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Biology > Pack 17 > Flashcards

Pack 17 Flashcards

1
Q

What is the ultimate source of energy for almost all organisms?

A

The sun.

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2
Q

Define a producer.

A

Photosynthetic organism that manufactures organic substances using light energy, water, carbon dioxide and mineral ions.

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3
Q

Define a consumer.

A

An organism that obtains its energy from consuming other organisms rather than directly using the suns energy.

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4
Q

What is a primary, secondary and tertiary consumer?

A
  • Primary - a consumer that consumes producers
  • Secondary - a consumer that consumes primary consumers.
  • Tertiary - a consumer that consumes secondary consumers.
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5
Q

Other than predators what may secondary (+) consumers be?

A

• Scavengers or parasites.

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6
Q

What is a saprobiont?

A
  • A decomposer.

* hydrolyses complex materials in dead organisms into simple ones, releasing valuable mineral ions and elements.

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7
Q

What type of organism can absorb the nutrients released by saprobionst?

A

Plants.

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8
Q

What type of organisms are the majority of saprobionts?(2)

A
  • Bacteria

* Fungi

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9
Q

What is a food chain?

A

• Describes the feeding relationship between organisms.

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10
Q

What is a trophic level?

A

Each stage of a food chain. E.g. producers, primary consumers etc.

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11
Q

What is a food web?

A

Like a food chain but intertwined because in reality organism rely on more than one food source.

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12
Q

Define biomass.

A

The total mass of living material in a specific area at a given time.

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13
Q

What makes fresh biomass unreliable?

A

Varying amount of water content.

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14
Q

What is the issue with using dry mass to measure biomass of an area.

A

Organisms have to be killed to measure their dry biomass. Usually measured on a small sample which may not be representative.

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15
Q

What units is biomass measured in? (2) Give examples of when both would be used.

A
  • gm⁻⁻² - e.g. a field
  • gm⁻³ - e.g. a pond
  • At a given time
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16
Q

What is calorimetry.

A

Measuring of the chemical energy store of some dry mass.

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17
Q

Describe the process of bomb calorimetry?

A
  • A sample of dry mass is weighed.
  • Burnt in pure oxygen sealed within a chamber called a bomb.
  • The bomb is surrounded by a water bath.
  • The amount of chemical energy stored can be measured as we know how much energy is required to raise the temperature of 1g of water by 1ᴼC.
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18
Q

What is directly measured during bomb calorimetry?

A
  • Temperature increase of the water.
  • Mass of the material
  • Volume of the water.
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19
Q

What % of the suns energy is captured by green plants?

A

1-3%

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20
Q

Why is most of the suns energy not converted to organic matter? (4)

A
  • 90% of the suns energy is reflected by clouds, dust or absorbed into the atmosphere.
  • not all wavelengths of light can be absorbed and used for phtosynthesis
  • light may not fall on chlorophyll molecule
  • A factor, such as low carbon dioxide levels, may limit the rate of photosynthesis so light can be used.
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21
Q

Define gross primary product? (GPP)

A

The total quantity of chemical energy store in a plant biomass in given area volume in a given time.

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22
Q

How much GPP is used in respiration?

A

20-50%

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23
Q

Define net primary production

A

The chemical energy store after respiratory losses.

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24
Q

What is the equation linking NPP GPP and Respiratory losses (R)

A

NPP=GPP-R

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25
Q

Define productivity. How does it differ to production.

A

Productivity is the rate at which energy is added to the bodies of a group of organisms (such as primary producers) in the form of biomass.

Involves time whereas production doesn’t.

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26
Q

What is available to primary consumers from plants (in terms of energy)?

A

Net Primary Production (NPP)

27
Q

Why is only a percentage of energy transferred from one trophic level to the next? (4)

A
  • Some parts of the organism aren’t consumed.
  • Some parts cannot be digested - lost through faeces.
  • Some of the energy is lost in excretory materials e.g. urine.
  • Some energy losses occur as heat from respiration to the environment. High in mammals and birds because of their high body temperature.
28
Q

What is the equation involving the net production of consumers?

A

N = I - (F+R)

  • N - Net production
  • I - energy store in ingested food
  • F - energy lost in faeces and urine
  • R - energy lost in respiration.
29
Q

What three things does the relative inefficienty of energy transfer between trophic levels explain?

A
  • Why most food chains only have 4/5 trophic levels (insufficient energy to support a large enough breeding population at high levels).
  • Biomass (give time and area) is less at higher trophic levels.
  • The total amount of energy available is less at each level.
30
Q

What differs between the supply of energy and nutrients to organism.

A
  • Energy from sun is effectively infinite.

* Nutrients are limited so occur in cycles.

31
Q

What are the 5 basic steps of a nutrient cycle.

A
  • Nutrient is taken up by producers as inorganic molecules.
  • The producer incorporates the nutrient into complex organic molecules.
  • Producer is eaten, nutrients pass to consumer.
  • Passes along food chain to other consumers.
  • Dead producers and consumers die. Saprobionts breakdown their molecules into the original form. Completing the cycle.
32
Q

What molecules contain nitrogen in living organisms?

A

Proteins, nucleic acids, ATP, urea

33
Q

How to plants obtain most of their nitrogen? What form and what process?

A
  • Nitrate ions in the soil

* Active transport

34
Q

How do animals obtain nitrogen?

A

By consuming plants

35
Q

Why do nitrate ions need to be replaced in the soil regularly?

A

• The are very soluble and easily leach away out of reach of plants.

36
Q

What are the 4 main stages of the nitrogen cycle? What type of organism does each stage involve?

A
  • Ammonification
  • Nitrification
  • Denitrification
  • Nitrogen fixation

• Saprobionts

37
Q

Describe the process of ammonification.

A
  • Saprobionts feed on faeces, urine and dead organisms.
  • Release ammonia from organic N containing compounds.
  • This ammonia forms ammonium ions in the soil.
38
Q

Describe the process of nitrification in terms of molecules produced? (2) What type of reaction?

A
  • Ammonium ions oxidised to nitrites
  • Nitrites oxidised to nitrates

• Oxidation

39
Q

What types of organisms carry out nitrification? Why do they do it?

A
  • Nitrifying bacteria (free living)
  • They obtain their energy from these reactions
  • Oxidation so releases energy for them
40
Q

What is required for nitrification to take place? (conditions) (1) Therefore give two ways farmers improve soil nitrate content?

A

Oxygen

  • Ploughing to produce air spaces.
  • Good drainage prevents air spaces being filled with water
41
Q

Describe briefly what nitrogen fixation is and the two types in micro-organisms.

A
  • Gaseous nitrogen is converted to nitrogen containing compounds.
  • Mutualistic
  • Free living
42
Q

Describe the process of free living nitrogen fixing bacteria. (3)

A
  • Reduce gaseous N to ammonia
  • They use to manufacture amino acids.
  • Nitrogen rich compounds are released when they die and decay.
43
Q

Describe the process of mutualistic nitrogen fixing bacteria.

A
  • They live in nodules on a legume’s root.
  • They obtain carbohydrates from the plant.
  • The plant obtains amino acids produced from N gas by the bacteria.
44
Q

In what conditions does denitrification occur and by what type of bacteria?

A
  • Anaerobic - waterlogged soils.

* Anaerobic denitrifying bacteria.

45
Q

What do denitrifying bacteria produce and from what? What is the consequence of this for farming? What must farmers therefore insure about their fields?

A
  • N gas from nitrates.
  • Lower nitrogen containing compounds availability.
  • Must insure the field is drained to prevent denitrifying bacteria reproducing.
46
Q

What compounds is phosphors used in?

A

ATP, Nucleic acids, phospholipids, TP, GP etc.

47
Q

What phase does the phosphorus cycle lack that the nitrogen and carbon cycle have? Therefore where is the main reservoir of phosphorus?

A
  • A gaseous phase.

* In mineral form, rocks

48
Q

In what form does phosphorus mainly exist?

A

Phosphate ions.

49
Q

Describe the phosphorus cycle. (7)

A
  • Sedimentary rock deposits containing phosphate in seas brought to the surface by uplifting of rocks.
  • Weathering and erosion of rocks helps phosphate ions become dissolved and so available for absorption by plants.
  • plants incorporate them into their biomass
  • Pass into consumers.
  • Excreted by animals/waste e.g. guano (sea bird faeces)
  • Saprobionts break down dead plants and animals releasing phosphate ions.
  • Transported by streams and rivers into oceans and lakes by erosion of rocks, remains and excretion where they form sedimentary rocks.
50
Q

What are mycorrhizae?

A

Associations between certain fungi and almost all plant roots.

51
Q

Describe the relationship between mycorrhizae and plants.

A
  • Act like root extensions. Large surface area for absorption of mineral ions and water.
  • Plant can resist drought. Improves mineral ion uptake.
  • Acts like a sponge connecting neighbouring plants.
  • Mutualistic - as the fungi receive organic compounds e.g. sugars and amino acids.
52
Q

Why is fertiliser needed in agricultural ecosystems? (5)

A
  • Plants need mineral ions (especially nitrates)
  • Intensive food production means areas of land are repeatedly used maximum yield.
  • Mineral ions taken up by crops which are removed for food.
  • When harvested the mineral ions are removed with the crops.
  • Reduced concentrations becomes a limiting factor for growth.
53
Q

Why are fertilisers not needed in natural ecosystems? (2)

A
  • Minerals removed from the soil by plants are returned why they die and are decomposed.
  • Also dead animals remains aren’t removed.
54
Q

How are natural fertilisers obtained? (3 example)

A
  • Decaying legumes
  • Animal waste
  • Bone meal
55
Q

How are artificial fertilisers obtained?

A

Mined from rocks/deposits.

• Blended to give the right balance (NPK)

56
Q

How do fertilisers increase productivity? (4)

A
  • Plants require minerals for growth.
  • e.g. nitrogen is needed for DNA and amino acids and more.
  • Where nitrate ions are present the plant will grow earlier taller and larger leaf area.
  • Increasing photosynthesis and productivity.
57
Q

Why don’t farmers add high concentrations of fertilisers? (2)

A
  • Cost outweighs profit.

* toxic in high concentrations

58
Q

Name three negative effects of the use of nitrogen-containing fertilisers. (3)

A
  • Reduced species diversity - favours growth of grasses.
  • Leaching - solutions of watercourses
  • eutrophication - caused by leaching.
59
Q

How can the use of nitrogen-containing fertilisers lead to a reduction in species diversity?

A

• N rich soils favour grasses and nettles. Out compete other species.

60
Q

What is leaching

A

The process by which nutrients are removed from the soil.

61
Q

How does leaching occur? (3)

A
  • Rainwater dissolves minerals.
  • Carry them deep into the soil beyond plant roots.
  • Make their way into watercourses.
62
Q

What are the dangers of leaching? (2)

A
  • Harmful to consume contaminated water.

* Eutrophication

63
Q

Describe eutrophication. (11)

A
  • In most waters there is a low nitrate conc.
  • Nitrate conc. increases due to leaching, no longer limiting factor for algal growth.
  • Algal bloom on surface.
  • Absorb light prevent it from reaching depths.
  • Light is limiting factor for plants growth underneath. so they die.
  • Lack of dead organisms is no longer a limiting factor for saprobionts. They grow in population.
  • Saprobionts require oxygen. Increased BOD (biological oxygen demand)
  • Oxygen conc. decreases. Nitrates released from decaying organisms.
  • Oxygen becomes limiting factor for aerobes such as fish. They die.
  • Less competition for anaerobes. Populations rise.
  • Anaerobes decompose deda material releasing more nitrates and some toxic waste such as hydrogen sulphide.

Biology (18 decks)

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