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Biology A-Level > Chapter 13: Energy and ecosystems > Flashcards

Chapter 13: Energy and ecosystems Flashcards

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1
Q

What is an ecosystem?

A

An ecosystem includes all the organisms and non-living abiotic conditions in a particular area

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2
Q

What is meant by the word ‘biomass’?

A

Biomass refers to all the living material in a given area at a given time.
The total mass of biological molecules
The chemical energy stored in the plant

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3
Q

Energy is transferred through an ecosystem / the living organisms of an ecosystem when…

A

…organisms eat each other

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4
Q

How can the dry mass of an organism be measured?

A 
A sample of the organism is taken and heated in an oven
At high temperatures
To destroy the 
A constant mass means
All the water has been removed
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5
Q

How can the amount of chemical energy stored in biomass be measured?

A

Biomass is burned in a
Colorimeter
The energy released is used to
Heat a known mass volume of water
The change in temperature of the water is used to
Claculate the chemical energy of the dry biomass

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6
Q

What does GPP stand for?

A

GPP stands for Gross Primary Production

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7
Q

What does NPP stand for?

A

NPP stands for Net Primary Product

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8
Q

What is meant by the term ‘GPP’?

A

GPP is the total amount of chemical energy initially made from light energy

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9
Q

What is respiratory loss?

A

Chemical energy lost to the environment as heat during respiration
Respiratory loss is represented by the letter R

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10
Q

What is meant by the term NPP?

A

NPP is the energy available to a plant for growth and reproduction
the energy stored inside the plant’s biomass
Thr energy available for other organisms at the next trophic level/stage in the food chain
the energy left over from the total amount of energy is converted to when respiratory loss is taken out

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11
Q

What is a trophic level?

A

A trophic level is name given to a stage/level in a food chain

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12
Q

What is the equation for calculating the chemical energy store left when losses to respiration are taken away?

A

NPP = GPP - R

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13
Q

Around what percentage of the gross primary production is lost to the environment as heat?

A

Approx. 50%

Plants use 20%-50% of GPP in respiration

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14
Q

How is the net production of consumers calculated?

A

The net production of consumers can be calculated using the formula:

N = I - (F + R)
where...
N = net production
I = chemical energy in ingested food
F = chemical energy lost in excretion (faeces, urine)
R = energy lost through respiration
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15
Q

Why isn’t all the energy consumers ingest transferred to the next tropic level?

A

not all the food is eaten
some parts of ingested food are indigestible
so they are egested as waste
some energy is lost through respiration

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16
Q

How would you calculate the percentage efficiency of an energy transfer from one tropic level to another?

A

percentage efficiency = (net production ÷ amount of energy received) x 100

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17
Q

Briefly explain why not all the energy from one trophic level gets transferred to the next trophic level.

A

in plants some energy is lots as heat from respiration

in consumers about 90% of energy in ingested food is lost to the environment as waste or heat from respiration

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18
Q

Food webs and food chains show…

A

how energy is transferred through an ecosystem and in particular how energy is transferred between organisms

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19
Q

What is a food web?

A

show lots of food chains in an ecosystem

how the food chains overlap

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20
Q

What is a food chain?

A

show simple lines of energy transfer

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21
Q

How does simplifying a food web involving a crop increase the productivity of the crop?

A

…

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22
Q

How does reducing respiratory losses increase the productivity of livestock

A

…

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23
Q

What is eutrophication?

A

minerals ions leached into body of water
from fertilised fields

taken up by algae
algae photosynthesis rapidly
algal bloom

blocks out sunlight
plants die
unable to photosynthesise

bacteria feed on dead plant matter
reduce oxygen concentration
during anaerobic respiration

not enough dissolved oxygen
fish/aquatic organisms die

24
Q

What is a nutrient cycle

A

shows how nitrogen is recycled

nitrogen needed for proteins and nucleic acids

25
Q

What is nitrogen fixation

A

nitrogen gas in the atmosphere is turned into nitrogen-containing compounds

carried out by bacteria

bacteria turn nitrogen into ammonia

26
Q

What is ammonification?

A

nitrogen compounds from dead organisms turned into ammonia
carried out by saprobionts
forms ammonium ions

27
Q

What is nitrification?

A

when ammonium ions in soil are turned into nitrogen compounds
nitrifying bacteria change ammonium

28
Q

denitrification

A

nitrates in soil are converted to nitrogen gas

carried out by denitrifying bacteria
use nitrates to carry out respiration
produce nitrogen gas

under anaerobic conditions

29
Q

What is the phosphorous cycle?

A

shows how phosphorous is passed through an ecosystem

30
Q

What is leaching?

A

when minerals in soil are dissolved and washed away

31
Q

What are the 4 processes involved in the recycling of nitrogen?

A

nitrogen fixation
ammonification
nitrification
denitrification

32
Q

What are the aims of most farming practices?

A

The aims of most farming practices is to increase the amount of energy available for human consumption.

33
Q

What are 2 ways in which the efficiency of energy transfers can be increased, in reference to

A

the energy lost to other animals such as pests can be reduced
the energy lost through respiration/respiratory losses can be reduced

34
Q

Why is only 1 - 3% of the sun’s energy converted into organic matter by plants

A

over 90% is reflected back into the atmosphere
only some wavelengths of light can be absorbed and used 700nm, 680nm
light might not fall on chlorophyll pigments
factors can limit the rate of photosynthesis
low CO2

35
Q

Why is it that usually only less than 10% of a plant’s NPP is available to use by primary consumers

A

low energy transfer at each stage because

36
Q

What are saprobionts?

A

Saprobionts are a type of decomposer. They are microorganisms that feed on dead organic matter and the waste products of animals. Many bacteria and fungi are saprobionts.

37
Q

nitrogen fixation

A

When nitrogen gas in the atmosphere is turned into nitrogen-containing compounds. Nitrogen fixation can be caused by lightning.

38
Q

extracellular digestion

A

Extracellular digestion is a type of digestion in which digestive enzymes are secreted onto the food, allowing the organism to absorb the nutrients they need

39
Q

saprobiontic nutrition

A

Obtaining nutrients from dead organic matter by extracellular digestion

40
Q

guano

A

Bird poop with a high concentration of phosphorous, often used as a natural fertiliser

41
Q

mycorrhizae

A

the name of the symbiotic relationship formed by some fungi and the roots of a plant

42
Q

hyphae

A

Hyphae are long, thin strands that some fungi are made up of. They connect to the roots of a plant.

43
Q

What is the function of hyphae?

A

Hyphae:
increase the SA of the root system
the plant is able to absorb more ions usually in low concentrations
increase the uptake of water
fungi able to get organic compounds such as glucose from the plant in exchange

44
Q

Why do plants and animals need nitrogen?

A 
nucleic acids
DNA
RNA
amino acids
proteins
45
Q

Briefly describe the phosphorous cycle.

A

The weathering of rock releases phosphate ions into the soil and also into seas, lakes and rivers

The phosphate ions in soil are taken up by a plant’s roots - mycorrhizae greatly increase this uptake. Then transferred through the food chain as animals eat the plants and animals each other.

The phosphate ions in water are taken up by aquatic producers such as algae and transferred through the food chain to birds.

The phosphate ions are lost from animals in their waste
and in sea birds as waste called guano

Saprobionts are involved in breaking down the organic compounds in dead plants and animals and in urine and faeces

Releasing phosphate ions into the soil for plants to assimilate again

46
Q

What do plants and animals need phosphorous for?

A

phospholipids used in plasma membranes
DNA
ATP

47
Q

ammonification

A

When nitrogen compounds in dead organisms, urine and faeces are turned into ammonia by saprobionts
Ammonia goes on to form ammonium ions.

48
Q

nitrification

A

When ammonium ions in soil are converted to nitrogen compounds which can be used by plants

Nitrifying bacteria (Nitrosomonas) change ammonium ions into nitrites first

Other nitrifying bacteria (Nitrobacter) change nitrites into nitrates

49
Q

denitrification

A

When denitrifying bacteria use nitrates in soil to carry our respiration converting the nitrates into nitrogen gas. This happens in anaerobic conditions such as waterlogged soils.

50
Q

Describe the role of saprobionts in denitrification.

A

Saprobionts carry out extracellular digestion to break down organic molecules such as DNA into inorganic ions allowing nitrogen to be recycled

51
Q

biological nitrogen fixation

A

Nitrogen fixation that is carried out by bacteria.

These bacteria turn nitrogen gas into ammonia which can be used by plants

They are found inside root nodules of lugumious plants(peas, beans, clover) and form mutualistic relationships with them - providing the plant with nitrogen compounds and the plant gives them carbohydrates

52
Q

True or False: Plants are not able to use ammonia

A

False: Plants are able to use ammonia

53
Q

artificial fertilisers

A

inorganic

54
Q

natural fertilisers

A

organic

55
Q

Environmental issues caused by using fertilisers

A

Leaching
more fertiliser is applied than plants need
excess nutrients/minerals are washed away into lakes, ponds and rivers
can lead to eutrophication
death of aquatic plant and animal life

56
Q

Leaching

A

When water soluble compounds in soil are washed away

Biology A-Level (24 decks)

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