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2B > Energy Transfer in Organisms > Flashcards

Energy Transfer in Organisms Flashcards

1
Q

What is an ecosystem?

A

All of the organisms living in a particular area and all the abiotic conditions.

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2
Q

What are producers?

A

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

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3
Q

What are consumers?

A

Organisms that obtain their energy by feeding on (consuming) other organisms rather than using the energy of he sunlight directly.

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4
Q

What is a primary consumer?

A

Animals that directly eat producers (green plants)

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5
Q

What is a secondary consumer?

A

Animals that eat primary consumers

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6
Q

What is a tertiary consumer?

A

Animals earring secondary consumers.

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7
Q

What is a saprobiont?

A

A group of organisms that break down the complex material in dead organisms into simple ones.

In doing so, they release valuable minerals and elements in a form that can be absorbed by plants and so contribute to recycling. (Eg fungi, bacteria).

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8
Q

What is a food chain?

A

A feeding relationship in which the producers are eaten by primary consumers -> secondary consumers -> tertiary consumers -> quaternary consumers.

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9
Q

Define trophic level.

A

Each stage in the food chain.

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10
Q

Define food web.

A

Within a single habitat, many food chains are linked together to form a food web.

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11
Q

Define biomass.

A

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

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12
Q

How is biomass measured?

A

Dry mass per given area, in a given time.

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13
Q

What is calorimetry?

A

Pan estimation of the chemical energy store in dry mass.

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14
Q

Glucose is produced in photosynthesis. What is this sugar then used for?

A
  • respiration; to release energy for growth

- to make bio mols; eg cellulose (a component of cell walls). These make up the biomass.

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15
Q

How much carbon is in dry mass?

A

About 50% of dry mass is carbon.

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16
Q

Why is biomass given over a time period?

A

Because biomass changes over time. Eg deciduous trees lose their leaves in winter, so their biomass changes over the course of the year.

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17
Q

How do consumers get their energy?

A

By ingesting plant material, or animals that have eaten plant material.

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18
Q

Why isn’t all the chemical energy stored in consumer’s food transferred to the next tropic level?

A
  • not all food is eaten (eg plant roots, bones).
  • some are indigestible, so are egested as faeces (so chemical energy stored in these parts lost to the environment).
  • some energy lost to the environment through respiration / excretion of urine.
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19
Q

How much energy is lost from the producer -> consumer?

A

90%

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20
Q

How is energy transferred through an ecosystem?

A

When organisms eat other organisms. Eg the food chain.

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21
Q

What is gross primary production (GPP)?

A

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

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22
Q

What is the source of energy for ecosystems?

A

Sunlight

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23
Q

Only 2% of sunlight is converted to organic matter by photosynthesis. Most light energy isn’t. But why?

A
  • light may not fall on a chlorophyll molecule.
  • not all wavelengths of light can be absorbed and used for photosynthesis.
  • over 90% of the sun’s energy is reflected back into space by clouds and dust / absorbed by the atmosphere.
  • a factor, eg low CO2 levels, may limit the rate of photosynthesis.
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24
Q

What is respiratory loss?

A

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

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25
Q

What is net primary production (NPP)?

A

The chemical energy store which is left when the losses to deportation have been taken into account.

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26
Q

What is the equation of NPP?

A

NPP = GPP - respiratory losses

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27
Q

What is the NPP available for?

A

Plant growth and reproduction. Also available to the other trophic levels in the ecosystems, e.g. consumers and decomposers.

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28
Q

What is the net production of consumers equation?

A

N = I - (F+R)

Net production = chemical energy in Ingested food - (chemical energy lost in Faeces and urine + energy lost through Respiration)

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29
Q

Why do most food chains only have 4/5 trophic levels?

A

Because indifferent energy is available to support a large enough breeding population at trophic levels higher than these.

30
Q

The total mass of organisms in a particular place (biomass) is _______ at higher trophic levels.

Why?

A

Less

Due to the relative inefficiency of energy transfer between trophic levels.

31
Q

Why is the total amount of energy available less at each trophic level as you move up a food chain?

A

Because of the relative inefficiency of energytransfer between trophic levels.

32
Q

What is the role of decomposers in a food web?

A

Decomposers eg fungi break down dead / indigested material, allowing nutrients to be recycled.

33
Q

What are the two main ways in which farming practices increase the efficiency of energy transfer?

A
  • reduce the energy lost through respiration

- reduce the energy lost to other organisms eg pests

34
Q

What are pests?

A

Organisms that reduce the amount of energy available for crop growth and therefore NPP. Ultimately reducing the amount of energy for humans.

35
Q

How can a farmer reduce the energy loss to pests?

A

By simplifying the food web (ie getting rid of food chains that didn’t involve humans).

36
Q

What are the 3 ways in which farmers can simplify food webs to reduce energy loss to pests, in order to increase efficiency?

A
  • reduce pest numbers, using chemical pesticides.
  • use biological agents to reduce pest numbers, so crops lose less energy and biomass; increasing the efficiency of energy transfer to humans.
  • use integrated systems that combine both chemical and biological methods. This combined effect can reduce pest numbers even more than each individual method, meaning NPP is increase even more.
37
Q

Outline how insecticides are effective in increasing the efficiency of energy transfer.

A

Insecticides kill insect pests that eat and damage crops. This means less biomass is lost from the crops, so they grow to be larger and NPP is greater.

38
Q

Outline how herbicides can increase the efficiency of energy transfer for farmers.

A

Herbicides kill weeds (pests). This can remove direct competition with the crop for sunlight energy.

39
Q

Outline the way in which a farmer can reduce respiratory losses, meaning energy transfer is more efficient.

A

By controlling the conditions in which livestock live, so that more energy is used for growth and less is lost through respiration.
This means more biomass is produced and more chemical energy can be stored, increasing net production and the efficiency of energy transfer to humans.

40
Q

Give specific examples of how farmers reduce respiratory losses meaning energy can be transferred more efficiently.

A
  • animals kept in pens, where movement is restricted (as moving increases the rate of respiration).
  • indoor pens, so less energy is wasted by generating body heat.
41
Q

What’s the problem with enhancing net production by reducing respiratory losses?

A

Ethical issues. Eg people think that the conditions intensively reared animals are kept in cause the animals pain, distress and restricts their natural behaviour so shouldn’t be done.

42
Q

In what form does energy enter and leave an ecosystem?

A

Enters as sunlight.

Lost as heat.

43
Q

What is a natural ecosystem?

A

An ecosystem which hasn’t been changed by human activity.

44
Q

What are sapriobionts?

A

A type of microorganism that is a decomposer. It feeds in dead plants, animals and their waste products, breaking them down.

45
Q

Outline sacrobiotic nutrition.

A

Saprobionts secrete their enzymes and digest their food externally, then absorb the nutrients they need (extra cellular digestion).
During this, organic molecules are broken down into inorganic ions.

46
Q

What is ‘mycorrhizae’?

A

Fungi which firm symbolic relationships with the roots of plants.

47
Q

What is the role of mycorrhizae?

A

Mycorrhizae facilitates the uptake of water and inorganic ions by plants.

48
Q

Mycorrhizae facilitates the uptake of water and inorganic ions by plants. How?

A
  1. Fungi are made up of long, thin strands called hyphae (which connects to a plant’s roots).
  2. The hyphae increase SA of the plant’s root system, helping the plant to absorb ions from the soil that are usually scarce.
  3. Hyphae also increase the uptake of water by the plant.
  4. In turn, the fungi obtain organic compound eg glucose from the plant.
49
Q

What are hyphae?

A

Long thin strands that make up fungi. They’re connected to the plant’s roots.

50
Q

What is the importance of hyphae?

A

Hyphae greatly increase SA of the plant’s root system, helping the plant to absorb ions from the soil that are usually scarce.
They also increase the uptake of water by the plant.

51
Q

Why do plants and animals need nutrients?

A

To make proteins and nucleic acids (DNA and RNA).

52
Q

Despite the atmosphere containing 78% nitrogen. Why isn’t this useful?

A

Because plants and animals can’t use it in atmospheric form.

53
Q

What are the four processes in the nitrogen cycle?

A

Nitrogen fixation
Amminofication
Nitrification
Denitrification

54
Q

When can nitrogen fixation occur?

A

Either industrially or when lightening passes through the atmosphere or by microorganisms.

55
Q

In one sentence, what is nitrogen fixation?

A

The process by which nitrogen gas is converted into nitrogen containing compounds.

56
Q

What are the two main types of nitrogen fixation?

A
  • free living nitrogen fixing bacteria

- mutualistic nitrogen fixing bacteria

57
Q

Outline how free-living nitrogen fixing bacteria occur in nitrogen fixation.

A

Free-living nitrogen-fixing bacteria reduce atmospheric nitrogen to ammonia, which they then use to manufacture amino acids.

Nitrogen rich compounds are released from them when they die and decay.

58
Q

Outline how mutualistic nitrogen-fixing bacteria occur in nitrogen fixation.

A

They obtain carbs from the plant and the plant acquires AAs from the bacteria.
Mutualistic nitrogen-fixing bacteria live in nodules on the roots of plants eg peas.

59
Q

What is ammonification?

A

The production of ammonia from organic nitrogen-containing compounds (eg urea (from the breakdown of excess AAs), nucleic acids and vitamins (found in faeces and dead organisms)). Uses saprobionts.

60
Q

What is nitrification?

A

When ammonium ions in the soil are changed into nitrogen compounds that can then be used by plants (nitrates).

61
Q

Outline the processes involved in nitrification.

A
  • oxidisation of ammonium ions to nitrite ions (NO2-)

- oxidisation of nitrite ions to nitrate ions (NO3-)

62
Q

What is needed for nitrification?

A

Nitrifying bacteria require oxygen to carry out these conversions, and so they require a soul that has many air spaces (so farmers should aerate soil by ploughing).

63
Q

What is denitrification?

A

When nitrates are converted into gaseous nitrogen by anaerobic denitrifying bacteria.

64
Q

Where does denitrification occur?

A

Under anaerobic conditions, such as waterlogged soils.

65
Q

What is the main issue of denitrification?

A

It reduces the availability of nitrogen containing compounds for plants

66
Q

What can be done to prevent denitrification?

A

Crops must be kept aerated to prevent to build up of denitrifying bacteria in anaerobic conditions.

67
Q

Why do plants and animals need phosphorous?

A

To make bio mols eg phospholipids, ATP, nucleic acids.

68
Q

What is the main reservoir of phosphorous?

A

In mineral form - eg in rocks and dissolved in the oceans in the form of phosphate ions (Po4^3-).

69
Q

Outline the process of the phosphorous cycle.

A
  1. Phosphate ions in rocks are released into the soil by weathering.
  2. Phosphate ions then taken into plants via roots (mycorrhizae increase the rate at which this phosphate is assimilated).
  3. Phosphate ions are transferred through the food chains as animals eat the plants, then animal eat animals.
  4. Phosphate ions lost from the animals in waste products.
  5. When plants and animals die, saprobionts break down the organic compounds, releasing phosphate ions into the soil for assimilation by plants.
70
Q

How are phosphate ions transferred from the sea to the land?

A
  1. Phosphate ions in rocks are released into the seas, rivers etc by weathering. This is taken up by aquatic producers (eg algae) and passed along the food chain to birds.
  2. Guano (waste produced by birds) contains a high proportion of phosphate ions to soils. It’s often a natural fertiliser.

2B (26 decks)

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