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A-Level Biology > Energy and Ecosystems > Flashcards

Energy and Ecosystems Flashcards

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1
Q

What is an ecosystem?

A

All interacting abiotic and biotic factors in an area

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2
Q

What is a habitat?

A

Where the community is found

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3
Q

What is an omnivore?

A

An animal that eats both plants and animals, so can be a primary, secondary or tertiary consumer

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4
Q

What is a carnivore?

A

An animal that eats meat, so can be a secondary or tertiary consumer

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5
Q

What is a herbivore?

A

An animal that eats plants (producers), so is a primary consumer

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6
Q

What are saprobionts?

A

Group of organisms that break down complex materials in dead organism into simple ones

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7
Q

What is a producer?

A

Photosynthetic organisms that manufacture organic substances using light, water CO2, and mineral ions

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8
Q

What is a food chain?

A

A feeding relationship in which producers are eaten by primary consumers, who are eaten by secondary consumers, and who are eaten by tertiary consumers

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9
Q

How do plants use photosynthesised sugars?

A

Respiration

Synthesis other biological molecules

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10
Q

What is biomass?

A

The total dry mass of tissue or mass of carbon (without varying amounts of water) measured over a given time in a specific area

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11
Q

What are the units for biomass?

A

Kg m*-2

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12
Q

Why is dry mass used as a measure of biomass?

A

Because living tissue has a varying water content

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13
Q

How do you obtain dry mass?

A

Heat at 100 degrees in a furnace
Weigh at intervals
When mass constant = H2O removed

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14
Q

How can chemical energy store be calculated in dry biomass?

A

Energy (J) = specific heat capacity of H2O X vol of H2O X temp increase

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15
Q

Why is bomb calorimetry preferred over simple calorimetry?

A

Reduces heat loss to surroundings

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16
Q

What is calorimetry?

A

Process that estimates the amount of chemical energy stored in dry mass

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17
Q

How does calorimetry work?

A

Sample weighed and burnt in oxygen
Burning heats surrounding water
Temp change used to determine amount of energy

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18
Q

What is gross primary product (GPP)?

A

The total amount of chemical energy converted from light energy by plants, in a given area

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19
Q

What is net primary productivity (NPP)?

A

The total chemical energy available for pant growth, reproduction and energy transfer to other trophic levels after respiratory losses

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20
Q

What is the NPP equation for plants?

A

NPP = GPP - R

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21
Q

What is the net production equation for animals?

A 
N = I - (F+R)
I= chemical energy ingested from food
F= energy lost as faeces + urine
R= respiratory losses
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22
Q

What are respiratory losses?

A

50% of the GPP that is lost to the environment as heat when plants respire

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23
Q

How is energy lost in food chains?

A

Not all of organism eaten
Not all digested
Some lost as excretory materials
Heat loss to environment

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24
Q

Why is most of the sun’s energy not converted to organic matter?

A

Reflected back into space
Can’t absorb some wavelengths of light
Not all falls directly on chlorophyll molecule
Energy lost as heat during respiration

25
Q

How do farming practices increase efficiency of energy transfer?

A

Reduce energy loss to other organisms

Reduce energy loss through respiration

26
Q

What are some common farming practices?

A

Excluding predators
Artificial heating
Restricted movement
Feeding controlled

27
Q

Why do farmers try to simplify the food web?

A

Gets rid of food chains that don’t involve humans - eg. pests
Energy losses reduced
NPP of crop will increase

28
Q

Why do farmers use pesticides?

A

Kills pests that damage crops

Less biomass lost from crops so they grow larger = NPP greater

29
Q

Why do farmers use herbicides?

A

Kills weeds = removes direct competition with crop for energy
Also removes habitat/food source for pests = further reduced numbers + simplified food web

30
Q

How do farmers reduce respiratory losses?

A

Restricted movement
Pen indoor + kept warm
Means more biomass produced + more chemical energy can be stored
Increases NP + efficiency of energy transfer to humans

31
Q

Why is the length of food chains limited?

A

Energy lost at each trophic level

So insufficient energy to support higher trophic levels

32
Q

What are the general stages in the phosphorus cycle?

A 
Weathering
Runoff
Assimilation
Decomposition
Uplift
33
Q

Why is the phosphorus cycle slow?

A

No gas phase so no atmosphere cycle

Most stores as PO4*3- in rocks

34
Q

Describe the phosphorus cycle

A

Rocks weathered
Ions taken in via plant root
Mycorrihazae increase rate of assimilation
Ions transferred through food chain
Ions lost in animal + plant waste
When they die decomposed by saprobionts
Ions released into soil for assimilation by plants

35
Q

Describe uplift in the phosphorus cycle

A 
Weathered rocks release ions into water
Taken up by aquatic producers (algae)
Passed along to birds in food chain
Guano (sea bird waste) contains PO4*3-
Returned back to soil
36
Q

How does mining affect the phosphorus cycle?

A

Speeds up uplift

37
Q

What is the significance of nitrogen to living organisms?

A

Amino acids
Proteins
NAD/NADP

38
Q

What are the 4 main stages of the nitrogen cycle?

A

Nitrogen fixation
Ammonification
Nitrification
Denitrification

39
Q

Why can’t organisms use nitrogen directly from the atmosphere?

A

N2 very stable due to strong covalent triple bond

So need bacteria to convert it into nitrogen-containing compounds

40
Q

What is the role of mycorrhizae?

A 
Mutalistic relationship between pant and fungus
Increase SA of root 
Increases uptake of H2O + mineral ions
Drought resistance
Fungus gains amino acids + glucose
41
Q

What happens in nitrogen-fixation?

A

Nitrogen gas is turned into nitrogen-containing compounds by bacteria
Use the enzyme nitrogenase to reduce gaseous nitrogen into NH3

42
Q

What is the bacteria in nitrogen-fixation?

A

Rhizobium in root noodles of legumes

Form mutalistic relationship with plant

43
Q

What happens in ammonification?

A

Saprobionts feed on + decompose organic waste containing N2

Forms NH4*+

44
Q

What happens in nitrification?

A

NH4*+ changed back to nitrogen-containing compounds

Nitrites are oxidised to nitrates by nitrifying-bacteria

45
Q

What happens in denitrification?

A

Anaerobic denitrifying bacteria converts soil nitrates back into gaseous nitrogen

46
Q

What are the two types of fertilisers?

A

Natural (organic)

Artificial (inorganic)

47
Q

What is the difference between natural and artificial fertilisers?

A

Natural - decaying organic matter + animal waste

Artificial - pure chemicals mined from rocks converted into pellets or powder

48
Q

What are the 2 main environmental issues caused by fertilisers?

A

Leaching - nitrates dissolved in rainwater + “runoff” into water
Eutrophication - water source becomes putrid

49
Q

At a certain point, using fertilisers don’t increase crop yield. Why?

A

Limiting factor limits rate of photosynthesis so rate of growth can’t increase anymore

50
Q

How can the risk of eutrophication be reduced?

A

Sewage treatment marshes on farms
Pumping nutrient-enriched sediment out of water
Using phosphate-free detergent

51
Q

Describe the process of eutrophication

A 
Mineral ions leached into ponds/lakes
Algae bloom grows + blocks light
Plants die as unable to photosynthesise 
Saprobionts feed on dead matter + reduce O2
Dish die due to lack of O2
Water becomes putrid from toxic waste
52
Q

What are the pros of intensive farming?

A

Efficient energy cost
Low cost
Safety/easier to control
Uses less land

53
Q

What are the cons of intensive farming?

A 
Disease
Use of drugs - antibiotic resistance
Animal welfare
Reduction in genetic diversity
Pollution - lots of waste
Use of fossil fuels
54
Q

What is a mutalistic relationship?

A

The way 2 organisms of different species exist in a relationship in which each individual benefits from the activity of the other

55
Q

What is a food web?

A

Many food chains linked together, and are very complex

56
Q

What is a trophic level?

A

Each stage in a food chain, occupied by a producer or consumer

57
Q

What is a secondary consumer?

A

Those that eat a primary consumer

58
Q

What is a tertiary consumer?

A

Those that eat secondary consumers

A-Level Biology (21 decks)

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