EM Notes

[shoaib672002]

The element carbon is the present in all living organisms. It's recycled through various processes, which are described in the carbon cycle.

Nitrogen is essential for the formation of amino acids to make proteins. The nitrogen cycle describes the ways in which nitrogen is recycled.

Carbon cycle
Most of the chemicals that make up living tissue contain carbon. When organisms die the carbon is recycled so that it can be used by future generations. The model that describes the processes involved is called thecarbon cycle.

Steps in the carbon cycle

1. Carbon enters the atmosphere as carbon dioxide from respiration and combustion.
2. Carbon dioxide is absorbed by producers to make carbohydrates in photosynthesis.
3. Animals feed on the plant passing the carbon compounds along the food chain. Most of the carbon they consume is exhaled as carbon dioxideformed during respiration. The animals and plants eventually die.
4. The dead organisms are eaten by decomposers and the carbon in their bodies is returned to the atmosphere as carbon dioxide. In some conditions decomposition is blocked. The plant and animal material may then be available as fossil fuel in the future for combustion.

Carbon cycle in the sea - higher tier only
In the sea, marine animals may convert some of the carbon in their diet tocalcium carbonate which is used to make their shells. Over time the shells of dead organisms collect on the seabed and form limestone. Due to Earth movements this limestone may eventually become exposed to the air where it's weathered and the carbon is released back into the atmosphere as carbon dioxide. Volcanic action may also release carbon dioxide.

 

[shoaib672002]

Nitrogen cycle
Nitrogen is essential for the formation of amino acids in proteins. The nitrogen cycle is a model that explains how nitrogen is recycled.

There's lot of nitrogen in air – about 78% of the air is nitrogen. Because nitrogen is so unreactive, it cannot be used directly by plants to make protein. Only nitrates are useful to plants, so we are dependent on other processes toconvert nitrogen to nitrates in the soil.

1. Nitrogen gas is converted to nitrate compounds by nitrogen-fixing bacteriain soil or root nodules. Lightning also converts nitrogen gas to nitrate compounds. The Haber process converts nitrogen gas into ammonia used in fertilizers. Ammonia is converted to nitrates by nitrifying bacteria in the soil.
2. Plants absorb nitrates from the soil and use these to build up proteins. The plant may be eaten by an animal, and its biomass used to produce animal protein.
3. Urea and egested material is broken down by decomposers. This results in nitrogen being returned to the soil as ammonia.
4. Decomposers also break down the bodies of dead organisms resulting in nitrogen being returned to the soil as ammonia.
5. Higher only: In some conditions denitrifying bacteria in the soil break down nitrates and return nitrogen to the air. This is usually in waterlogged soil. Improving drainage reduces this effect, making the soil more fertile.

 

[shoaib672002]

Food chains, pyramids of numbers and pyramids of biomass are all ways of showing how energy is passed on from one organism to another.

Biomass is the food available for the next trophic level (feeding level) in a food chain. Biomass is used as a source of renewable energy to reduce our dependence on fossil fuels.

Food chains and pyramids
Food chains
Here is an example of a food chain. Grass is eaten by voles that are eaten by owls.

Food chain



A food chain shows how energy is passed on from one organism to another. The original source of energy is the Sun, which in this example provides the sunlightneeded by the grass for photosynthesis. The grass is the producer in this food chain. The vole and the owl are consumers.

Pyramid of numbers

A pyramid of numbers



The number of organisms in a food chain can be represented graphically in a pyramid. Each bar represents the number of individuals at each trophic level (feeding level) in the food chain.

In this example a large number of caterpillars living in a single oak tree provide food for several blue tits, which in turn are consumed by a sparrowhawk.

The pyramid of numbers usually shows that the number of organisms at each trophic level gets smaller towards the top. This particular case is an exception – one tree provides food for many caterpillars.

It usually takes a large number of plants to provide sufficient energy for the consumersin the food chain.

Pyramid of biomass

A biomass pyramid



A pyramid of biomass is a more accurate indication of how much energy is passed on at each trophic level.

Biomass is the mass of living material in each organism multiplied by the total number of organisms in that trophic level. This makes it easier to compare the food value of a small number of large organisms with a large number of small organisms. Pyramids of biomass usually are a true pyramid shape (each level is smaller than the one below it).

The biomass in each trophic level is always less than the trophic level below. This is because biomass is a measure of the amount of food available. When animals eat, only a small proportion of their food is converted into new tissue, which is the food for the next trophic level. Most of the biomass that animals eat is either not digested, or used to provide the energy needed for staying alive.

 

[shoaib672002]

Making an energy converter more efficient
To make the cow a more efficient energy converter it could be given food that's easier to digest, to reduce the energy lost by egestion. It could also be kept in conditions where it doesn't need to use as much energy in respiration – it could be kept warm, and prevented from moving around. These ideas are used in intensive farming techniques.

Energy and trophic levels
Each trophic level reduces the amount of energy available to the next trophic level by about 90%. This means that the top trophic levels receive very little energy unless they live in very fertile habitats. For this reason there's a limit to the number of trophic levels in a food chain.

Try the next animation to see how much energy is available to the top trophic level. Work out the efficiency of energy transfer at each trophic level. Note the units of energy used are kilocalories. One kilocalorie is equivalent to 4.2 kilojoules. The units should not affect your efficiency calculation.

 

[shoaib672002]

Biomass
Biomass is food for the next trophic level in a food chain.

It can also be used as a source of renewable energy, to reduce our dependence on fossil fuels, and to help reduce air pollution. Using biomass as fuel still puts carbon dioxide back into the atmosphere, but it's the same carbon dioxide taken from the air as the biomass was produced. The use of biomass for energy production is carbon neutral.

Examples of biomass

Biogas

Bacteria break down sewage in a digester
The methane in biogas can be used as a fuel for heating homes

 

[shoaib672002]

Ecosystems can be small-scale, covering a small area (such as a pond) or large-scale covering a large area (such as a tropical rainforest).

The world is divided up into ten major ecosystems. These large-scale ecosystems are called biomes.

What are the world’s major biomes?
Rainforest

Rainforest in Hawaii - photo courtesy of Sarah Camp

Biomes are large-scale ecosystems defined by abiotic factors. These are:

• climate
• relief
• geology
• soils
• vegetation

 

[shoaib672002]

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=8&ved=0CF8QFjAH&url=http://www.classzone.com/books/ml_science_share/vis_sim/em05_pg20_nitrogen/em05_pg20_nitrogen.swf&ei=sjmMU8XPMYKM7AaHzYDYBQ&usg=AFQjCNHN1FGL2zv01RJgVh_wqUT5tgHM5g&sig2=BzckZL6ftxoAWb_yRisp0A

 

[shoaib672002]

Tundra biomes are cold and treeless with very little precipitation. The landscape is quite bare with vegetation specially adapted to the low temperatures.

Characteristics and climate
Tundra areas include Northern parts of Canada, Russia and Alaska.

See where tundra are found across the world on this biomes map.

Climate graph for Baker Lake, Canada

The temperatures stay below 0°C most of the year. The ground remains frozen, apart from a few centimetres of thaw in the summer. The precipitation is gentle, mainly falling as snow. The winds can be very strong.

Summers may have many hours of continuous daylight. Winters are long, dark periods.

The climatic conditions mean that the landscape is quite bare, with little vegetation.

Arctic tundra in the Yukon Territory, Canada

 

[shoaib672002]

Vegetation adaptation

Tundra pond with cotton grass growing nearby, Arctic National Wildlife Refuge, Alaska

Vegetation needs to be able to tolerate cold. Very few species are able to do this. Plants are low growing, compact and rounded in order to help protect from the wind. The frozen ground means soils are waterlogged.

Cotton grass is one example of a plant able to survive these conditions. The features which make it able to survive are:

• low-lying - the snow covers it in winter which helps insulate it
• seeds that scatter in the wind
• narrow leaves helping to reducetranspiration
• adapted to a short growing season (so has a short life cycle)
• dense flowerheads reducing heat loss
• darker leaves helps absorb energy from Sun

 

[shoaib672002]

Coniferous or boreal forests occur in cold northern regions characterised by long cold winters and short summers. Although there is a lot ofprecipitation, most of it falls as snow.

Characteristics
Location and climate

This biome is found between 50° and 60° north of the equator and is characterised by evergreen coniferous trees with needles instead of leaves. It is also known as Taiga.

Typical trees include spruce, pine and fir. Animals commonly found in the region are reindeer, voles and hares.

At the most northern extent, summer temperatures rarely rise above 10°C. As you move further north, trees are shorter and less dense because of the shorter growing season. Winter temperatures can fall as low as minus 30°C. At its southern margins, the trees become taller and denser and merge with deciduous trees (those that lose their leaves). Temperatures here can rise as high as 20°C in the summer and can fall to minus 15°C in winter. Precipitation is 300–900 mm, and most falls as snow in winter.

Taiga climate graph

 

[shoaib672002]

Adaptations of vegetation

Conifers in the snow

• Coniferous trees have thick bark to protect against the cold. They are cone-shaped, with flexible branches which help them to cope with heavy snow fall.
• Pine cones protect the seeds during the harsh winter.
• The thin waxy needles reduce water loss.
• Their evergreen nature means that the needles can photosynthesize whenever there is sufficient sunlight.
• The dense forest creates warmth during the harsh winter.

 

[shoaib672002]

Taiga soils

• Soils are shallow due to lack of decomposition and weathering caused by the cold. They are acidic due to leaching from rainfall and they are also poor in nutrients.
• The litter layer is thick with needles due to slow decomposition.
• The humus (decomposed) layer is thin.
• There are clear boundaries between the layers in the soil as there are few worms to mix it in the cold conditions.
• Trees have shallow roots.
• The typical soil is a podsol, which has a distinctive ash grey layer (or horizon) above a red layer, which is rich in iron.

 

[shoaib672002]

Deciduous woodlands contain trees with broad leaves such as oak, beech and elm. They occur in places with high rainfall, warm summers and cooler winters and lose their leaves in winter.

Characteristics and climate
Temperate deciduous forests are found between 40° and 60° north and south of the equator.

See where deciduous forests are found across the world on this biomes map.

The rainfall is high, between 500-1,500 mm a year. The temperatures remain on average above 0°C even in the winter. The summer temperatures average between 25-20°C. The winter is cooler, encouraging the trees to shed their leaves.

Rainfall in a deciduous woodland



The trees have typically large broad leaves, such as oak, beech and elm. These form the canopy layer.

As some light can get through, the vegetation is layered. Beneath the taller trees is a shrub layer. The shrub layer contains species like hazel, ash and holly.Grass, bracken or bluebells can be found in the ground layer.

Holm oak leaves and acorns

A wood showing ground layer of bluebells and top canopy layer of tall trees

 

[shoaib672002]

Soils in deciduous woodland
The soil type is brown earth. This is a fertile soil. In the autumn the leaves fall from the trees. The leaves decompose and help to give the soil its nutrients. Earthworms in the soil help to mix the nutrients, and blend the layers within the soil.

The tree roots are deep and so help to break up the rock below. This helps to give the soil more minerals. The trees take up the nutrients in the soil as they grow. However, more nutrients are put back in the soil when the autumn comes.

 

[DarkEclipse]

Hats off to you
Awesome job!

 

[Tahir khan]

Soils in deciduous woodland
The soil type is brown earth. This is a fertile soil. In the autumn the leaves fall from the trees. The leaves decompose and help to give the soil its nutrients. Earthworms in the soil help to mix the nutrients, and blend the layers within the soil.

The tree roots are deep and so help to break up the rock below. This helps to give the soil more minerals. The trees take up the nutrients in the soil as they grow. However, more nutrients are put back in the soil when the autumn comes.

Is it possible if this notes are in the form of pdf please

 

[shoaib672002]

Hats off to you
Awesome job!

Thanks

P.S: The guinea pig motivated me

 

[shoaib672002]

Is it possible if this notes are in the form of pdf please

Nope
Sorry

 

[DarkEclipse]

Thanks

P.S: The guinea pig motivated me

Lol

 

[Awesome12]

funky brat