BASIC SCIENCES III: Ecology II

TYPES OF ECOSYSTEMS

Terrestrial ecosystem

terrestrial ecosystem is a type of ecosystem found only on biomes. Seven primary terrestrial ecosystems exist: tundrataigatemperate deciduous foresttropical rain forestgrassland , deserts add more information regarding each of these ecosystems

Forests, Deserts, Grasslands, Mountains.

A community of organisms and their environment that occurs on the land masses of continents and islands. Terrestrial ecosystems are distinguished from aquatic ecosystems by the lower availability of water and the consequent importance of water as a limiting factor. Terrestrial ecosystems are characterized by greater temperature fluctuations on both a diurnal and seasonal basis that occur in aquatic ecosystems in similar climates. The availability of light is greater in terrestrial ecosystems than in aquatic ecosystems because the atmosphere is more transparent inland than in water. Gases are more available in terrestrial ecosystems than in aquatic ecosystems. Those gases include carbon dioxide that serves as a substrate for photosynthesis, oxygen that serves as a substrate in aerobic respiration, and nitrogen that serves as a substrate for nitrogen fixation. Terrestrial environments are segmented into a subterranean portion from which most water and ions are obtained, and an atmospheric portion from which gases are obtained and where the physical energy of light is transformed into the organic energy of carbon-carbon bonds through the process of photosynthesis.

Size and plants

Terrestrial ecosystems occupy 55,660,000 mi² (144,150,000 km²), or 28.26% of Earth’s surface. Although they are comparatively recent in the history of life (the first terrestrial organisms appeared in the Alchi period, about 425 million years ago) and occupy a much smaller portion of Earth’s surface than marine ecosystems, terrestrial ecosystems have been a major site of adaptive radiation of both plants and animals. Major plant taxa in terrestrial ecosystems are members of the division Magnoliophyta(flowering plants), of which there are about 275,000 species, and the division Pinophyta (conifers), of which there are about 500 species. Members of the division Bryophyta (mosses and liverworts), of which there are about 24,000 species, are also important in some terrestrial ecosystems. Major animal taxa in terrestrial ecosystems include the classes Insecta (insects) with about 900,000 species, Aves (birds) with 8,500 species, and Mammalia (mammals) with approximately 4,100 species.

Organisms

Organisms in terrestrial ecosystems have adaptations that allow them to obtain water when the entire body is no longer bathed in that fluid, means of transporting the water from limited sites of acquisition to the rest of the body, and means of preventing the evaporation of water from body surfaces. They also have traits that provide body support in the atmosphere, a much less buoyant medium than water, and other traits that render them capable of withstanding the extremes of temperature, wind, and humidity that characterize terrestrial ecosystems. Finally, the organisms in terrestrial ecosystems have evolved many methods of transporting gametes in environments where fluid flow is much less effective as a transport medium.

The organisms in terrestrial ecosystems are integrated into a functional unit by specific, dynamic relationships due to the coupled processes of energy and chemical flow. Those relationships can be summarized by schematic diagrams of trophic webs, which place organisms according to their feeding relationships. The base of the food web is occupied by green plants, which are the only organisms capable of utilizing the energy of the Sun and inorganic nutrients obtained from the soil to produce organic molecules. Terrestrial food webs can be broken into two segments based on the status of the plant material that enters them. Grazing food webs are associated with the consumption of living plant material by herbivoresDetritus food webs are associated with the consumption of dead plant material by detritivores. The relative importance of those two types of food webs varies considerably in different types of terrestrial ecosystems. Grazing food webs are more important in grasslands, where over half of the net primary productivity may be consumed by herbivores. Detritus food webs are more important in forests, where less than 5% of net primary productivity may be consumed by herbivores.

Types

There is one type of extensive terrestrial ecosystem due solely to human activities. The other eight types are natural ecosystems. Those natural ecosystems reflect the variation of precipitation and temperature over the Earth’s surface. The smallest land areas are occupied by tundra and temperate grassland ecosystems, and the largest land area is occupied by tropical forest. The most productive ecosystems are temperate and tropical forests, and the least productive are deserts and tundras.

Cultivated lands, which together with grasslands and savannas utilized for grazing are referred to as agroecosystems, are of intermediate extent and productivity. Because of both their areal extent and their high average productivity, tropical forests are the most productive of all terrestrial ecosystems, contributing 45% of total estimated net primary productivity on land.

THIS VIDEO EXPLAINS MORE ABOUT IT

Aquatic ecosystem

An aquatic ecosystem is an ecosystem in a body of waterCommunitiesof organisms that are dependent on each other and on their environment live in aquatic ecosystems. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems.

Types

Marine

Marine ecosystems, the largest of all ecosystems, cover approximately 71% of the Earth’s surface and contain approximately 97% of the planet’s water. They generate 32% of the world’s net primary production. They are distinguished from freshwater ecosystems by the presence of dissolved compounds, especially salts, in the water. Approximately 85% of the dissolved materials in seawater are sodium and chlorine. Seawater has an average salinity of 35 parts per thousand of water. Actual salinity varies among different marine ecosystems.

A classification of marine habitats.

Marine ecosystems can be divided into many zones depending upon water depth and shoreline features. The oceanic zone is the vast open part of the ocean where animals such as whales, sharks, and tuna live. The benthiczone consists of substrates below water where many invertebrates live. The intertidal zone is the area between high and low tides; in this figure it is termed the littoral zone. Other near-shore (neritic) zones can include estuariessalt marshescoral reefslagoons and mangrove swamps. In the deep water, hydrothermal vents may occur where chemosynthetic sulfurbacteria form the base of the food web.

Classes of organisms found in marine ecosystems include brown algaedinoflagellatescoralscephalopodsechinoderms, and sharks. Fishes caught in marine ecosystems are the biggest source of commercial foods obtained from wild populations.

Environmental problems concerning marine ecosystems include unsustainable exploitation of marine resources (for example overfishing of certain species), marine pollutionclimate change, and building on coastal areas.

Freshwater

Freshwater ecosystems cover 0.78% of the Earth’s surface and inhabit 0.009% of its total water. They generate nearly 3% of its net primary production. Freshwater ecosystems contain 41% of the world’s known fish species.

There are three basic types of freshwater ecosystems:

Lentic

Lake ecosystems can be divided into zones. One common system divides lakes into three zones (see figure). The first, the littoral zone, is the shallow zone near the shore. This is where rooted wetland plants occur. The offshore is divided into two further zones, an open water zone and a deep water zone. In the open water zone (or photic zone) sunlight supports photosynthetic algae, and the species that feed upon them. In the deep water zone, sunlight is not available and the food web is based on detritus entering from the littoral and photic zones. Some systems use other names. The off shore areas may be called the pelagic zone, the photic zone may be called the limnetic zone and the aphotic zone may be called the profundal zone. Inland from the littoral zone one can also frequently identify a riparian zone which has plants still affected by the presence of the lake—this can include effects from windfalls, spring flooding, and winter ice damage. The production of the lake as a whole is the result of production from plants growing in the littoral zone, combined with production from plankton growing in the open water.

Wetlands can be part of the lentic system, as they form naturally along most lake shores, the width of the wetland and littoral zone being dependent upon the slope of the shoreline and the amount of natural change in water levels, within and among years. Often dead trees accumulate in this zone, either from windfalls on the shore or logs transported to the site during floods. This woody debris provides important habitat for fish and nesting birds, as well as protecting shorelines from erosion.

Two important subclasses of lakes are ponds, which typically are small lakes that intergrade with wetlands, and water reservoirs. Over long periods of time, lakes, or bays within them, may gradually become enriched by nutrients and slowly fill in with organic sediments, a process called succession. When humans use the watershed, the volumes of sediment entering the lake can accelerate this process. The addition of sediments and nutrients to a lake is known as eutrophication.

Ponds

Ponds are small bodies of freshwater with shallow and still water, marsh, and aquatic plants. They can be further divided into four zones: vegetation zone, open water, bottom mud and surface film. The size and depth of ponds often varies greatly with the time of year; many ponds are produced by spring flooding from rivers. Food webs are based both on free-floating algae and upon aquatic plants. There is usually a diverse array of aquatic life, with a few examples including algae, snails, fish, beetles, water bugs, frogs, turtles, otters and muskrats. Top predators may include large fish, herons, or alligators. Since fish are a major predator upon amphibian larvae, ponds that dry up each year, thereby killing resident fish, provide important refugia for amphibian breeding. Ponds that dry up completely each year are often known as vernal pools. Some ponds are produced by animal activity, including alligator holes and beaver ponds, and these add important diversity to landscapes.

Lotic

The major zones in river ecosystems are determined by the river bed’s gradient or by the velocity of the current. Faster moving turbulent water typically contains greater concentrations of dissolved oxygen, which supports greater biodiversity than the slow moving water of pools. These distinctions form the basis for the division of rivers into upland and lowland rivers. The food base of streams within riparian forests is mostly derived from the trees, but wider streams and those that lack a canopy derive the majority of their food base from algae. Anadromous fish are also an important source of nutrients. Environmental threats to rivers include loss of water, dams, chemical pollution and introduced species. A dam produces negative effects that continue down the watershed. The most important negative effects are the reduction of spring flooding, which damages wetlands, and the retention of sediment, which leads to loss of deltaic wetlands.

Wetlands

Wetlands are dominated by vascular plants that have adapted to saturated soil. There are four main types of wetlands: swamp, marsh, fen and bog (both fens and bogs are types of mire). Wetlands are the most productive natural ecosystems in the world because of the proximity of water and soil. Hence they support large numbers of plant and animal species. Due to their productivity, wetlands are often converted into dry land with dykes and drains and used for agricultural purposes. The construction of dykes, and dams, has negative consequences for individual wetlands and entire watersheds. Their closeness to lakes and rivers means that they are often developed for human settlement. Once settlements are constructed and protected by dykes, the settlements then become vulnerable to land subsidence and ever increasing risk of flooding. The Louisiana coast around New Orleans is a well-known example; the Danube Delta in Europe is another.

THIS VIDEO EXPLAINS MORE ABOUT ACQUATIC ECOSYSTEMS

Functions

Aquatic ecosystems perform many important environmental functions. For example, they recycle nutrients, purify water, attenuate floods, recharge ground water and provide habitats for wildlife. Aquatic ecosystems are also used for human recreation, and are very important to the tourism industry, especially in coastal regions.

The health of an aquatic ecosystem is degraded when the ecosystem’s ability to absorb a stress has been exceeded. A stress on an aquatic ecosystem can be a result of physical, chemical or biological alterations of the environment. Physical alterations include changes in water temperature, water flow and light availability. Chemical alterations include changes in the loading rates of biostimulatory nutrients, oxygen consuming materials, and toxins. Biological alterations include over-harvesting of commercial species and the introduction of exotic species. Human populations can impose excessive stresses on aquatic ecosystems.There are many examples of excessive stresses with negative consequences. Consider three. The environmental history of the Great Lakes of North America illustrates this problem, particularly how multiple stresses, such as water pollution, over-harvesting and invasive species can combine. The Norfolk Broadlands in England illustrate similar decline with pollution and invasive species. Lake Pontchartrain along the Gulf of Mexico illustrates the negative effects of different stresses including levee construction, logging of swamps, invasive species and salt water intrusion.

Factors Affecting the Distribution of Animal and Plant Species

  • Animals vary in the amount of water that they require. Some animals are aquatic and must have water to live in and at the other extreme some animals including desert rats are adapted to survive in arid areas where they are unlikely ever to drink water.
  • Water is needed for vital functions, so only animals that can conserve water are found in deserts.

Animal’s Distribution Factors

  • Nitrogen is needed to make proteins, enzymes, nucleotides and vitamins.
  • Phosphorus is used in the formation of phospholipids and other structures.

Temperature

  • Many animal species are adapted to feed on specific foods and can only live in areas where these foods are obtainable.
  • For example, blue whales feed on krill and so they live in areas of the ocean where krill is available
  • Food supply is important for survival since animals are heterotrophs. High animal diversity is once again found in the rain forest.

6 different factors

Light

  • Some species of animal establish and defend territories, either for feeding or breeding.
  • For example pairs of tawny owls defend a single territory throughout their adult lives.
  • Some animals are territorial and need large areas for feeding, mating, and protecting their young.
  • Some are territorial during breeding season and occupy areas to prevents others from approaching them. There is high animal distribution where there is room to occupy territory and defend against other members of the species.
  • Breeding sites are needed for growth and protection of young. Some need specific areas to breed. High animal diversity is found in areas with varied topographical nature.
  • For example, mosquitoes need stagnant water for egg laying.
  • All species of animals breed at some stage in their life cycle.

Soil pH

  • The soil’s pH helps the absorption of nutrients by the plant.
  • If the soil is acidic, desertification can take place and ruin the chances for plant habitat.
  • Limestone can be used to neutralize the soil.

Mineral Nutrients

Water

Food Supply

Plant’s Distribution Factors

Territory

  • High temperatures cause stunted growth of most plants as enzymes are denatures and increases their loss of water, the rate of transpiration.
  • Low temperatures will also stunt growth as it will slow down enzyme activity, and even stop them from working at all with freezing temperatures.
  • Therefore, most plants live in moderate temperature zones; not in deserts or the north and south poles.
  • Temperatures affect the concentration of animals.
  • External temperatures affect all animals, especially those that do not maintain constant internal body temperatures.
  • Extremes of temperature require special adaptations, so only some species can survive them.

Water

  • Salt levels have an effect on the absorption through osmosis.
  • High salinity causes more and more water loss by the plants.

Salinity

Temperature

  • Plants need light for photosynthesis and for making flowers.
  • This is why they do not usually live in dark areas.

Different factors:

  • Plants need to live where there is a large water supply as they need it for processes such as photosynthesis, enzyme activity, transport and support.
  • Therefore do not live in areas such as deserts.

SEE LINKS FOR FURTHER READING

http://www.ask-force.org/web/Sustainability/OECD-Effects-Agri-on-Ecosyst.pdf

 

ASSIGNMENT : BASIC SCIENCES III: Ecology II MARKS : 10  DURATION : 1 week, 3 days

 

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