Recycling Within Ecosystems

What is decomposition?

A chemical process in which a compound is broken down into smaller molecules, or its constituent elements.

What is a decomposer?

An organism that feeds on and breaks down dead plant or animal matter. thus turning organic compounds into inorganic ones (nutrients) available to photosynthetic producers in the ecosystem.

Why are decomposers saprotrophs?

They obtain their energy from dead or waste material.

What does the enzymes of decomposers break down?

Complex organic molecules into simpler soluble molecules which are then absorbed by decomposers. Through this process, decomposers release stored inorganic compounds and elements back into the environment.

What type of digestion do decomposers perform?

External, by secreting enzymes onto dead organisms or organic waste matter.

What are detrivores?

Organisms that help to speed up the decay process by feeding on dead and decaying material - they break it down into smaller pieces of organic material, which increases the SA for the decomposers to work on.

What is nitrogen an essential element for?

Making amino acids and nucleic acids in both plants and animals.

How do animals obtain the nitrogen they need?

From the food they eat.

How do plants obtain the nitrogen they need?

From the environment.

Is there a lot of nitrogen in the atmosphere?

Yes, 75% of the air is nitrogen gas.

Can atmospheric nitrogen be taken up by plants?

No, it needs to be combined with other elements such as oxygen and hydrogen.

What does bacteria play a big role in?

Converting nitrogen into a form useable for plants, without it, nitrogen would quickly become a limiting factor.

What is nitrogen fixation?

The process where atmospheric nitrogen is converted into nitrogen containing compounds like ammonia.

What bacterias are involved in nitrogen fixation?

Azobacter and Rhizobium.

Where is azobacter found?

Free in the soil.

Where is rhiizobium found?

Outside root nodules.

What is the relationship between nitrogen fixing bacteria and the plant they are on?

It is a symbolic mutualistic relationship - both organisms benefit:

• The plant gains amino acid from rhizobium, which are produced by fixing nitrogen gas in the air into ammonia in the bacteria.

What is nitrification?

The process by which ammonium compounds in the soil are covered into nitrogen-containing molecules that can be used by plants. Free living nitrifying bacteria in the soil are involved.

What type of reaction is nitrification?

An oxidation reaction, and so only occurs in well aerated soil.

What are the two steps in nitrification?

1. Nitrifying bacterial (eg Nitrosomonas) oxidizes ammonium compounds into nitrites.

2. Nitrobacter oxidises nitrites into nitrates.

What is denitrification?

The conversion of nitrates in the soil back to nitrogen gas.

What kind of conditions does denitrification occur under?

Anaerobic conditions.

What is ammonification?

The process where decomposers convert nitrogen containing molecules in dead organisms, faeces and urine into ammonium compounds.

What is carbon a component of?

All the major organic molecules present in living organisms such as fats, carbohydrates and proteins. The main source for land living organisms is the atmosphere.

When does photosynthesis take place, and what does this mean for carbon dioxide levels?

It only takes place in the light so during the day, photosynthesis removes carbon dioxide from the atmosphere.

Why are carbon dioxide levels higher at night than in the day?

Because respiration is carried out by all living organisms throughout the day and night, releasing carbon dioxide at a relatively constant rate into the atmosphere.

Why are carbon dioxide levels lower on a summer day than a winter’s day?

Because photosynthesis rates will be higher on a summer day (due to there being more light).

Over the past 200  years, what has happened  to the the levels of global atmospheric carbon dioxide levels?

They have significantly increased.

What are the main reasons for the rise in atmospheric carbon dioxide levels?

• Combustion of fossil fuels - releases CO2 back into the atmosphere.

• Deforestation - removes significant quantities of photosynthesis biomass from earth.

What do increased levels of atmospheric carbon dioxide levels trap?

More thermal energy in the atmosphere - as a result, less carbon dioxide is removed from the atmosphere. 

What is the amount of carbon dioxide levels dissolved in the seas and oceans affected by?

The temperature of the water - the higher it is, the less gas is dissolved. 

What does global warming decrease?

The carbon bank in the oceans and releases more carbon dioxide into the atmosphere in a positive feedback loop.`