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Advanced Biology
Ecology Unit
What is an ecosystem?
An ecosystem is a community of living organisms (plants and animals) sharing an environment. The largest ecosystems are called biomes.
Ecosystems A. The SUN.
This is the source of energy in an ecosystem. Light energy from the sun is absorbed by green plants through Photosynthesis. The energy is stored in plant tissue.B. PLANTS.As well as getting energy from the sun, plants absorb nutrients like calcium and nitrogen from the soil, through their roots. C. ANIMALS.These eat the plants. Some animals only eat plants, these are called Herbivores. By eating plants, the energy and nutrients are transferred to the animals and are stored in their bodies as muscle and fat.D. ANIMALS.Carnivores eat other animals. The energy and nutrients are transferred again. Some animals eat plants and animals, these are called Omnivores. E. DECOMPOSITION.When organisms die, the nutrients are returned to the soil. Fungi and bacteria decompose the dead material, making it ready for re-use. The whole process can then start again
What is a biome?
A biome is a very large ecosystem e.g. Tropical Rainforest. The map in next slide shows 9 of the world's main biomes.
Biomes
The Earth is made up of a number of habitats or biomes. These are large-scale communities of plants and animals that exist together in harmony (equilibrium) with the environment. While scientists disagree on the number of biomes there are in the world, some of the main ones are described below:
The Map below shows six of the world's main biomes.
Desert facts Deserts include the world’s driest lands and may be hot like the Sahara or icy
cold like Antarctica. All deserts have one feature in common: an annual rainfall of less than 400mm. Almost one eighth of Earth’s surface is dry desert and these may have temperatures in excess of 40ºC during the day and yet at night, the temperature can fall to 4ºC. This is because other biomes are insulated by their humidity (water vapor in the air). Biomes like temperate forests may have in the region of 80% humidity during the day and this water absorbs and reflects sunlight and the energy it brings. At night the water acts like a blanket, trapping heat inside the forest. Since deserts usually have only between 10 – 20% humidity to trap and have few trees or vegetation to trap heat, they cool down quickly when the sun sets and heat up quickly after the sun rises.
World’s largest Deserts Desert Location Area in km sq Antarctica Antarctica 14,245,000 Sahara North Africa 9,065,000 Gobi Mongolia - China 1,295,000 Kalahari Southern Africa 582,000 Great Victoria Australia 358,000 Great Sandy Australia 358,000
Deserts
Where are Deserts found? Deserts are mainly found around the Tropics of Cancer and Capricorncorn.
What are Deserts? Deserts are areas of the earth's surface which receive less than 25cm or 10 inches of rainfall every year. They contain little or no vegetation. The main characteristics of deserts are:
rare clouds little rain very hot days very cold nights
How did Desert get like this?
You may be wondering "If deserts are so hot......why are they found along the tropics and not at the equator where the earth's temperatures are the highest?". The diagram on the left should explain this! A. As you would expect, temperatures at the equator are highest. Warm air rises containing evaporated moisture. B. The air cools, condenses and forms clouds. C. Heavy equatorial rainfall occurs (like in the rainforest!) D. The cool, dry air then begins descending. The air warms up. Any moisture in the air is held as water vapor (invisible).
Thus,
Because the tropics are largely cloudless they get very hot during the day. There are few clouds to insulate these areas during the night. Therefore, temperatures drop to very low levels overnight. It's just like going to bed without any blankets!
Temperate Deciduous Forests
Temperate forests have four seasons, spring, summer, autumn and winter and grow where rainfall, temperature and hours of sunlight change a lot through the year. Animals and plants living within this biome have special adaptations to cope with these yearly changes (while trees shed their leaves in winter, the animals might keep active, migrate or hibernate).
More on forests
Forests are considered the richest of all the biomes as they are home to at least 50% of the world’s species. They produce nearly half the world’s total organic matter and contain about half its total carbon store. Forests prevent soil from being washed away by rain. They also act as Earth’s lungs by producing oxygen from carbon dioxide, restoring oxygen levels in the atmosphere.
Grasslands
Grasslands are big open spaces and seem like an endless ocean of grass. Grasslands receive between 250 and 800mm per year. If they received more rain, the grasslands would become forest and if they received less, the grasslands would become desert. The plants are adapted to survive poor-quality soil, frequent droughts, and fires. Grasslands include dry grasslands, scrublands, and shrub-lands.
Grasslands
Type Principal LocationsTemperate Australia, China, Russia,
North AmericaTropical Sub-Saharan Africa,
Mexico, BrazilBefore it was reduced by the spread of ranching and crop farming, grassland covered as much as two-fifths of Earth’s land surface. Temperate grasslands in Europe are called steppe while in Africa the tropical grassland is known as savanna.
What is Savanna?
Savanna is similar to grassland but with scattered trees. These areas have seasons: cool and dry, hot and dry followed by warm and wet. All savanna areas have a wet and dry season
Tropical Rain Forests
Where are tropical rainforests found? Tropical rainforests are located around the equator
where temperatures stay near 80 degrees year round. Rainforests receive 160 to 400 inches (400-1000 cm) of rain each year. The largest rainforests are in Brazil (South America), Zaire (Africa) and Indonesia (South East Asia). Other tropical rainforest places are in Hawaii and the islands of the Pacific & Caribbean.
What is the tropical rainforest? The Tropical Rainforest is a forest occurring in tropical
areas of heavy rainfall. It is abundant with many species of wildlife and vegetation. Rainforests cover less than two percent of the Earth's surface. They are home to some 50 to 70 percent of all life forms on our planet. Rainforests are the most productive and most complex ecosystems on Earth.
Tundra
Where is Tundra found? Tundra is found in the extreme North of Canada and Asia. What is Tundra? Arctic tundra is located in the northern hemisphere that
encircles the north pole and extends to south of the coniferous forests of the taiga. The tundra covers about one fifth of the land surface found on Earth. Tundra is the coldest and driest of all the biomes. Tundra comes from the Finnish word tunturia, meaning treeless plain. The ground is subject to permafrost (land that is permanently frozen), but the surface layer melts in the summer. Soil conditions are poor, being marshy and waterlogged. Little plant life can survive. Only grasses, mosses, lichens and dwarf shrubs exist in this area.
Taiga (Coniferous Forest)
Where is Taiga found? Taiga (or Boreal Forests) represent the largest terrestrial
biome. Occurring between 50 and 60 degrees north latitudes, boreal forests can be found in the broad belt of Eurasia and North America: two-thirds in Siberia, while the rest--in Scandinavia, Alaska, and Canada. Taiga is found in the Northern parts of North America, Europe and Asia.
What is Taiga? Taiga is a belt of coniferous forest found in the northern
hemisphere, close to Arctic Tundra. Coniferous trees are needle-leaved trees that are usually evergreen and shallow rooted and usually bear cones.
How have humans affected the ecosystems?
All of us at some point have affected an ecosystem by simply walking in the wilderness or destroying the land for a new car park or building but a more important factor is that throughout the world, climate change is already showing a significant impact on a range of ecosystems. Glaciers, coral reefs, mangroves, tropical forests, color and alpine regions, prairie wetlands and atolls are all particularly vulnerable to irreversible damage.
Facts
Over the past few decades, the world has lost approximately 20% of its coral reefs with a further 20% significantly degraded. Changes in the temperature of oceanic waters, alterations in its salinity and increases in its concentrations of carbon dioxide will all place a great deal of stress on world fish stocks. Many people rely on fish as their primary source of protein (around 1 billion people) and the consequences of these changes within the waters will also have a significant impact on the human race.
This is just one factor, we also have to consider what effect it would have by degrading the land ecosystem; without any resources, animals such as sheep and cows will be without their vital needs which again, related back to a major impact on the human race.
Types of coastal ecosystems
Freshwater ecosystem
Some marine stats
Marine 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 (ppt) of water. Actual salinity varies among different marine ecosystems.
Marine ecosystems
• Neritic (the relatively shallow part of the ocean that lies over the continental shelf);
• profundal (bottom or deep water);
• benthic (bottom substrates);
• intertidal (the area between high and low tides);
• estuaries.
