The Efficiency Of Ecosystems

Question 1

What is a trophic level?

Answer 1

A trophic level describes the position of an organism in a food chain or web and describe its feeding relationship with other organisms

Question 2

What do producers do?

Answer 2

Make food. In photosynthesis plants and algae trap light from the sun and this drives the production of ATP which they then use to make glucose from carbon dioxide and water

Question 3

What are primary consumers?

Answer 3

The organisms (mainly animals) that eat producers. They are herbivores. They use the molecules in plants to supply the raw materials needed for metabolic reactions

Question 4

What are secondary consumers?

Answer 4

They are the animals that feed on herbivores. They are carnivores. They use the molecules in the herbivores to supply the raw materials needed for their metabolic reactions

Question 5

What are tertiary consumers?

Answer 5

Animals that feed on other carnivores. They are usually the top predators in the area. They use the molecules in the carnivores to supply the raw materials needed for their metabolic reactions

Question 6

What are decomposers?

Answer 6

The final trophic level in any set of feeding relationships. They are the microorganisms, such as bacteria and fungi, that break down the remains of animals and plants and return the mineral nutrients to the soil

Question 7

The food chain is now recognised as an oversimplification. What are most animals now thought to have existed in?

Answer 7

Interconnected food webs

Question 8

If there is a change in one thing in either a food chain or a food web what will be more catastrophic and why?

Answer 8

A change in a food chain as it will effect all the organisms in the food chain. Whereas in a food web although it mah potentiall affect the balance of an ecosystem it is far less likely to have catastrophic effect and so the system will be more stable

Question 9

What are pyramids of numbers?

Answer 9

It represents the numbers of organisms at each trophic level in a food chain

Question 10

What happens to the number of organisms in each trophic level in most food chains?

Answer 10

They decrease

Question 11

What is a pyramid of biomass?

Answer 11

Represents the biomass of the organisms at each trophic level in a food chain

Question 12

Why does a pyramid of biomass give a much more realistic model than a pyramid of numbers?

Answer 12

As in many situations a pyramid of numbers does not accurately reflect what is happening in an ecosystem. E.g. primary consumers may be supported by just one tree

Question 13

why is wet biomass very inaccurate?

Answer 13

It is affected by water uptake in the soil, transpiration in plants, and drinking, urinating, defaecating and in some cases sweating in animals

Question 14

Dry biomass is more accurate than wet biomass. What is the problem with it?

Answer 14

It involves destroying the material

Question 15

How can you avoid destructing a whole habitat when obtaining dry biomass?

Answer 15

By taking a small sample of all the organisms involved and obtaining the dry biomass

Question 16

How can you avoid destructing a whole habitat when obtaining dry biomass?

Answer 16

By taking a small sample of all the organisms involved and obtaining the dry biomass

Question 17

What are the limitations of pyramids of biomass?

Answer 17

It only takes into account biomass at a particular time and not how quickly organisms reproduce

Question 18

What are pyramids of energy?

Answer 18

It represents the total energy store of the organisms at each trophic level in a food chain

Question 19

What happens as you move along a food chain with regard to energy?

Answer 19

Less energy is stored in the organisms and more is stored in the surrounding atmosphere

Question 20

Where is the chemical energy store from plants lost to in animals?

Answer 20

• some is lost to the animal as undigested therefore unused material in the faeces
• much of the material that is digested is used to drive respiration.
• some of the plant material is lost in metabolic waste products such as urea

Question 21

What is secondary production?

Answer 21

The process of making new animal biomass from plant material that has been eaten. Only a small amount of the chemical store of the plant becomes new animak material (and so part of the energy store of the animal) the rest is dissipated to the surroundings

Question 22

What is a measure of the efficieny of energy transfer in terms of trophic levels?

Answer 22

The energy store in the biomass of an organisms compared with the energy store that ends up in an organism in the next trophic level

Question 23

Why are pyramids of biomass more commonly used than pyramids of energy?

Answer 23

Pyramids of energy are extremely difficult to measure practically so pyramids of biomass are more commonly used

Question 24

What is gross primary productivity (GPP) in plants?

Answer 24

The rate at which light from the sun catalyses the production of new plant material

Question 25

What units is GPP measured in?

Answer 25

• it may be measured in units of biomass/area/time such as g m-2 year-1 or g C (grams of carbon assimilated) m-2 year -1.

Question 26

How is productivity usually measured?

Answer 26

It usually involves finding the mass of representative samples of biomass and then mulitplying up to represent a whole ecosystem

Question 27

How is biomass converted to energy?

Answer 27

Through theoretical calculations rather than empirical measurements

Question 28

What is the Net Primary productivity (NPP)?

Answer 28

The material produced by photosynthesis stored as new plant body tissues

Question 29

How do you work out the NPP?

Answer 29

NPP = GPP - R (respiration)

Question 30

Why do different ecosystems contribute different amounts to the NPP of the earth?

Answer 30

Ecosystems with more water available, ambient temperatures ect. Will have a higher productivity so will have a higher NPP

Question 31

What do you have to take into account when looking at energy transfers between trophic levels?

Answer 31

• include the decomposers as well as the herbivores and carnivores
• temperature, water availability, and especially in temperate zones the season of the year

Question 32

How is the percentage energy or biomass transfer calculated?

Answer 32

Just by a simple percentage calculation. E.g. amount transfered/total x 100

Question 33

Why us it very difficult to measure energy transfers for whole ecosystems?

Answer 33

Many assumptions need to be made in calculating the energy in all the organisms:
You need to be certain you have identified all the most abundant species in the ecosystem, you also need to know how many there are, what an average body size is, how much energy that body size represents, how much of the biomass is transferred into decomposers at any stage of the life of the animal or plant ect.

Question 34

What will the differences be in terms of energy store in summer and winter in temperate regions?

Answer 34

In temperate regions there is likely to be more biomass and therefore a bigger energy store in plant and animal bodies during the summer and more in decomposers during the winter

Question 35

Why do the mean values from calculations of measuring energy transfer usually have large standard errors?

Answer 35

Because many assumptions have to be made during the calculation

Question 36

What do scientists now recognise that the efficiency if energy transfer depends on rather than specific positions in a food chain?

Answer 36

Depends on tbe physiology and behaviour of the organisms involved and the climatic conditions

Question 37

How much of the energy from the sunlight is used to produce plant material?

Answer 37

About 3%

Question 38

What is one of the main effects of the relatively inefficient transfers through food chains and webs?

Answer 38

To limit the number of trophic levels. At higher trophic levels the organisms usually need to range over larger distances so by the fourth and fifth trophic level, it could take more energy to get food and a mate than is needed for growth and reproduction, and so survival is impossible.

Question 39

What do nutrient cycles involve (in terms of phases)?

Answer 39

It consists of a biotic phase phase where the inorganic ions are incorporated in the tissues of living things, and an abiotic phase, where the inorganic ions are returned to the noniving part of the ecosystem

Question 40

How are the nutrients helf in tbe bodies of dead animals, plants, aninal droppings and urine released back into the soil and air?

Answer 40

By the action of the bacteria and fungi that make up the decomposers. These decomposers feed on the droppings and dead bodies digesting them and using the nutrients for respiration; to build their own cells and for reproduction. The microorganisms also release waste products, and these provide the nutrients in a form that plants can use once more

Question 41

What temperature is best for recycling nutrients and why?

Answer 41

Warm conditions as the chemical reactions that take place in mucroorganisms like those in all organisms work best in warm conditions. However since the reactions are controlled by enzymes if the temperature gets too hot they stop altogether as the enzymes denature. They also stop if the conditions are too cold

Question 42

Why do most microorganisms grow better in moist conditions?

Answer 42

They make it easier to dissolve their food and also prevent them from drying out

Question 43

What does the cycling of resources play a vital role in?

Answer 43

Maintaining the fertility of our soil and the health of our atmosphere. In a stable community of plants and animals living in an environment the processes that remove materials from the soil are balanced by processes that return materials.

Question 44

What are the best conditions for recycling nutrients?

Answer 44

Warm moist conditions

Question 45

What is the nitrogen cycle?

Answer 45

The recycling of nitrogen between living things and the environment by the actions of microorganisms

Question 46

What us nitrogen a vital part of?

Answer 46

The structure of many biologically important molecules including amino acids and proteins and it is also part of the molecules of inheritance, DNA and RNA

Question 47

Why can plants not use the nitrogen in the air and what is the useful form of nitrogen for plants and where do they get this?

Answer 47

Becuase nitrogen is an inert gas and so unreactive.

Only nitrogen in the form of nitrates is useful to plants and they absorb this from the soil water

Question 48

What do plants use nitrates for?

Answer 48

To make proteins and then these proteins are passed along the food chain

Question 49

How are nitrates returned to the soil,

Answer 49

• Urine contains urea which is a breakdown product of proteins
• Proteins are passed out in the faeces
• when animals and plants die their bodies contain a large proportion of protein. Some of the decomposers act specifically on the proteins breaking them down to form ammonium compounds. These ammonium compounds are then oxidised by nitrifying bacteria that convert them to nitrates. These are then returned to the soil

Question 50

Where do the nitrates in the soil come from that do not come frin the process of decay?

Answer 50

Nitrogen fixing bacteria in the soil can convert nitrogen from the soil air into ammonia and themis then converted into nitrates by the nitrifying bacteria of the nitrogen cycle

Question 51

What are legumes and why are they so important in the nitrogen cycle?

Answer 51

They are plants such as peas, beans and clover. They have nodules on their roots that are full of nitorgen fixing bacteria so they help convert the soil air into ammonia

Question 52

What is mutalism and how does this work with legumes and nitrogen fixing bacteria?

Answer 52

It is where two organisms living together and both benefit. The bacterua get protection and a supply of organic food from the plant while the plant gets ammonia that it can use to form ami o acids

Question 53

What are denitrifying bacteria?

Answer 53

They use nitrates as an energy source and break them down into nitrogen gas. They reduce the amount of nitrates in the soil

Question 54

Why is carbon vital for living organisms?

Answer 54

Because all of the main molecules of life - carbohydrates, proteins, fats and DNA are based on carbon atoms in combination with ither elements

Question 55

What is the carbon cycle?

Answer 55

The series of reactions by which carbon is constantly recycled between living things and the environment

Question 56

What are denitrifying bacteria?

Answer 56

They break down nitrates to power the production of ATP producing nitrogen gas as a waste product

Question 57

How is carbon taken out of the environment?

Answer 57

CO2 is removed from the air by green plants in the process of photosynthesis. It is used to make the carbohydrates, proteins and fats that make up the body of the plant. When the plants are eaten by animals and those animals are eaten by predators the carbon is passed on and becomes part of the animals bodies

Question 58

How is carbon returned to the atmosphere?

Answer 58

• when green plants respirw any carbon dioxide not used for photosynthesis is returned to the atmosphere.
• when animals respire they release carbon dioxide as a waste product into the air
• when plants and animals die their bodies are broken down by the action of decomposers and when these microbes respire they releass carbon into the atmosphere as carbon dioxide
• carbon dioxide is returned to the atmosphere by combustion when anything that has been living is burnt

Question 59

Some of the bacteria involved in the carbon cycle produce cellulase. What does this enzyme do?

Answer 59

Breaks down the cellulose in plant cell walls to produce sugars that can then be used as food by a wide range of other organisms

Question 60

What is a carbon sink?

Answer 60

A reservoir where carbon is removed from the atmosphere and ‘locked up’ in organic or inorganic compounds

Question 61

What happens in biotic carbon sinks?

Answer 61

Carbon is removed feom the atmosphere by photosynthesis and stored in the bodies of living organisms.

Soil also contains great amounts of organic carbon rich compounds in the form of hummus

Question 62

What happens in abiotic carbon sinks?

Answer 62

Rocks such as limestone, chalk and fossil fuels hold vast stores of carbon

Question 63

Why is the atlantic ocean a more important carbon sink than the southern ocean despite it being smaller?

Answer 63

• due to water temperature
• ocean currents in the atlantic that move carbon rich water downwards and bring more water up from the depths to absorb morw carbon

Question 64

What is the quantity of carbon stored in the different sinks measured in and how many tonnes is one of these?

Answer 64

Pentagrams

1 pentagram is 10’15g or 1 billion tonnes

Question 65

What is threatening the balance of the carbon cycle?

Answer 65

Human activity. The industrial revolutuon coupled with the development if the internal combustion engine and its use in cars from the 19th century onwards. All the fossil fuels being burnt ect.