations (e.g. waxy leaf coating, deep roots, estivation, migration) that enable them to survive the dry season.

Savanna

Savanna

• Receives less precipitation than tropical dry forests, but more than deserts; usually has a distinct rainy season
• Grasses interspersed with groups of trees
• Tree growth limited by frequent fires and strong winds
• Plants are adapted to dry conditions; tend to be deciduous with deep roots, thick bark, and waxy coatings on leaves.
• Many animals migrate to find water, or burrow when water is scarce.

Desert

Desert

• Receives less than 25 cm (9.8 in.) of precipitation per year
• Temperatures vary widely from day to night.
• Plants tend to have thick, leathery leaves, store water in their tissues, and have shallow roots.
• Animals get most of their water from the food they eat, and they tend to be nocturnal. Mammals have exaggerated appendages to help regulate body temperature.
• Cactus spines are modified leaves that protect the plant from thirsty animals. Photosynthesis occurs within the green stems and trunks.

Temperate Rain Forest

Temperate Rain Forest

• Year-round moderate temperatures and heavy rainfall
• Largest extent found in Pacific Northwest of United States
• Characterized by tall evergreen trees, such as cedars and hemlocks, that don’t lose leaves annually; many are conifers (produce seed-bearing cones)
• Forest floor is shaded, damp, covered in moss.
• Animals that require moisture, such as amphibians, thrive here.

Temperate Forest

Temperate Forest

• Precipitation evenly spread throughout the year
• Varied temperatures (hot summers, cold winters)
• Plants tend to be broad-leafed and deciduous.
• Soil is enriched with nutrients from annual leaf drop.
• Animals may migrate, hibernate, or store food to survive cold conditions.

Temperate Grassland (Prairie)

Prairie

• Moderate seasonal precipitation and fairly extreme seasonal temperatures; droughts and fires common
• Not enough precipitation to support large trees; grasses, which grow from their base, thrive despite droughts, fires, animals grazing
• Animals are adapted to deal with lack of cover.
• Soil tends to be rich in nutrients; most of world’s grasslands have been converted to farmland.

Chaparral

Chaparral

• Highly seasonal conditions with mild, wet winters and warm, dry summers
• Prolonged hot, dry periods; droughts and fires common
• Plants are drought-resistant; many have thick, waxy leaves or leaves with hairs that trap moisture; succulents are common.
• Plants may have thick bark and deep roots to resist fire; some plants require fire to germinate.
• Many animals burrow or are nocturnal to avoid heat.
• Some chaparral plants contain oily compounds that facilitate the spread of fire.

Boreal Forest (Taiga)

Taiga

• Long, cold winters; short, cool summers
• Nutrient-poor, slightly acidic soils
• Low species diversity
• Coniferous trees with waxy needles and conical shape, adapted to harsh, snowy conditions are common.
• Animals feed, breed, and care for young mostly during short warm season; year-round residents tend to have thick insulation and small extremities that maintain heat.

Tundra

Tundra

• Extremely cold, dark winters; relatively sunny and cool summers
• Found at very high latitudes in the Northern Hemisphere
• Harsh winds, nutrient-poor soil, and freezing temperatures limit plant growth; no tall trees; mosses and lichens common
• Characterized by permafrost (underground soil that is frozen year-round)
• Birds and caribou migrate to the tundra during the mild summer to feed on insects and lichens; only a few species live here year-round.

Polar Ice and Mountains

Others

• Not classified as biomes
• No land under polar ice in Northern Hemisphere; ice sits atop Antarctica in Southern Hemisphere
• Very few plants; most life is in surrounding ocean
• Mountain communities change with elevation, similar to how biome communities change with latitude.

Ponds, Lakes, Inland Seas

Freshwater

• Salinity is less than 0.5 ppt (parts per thousand)
• Ponds and lakes are similar, except in size, but inland seas contain organisms adapted for open water.
• Ponds and lakes are divided horizontally into zones: littoral and limnetic

Estuaries

Brackish

• Occur where a river flows into the ocean or an inland sea
• Coastal estuaries are brackish ecosystems; organisms must tolerate wide salinity and temperature ranges.
• Coastal estuaries are home to salt marshes and mangrove forests.
• Like wetlands, estuaries help prevent flooding and soil erosion as well as provide habitats.

Oceans

Salt

• Currents are driven by water temperature and density differences, wind, and gravity.
• Surface winds and heating generate vertical currents that transport nutrients and oxygen.
• Horizontal ocean zones: intertidal, neritic, open ocean
• Vertical ocean zones: photic, aphotic, benthic