Summary
Summary ZOL 3702 learning unit 10
- Course
- ZOL3702 - Ecology (ZOL3702)
- Institution
- University Of South Africa (Unisa)
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ZOL 3702 LEARNING UNIT 10NATURAL ECOSYSTEM TYPES AND BIOMES:
Textbook reference: pg 20 -25
Learning outcomes:
Describe and evaluate the most important differences between terrestrial and aquatic ecosystems and
apply this knowledge (especially the different factors that affect the adaptation of organisms in the
ecosystem)
Discuss the importance of biomes and their application for ecology.
Describe and evaluate the most important differences between aquatic ecosystems (freshwater and
marine) and apply this knowledge (such as the different factors that affect organism adaptation)
Classify organisms and zones within the different ecosystems.
TERRESTRIAL ECOSYSTEMS: pg 20 – 25
The terrestrial environment is regarded the most viable of the 3 main environments.
Larger groupings or biomes, in which biogeographers recognize marked differences in the flora and fauna
of different parts of the world.
The number of biomes that are distinguished is a matter of taste.
They certainly grade into one another, and sharp boundaries are a convenience for cartographers rather
than a reality of nature.
We describe 8 terrestrial biomes and their global distribution in figure 1.17
TUNDRA:
Occurs around the Arctic Circle, beyond the tree line.
Small areas also occur on sub-Antarctic islands in the southern hemisphere.
Alpine tundra is found under similar conditions but at high altitude.
The environment is characterised by the presence of permafrost – water permanently frozen in the soil –
while liquid water is present for only short periods of the year.
The typical flora includes lichens, mosses, grasses, sedges and dwarf trees.
Insects are seasonal in their activity, and the native bird and mammal fauna is enriched by species that
migrate from warmer latitudes in the summer.
In the colder areas, grasses and sedges disappear, leaving nothing rooted in permafrost.
, Vegetation that consists only of lichens and mosses gives way in turn to the polar desert.
The number of species of higher plants decreases from the Low Arctic to the High Arctic.
In contrast, flora of the Antarctica contains only 2 native species of vascular plant and some lichens and
mosses that support a few small invertebrates.
The biological productivity and diversity of Antarctica are concentrated at the coast and depend on
resources from the sea.
TAIGA:
Taiga or northern coniferous forest occupies a broad belt across North America and Eurasia.
Liquid water is unavailable from much of the winter, and plants and many of the animals have a
conspicuous winter dormancy where metabolism is very slow.
The tree flora is very limited.
In areas with less severe winters, the forests may be dominated by pines and deciduous trees.
Farther north, these species give way to single-species forests of spruce covering immense areas.
The overriding environmental constraint in northern spruce forests is the presence of permafrost, creating
drought except when the sun warms the surface.
The root system of spruce can develop in the superficial soil layer, from which the trees derive all their
water during the short growing season.
TEMPERATE FORESTS:
Range from mixed conifer and broad-leaved forests of much of North America and northern central
Europe, to the moist dripping forests of broad-leaved evergreen trees found at the biome’s low latitude
limits.
In most temperate forests, however, there are periods of the year when liquid water is in short supply,
because potential evaporation exceeds the sum of precipitation and water available from the soil.
Deciduous trees, which dominate in most temperate forests, lose their leaves in fall and become dormant.
On the forest floor, diverse floras of perennial herbs often occur, partially those that grow quickly in the
spring before new tree foliage has developed.
Provide food resources for animals that are usually very seasonal in their occurrence.
Many birds of temperate forests are migrants that return in spring but spend the remainder of the year in
warmer biomes.
GRASSLAND:
Occupies drier parts of temperate and tropical regions.
Temperate grassland has many local names: the steppes of Asia, the prairies of North America. The
pampas of South America and veldt of SA.
Tropical grassland or savanna refers to tropical vegetation ranging from pure grassland to some trees with
much grass.
Almost all of these temperate and tropical grasslands experience seasonal drought, but the biggest impact
is the effect of grazing animals that limit the species present to those that can recover from frequent
defoliation.
In the savanna, fire is also a common hazard in the dry season and tips the balance in the vegetation
against trees and towards grassland.
There is a seasonal glut of food, alternating with shortage, and as a consequence larger grazing animals
suffer famine and mortality in drier years.
A seasonal abundance of seeds and insects supports large populations of migrating birds, but only a few
species can find sufficiently reliable resources to be resident year-round.
Many grasslands have been cultivated and replaced by arable annual grasslands of wheat, oats, barley, rye
and corn, providing staple foods.
At the drier margins of the biome, many grasslands are managed for meat or milk production.
Of all the biomes, this one is most used and transformed by humans.
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