what is an ecosystem?
natural system made up of plants, animals and the environment. Often interrelationships (links) between the living and no-living components of an ecosystem
- Biotic components are the living features of an ecosyetm such as plants and fish.
- Abiotic components are non-living environmental factors such as climate (temperature and rainfall), soil, water temperature and light.
Can be identified at different levels:
- a local small-scale ecosytem can be a pond, hedgerow or woodland
- a global- scale ecosystem can be a tropcal rainforest or deciduos woodland- these global ecosytems are called BIOMES.
Terms you have to know-
Producers- convert energy from the environment (mainly sunlight) ingot sugars (glucose). the most obvious producers are plants than convert energy from the sun by photosynethesis
Consumers- get energy from sugars produced by the producers. A pond snail is a good example of a consumer because it eats plants.
Decomposers- break down plant and animal material and return the nutrients to the soil. Bacteria and fungi are good examples of decomposers.
Food chain- shows the direct links between producers and consumers in the form of a simple line
Food web- shows all the connections between producers and consumers in a rather more complex way
Nutrient cycling- nutrients are foods that are used by plants or animals to grow. Two main sources of nutrients:
- rainwater washes chemicals out of the atmosphere
- weathered rock releases nutrients in the soil
when plants or animals die, the decomposers help to recycle the nutrients making them available once again for the growth of plants or animals. This is the nutrient cycle.
Small- scale ecosystem
Freshwater pond ecosystem
- plants like reeds grow in the water around the edge of the pond
- on the banks grow grasses, bushes and trees
- at the edges of the pond, the water is shallow and there will be plants like water lillies
- on the surface are ducks and small insects such as water boatman
- at the centre the water is deeper and there will be fish such as perch (predatory) and small fish like stickleback
– Pond margin- plenty of oxygen and light here. Plenty of shelter for plans and insects, for small animals to eat,
– Pond surface- plenty of oxygen and light here. Animals breathe through their gills, lungs and skin
–Above the pond surface- birds and animals breathe oxygen. Food is found in or on the water, or in the margins.
– Mid-water- animals breathe through gills or skin. Fish are the main predators. Food is found on the surface or in the pond
– Pond bottom- little oxygen or light. Plenty of shelter (rotting plants and stones) and food. Decomposers and scavangers live here.
Page 53 for food chain and web of a typical freshwater pond ecosytem.
what are the impacts of change on an ecosytem and what causes change to ecosystems?
Ecosystems can take hundreds if not thousands of years to develop. If an ecosytem us ti be sustainable it needs to be in balance. If there is a change to one of the components it may well have knock-on effects for the rest of the ecosystem.
What causes change?
- can occur naturally or result from huma acitivites. Change can take place on different scales:
- global-scale changes, such as climate change
- local-scale change, such as changes to a habitat– for example, when a hedge is removed.
Human and natural changes which can affect an ecosystem
Natural changes
- ecosystems can adapt to slow natural changes with few harmful effects. But rapid changes can have serious impacts. Extreme weather events like droughts can be devastating to ponds and lakes. They could dry up in places, which changes the edge-of-pond environment. Plants will dry out and die. Fish, starved of oxygen, might not survive.
Changes due to human activities
- Agricultural fertilisers can lead to eutrophication: nitrates increase growth of algae, which will deplete oxygen and fish may die
- ponds may be drained to use for farming. Aquatic plants will die, as well as fish and other pond life
- woods cut down, destroying habitats for birds and affecting the nutrient cycle
- Hedgerows removed to increase size of fields. Habitats will be destroyed, altering the plant/animal balance.
How can changes affect the pond ecosystem?
what if the pond owner added more perch?
The perch will eat more of the smaller fish and smaller animals, like frogs
then
this will reduce the amount of food for creatures further up the food chain, like herons
then
with fewer frogs, there will be an increase of creatures below frogs in the food chain like slugs.
Avington Park lake, Winchester, Hampshire
- country estate close to Wnchester in Hampshire
- the lake in the grounds is of historical and ecological importance
lack of maintenance in recent years resulted in the accumilation of silt and the growth of vegetation - created an excellent habitat for birds, but the impressive view of the lake had been lost
- restoration of the lake took place in 2014
- aim was to restore the lake as part of the landscape, and to preserve and improve its function as a habitat for birds
- restoration involved desilting and redefining the lake and creating new waterside habitats to attract nesting birds and waterfowl
- following restoration, the lake can again be seen from the house, and has become a healthy ecosyetm for a diverse range of wildlife.
distribution of global ecosystems
Large-scale ecosystems are known as global ecosystems (or biomes). There are defined mainly by the dominant type of vegetation that grows in the region, such as tropical rainforest or tundra.
- They form broad belts across the world from west to east, parallel to the lines of latitude. This is because the climate and characteristics of ecosystems are determined by global atmospheric circulation
Variations in these west-to-east belts of vegetation are due to factors such as
- ocean currents
- winds
- the distribution of land and sea
These factors produce small variations in temp and moisture which in turn affect the ecosystems. For example the Mediterranean region- with its dry, hot summers and warm, wet winters - has its own global ecosystem.
(SEE MAP ON PAGE 56 FOR DISTRIBUTION)
characteristics of global ecosystems- tropical rainforest
Location
- close to the equator
Links to global atmospheric circulation
- High temperatures and heavy rainfall associated with equtorial low pressure belt creates ideal conditions for plants to grow.
- Rainforests cover 6% of the Earth’s land surface
- More than half the world’s species of plants and animals live in this global ecosystem
- A quarter of all medicines come from rainforest plants
characteristics of global ecosystems- desert
Location
- roughly 30 degrees north and south of the equator
Links to global atmospheric circulation
- deserts cover 1/5 of the world’s land surface
- hot derserts are associated with the sub-tropical high pressure belts
- sinkong air stops clouds from forming, resulting in high daytime temps, low nightime temps and low rainfall.
- plants and animals have to be well dapated to survive in these conditions
characteristics of global ecosystems- polar
Location
- Arctic/Antarctica
Links to global atmospheric circulation
- Cold air sinks at the north and south Poles, resulting in very low temps and dry condtions
- The main polar regions are antarctica and greenland where temperatures can fall below -50 celcius.
characteristics of global ecosystems- decidous and coniferous forests
Location
- roughly 50-60 north of the equator
Links to global atmospheric circulation
- Decidous trees shed their leaves in winter to retain moisture.
- confierous trees are cone-bearing evergreens, retaining their leaves to maximise photosynthesis during the brief summer months
- The UK’s natural vegetation is decidous forest.
- Further North, for example in Canada and Scandinavia, coniferous forests dominate as they are better suited to colder climates.
characteristics of global ecosystems- temperate grassland
Location
- roughly 30-40 degrees north and south of the equator. Inland away from coasts, with hot summers and cold winters
Links to global atmospheric circulation
- This includes the vast areas of grassland in North America (prairies) and Eastern Europe (steppes).
- These areas experience warm, dry summers and cold winters.
- Grasses can tolerate these conditions and this land is mainly used for grazing animals.
characteristics of global ecosystems- mediterranean
Location
- roughly 40-45 degrees north of the equator. Also isolated locations south of the Equator (South Africa, Western Australia)
Links to global atmospheric circulation
- Countries around the mediterranean enjoy hot, sunny and dry summers, with mild winters
- this is due to the pressure belts migrating slightly north and south during the year
- mediterranean vegetation includes olive trees and fruit trees, such as lemons and oranges
- Other parts of the world have similar climate, for example California (USA), South Africa and parts of Australia
characteristics of global ecosystems- tropical grassland (savanna)
Location
- between 15-30 degrees north and south of the Equator
Links to global atmospheric circulation
- The tropical climae in these low latitudes is characterised by distinct wet and dry seasons.
- The dry season can be very hot and wild fires can break out.
- Violent thunderstorms can occur during the wet season
- Large herds of animals graze on these grasslands, along with predators such as lions and leopards.
characteristics of global ecosystems- tundra
Location
- From the Arctic Circle to about 60-70 degrees north (e.g. Canada, Northern Europe). There are only very small areas of tundra in the southern hemisphere due to the lack of land at these latitudes.
Links to global atmospheric circulation
- Tundra is charcaterised by low-growing plants adapted to retain heat and moisture in the cold, windy and dry conditions.
- These regions are found in northern Canada and across Northern Europe.
- It is a fragile ecosystem, easily damaged by humans and threatened by developments such as oil exploitation and tourism.
- Animals such as reindeer are adapted to survive the cold.
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How Are Tropical Storms Formed0
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Social Challenges In Rio8
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Urban world and megacities7
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Natural Hazards3
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Tectonic hazards35
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Weather hazards33
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climate change15
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ecosystems16
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tropical rainforests6
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cold environments14
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uk landscapes5
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coastal landscapes0
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river landscapes52
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glacial landscapes26
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urban world0
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urban change in the uk0
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urban sustainability0
