The Nitrogen Cycle

The Nitrogen Cycle:

Nitrogen is used to make proteins and other substances for organisms as they grow. Plants and animals get nitrogen from nitrogen-containing substances. Plant roots absorb nitrogen compounds from the soil and use them to make nitrogen compounds in their biomass.

Animals get nitrogen compounds in their food. Most of which are sued to make nitrogen compounds in new biomass but some are lost in faeces and urine.

Plants would die out if there wasn't a way to convert nitrogen compounds back to nitrates in the soil.. So when decomposers feed on waste they break down some proteins and urea (a nitrogen rich substance in urine) to ammonia and release it in the soil.

The soil contains nitrogen-fixing bacteria that fixes nitrogen gas into ammonia.

In legume roots  mutualistic nitrogen-fixing bacteria is found. This bacteria lives inside root nodules and provide plants directly with ammonia.

Plants grow better with nitrates. So some nitrifying bacteria in soil converts ammonia to nitrates.

If soil starts lacking in oxygen the dentrifying bacteria will convert nitrates back to nitrates and others convert nitrates back to nitrogen gas.

Lightning can occasionally provide energy to combine oxygen and nitrogen gases in the air that quickly form nitrates.

Key Words:

Urea

Nitrogen-fixing bacteria

Root nodules

Nitrifying bacteria

Denitrifying bacteria

Questions:

1. Why are decomposers important in the nitrogen cycle?

2. Why does adding manure to soil increase the nitrate content?

What you should know:

An understanding of how nitrogen is recycled:

a. nitrogen gas in the air cannot be used directly by plants and animals.

b. nitrogen-fixing bacteria living in root nodules or the soil can fix nitrogen gas

c. the action of lightning can convert nitrogen gas into nitrates

d. decomposers break down dead animals and plants

e. soil bacteria convert proteins and urea into ammonia

f. nitrifying bacteria convert this ammonia to nitrates

g. plants absorb nitrates from the soil

h. nitrates are needed by plants to make proteins for growth

i. nitrogen compounds pass along a food chain or web

j. denitrifying bacteria covert nitrates to nitrogen gas

The Carbon Cycle

The Carbon Cycle:

Carbon atoms that are part of a carbon dioxide molecule in the atmosphere could diffuse into a leaf. During photosynthesis the carbon atom will become part of glucose.

If glucose is used by a plant for respiration the carbon atom will become part of carbon dioxide and release back in the atmosphere. But it could be changed into other carbon compounds and used to make plant biomass.

Carbs, fats and protein in plants all contain carbon atoms so when a animals eats it some are broken down and taken to the body while others come out a s faeces.

If plants and animals aren't eaten and just die, like decomposer organisms such as fungi, they start the process of decay. They feed on animal waste and break down carbon-containing compounds using some for respiration and some to build more complex compounds in their body.

If many dead plants are buried to quickly so decomposer organisms can't feed on them, they may be changed by heat and pressure into coal. Oil and natural gas are also formed dead sea plants or animals aren't decomposed.

They're all fossil fuels which contain carbon compounds. 

Combustion is a chemical reaction when substances burn, combining with oxygen to produce heat and waste products such as carbon dioxide.

The Carbon cycle is the movement of carbon through dead and living organisms and the atmosphere. 

Key Words:

Faeces
Decomposer
Decay
Fossil fuels
Combustion
Carbon cycle

Questions:

1. What process removes carbon dioxide from the air?
2. Which process releases carbon dioxide in the air?


What you should Know:

An understanding of how carbon is recycled:
a. during photosynthesis plants remove carbon dioxide from the atmosphere
b. carbon compounds pass along a food chain
c. during respiration organisms release carbon dioxide into the atmosphere.
d. decomposers release carbon dioxide into the the atmosphere.
e. combustion of fossil fuels releases carbon dioxide into the atmosphere.

Pollution Indicators

Pollution Indicators:

The more pollution caused the more harm there is to habitats.Indicator species are organisms that are so sensitive to polluting chemicals that we use them to help show us the presence of pollution. E.g. Blackspot fungus are when roses are infected and killed by sulfur dioxide in the air.

Lichens are mutualistic relationship between a fungus and alga, different species of lichens are affected differently by air pollution, so they can be used as pollution indicators.

Different animals that live in water need different amounts of oxygen. E.g. Stonefly larvae and freshwater shrimps need lots of oxygen whereas bloodworms and sludgeworms need little.

The UK produces a lot of waste which ends up being buried in landfill sites. There is a risk of pollution which means materials can't be used again. We're in danger of running out of some raw material.

Recycling is taking materials out of waste and converting them into new products that we can use:

• Metals can be melted down and recycled as new drinks cans or part of a car
• Paper can be recycled as more paper or cardboard
• Plastic bottles can be recycled as fleece clothing.

Key Words:

Indicator species
Blackspot fungus
Lichens
Stonefly larvae 
Freshwater shrimps
Bloodworms
Sludgeworms
Recycling

Questions:

1. What is indicator species?
2. Why is clean air not good for rose growers?
3. Why do animals need oxygen?
4. What are the advantages of recycling?

What you should Know:

An understanding of how scientists can use the presence or absence of indicator species as evidence to assess the level of pollution:
a. polluted water indicator - bloodworn, sludgeworm
b. Clean water indicator - stonefly, freshwater shrimps
c.air quality indicator - lichen species, blackspot fungus on roses

An understanding of how recycling can reduce the demand for resources and the problem of waste disposal, including paper, plastics and metals.

Pollutants and Plant Growth

Pollutants and Plant Growth:

Gas clouds in volcanoes contain  a lot of sulfur dioxide which can cause damage. Sulfur dioxide dissolves in water vapour in the air and makes a very strong acid.

Sulfur dioxide can also be produced by power stations. It dissolves in water vapour in clouds and forms sulfuric acid which falls as acid rain. Acid rain destroys trees and can make lakes too acidic for organisms to live in.


What you should Know:

The effects of pollutants on plant germination and growth.

Pollution

Pollution:

Population growth is an increase in population over time. There is increases in food production, medicines and better living conditions which means more babies survive to have young of their own.

As the human population increases we need more water and more food. Crops often grow better with fertiliser added to soil. 

Everything that we use every day requires resources, this includes fossil fuels to generate electricity to make them.

If we aren't careful about making resources we risk releasing pollutants and damaging organisms. Sulfur dioxide gas is released when fossil fuels are burnt. It pollutes the air if concentration is too high.

Eutrophication is the addition of chemicals to water, nitrates and phosphates, which encourage plant growth.

As nutrient concentration increases organisms in the water are affected. This leads to decrease in oxygen concentration and death of many animals.

Key Words:

Population growth

Fertiliser

Pollutants

Eutrophication

Questions:

1. Why is there an increase in population?

2. Why is fertiliser use increasing?

3. How is eutrophication caused?

4. How can it damage the environment?

What you should Know:

How to analyse interpret and evaluate data on global population change.

How the increase in human population contributes to an increase in th eproduction of pollutants, including phosphates, nitrates and sulfur dioxide.

How eutrophication occurs and the problems associated in a aquatic environment.

Parasites and Mutualists

Parasites and Mutualists:

In most feeding relationships the predator kills and eats it's prey. Parasitism is a feeding relationship in which two organisms live together in which one is feeding off the other. The organisms that feeds is called a parasite and the organisms it feeds on is the host.

Some parasites live outside a host's body e.g. Headlice. Others live inside. The tapeworm live in the intestines of vertebrates. Tapeworms eggs live the host's body through it's faeces. Their eggs are then swallowed by other animals and tapeworms grow inside them.

Parasites harm their hosts. Tapeworms take nutrients from the host's gut. This can cause the host to lose weight.

European mistletoe is a parasite plant. It's leaves photosynthesis but its roots grow into the veins of a host tree and absorb its mineral salts.

Mutualism is when two organisms live together but both organisms benefit. One such pair are oxpeckers and large herbivores in Africa. Oxpeckers eat parasitic insects that live on the herbivore . The herbivore carrier around the oxpecker on its head.

Another such example is when cleaner fish eat parasites from the skin of larger fish while the larger fish carry them around.

Some organisms live in mutualistic relationships inside other organisms. Nitrogen-fixing bacteria is a bacteria that can turn nitrogen in the air into nitrogen compounds. Some live in the roots of legumes (plants that produce pods). The bacteria gains chemical substances from the plant which they use as food. The plant gains nitrogen compounds so it can grow well.

Chemosynthetic bacteria are producers who get their energy from chemical substances rather then light. Some live inside tubeworms. Tubeworms get chemicals the bacteria needs and tubeworms feed on substances made by bacteria.


Key Words:

Prey 
Predator
Parasitism
Parasite
Host
Mutualism
Cleaner fish
Nitrogen-fixing bacteria
Legumes
Chemosynthetic bacteria


Questions:

1. How do headlice benefit from parasitism
2. How can a tapeworm kill its host?
3. How do both the oxpecker and herbivore benefit from mutualistic relationship?
4. What is the difference between parasitic and mutualistic relationships?


What you should Know:

How the survival of some organisms may depend on the presence of another species:
a. Parasitism including:
i. fleas
ii. head lice
iii. tapeworms
iv. mistletoe
b. Mutualism including:
i. oxpeckers
ii. cleaner fish
iii. nitrogen-fixing bacteria in legumes
iv. Chemosynthtic bacteria in tube worms in deep-sea vents.

Interdependence and Food webs

Interdependence and Food Webs:

All organisms need food. Some are producers whom make their own food. Others get their food from other organisms. Primary consumers eat plants and secondary consumers eat primary consumers.

Food chains show what organisms eat what. The organisms that feed at the same level in a food chain are at the same trophic level. Food chains can be joined together to create a food web. This shows the feeding relationships between different organisms. Interdependent organisms depend on each other for food. 

Energy stored in food is released during respiration. Some energy is transferred into biomass. Biomass is substances that form tissues. Energy in biomass is transferred to the next organisms in a food chain when it's eaten.

But some energy that's released in respiration is transferred into forms of energy that aren't useful. So this energy is wasted.

If we measured the biomass of all the organisms in a food chain we could draw a pyramid of biomass.
Here is an example:

Key Words:

Producers
Primary consumers
Secondary consumers
Food chains
Trophic level
Food web
feeding relationships
Interdependent
Respiration
Biomass
Pyramid of biomass


Questions:

1. What is a producer?
2. Why do food chains start with a producer?
3. What happens to the biomass in a food chain as you go up the trophic levels?
4. How are living things interdependent?

What you should Know:

That interdependence is they dynamic relationship between all living things.

An understanding of how some energy is transferred to less useful forms at each trophic level and this limits the length of a food chain.

An understanding that the shape of a pyramid of biomass is determined by energy transferred at each trophic level