Ecosystems + Energy

Question 1

Producer?

Answer 1

Photosynthetic organisms

Question 2

Primary consumer?

Answer 2

Eat producers, herbivores

Question 3

Secondary consumer?

Answer 3

Eat primary consumers, carnivores

Question 4

Tertiary consumers?

Answer 4

Eat secondary consumers, top predators

Question 5

Trophic level?

Answer 5

Levels of food chain

Question 6

What are Saprobionts?

Answer 6

Group of organisms that break down the complex material in dead organisms.

Question 7

What is Biomass?

Answer 7

Total mass of living material in a specific are in a given time, usually measured in grams per square metre.

Question 8

Negative of biomass?

Answer 8

Unreliable as it is constantly changing, should be dry, need to use samples.

Question 9

Where does energy come from in the ecosystem and explain?

Answer 9

The sun

-90% is reflected back into space
-Not all wavelengths of light can be absorbed by plants
-Light may not fall on a chlorophyll molecule

Therefore plants cannot convert all energy into organic matter: 1-3%

Question 10

Explain the role of Mycorrhizae

Answer 10

-Certain fungi growing in soil can form associations with plant roots.

-Can be described as mutualistic symbiosis because fungi gain from sugars in plants, and plants obtain mineral ions and water from the fungus.

-Fungi can form structures called mycorrhizae, either on the outside or inside the roots for this transfer.

-Mycorrhizae are important in the absorption of phosphate ions and a variety of other plant mineral nutrients which are not so easily available.

Question 11

How do saprobionts gain energy?

Answer 11

From chemical conversions of organic molecules, principally by oxidation of carbon compounds, and they break down complex chemical components of biological origin into simpler forms.

Question 12

How are agricultural ecosystems different from natural ecosystems?

Answer 12

The crops or livestock will be removed from the fields instead of dying and decomposing like it would naturally.

Question 13

Why are agricultural ecosystems a problem?

Answer 13

As the crops and livestock are removed:

-Mineral ions contained in the bio mass are not returned to the soil.
-Interrupts crucial process of nutrient recycling.
-If this occurs for a long time, conc of nutrients in the soil will decrease and decrease crop yields, or meat and milk yield.

Question 14

What is a way of replacing mineral lost from agricultural ecosystems?

Answer 14

Fertilisers

Ensures crops and livestock continue to grow and increase in biomass

Question 15

What do fertilisers do, and what are the types?

Answer 15

Add important minerals e.g. nitrogen, phosphorus, and potassium (ions)

Natural fertilisers
Artificial fertilisers

Question 16

What are natural fertilisers?

Answer 16

-Made up of organic matter, dead and decomposing remains of organisms and their waste products e.g. manure, veg, sewage

Question 17

What are artificial fertilisers?

Answer 17

-Made of inorganic matter in the form of powders or pellets that contain pure chemical compounds.

Question 18

Pros and cons of natural fertilisers

Answer 18

+Improve soil structure, helps reduce erosion increasing the water holding ability of the soil

+Nutrients are released over long periods of time

-Nutrients are not very conc so large amounts needed.

Question 19

Pros and cons of artificial fertilisers

Answer 19

+Exact chemical composition is known so easier to know how much to apply and the effects they will have on crop yields.

+Nutrients present are conc so smaller amounts are needed

+Easy to apply evenly and are clean

Question 20

Explain the process of Eutrophication

Answer 20

1. Excess nutrients from fertilisers run off from the land into water
2. Aquatic plants flourish, growing rapidly
3. Algae also show rapid growth
4. Algal bloom prevents sunlight reaching the aquatic plants, water oxygen levels fall.
5. Decomposition rate increases, aerobic respiration of decomposers reduces dissolved oxygen even further.
6. Death of organisms requiring dissolved oxygen in water (fish)

Question 21

The biomass of an organism is…

Answer 21

-Mass of living material
-The chemical energy that is stored within the organism or tissue

Question 22

What can biomass be measured in?

Answer 22

-Dry mass (after all water has been removed)
-Mass of carbon
-Mass of carbon of a sample is generally 50% of the dry mass

Question 23

For dry mass, you have to dehydrate the sample, briefly explain how you would do that?

Answer 23

Place sample in oven on low heat and measure mass at regular intervals.

Once mass is constant, its fully dehydrated.

Question 24

How would you find the energy released by a sample of plant biomass?

Answer 24

Use a calorimeter

-This burns the dried sample and uses that heat energy to heat a known vol of water
-Measure change in temp

1 kilojoule is the amount of energy needed to raise the temp of 240ml by 1 degree

Question 25

What is ‘Gross Primary Production’?

Answer 25

Total quantity of chemical energy stored in plant biomass.

Question 26

How do you calculate net primary production?

Answer 26

NPP= GPP - R

GPP= gross primary product
R= respiratory losses

Question 27

Why might not all net primary production be passed on?

Answer 27

-Not all of the plant is consumed
-Lost in faeces
-Lost in excretory materials
-Lost as heat

Question 28

How do you calculate the net primary production with its losses?

Answer 28

N= I - (F+R)

N= net
I= chemical energy from ingested food
F= lost in faeces/urine
R=lost in respiration

Question 29

All life requires nitrogen compounds… where do plants and animals secure theirs from?

Answer 29

Plants= in a ‘fixed’ form such as nitrate ions or ammonia

Animals= from plants, or other animals that have fed on plants

Question 30

What are the 4 biological processes involved in the nitrogen cycle?

Answer 30

1. Nitrogen fixation
2. Decomposition
3. Nitrification
4. Denitrification

Question 31

True or false: the nitrogen molecule is inert

Answer 31

True

Requires lots of energy to break apart for other compounds to combine with it.

Question 32

Define ‘Nitrogen Fixation’ and explain it as part of the nitrogen cycle

Answer 32

The process of converting nitrogen in the atmosphere into nitrogen compounds (ammonia) that are useful for other biochemical processes.

-Biological fixation: by certain microbes
-Atmospheric fixation: by lightening
-Industrial fixation: the Haber Process

Rhizobium (bacteria) has an the enzyme nitrogenase that converts nitrogen and hydrogen to ammonia, which is used to make amino acids which a legume can use to make proteins.

Question 33

Explain ‘decomposition’ in the nitrogen cycle

Answer 33

Nitrogen compounds in waste products (e.g. urine and faeces) and dead organisms are converted into ammonia by saprobionts (a type of decomposer including some fungi and bacteria)

-This ammonia forms ammonium ions in the soil

Question 34

Explain ‘Nitrification’ as a step in the nitrogen cycle

Answer 34

The ammonium ions in the soil are converted by nitrifying bacteria into nitrogen compounds that can be used by plants, known as nitrates

1. Initially, nitrifying bacteria such as Nitrosomonas convert ammonium ions into nitrites
2. Different nitrifying bacteria such as Nitrobacter then convert these nitrites into nitrates

Question 35

Explain ‘Denitrification’ as a step in the nitrogen cycle

Answer 35

The 3 previous processes remove nitrogen from the atmosphere.

-Denitrifying bacteria use nitrates in the soil during respiration

-This process produces nitrogen gas, which returns to the atmosphere

-This process occurs in anaerobic conditions