Introduction to Biomes
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What are the characteristics of the terrestrial biomes?

Characteristics of biological communities vary with temperature, precipitation, and latitude. Hot, humid regions generally have greater biological productivity than cold or dry regions.

What are climate graphs used for?

Climate graphs are used to describe and compare precipitation and temperature in different biomes.

If we know the general temperature range and precipitation level of an area, what can we predict in the absence of human disturbance?

We can predict the kind of biological community likely to occur there.

What is vertical zonation?

<p>Vertical zonation occurs as vegetation type change rapidly from warm and dry to cold and wet as you go up a mountain.</p> Signup and view all the answers

Cloud forests occur in high mountains where fog and mist keep vegetation wet all the time.

<p>True</p> Signup and view all the answers

What type of soil do tropical moist forests tend to have?

<p>Old</p> Signup and view all the answers

Tropical rainforests occur where rainfall is abundant - more than 200 cm (80 in) per year - and temperatures are warm to hot year-round.

<p>True</p> Signup and view all the answers

It has been estimated that one-half to two-thirds of all species of terrestrial plants and insects live in tropical forests.

<p>True</p> Signup and view all the answers

Tropical seasonal forests are often called Dry Tropical Forests because they are dry much of the year.

<p>True</p> Signup and view all the answers

Seasonal forests are often open woodlands that grade into savannas.

<p>True</p> Signup and view all the answers

What is the difference between grasslands and savannas?

<p>Grasslands receive between 25 and 75 cm of rain per year while savannas receive between 50-150 cm of rain per year.</p> Signup and view all the answers

Tropical savannas and grasslands have a rainy season, but generally the rains are less abundant or less dependable than in a forest.

<p>True</p> Signup and view all the answers

During dry seasons, fires can sweep across grassland, killing off young trees and keeping the landscape open.

<p>True</p> Signup and view all the answers

Grazing pressure from domestic livestock is an important threat to both the plants and animals of tropical grasslands and savannas.

<p>True</p> Signup and view all the answers

Deserts occur where precipitation is rare and unpredictable, usually with less than 30 cm of rain per year.

<p>True</p> Signup and view all the answers

Desert vegetation is sparse, but it can be surprisingly diverse and most desert plants and animals are highly adapted to survive long droughts and extreme heat.

<p>True</p> Signup and view all the answers

Desert is more vulnerable because sparse, slow-growing vegetation is quickly damaged by off-road vehicles.

<p>True</p> Signup and view all the answers

Desert soils recover slowly.

<p>True</p> Signup and view all the answers

Desert is also vulnerable to overgrazing.

<p>True</p> Signup and view all the answers

What is a major environmental problem in Africa's Sahel region?

<p>Livestock are destroying much of the plant cover. Bare, dry soil becomes drifting sand, and restabilization is extremely difficult.</p> Signup and view all the answers

In tropical latitudes, temperate (mid-latitude) grasslands occur where there is enough rain to support abundant grass but not enough for forests.

<p>True</p> Signup and view all the answers

Most grassland is a complex, diverse mix of grasses and flowering herbaceous plants, generally known as forbs.

<p>True</p> Signup and view all the answers

Deep roots help plants in temperate grasslands and savannas survive drought, fire, and extreme heat and cold.

<p>True</p> Signup and view all the answers

Deep roots, together with an annual winter accumulation of dead leaves on the surface, produce thick, organic-rich soils in temperate grasslands.

<p>True</p> Signup and view all the answers

Evergreen shrubs with small, leathery, sclerophyllous (hard, waxy) leaves form dense thickets in temperate shrublands called chaparral.

<p>True</p> Signup and view all the answers

Scrub oaks, drought-resistant pines, or other small trees often cluster in sheltered valleys in temperate shrublands.

<p>True</p> Signup and view all the answers

Periodic fires burn fiercely in this fuel-rich plant assemblage and are a major factor in plant succession in temperate shrublands.

<p>True</p> Signup and view all the answers

In California, the landscape of temperate shrublands is called chaparral, Spanish for “thicket”.

<p>True</p> Signup and view all the answers

Temperate shrublands are inhabited by drought-tolerant animals such as jackrabbits, kangaroo rats, mule deer, chipmunks, lizards, and many bird species.

<p>True</p> Signup and view all the answers

Very similar landscapes to temperate shrublands are found along the Mediterranean coast as well as southwestern Australia, central Chile, and South Africa.

<p>True</p> Signup and view all the answers

Broadleaf forests occur throughout the world where rainfall is plentiful.

<p>True</p> Signup and view all the answers

In mid latitudes, these forests are deciduous and lose their leaves in winter.

<p>True</p> Signup and view all the answers

At lower latitudes, broadleaf forests may be evergreen or drought-deciduous.

<p>True</p> Signup and view all the answers

Coniferous forests grow in a wide range of temperature and moisture conditions.

<p>True</p> Signup and view all the answers

Coniferous forests often occur where moisture is limited, in cold climates, moisture is unavailable (frozen) in winter, hot climates may have seasonal drought, sandy soils hold little moisture, and they are often occupied by conifers.

<p>True</p> Signup and view all the answers

Coniferous forests provide most wood products in North America.

<p>True</p> Signup and view all the answers

Coniferous forests of the Pacific coast grow in extremely wet conditions. The wettest coastal forests are known as temperate rainforests, a cool, rainy forest often enshrouded in fog.

<p>True</p> Signup and view all the answers

The Coniferous Forest is the largest terrestrial biome, found in the northern parts of Europe, North America and Asia.

<p>True</p> Signup and view all the answers

Boreal forests, or Northern Forests, lie between about 50° and 60° north.

<p>True</p> Signup and view all the answers

Mountainous areas at lower latitudes may also have many characteristics and species of the boreal forest.

<p>True</p> Signup and view all the answers

Dominant trees in boreal forests are pines, hemlocks, spruce, cedar, and fir.

<p>True</p> Signup and view all the answers

Some deciduous trees are also present in boreal forests, such as maples, birch, aspen, and alder.

<p>True</p> Signup and view all the answers

These forests are slow-growing because of the cold temperatures and a short frost-free growing season.

<p>True</p> Signup and view all the answers

The extreme, ragged edge of the boreal forest, where forest gradually gives way to open tundra, is known by its Russian name, Taiga.

<p>True</p> Signup and view all the answers

Tundra is a treeless landscape that occurs at high latitudes or on mountaintops, has a growing season of only two or three months, and it may have frost any month of the year.

<p>True</p> Signup and view all the answers

Tundra is a variant of grasslands because it has no trees.

<p>True</p> Signup and view all the answers

Tundra is a very cold desert because water is unavailable (frozen) most of the year.

<p>True</p> Signup and view all the answers

Arctic Tundra is an expansive biome that has low productivity because it has a short growing season.

<p>True</p> Signup and view all the answers

During midsummer, 24-hour sunshine supports a burst of plant growth and an explosion of insect life in arctic tundra.

<p>True</p> Signup and view all the answers

Alpine Tundra occurs on a near mountain top and has environmental conditions and vegetation similar to arctic tundra. These areas have a short, intense growing season.

<p>True</p> Signup and view all the answers

Many alpine tundra plants also have deep pigmentation and leathery leaves to protect against the strong ultraviolet light in the thin mountain atmosphere.

<p>True</p> Signup and view all the answers

Coral reefs and estuaries are among the world's most productive and diverse ecosystems.

<p>True</p> Signup and view all the answers

Vertical stratification is a key feature of aquatic ecosystems, mainly because light decreases rapidly with depth, and communities below the photic zone (light zone, often reaching about 20 m deep) must rely on energy sources other than photosynthesis to persist.

<p>True</p> Signup and view all the answers

Temperature also decreases with depth in aquatic ecosystems.

<p>True</p> Signup and view all the answers

Deep ocean species often grow slowly in part because metabolism is reduced in cold conditions, affecting the amount of oxygen and other elements that can be absorbed in water.

<p>True</p> Signup and view all the answers

Phytoplankton are microscopic floating algae that carry on photosynthesis and zooplanktons are small, weakly swimming animals that feed on phytoplankton.

<p>True</p> Signup and view all the answers

Benthic communities occur on the bottom of the ocean, while pelagic zone communities are found in the water column.

<p>True</p> Signup and view all the answers

The epipelagic zone, where photosynthetic organisms are found, is the uppermost layer of the pelagic zone.

<p>True</p> Signup and view all the answers

Below the epipelagic zone are the mesopelagic (meso = medium), and bathypelagic (bathos = deep) zones.

<p>True</p> Signup and view all the answers

The deepest layers of the ocean are the Abyssal Zone (to 4,000 m) and Hadal Zone (deeper than 6,000 m).

<p>True</p> Signup and view all the answers

Littoral Zones are shorelines, and the Intertidal Zone is the area exposed by low tides.

<p>True</p> Signup and view all the answers

Coral Reefs are among the best-known marine ecosystems because of their extraordinary biological productivity and their diverse and beautiful organisms.

<p>True</p> Signup and view all the answers

Mangroves are trees that grow in salt water and occur along calm, shallow, tropical coastlines around the world.

<p>True</p> Signup and view all the answers

Mangrove forests or swamps help stabilize shorelines and they are also critical nurseries for fish, shrimp, and other commercial species.

<p>True</p> Signup and view all the answers

Estuaries are bays where rivers empty into the sea, mixing fresh water with salt water.

<p>True</p> Signup and view all the answers

Salt marshes are shallow wetlands flooded regularly or occasionally with seawater and occur on shallow coastlines, including estuaries.

<p>True</p> Signup and view all the answers

Tide Pools are depressions in a rocky shoreline that are flooded at high tide but retain some water at low tide.

<p>True</p> Signup and view all the answers

These areas remain rocky where wave action prevents most plant growth or sediment (mud) accumulation in tide pools.

<p>True</p> Signup and view all the answers

Barrier Islands are low, narrow, sandy islands that form to parallel to a coastline, occurring where the continental shelf is shallow and rivers or coastal currents provide a steady source of sediments.

<p>True</p> Signup and view all the answers

Freshwater ecosystems vary according to depth and light penetration, which control size and types of vegetation.

<p>True</p> Signup and view all the answers

Freshwater ecosystems are often small but they are disproportionately important in biodiversity.

<p>True</p> Signup and view all the answers

Like marine environments, freshwater lakes have distinct vertical zones.

<p>True</p> Signup and view all the answers

The Benthos is the bottom of a freshwater lake, occupied by a variety of snails, burrowing worms, fish and other organisms.

<p>True</p> Signup and view all the answers

The Epilimnion is a warmer upper layer that is mixed by wind and warmed by the sun, while the Hypolimnion is a colder, deeper layer that is not mixed.

<p>True</p> Signup and view all the answers

The Thermocline is the sharp temperature boundary between the epilimnion and hypolimnion.

<p>True</p> Signup and view all the answers

The Mesolimnion is below the thermocline, where the water is much colder.

<p>True</p> Signup and view all the answers

Wetlands are shallow ecosystems in which the land surface is saturated or submerged at least part of the year.

<p>True</p> Signup and view all the answers

Wetlands have vegetation that is adapted to grow under saturated conditions.

<p>True</p> Signup and view all the answers

Swamps are also known as wooded wetlands, while marshes are wetlands without trees.

<p>True</p> Signup and view all the answers

Bogs are areas of saturated ground, and usually the ground is composed of deep layers of accumulated, undecayed vegetation known as peat.

<p>True</p> Signup and view all the answers

Fens are similar to bogs except that they are mainly fed by groundwater, so that they have mineral-rich water and specially adapted plant species.

<p>True</p> Signup and view all the answers

Humans have become dominant organisms over most of the earth, damaging or disturbing more than half of the world's terrestrial ecosystems to some extent.

<p>True</p> Signup and view all the answers

Humans preempt about 40 percent of the net terrestrial primary productivity of the biosphere either by consuming it directly, by interfering with its production or use, or by altering the species composition or physical processes of human-dominated ecosystems.

<p>True</p> Signup and view all the answers

Conversion of natural habitat to human uses is the largest single cause of biodiversity losses.

<p>True</p> Signup and view all the answers

The greatest impacts of human disturbance have been in Europe, parts of Asia, North and Central America, and islands such as Madagascar, New Zealand, Java, Sumatra, and those in the Caribbean.

<p>True</p> Signup and view all the answers

Temperate broadleaf forests are the most human-dominated biome, with 81.9% human dominated.

<p>True</p> Signup and view all the answers

Tundra and arctic desert have the lowest human-dominated biome, at 0.3%.

<p>True</p> Signup and view all the answers

Study Notes

Introduction to Biomes

  • Biomes are general types of communities sharing similar climate conditions, growth patterns, and vegetation.
  • Marine and freshwater ecosystems are also considered in the discussions.
  • The overall patterns of human disturbance in world biomes are presented.

Learning Outcomes

  • Acquire a high level of awareness about the environment and its significance.
  • State the characteristics of major terrestrial biomes and the factors determining their distribution.

Terrestrial Biomes

  • Biome characteristics change with temperature, precipitation, and latitude.
  • Hot, humid regions have higher biological productivity than cold or dry regions.

Climate Graphs

  • Climate graphs (temperature and precipitation) are important for biome distribution.
  • Predicting the type of biological community can be done using a biome's climate characteristics.
  • Biome types change rapidly with altitude.

Major World Biomes

  • Listed examples include tropical rainforests, subtropical moist forests, seasonal forests, grasslands, deserts, temperate rainforests, temperate conifer forests, temperate broadleaf and mixed forests, Mediterranean woodlands and scrub, temperate grasslands and savannas, boreal forests, tundra, rock and ice, and montane grasslands and shrublands.

### Tropical Moist Forests

  • Cloud forests are found high in mountains, maintaining wet vegetation.
  • Tropical rainforests receive high rainfall year-round (over 200 cm or 80 in).
  • Tropical moist forest soils are often thin, acidic, and nutrient-poor, despite high species diversity.
  • High concentrations of insects and other species live in tropical forests.

Tropical Seasonal Forests

  • Also called dry tropical forests, they are drought-tolerant, looking brown and dormant during dry seasons.
  • They have a distinct rainy season, essential for tree growth.
  • Many trees are drought deciduous, losing leaves when water is scarce.
  • These forests often transition into savannas or open woodlands.

Tropical Savannas and Grasslands

  • Grasslands have 25-75 cm of rain per year.
  • Savannas have 50-150 cm of rain per year.
  • They have a distinct rainy season, but rainfall is less abundant/less dependable compared to forests.
  • Fires are common during dry seasons, helping maintain the open grassland structure.
  • Plant adaptations are vital for their survival in drought, heat, and fire.

Deserts

  • Precipitation is scarce and unpredictable, typically less than 30 cm per year.
  • Vegetation is sparse but diverse, with plants adapted to survive extreme conditions (drought, heat, cold).
  • Deserts and their soils are highly vulnerable to overgrazing.

Temperate Grasslands

  • Occur where rainfall supports grass but not forests.
  • Grasses and forbs (flowering herbs) are dominant.
  • Deep roots aid in drought, fire, and heat/cold tolerance.

Temperate Shrublands

  • Dense, evergreen shrubs dominate.
  • Small, leathery leaves reduce water loss.
  • Frequent fires are a crucial part of the plant succession process.

Temperate Forests

  • Deciduous forests are located in areas with abundant rainfall.
  • Trees lose leaves in winter.
  • Evergreen or drought deciduous types exist in other latitudes.

Coniferous Forests

  • Grow in various temperature and water conditions.
  • Often occur where water is scarce in cold or hot regions.
  • Essential wood sources.
  • Some coastal coniferous forests are temperate rainforests, characterized by dense fog.

Boreal Forests

  • Also known as Northern Forests or Taiga
  • Found between 50° and 60° north latitude.
  • Dominated by conifers (pines, hemlocks, spruce, cedar, and fir).
  • Often have a short growing season and cold temperatures.

Tundra

  • Treeless, exposed landscapes.
  • Growing season is short (two or three months) and can have frost any time of the year.
  • Mostly cold and dry.
  • Arctic tundra is expansive and has low productivity; alpine tundra is similar but higher in mountains.

Marine Ecosystems

  • Characterized by depth, temperature, and salinity.
  • Coral reefs and estuaries are among the world's most productive ecosystems.
  • Vertical stratification affects light penetration, impacting energy sources.

Coastal Zones

  • Includes coral reefs, estuaries, salt marshes, wetlands.
  • These are highly productive and diverse areas.

Freshwater Ecosystems

  • Characteristics depend on depth and light penetration.
  • Freshwater lakes have distinct vertical zones (benthos, epilimnion, hypolimnion, thermocline, mesolimnion).

Wetlands

  • Shallow ecosystems, saturated or submerged.
  • Adapted vegetation for saturated conditions.

Swamps, Marshes, and Bogs

  • Types of wetlands
  • Swamps are wooded wetlands
  • Marshes have no trees.
  • Bogs have thick layers of accumulated, undecayed vegetation (peat).
  • Fens are like bogs but fed by groundwater.

Human Disturbance

  • Human activities drastically impact most of the world's ecosystems.
  • Conversion of natural habitats is a significant cause of biodiversity loss.
  • Data from Conservation International has mapped the extent of human impact, showing high disturbance in many regions.

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Explore the essential characteristics of various biomes, including their climate conditions, growth patterns, and vegetation. This quiz covers major terrestrial biomes, marine and freshwater ecosystems, and the impact of human activities on these environments. Gain valuable insights into the significance of biomes in maintaining ecological balance.

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