Life in the Tundra
Deserts, grasslands, rainforests, coral reefs, and tundra may seem quite different, but they are all
examples of biomes. A definition for biome is “a living community characterized by distinctive
plant and animal species and maintained under the climatic conditions of the region.” Biomes are
made of many similar ecosystems (communities of organisms and the environments in which
they live).
A biome is characterized by abiotic (nonliving) factors such as geography and climate and by
biotic (living) factors such as plant and animal species.
Life in any biome includes producers (plants and other photosynthetic organisms) and
consumers (organisms that obtain their energy from producers). These consumers may be
further classified as herbivores (plant eaters), carnivores (meat eaters), or omnivores (feed on a
combination of animals and plants).
In addition, all ecosystems are dependent on detritivores (decomposers) — bacteria and other
microorganisms that obtain energy from breaking down organic matter.
The flow of energy from the sun through an ecosystem can be illustrated in a food chain, such as
this generalized one:
Generalized food chain.
Energy is lost in the form of heat at each level of a food chain, which means that the number of
individuals at each successive level decreases. For example, within a food chain there are always
more producers than primary consumers, and more primary consumers than secondary
consumers or tertiary consumers. Decreasing available energy and population sizes in a food
chain are illustrated by an energy (or ecological) pyramid:
Image courtesy of Wikimedia.
While food chains are a useful teaching tool, their simplicity doesn’t usually capture the complex
relationships within a biome or the fact that any one organism may be part of several food
chains. A food web, which illustrates the overlap between multiple food chains, more accurately
captures the flow of energy in an ecosystem.
A food web shows overlap between multiple food chains in an ecosystem.
Living organisms in any biome interact through a variety of relationships. Organisms compete
for food, water, and other resources. Predators hunt their prey. Some organisms coexist in
mutually beneficial relationships (symbiosis), while others harm organisms for their own benefit
(parasitism). Still others benefit from a relationship that neither helps nor harms the other
organism (commensalism).
Biomes (and their food webs) can change as a result of natural hazards or human activities.
Changes in environmental conditions may limit the availability of resources (food, water, space
or shelter), reducing the number of organisms that can survive in a given environment. A change
at any level of a food web will impact all other organisms in that web in some way. Some species
are considered keystone species because of the critical role they play in an ecosystem’s food
web. Examples of keystone species include grizzly bears, sea stars, and sea otters.
TUNDRA
The tundra is a biome characterized by an extremely cold climate, little precipitation, poor
nutrients, and a short growing season. Other characteristics include low biodiversity, simple
plants, limited drainage, and large variations in populations.
There are two types of tundra: arctic and alpine. Arctic tundra is located in the Northern
Hemisphere; alpine tundra is located at high elevations on mountains throughout the world.
Tundra is also found to a limited extent in Antarctica – specifically, the Antarctic Peninsula.
ARCTIC TUNDRA
Arctic tundra is found along the northern coasts of North America, Asia, and Europe, and in
parts of Greenland. It extends south to the edge of the taiga (a biome characterized by coniferous
forests). The division between the forested taiga and the treeless tundra is known as the
timberline or tree line.
Location of arctic tundra across the Northern Hemisphere. Image courtesy of Wikimedia.
The tundra is known for cold conditions, with an average winter temperature of -30 degrees F (34 degrees C), and an average summer temperature ranging from 37 degrees to 54 degrees F (3
degrees to 12 degrees C). The growing season lasts from 50 to 60 days. The biome is also
characterized by desertlike conditions, with an average of six to ten inches (15 to 25 cm) of
yearly precipitation, including snow melt. Winds often reach speeds of 30 to 60 miles (48 to 97
km) an hour.
Another hallmark of the tundra is permafrost, a layer of permanently frozen subsoil and
partially decayed organic matter. Only the top nine or ten inches of soil thaw, leading to the
formation of bogs and ponds each spring.
Ice wedges in the permafrost can crack and cause the formation of polygonal ground. This
picture also illustrates the formation of ponds as the snow melts each spring. Photo courtesy of
U.S. Fish and Wildlife Service.
Tundra and taiga permafrost stores about one-third of the world’s soil-bound carbon. Warming
Arctic temperatures due to climate change are causing the permafrost to thaw, releasing the
carbon in the form of carbon dioxide (a greenhouse gas). Additional carbon dioxide in the
atmosphere will intensify warming, leading to increased thawing and the release of even more
carbon dioxide. This positive feedback loop thus has the potential to significantly increase the
rate and effects of climate change.
Approximately 1,700 species of vascular plants are found across the Arctic tundra, including
flowering plants, low shrubs, sedges, grasses, and liverworts. Lichens, mosses, and algae are also
common. In general, tundra plants are low growing, have shallow root systems, and are capable
of carrying out photosynthesis at low temperatures and with low light intensities.
Animals found in the Arctic tundra include herbivorous mammals (lemmings, voles, caribou,
arctic hares, and squirrels), carnivorous mammals (arctic foxes, wolves, and polar bears), fish
(cod, flatfish, salmon, and trout), insects (mosquitoes, flies, moths, grasshoppers, and blackflies),
and birds (ravens, snow buntings, falcons, loons, sandpipers, terns, and gulls). Reptiles and
amphibians are absent because of the extremely cold temperatures. While many of the mammals
have adaptations that enable them to survive the long cold winters and to breed and raise young
quickly during the short summers, most birds and some mammals migrate south during the
winter. Migration means that Arctic populations are in continual flux.
A generalized food web for the Arctic tundra begins with the various plant species (producers).
Herbivores (primary consumers) such as pikas, musk oxen, caribou, lemmings, and arctic hares
make up the next rung. Omnivores and carnivores (secondary consumers) such as arctic foxes,
brown bears, arctic wolves, and snowy owls top the web. Bacteria and fungi play the important
role of breaking down organic matter and returning nutrients to the soil for re-use. Of course, the
exact species involved in this web vary depending on the geographic location.
A generalized tundra food web. Exact relationships and species depend on geographic location.
The interconnected nature of a food web means that as numbers of one species increase (or
decrease), other populations change in response. An often-discussed tundra example is the
lemming population. Lemmings are small rodents that feed on plants. Populations of lemmings
fluctuate radically (from large populations to near extinction) in regular intervals. While
scientists believed that populations of lemming predators (foxes, owls, skuas, and stoats) also
fluctuated in response to these changes, there is now evidence that suggests that the predators
themselves drive the changes in lemming populations.
Climate change is affecting tundra ecosystems in many ways. Thawing permafrost not only
releases carbon dioxide but also leads to coastal erosion- an increasing problem in Alaska where
villages are at risk. Warming also means that seasons are arriving earlier – a shift not only in
temperatures but also in the emergence and flowering of plants. Biologists suspect that a
mismatch between plant availability and calving is increasing mortality rates of caribou calves.
Finally, species distributions may change as birds and other animals shift their range or
migration patterns in response to changing temperatures.
ANTARCTIC TUNDRA
Much less extensive than Arctic tundra, Antarctic tundra is found on the Antarctic Peninsula and
several Antarctic and subantarctic islands. These areas have rocky soil that supports minimal
plant life: two flowering plant species, mosses, algae, and lichens. Antarctic tundra does not
support mammals, but marine mammals and birds inhabit areas near the coast. All species in
Antarctica and the Antarctic Islands (south of 60 degrees S latitude) are protected by the
Antarctic Treaty.
LINKS
The World’s Biomes
An overview of biomes and information on six major types: freshwater, marine, desert, forest,
grassland, and tundra.
Biomes and Ecosystems
General information about biomes and ecosystems, with links to pages about tundra, taiga,
temperate forest, tropical rainforest, desert, grassland, and ocean biomes. This site may also be
used with upper-elementary students.
Geography4Kids: Biosphere
Includes pages on ecology, ecosystems, food chains, populations, and land biomes. Appropriate
for use with upper-elementary students.
NATIONAL SCIENCE EDUCATION STANDARDS: SCIENCE CONTENT
STANDARDS
The entire National Science Education Standards document can be read online or downloaded
for free from the National Academies Press web site. The following excerpt was taken from
Chapter 6.
Teaching about biomes (including the tundra) can meet a wide variety of fundamental concepts
and principles, including:
K-4 Life Science
The Characteristics of Organisms
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Organisms have basic needs. For example, animals need air, water, and food; plants
require air, water, nutrients, and light. Organisms can survive only in environments in
which their needs can be met. The world has many different environments, and distinct
environments support the life of different types of organisms.
Organisms and their Environments
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All animals depend on plants. Some animals eat plants for food. Other animals eat
animals that eat the plants.
An organism’s patterns of behavior are related to the nature of that organism’s
environment, including the kinds and numbers of other organisms present, the availability
of food and resources, and the physical characteristics of the environment. When the
environment changes, some plants and animals survive and reproduce, and others die or
move to new locations.
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All organisms cause changes in the environment in which they live. Some of these
changes are detrimental to the organism or other organisms, whereas others are
beneficial.
Humans depend on their natural and constructed environments. Humans change
environments in ways that can be either beneficial or detrimental for themselves and
other organisms.
K-4 Science in Personal and Social Perspectives
Changes in Environments
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Environments are the space, conditions, and factors that affect an individual’s and a
population’s ability to survive and their quality of life.
Changes in environments can be natural or influenced by humans. Some changes are
good, some are bad, and some are neither good nor bad. Pollution is a change in the
environment that can influence the health, survival, or activities of organisms, including
humans.
Some environmental changes occur slowly, and others occur rapidly. Students should
understand the different consequences of changing environments in small increments
over long periods as compared with changing environments in large increments over
short periods.
5-8 Life Science
Populations and Ecosystems
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A population consists of all individuals of a species that occur together at a given place
and time. All populations living together and the physical factors with which they interact
compose an ecosystem.
Populations of organisms can be categorized by the function they serve in an ecosystem.
Plants and some microorganisms are producers – they make their own food. All animals,
including humans, are consumers, which obtain food by eating other organisms.
Decomposers, primarily bacteria and fungi, are consumers that use waste materials and
dead organisms for food. Food webs identify the relationships among producers,
consumers, and decomposers in an ecosystem.
For ecosystems, the major source of energy is sunlight. Energy entering ecosystems as
sunlight is transferred by producers into chemical energy through photosynthesis. That
energy then passes from organism to organism in food webs.
The number of organisms an ecosystem can support depends on the resources available
and abiotic factors, such as quantity of light and water, range of temperatures, and soil
composition. Given adequate biotic and abiotic resources and no disease or predators,
populations (including humans) increase at rapid rates. Lack of resources and other
factors, such as predation and climate, limit the growth of populations in specific niches
in the ecosystem.