Natural Ecosystems

Ecosystems

  • An ecosystem includes all the biotic and abiotic parts in an area, and it is the interdependence of climate, soil, water, plants and animals
  • A food chain shows what eats what and a food web shows lots of food chains and how they overlap
  • The organisms can be classed as producers, consumers or decomposers
    • A producer is an organism that uses sunlight energy to produce food
    • A consumer is an organism that gets its energy by eating other organisms
    • A decomposer is an organism that gets its energy by breaking down dead matter, returning nutrients in the soil to be used by plants
      • Bacteria and fungi are decomposers
  • Within every ecosystem there are stores and flows of nutrients, water and energy

Global Ecosystems

  • Polar regions are found around the north and south poles
    • This is the Arctic and Antarctica
    • Polar areas are very cold with temperatures usually less than 10°C
      • Winters are normally below -40°C and can reach almost -90°C
      • Precipitation is low – no more than 500mm in the year, mainly in the summer
      • There are clearly defined summers and winters which are even colder
    • There are few florae
      • Some lichens and mosses are found on rocks, and there are a few grasses and flowering plants on the coast where its warmer
      • Plants grow slowly and don’t grow very tall – grasses are the most common plants
      • Closer to the poles, only mosses and lichen can survive
      • Some small, short trees and shrubs grow in warmer, sheltered areas
        • They grow close to the ground because it is too windy
        • They grow slowly because soil lacks nutrients
        • They have small leaves and lose little moisture
    • There are relatively few different species of faunae
      • Polar bears, penguins and marine mammals like whales, seals, and walruses are examples of animals found there
  • Coral reefs are mostly found between 30° north and south of the equator, a few miles off the coast
    • For example, the Great Barrier Reef, Australia
    • Coral reefs are most common in warm areas that receive a lot of sunlight
      • They grow best in shallow, clear, salty water
    • Coral reefs form underwater, so few florae grow there
      • Tiny algae live inside the tissue of corals
        • The algae and coral depend on each other for nutrients
    • Coral itself is a fauna – it’s a bit like a sea anemone, but some species create a hard-outer coating for protection
      • Around 25% of all marine species live in coral reefs, including fish, molluscs, sea snakes, turtles and shrimps
      • Many fish have flat bodies so they can easily swim through and hide in small gaps in the coral
  • There are two types of grasslands
    • Tropical savannah grasslands are found between the tropics
      • For example, the African Savanna in central Africa (Kenya and Tanzania)
      • There are distinct wet and dry seasons
        • They have quite low rainfall at 800-900mm a year
        • Temperatures are highest, around 35°C, just before the wet season
        • Temperatures are lowest, around 15°C, just after the wet season
      • They are home to grass, scrub and small florae with a few scattered trees
        • Plants are adapted to cope with low levels of rainfall with long roots and small waxy leaves
      • They are home to lots of insects and fewer large faunae
        • There are many species of grasshoppers, beetles and termites
        • There are lions, elephants, giraffes, zebras and antelope
        • Grazing animals, such as antelope, travel long distances in search of food and water, while other animals, such as mole rats, dig burrows to escape the harsh climate
    • Temperate grasslands are found at mid-latitudes
      • For example, the veldts of Africa and the pampas of South America
      • There are hot summers and cold winters
        • Temperatures reach 40°C and -40°C
        • They receive 250-500mm of precipitation each year, mostly in late spring and early summer
      • They are home to grasses and small florae, with very few trees
        • Grasses have wide-spread roots
      • There are fewer fauna species than savannah grasslands
        • Mammals include bison and wild horses, and rodents
        • Grazing animals, such as antelope, travel long distances in search of food and water, while other animals, such as mole rats, dig burrows to escape the harsh climate
  • Temperate forests are found mainly in the mid-latitudes, between the tropics and the polar regions
    • For example, the Valdivian forest on the south-western coast of South America (Chile and Argentina)
    • There are four distinct seasons
      • The summers are warm, and the winters are cool
      • Rainfall is very high, up to 1500mm a year, with rain all year round
    • Temperate forests are full of trees, florae type depends on the type of forest
      • Deciduous forests have broad-leaved trees that drop their leaves in autumn, shrubs and undergrowth
        • These include oak trees, brambles and ferns
        • Forest-floor plants, such as bluebells, tend to flower in spring before the trees grow leaves and block out light
      • Coniferous forests have evergreen trees and an understory of grasses and low-lying plants
        • These include pine and fir trees
    • They support lots of different fauna species
      • Mammals include foxes and squirrels, birds include woodpeckers and cuckoos and insects include beetles and moths
      • Streams and ponds are habitats for insects to breed
        • Insects provide food for fish, including trout and salmon
  • Tropical forests are found around the equator, between the tropics
    • For example, Daintree National Park, Australia
    • The climate is consistent all year round, with no definitive seasons
      • It’s hot, at around 20-28°C, because the Sun is overhead all year round
      • Rainfall is very high, around 2000mm a year
        • It rains daily, usually in the afternoon
    • There are four layers of florae – emergent layer, canopy, understory and forest floor
      • Most trees are evergreened to take advantage of the continual growing season
      • Vegetation cover is very dense, so very little light reaches the forest floor
      • There are lots of epiphytes such as orchids and ferns
      • Emergent trees have buttress roots to support their trunk and only have branches at their crown, where the light can reach
      • Plants lower down the canopy have broad leaves in order to absorb as much light as possible
    • Rainforests contain more fauna species than any other ecosystem
      • Gorillas, jaguars, anacondas, tree frogs and sloths inhabit rainforests
      • There are many bird and insect species
      • Many animals are camouflaged to hide from predators
        • Leaf-tailed geckos look like leaves to hide from predators
      • Some animals are nocturnal to save energy by feeding in cooler hours
        • Sloths are only active at night
  • Hot deserts are found between 15° and 35° north and south of the equator
    • For example, the Sahara Desert, northern Africa
    • Temperatures are very extreme between day and night
      • They range between 40°C during the day to 0°C at night
      • There’s less than 250mm of rainfall a year
        • The time of rain varies, sometimes only once in a couple of years
    • Flora growth is scarce due to the lack of rainfall
      • Cacti and thorn bushes grow
      • Plant roots are very long to reach deep water supplies, or very wide near the surface to reach as much rainwater as possible
      • Some plants have fleshy stems and thick, waxy skin
    • Fauna are adapted to cope with the harsh climates
      • Lizards, snakes, insects and scorpions are common in desserts as small animals can hide under the sand when it is too hot
      • Many birds migrate when it gets too hot
      • Many animals are nocturnal and live in burrows during the day
      • Larger animals, such as camels, have evolved to tolerate dehydration and reduce water loss