Biomes Flashcards
What is a biome?
A biome is a large area characterized by its vegetation, soil, climate, and wildlife. It is therefore a geoclimatic zone that is identifiable on a global scale. There are five major types of biomes: aquatic, grassland, forest, desert, and tundra, though some of these biomes can be further divided into more specific categories, such as freshwater, marine, savanna, tropical rainforest, temperate rainforest, and taiga.
Explain global air circulation
The reason we have different weather patterns, jet streams, deserts and prevailing winds is all because of the global atmospheric circulation caused by the rotation of the Earth and the amount of heat different parts of the globe receive.
The sun is our main source of heat, and because of the tilt of the Earth, its curvature, our atmosphere, clouds and polar ice and snow, different parts of the world heat up differently. This sets up a big temperature difference between the poles and equator but our global circulation provides a natural air conditioning system to stop the equator becoming hotter and hotter, and poles becoming colder and colder.
Over the major parts of the Earth’s surface there are large-scale wind circulations present. The global circulation can be described as the world-wide system of winds by which the necessary transport of heat from tropical to polar latitudes is accomplished.
In each hemisphere there are three cells (Hadley cell, Ferrel cell and Polar cell) in which air circulates through the entire depth of the troposphere. The troposphere is the name given to the vertical extent of the atmosphere from the surface, right up to between 10 and 15 km high. It is the part of the atmosphere where most of the weather takes place.
Main characteristics of the Tundra.
Tundra is the coldest of all the biomes (average temperature of -5). Tundra comes from the Finnish word tunturi, meaning treeless plain. It is noted for its frost-molded landscapes, extremely low temperatures, little precipitation, poor nutrients, and short growing seasons. Dead organic material functions as a nutrient pool. This organic rich soil is called peat. The two major nutrients are nitrogen and phosphorus. Nitrogen is created by biological fixation, and phosphorus is created by precipitation.
Main characteristics of tundra include:
Extremely cold climate Low biotic diversity Simple vegetation structure Limitation of drainage Short season of growth and reproduction Energy and nutrients in the form of dead organic material Large population oscillations
Main characteristics of the Boreal forest.
Boreal forests, or taiga, represent the largest terrestrial biome. Occurring between 50 and 60 degrees north latitudes, boreal forests can be found in the broad belt of Eurasia and North America: two-thirds in Siberia with the rest in Scandinavia, Alaska, and Canada. Seasons are divided into short, moist, and moderately warm summers and long, cold, and dry winters. The length of the growing season in boreal forests is 130 days.
Main characteristics:
Temperatures are very low.
Precipitation is primarily in the form of snow, 40-100 cm annually.
Soil is thin, nutrient-poor, and acidic.
Canopy permits low light penetration, and as a result, understory is limited.
Flora consist mostly of cold-tolerant evergreen conifers with needle-like leaves, such as pine, fir, and spruce.
Fauna include woodpeckers, hawks, moose, bear, weasel, lynx, fox, wolf, deer, hares, chipmunks, shrews, and bats.
Main characteristics of the Temperate forest.
Temperate forests occur in eastern North America, northeastern Asia, and western and central Europe. Well-defined seasons with a distinct winter characterize this forest biome. Moderate climate and a growing season of 140-200 days during 4-6 frost-free months distinguish temperate forests.
Main characteristics:
Temperature varies from -30° C to 30° C.
Precipitation (75-150 cm) is distributed evenly throughout the year.
Soil is fertile, enriched with decaying litter.
Canopy is moderately dense and allows light to penetrate, resulting in well-developed and richly diversified understory vegetation and stratification of animals.
Flora is characterized by 3-4 tree species per square kilometer. Trees are distinguished by broad leaves that are lost annually and include such species as oak, hickory, beech, hemlock, maple, basswood, cottonwood, elm, willow, and spring-flowering herbs.
Fauna is represented by squirrels, rabbits, skunks, birds, deer, mountain lion, bobcat, timber wolf, fox, and black bear.
Further subdivisions of this group are determined by seasonal distribution of rainfall:
- moist conifer and evergreen broad-leaved forests: wet winters and dry summers (rainfall is concentrated in the winter months and winters are relatively mild).
- dry conifer forests: dominate higher elevation zones; low precipitation.
mediterranean forests: precipitation is concentrated in winter, less than 100 cm per year. - temperate coniferous: mild winters, high annual precipitation (greater than 200 cm).
- temperate broad-leaved rainforests: mild, frost-free winters, high precipitation (more than 150 cm) evenly distributed throughout the year.
Main characteristics of the Prairies and grasslands.
Grasslands are characterized as lands dominated by grasses rather than large shrubs or trees. They are climatically similar to temperate forests but dryer.
Main characteristics:
Precipitation ranges from a low 40mm to a high 80cm
Home to numerous herbivores - grazing is an important ecological factor here
Heat and aridity are important evolutionary factors (panting, sweating, large ears, evapotranspiration)
Native grazers prevent any single plant from out competing the others.
Soils are very rich
Fire is a very important component of grasslands: some areas my burn every three to five years due to lightning. This keeps trees from becoming established.
Main characteristics of the Chaparral
In many coastal regions that border on deserts we find fairly small patches of a biome known as temperate shrubland or chaparral. Closeness to the sea provides a slightly longer winter rainy season than nearby temperate deserts have, and fogs during the spring and fall re-duce evaporation. These biomes are found along coastal areas of southern California in the United States, the Mediterranean Sea, central Chile, southern Australia, and southwestern South Africa.
Main characteristics:
- Wet and mild winter climate, dry and mild summer (mediterranean)
- Summer drought is what drives this biome’s ecology
- Some plants limit the usage of water by producing small hard leaves: most are evergreen so they can photosynthesize during the wet part of the year.
- Some plants gain as much water as possible: deep tap roots, extensive root system (bare ground between plants).
- Eradication of top predators when these areas are settled leads to a proliferation of herbivores
Main characteristics of the Desert
In a desert, annual precipitation is low and often scattered unevenly throughout the year. During the day, the baking sun warms the ground and causes evaporation of moisture from plant leaves and soil. But at night, most of the heat stored in the ground radiates quickly into the atmosphere. Desert soils have little vegetation and moisture to help store the heat, and the skies above deserts are usually clear. This explains why, in a desert, you may roast during the day but shiver at night.
Main characteristics:
- Too dry to support most life forms
- Cloudless skies permit wide temperature fluctuations
- Desert plants and animals must be obsessive about water retention
- Animals come out when temperatures are lower
- Top predators are snakes and lizards
- Evolution has shaped desert plants to minimize exposure to the sun (cacti).
Main characteristics of the Tropical forest
Tropical rainforest are luxuriant forest found in wet tropical uplands and lowlands around the Equator. Tropical rainforests, which worldwide make up one of Earth’s largest biomes (major life zones), are dominated by broad-leaved trees that form a dense upper canopy (layer of foliage) and contain a diverse array of vegetation and other life.
Main characteristics:
- Constant temperature - average from one month to the other changes +/- 2 degrees.
- Lots of rain: annual ranges between 2-15 thousands mm
- Wet and dry seasons: length of dry season determines the ecology
- Long dry season (6 to 8 months): many trees lose their leaves to prevent overheating
- Short dry season (less than 3 months): more rain per year, extreemes up to 50m per year
- Huge diversity: 50 to 70% of organisms on Earth inhabit these forests. Rainforests can support more than 350-450 tree species per hectare (temperate forests around 20-30)
- Most productive terrestrial biome: high temperatures, moisture, uninterrupted growing season, decomposers and nutrient cycling.
Describe the aquatic biome
The aquatic biome is the largest of all the biomes, covering about 75 percent of Earth’s surface. This biome is usually divided into two categories: freshwater and marine. Typically, freshwater habitats are less than 1 percent salt. Marine life, however, has to be adapted to living in a habitat with a high concentration of salt. Freshwater habitats include ponds, lakes, rivers, and streams, while marine habitats include the ocean and salty seas.
Limiting factors in aquatic biomes:
- Salinity
- Dissolved oxygen
- Sunlight: different layers according to penetration of light - photic (top layer with producers and consumers), Aphotic (consumers only), Benthic (bottom with scavengers and decomposers).
What are the major aquatic life zones?
- Saltwater/Marine
- Oceans
- Estuaries
- Coastal wetlands
- Shoreline
- Coral reefs
- Mangrove forests (roots of trees are into the water)
- Freshwater (less than 1% salt concentration)
Main characteristics of lakes
Lakes and Ponds represent a freshwater biome type that is generally referred to in the scientific community as a lentic ecosystem (still or standing waters). Scientists that study lakes and ponds are known as limnologists.
Lakes are larger and deeper than ponds. Plant growth is limited to the shoreline –> sunlight does not penetrate to the bottom. A lake can be divided into different zones: the littoral zone, the limnetic zone (open water), the euphotic zone and the benthic zone (along the terrain of the lake).
Intense heating of the surface waters of a lake help create a strong stratification of lake waters. The upper layer is known as the epilimnion. This layer is affected by winds and stays fairly well mixed. Just below the epilimnion is the thermocline where the water stops mixing. It serves as a boundary layer for the cold, deep water below. The hypolimnion is the cold, deep-water, stagnant layer. This layer often has very low oxygen in the water. This is often accompanied by dissolved hydrogen sulphide and other sulfurous gases.
What are other freshwater life zones other than lakes?
Ponds: are small, shallow and sunlight penetrates all the way to the bottom. Most ponds are completely filled with plant material –> high amount of nutrients.
Rives: water moves slower and debris settles on the bottom. Rivers tend to have more nutrients and less dissolved oxygen.
Streams: faster flowing therefore more dissolved oxygen.
Inland wetlands
Main characteristics of marine biome
Marine regions cover about three-fourths of the Earth’s surface and include oceans, coral reefs, and estuaries. Marine algae supply much of the world’s oxygen supply and take in a huge amount of atmospheric carbon dioxide. The evaporation of the seawater provides rainwater for the land.
All of the Earth’s ocean are connected, but differ from each other in sunlight exposure, temperature, density, and salinity. Like ponds and lakes, the ocean regions are separated into separate zones: intertidal, pelagic, abyssal, and benthic.
- The intertidal zone is where the ocean meets the land — sometimes it is submerged and at other times exposed, as waves and tides come in and out. Because of this, the communities are constantly changing.
- The pelagic zone includes those waters further from the land, basically the open ocean. The pelagic zone is generally cold though it is hard to give a general temperature range since, just like ponds and lakes, there is thermal stratification with a constant mixing of warm and cold ocean currents. The flora in the pelagic zone include surface seaweeds. The fauna include many species of fish and some mammals, such as whales and dolphins. Many feed on the abundant plankton.
- The benthic zone is the area below the pelagic zone, but does not include the very deepest parts of the ocean (see abyssal zone below). The bottom of the zone consists of sand, slit, and/or dead organisms. Here temperature decreases as depth increases toward the abyssal zone, since light cannot penetrate through the deeper water. Flora are represented primarily by seaweed while the fauna, since it is very nutrient-rich, include all sorts of bacteria, fungi, sponges, sea anemones, worms, sea stars, and fishes.
- The deep ocean is the abyssal zone. The water in this region is very cold (around 3° C), highly pressured, high in oxygen content, but low in nutritional content. The abyssal zone supports many species of invertebrates and fishes.
