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A Level Biology Paper 2 > Section 5 - Chapter 13: Energy and Ecosystems - old > Flashcards

Section 5 - Chapter 13: Energy and Ecosystems - old Flashcards

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1
Q

What do plants convert light energy into and what is it used for?

A
  • Plants convert light energy into chemical energy
    • In order to make organic compounds like glucose
    • Make other groups of biological molecules forming biomass
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2
Q

What are the 3 groups of organisms according to how they obtain energy?

A
  • Producers - photosynthetic organisms that produce their own energy
  • Consumers: Eat other organisms
  • Saprobionts: (decomposers) break down dead organisms. Contribute to recycling of nutrients as they release minerals to plants.
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3
Q

What is a food chain

A
  • Describes a feeding relationship in which producers are eaten by primary consumers then secondary consumers.
  • Each stage is referred to a trophic level.
  • Arrows show energy flow
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4
Q

What is a Food Web

A
  • Many food chains linked together.
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5
Q

What is Biomass and what is its units

A
  • Is the total mass of living material in a specific area at a given time.
  • Biomass is measured using dry mass as fresh mass has varying water
  • Units are gm-2 on land and gm-3 on water
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6
Q

How to prepare fresh mass into dry mass

A
  1. Heating a sample up to 100 degrees to evaporate water
  2. Weighing until no further change in mass
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7
Q

Why is Calorimetry used

A
  • Calorimetry can be used to estimate the chemical energy store in biomass (the amount)
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8
Q

How does Calorimetry work

A
  1. Weighing dry material and burning it in pure oxygen in a sealed chamber - bomb
  2. Bomb surrounded by water bath and measuring the temp rise of surrounding water
  3. We know the specific heat capacity, know volume and temp rise. Can calculate energy released by the mass of burnt biomass (KJkg-1)
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9
Q

Exam Questions:

a) Suggest how you could determine the dry mass of a sample of plant material (2)
b) What is the advantage of using dry mass and not fresh mass to compare the yield of a plant?

A
  • a) 1. Heat at 100 degrees to evaporate water. 2. Weigh and heat until no further change in mass
  • b) 1. Amount of water will vary. 2. Will affect fresh mass/ not dry mass
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10
Q

How much solar energy is used to make new plant biomass

A
  • Only a tiny percent of solar energy available is incorporated into new plant molecules
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11
Q

Why is the % of solar energy available used in plants so low?

A
  • Over 90% of the sun’s energy is reflected back into space by clouds and dust.
  • Not all wavelengths of light can be absorbed for photosynthesis
  • Light may not fall on a chlorophyll molecule
  • Limiting factors may limit rate of photosynthesis and energy storage (CO2)
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12
Q

What is GPP

A
  • Gross Primary Production
  • The total quantity of the chemical energy stored in plant’s biomass, in a given area and time is GPP
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13
Q

How much of the GPP is used in respiration and in the plant’s biomass

A
  • Plants use 20-50% of the GPP in respiration
  • The remaining energy is stored as biomass
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14
Q

What is the calculation to calculate NPP

A
  • NPP = GPP - Respiratory losses
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15
Q

What is NPP

A
  • Net primary production
  • Amount of energy left after respiration which is available for plant growth and reproduction
  • Available to primary consumers in the next trophic level.
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16
Q

What is the % of npp used by primary consumers, secondary/tertiary

A
  • Less than 10% of npp is used for primary consumers
  • Secondary and tertiary are slightly more efficient 20%
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17
Q

Why is a low percentage of energy transferred at each stage

A
  • The whole organism is not consumed
  • Some of the energy is lost through urine and faeces
  • Some energy is lost to the environment as heat from respiration
  • Some parts of organism are not digested
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18
Q

It is the relative inefficiency of energy transfer between trophic levels that explains why:

A
  • Most food chains have only 4-5 trophic levels
  • Total mass of organisms (biomass) is less at higher trophic levels
  • Total amount of energy available is less at each level
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19
Q

What is calculating the NPP good to scientists. Which has a higher NPP: Desert or Tropical Rainforest

A
  • Can compare different ecosystems.
  • The availability of light, water, nutrients are different in areas,
  • Tropical Rainforest has higher NPP than Desert
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20
Q

How can farmers increase Primary Productivity

A
  • Removing factors that inhibit plant growth such as predators and disease
  • Improving conditions for photosynthesis
  • Increasing ground coverage - allows maximum solar energy to be used
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21
Q

Exam Question: Explain how farming practices increase the productivity of agricultural crops

A
  • Fertilisers/ named nutrient e.g. nitrate - proteins, phosphate - ATP
  • Pesticides/herbicides (removing competition)
  • Selective Breeding/ genetic modification
  • Greenhouses enhance conditions for photosynthesis
  • Ploughing - aerates soil
  • Crop rotation
  • Watering
  • Protection of crops
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22
Q

What happens when fertilisers are used - advantages

A
  • Nitrogen used to make ATP and DNA
  • Causes plants to grow and have big Surface Area
  • Increases rate of photosynthesis
  • Increased Productivity
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23
Q

What are the problems with fertilisers and what can they do to harm the environment

A
  • Eutrophication - leaching causes over-enrichment of water with nutrients leading to excessive algal growth and reduced oxygen levels
  • Reduced Species Diversity - Nitrogen rich soils can favour species which can out compete others
24
Q

What is leaching

A
  • Soluble chemical/ mineral drain away from soil by the action of percolating liquid (rainwater)
  • Eutrophication :Ends up in freshwater/ drinking lakes - stomach cancers, oxygen transport
25
Q

What is algae

A
  • Large group of eukaryotic, simple non-flowering plants containing chlorophyll but lacking true stems, roots and leaves
26
Q

What is Phytoplankton

A
  • Photosynthesising microscopic organisms that inhabit the upper sunlit layer of almost all oceans and lakes
27
Q

What is Cyanobacteria

A
  • Blue/green bacteria/ algae that obtain their energy through photosynthesis
28
Q

Exam Question: Nitrate from fertiliser is applied to crops may enter ponds and lakes. Explain how nitrate may cause the death of fish in fresh water

A
  1. Growth of algae blocks light
  2. Reduced photosynthesis so submerged plants die
  3. Saprobiotic bacteria
  4. Aerobically respire
  5. Less oxygen for fish to respire so aerobic organisms die
29
Q

How can humans increase secondary productivity energy transfer between producer and consumer

A
  • Animals are culled when they are young, as they have a higher secondary productivity
  • Antibiotics used to avoid any energy loss to pathogens
  • Selective breeding produce livestock with faster growing rates and increased production
  • Some animals are kept in confined spaces
30
Q

What is factory farming and what happens to the animals

A
  • Keeping animals in small enclosures can help reduce energy loss
  • This restricts movement, decreasing energy lost in muscle contraction
  • Feeding is controlled to prevent wastage and provide optimum amount of food
  • This enclosure excludes predators
31
Q

What are the advantages of factory farming

A
  • Efficient energy conversion
  • Produces low cost food
  • Easier to prevent disease from being introduced
  • Easier to isolate ill animals
32
Q

What are the disadvantages of factory farming

A
  • Animals vulnerable to spread of disease
  • Use of drugs - leads to antibiotic resistance
  • Unnatural conditions may cause stress to the animal
  • Restricted movement may cause osteoporosis and join pain
33
Q

Exam Question: Give a biological molecule that contains: Nitrogen and Phosphorous

A
  • Nitrogen - Amino acid/ protein/ enzyme/ DNA/ RNA
  • Phosphorous - DNA/RNA/ ATP/ ADP/ NADP
34
Q

What form can plants take nitrogen by which can they not?

A
  • Can’t use nitrogen in the gaseous form
  • Most of the plant’s N is taken up at the root hairs in NO3 by active transport
35
Q

What is the sequence of all nutrient cycles

A
  • The nutrient is taken up by producers as simple, inorganic molecules
  • The producer incorporates the nutrient into complex organic molecules
  • When the producer is eaten, nutrients pass into consumers
  • It then passes along food chains
  • When the producers and consumers die, their complex molecules are broken down by saprobiontic microorganism
36
Q

What are the key stages of the nitrogen cycle

A
  1. Nitrogen Fixation
  2. Ammonification
  3. Nitrification
  4. Denitrification
37
Q

What happens in Nitrogen Fixation

A
  • The fixing of gaseous Nitrogen into N containing compounds to ammonium ions then to ammonia
38
Q

Briefly explain what happens to nitrogen in nitrogen fixation

A
  • Done by 2 ways:
  • Mainly done by free living nitrogen fixing bacteria - these bacterias reduce gaseous nitrogen into ammonia
  • Mutualistic nitrogen-fixing bacteria - these bacteria live in nodules of leguminous plants like peas and beans. Provides plant with nitrogen compounds and the plant provides the bacteria with carbohydrates
39
Q

What happens in Ammonification

A
  • Following death - breakdown of N compounds into ammonia
  • Faecal waste brwakdown : releases ammonia by saprobionts which release ammonium ions into the soil
  • Dead organisms: during breakdown get removal of NH2 to form ammonium ions.
40
Q

What do saprotrophic micro-organisms do in the final stages of decomposition

A
  • They release hydrolytic enzymes from their hyphae, breaks down complex organic molecules.
  • The digested products can then be absorbed and used for respiration
41
Q

What happens in Nitrification

A
  • Carried out by free-living soil microorganisms called nitrifying bacteria called nitrifying bacteria
  • Occurs in 2 stages:
    • Oxidation of ammonium ions into nitrite ions
    • Oxidation of nitrite ions into nitrate ions
42
Q

What do nitrifying bacteria require

A
  • Requires oxygen to carry out these conversions.
43
Q

Exam Question: Describe the role of microorganisms in producing nitrates from the remains of dead organisms

A
  • Saprobiotic break down remains into ammonium
  • Ammonium ions into nitrite ions then nitrate by nitrifying bacteria
44
Q

Exam Question: Denitrification requires anaerobic conditions. Ploughing aerates the soil. Explain how ploughing would affect the fertility of the soil

A
  • Fertility increased as more nitrate formed
  • Less/ no denitrification
45
Q

What happens in denitrification

A
  • Anaerobic denitrifying bacteria using nitrate in respiration
  • Converts nitrates back into gaseous nitrogen
46
Q

Why do plants and animals need phosphorous

A
  1. Need phosphorous to make biological molecules such as phospholipids, DNA and ATP
47
Q

Where is phosphorous found and form is is when it is dissolved

A
  • Phosphorous is found in rocks and exists mostly as phosphate ions when it is dissolved
48
Q

Describe the Phosphorous Cycle

A
  1. Phosphate ions in rocks are released into the soil by weathering
  2. Phosphate ions are taken up by plants through the roots
  3. Ions transferred through food chains (animal eats plants)
  4. Ions lost from animals in waste
  5. When plants and animals die, saprobionts are involved in breaking down organic compounds, urine and faeces, releasing phosphate ions back into soil
  6. Weathering of rocks also releases phosphate ions to rivers which is taken up by aquatic producers (algae)
  7. Geological uplift pushes new rock to the surface
    8.
49
Q

Exam Question: Other than spreading fertilisers, describe and explain how 1 farming practice results in addition of nitrogen-containing compounds

A
  • Growing Legumes, Allow cattle to graze, add dung, spread/add manure
50
Q

What is a mycorrhiza composed of

A
  • It is a symbiotic association composed of a fungus and roots of a vascular
51
Q

What do mycorrhiza do

A
  • Acts like a sponge
  • The fungi colonize the root system of a host plant acting like extensions of the root system increasing the surface area for water and nutrient absorbance
  • They have mutualistic relationship with the plant as the plant provides the fungi with carbohydrates
52
Q

Exam Question: Suggest 1 source of the phosphate in the lake

A
  • Fertilisers, detergents, manure, slurry
53
Q

Exam Question: Suggest and explain why a poor supply of phosphate ions results in poor growth of plants

A
  • Required to make ATP/ GP so less respiration
  • Required to make nucleotides so less DNA, mRNA, tRNA for cell division or production of proteins
  • Required to make RuBP/NADP so less CO2 reduced into sugar
  • Required to make phospholipids for membranes
54
Q

What are the 2 types of fertilisers

A
  • Natural
  • Artificial
55
Q

What do natural fertilisers consist of

A
  • Dead/decaying remains of plants and animals and their waste
56
Q

What do artificial fertilisers consist of

A
  • Mined from rocks and deposits are converted into a form that has an appropriate balance of minerals
  • Nitrogen, phosphorous and potassium are always present

A Level Biology Paper 2 (10 decks)

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