Nutrient Cycles

Question 1

What are saprobiotic microorganisms?

Answer 1

Decomposers that obtain their food from dead or decaying remains of other organisms

Question 2

What are the main reasons for the increased CO2 and methane levels in the atmosphere?

Answer 2

• burning of fossil fuels
• deforestation
• farming
• industry

Question 3

What are greenhouse gases?

Answer 3

Gases such as methane and carbon dioxide which in the atmosphere cause more heat energy to be trapped, so raising the temperature at the earths surface

Question 4

How is carbon dioxide taken out of the atmosphere?

Answer 4

It is absorbed by plants when they carry out photosynthesis

Question 5

How is carbon dioxide put back into the atmosphere?

Answer 5

By respiration and combustion of fossil fuels

Question 6

Which part of the day is carbon dioxide concentration in the atmosphere at it’s highest and why?

Answer 6

At night as it is no longer been taken up by plants by photosynthesis and is released when organisms respire

Question 7

When does respiration occur?

Answer 7

It is carried out constantly through the day and night

Question 8

Which part of the day is carbon dioxide concentration in the atmosphere at it’s lowest and why?

Answer 8

During hours of daylight as plants are absorbing light energy for photosynthesis

Question 9

What are the main causes of global warming?

Answer 9

Increasing carbon dioxide and methane concentrations

Question 10

What is meant by the term global warming?

Answer 10

A term used to describe the increase in the average global temperature over the last centaury

Question 11

What is responsible for increase in global temperature?

Answer 11

Human activity

Question 12

What is meant by the greenhouse effect?

Answer 12

The trapping of the sun’s warmth in a planet’s lower atmosphere, it is the effect of greenhouse gases absorbing outgoing energy

Question 13

Why is the greenhouse effect essential?

Answer 13

To keep the planet warm, but too much means the planet warms up

Question 14

What are the main effects of global warming?

Answer 14

• changing climate patterns
• melting of ice caps
• increased crop yield
• survival of certain species
• rising sea levels
• changes in rainfall patterns
• storms

Question 15

What are the four stages of the nitrogen cycle?

Answer 15

Nitrogen fixing, ammonification (by decomposers), nitrification and denitrification

Question 16

Why do plants and animals require nitrogen?

Answer 16

To make proteins and nucleic acids (DNA and RNA) but first they need bacteria to convert the nitrogen into nitrogen compounds first

Question 17

How is nitrogen removed from the atmosphere?

Answer 17

Nitrogen fixation

Question 18

How is nitrogen put back into the atmosphere?

Answer 18

Denitrification

Question 19

What do each stages of the nitrogen cycle involve?

Answer 19

Saprobiotic microorganisms

Question 20

What are nitrifying bacteria?

Answer 20

Microorganisms that convert ammonium compounds to nitrites and nitrates

Question 21

What does nitrogen fixation involve?

Answer 21

Where nitrogen gas from the atmosphere is converted into nitrogen-containing compounds ,such as ammonia, by nitrogen fixing bacteria

Question 22

What are the two types of nitrogen fixation bacteria?

Answer 22

Free living and mutualistic

Question 23

What do free living nitrogen fixing bacteria do?

Answer 23

Reduce nitrogen gas to ammonia, which they then use to make amino acids. When they die and decay, nitrogen-rich compounds are released

Question 24

What do mutualistic nitrogen fixing bacteria do?

Answer 24

They live in root nodules such as peas and beans plants, they obtain carbohydrates from the plant and the plant acquires their amino acids from these bacteria (mutualistic relationship)

Question 25

What does ammonification involve?

Answer 25

When nitrogen compounds from dead organisms are turned into ammonium compounds by saprobiotic microorganisms (decomposers)

Question 26

What does nitrification involve and what type of reaction occurs?

Answer 26

When ammonium compounds in the soil are changed into nitrogen compounds that can be used by the plant

ammonium compounds -> nitrites -> nitrates

oxidation

Question 27

What sort of conditions do nitrifying bacteria require?

Answer 27

A soil that has many air spaces as they require oxygen

Question 28

What does denitrification involve?

Answer 28

When nitrates in the soil are converted into nitrogen gas by denitrifying bacteria

Question 29

What things and conditions do denitrifying bacteria need?

Answer 29

Nitrates in the soil for respiration and anaerobic conditions e.g. waterlogged soil

Question 30

What are the effects of nitrogen fertiliser?

Answer 30

• Reduced species diversity
• Leaching
• Eutrophication

Question 31

What is leaching and how does it occur?

Answer 31

Nutrients are removed from the soil by dissolving into rain water in which they are washed away into water courses e.g. lakes and ponds which leads to pollution and eutrophication

Question 32

What is eutrophication?

Answer 32

Consequence of an increase in nutrients, mainly nitrates in fresh water courses, that often lead to a decrease in species diversity

Question 33

What are the stages of eutrophication?

Answer 33

• Nitrates are leached into waters, and causes an algal bloom
• Dense layer of algae absorb light and prevents it from reaching the plants below
• Light is the limiting factor for growth of plants and they die as they are unable to photosynthesis
• Saprobiotic bacteria feed on dead plant matter
• They require oxygen for their respiration, and so reduce the oxygen concentration of the water by aerobic respiration
• Oxygen is limiting factor for fish and other aquatic aerobic organisms
• Fish die due to lack of oxygen
• Anaerobic organisms further decompose the dead matter, releasing more nitrates and toxic waste into the water, polluting it even more

Question 34

What is the main cause of eutrophication?

Answer 34

Leaching of artificial fertilisers

Question 35

What is meant by a limiting factor?

Answer 35

Resources that are environmental conditions that limit the growth, abundance, or distribution of an organism or a population of organisms in an ecosystem.