Energy and ecosystems

Question 1

What are the producers

Answer 1

photosynthetic organisms e.g. plants that use water, light energy, carbon dioxide to make organic substances

Question 2

What are the consumers

Answer 2

they are organisms which obtain energy from eating the consumers rather than producing their own

Question 3

What are the primary, secondary and tertiary consumers

Answer 3

primary - consumers that directly eat the producers e.g. green plants

secondary - animals eating the primary consumers

tertiary - predators which eat the secondary consumers

Question 4

What are saprobionts (bacteria/fungi)

Answer 4

they are decomposers which break down complex dead organisms into simpler valuable minerals which can be absorbed by plants

Question 5

What is the definition of an ecosystem

Answer 5

it is all the populations of living organisms and all of the abiotic features within in a certain environment

Question 6

What does a food chain show

Answer 6

the relationship in which the producers are eaten by the consumers

Question 7

What is a trophic level

Answer 7

each stage in the food chain where a primary consumer is eaten by a secondary consumer and so on

Question 8

What is a food web

Answer 8

where many food chains are linked because animals don’t rely on one food source within there habitat

Question 9

What meant by biomass

Answer 9

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

Question 10

how can chemical energy store in dry mass be estimated using calorimetry

Answer 10

• using a bomb calorimeter the dry material is weighed then burned using pure oxygen within a sealed chamber
• the sealed chamber in surrounded by a water bath
• the heat energy in the chamber rises the temperature of the water surrounding it
• in KJkg^-1

Question 11

Why is a very low percentage of the suns light energy converted into organic matter

Answer 11

• over 90% of the suns light is either reflected or absorbed by the atmosphere
• not all wavelengths of light are converted by the photosynthesis
• not all light reaches the plants chlorophyll
• low carbon dioxide levels may slow the rate of photosynthesis

Question 12

Why does the energy flow between trophic levels decrease

Answer 12

• not all energy is transferred as energy is lost through:
• heat energy during respiration
• waste products e.g. faeces
• excretory materials e.g. urine
• not all of the animal is eaten e.g. bones

Question 13

How do you calculate net primary production

Answer 13

NPP = gross primary production - respiratory losses

Question 14

Why do most food chains have no more than 4 trophic levels

Answer 14

there would be an insufficient amount of energy available to the support the breeding population

Question 15

What are farming practises that increase energy-conversion rate

Answer 15

• restricted movement so no energy lost from muscle contraction
• a warm environment so no energy lost from respiration
• feeding can be controlled for the optimum amount of food for maximum growth and minimal waste
• excluded from predators so no loss to other organisms in the food web

Question 16

What is the nutrient cycle

Answer 16

• nutrients e.g. inorganic molecules are taken up by the producers e.g. the plants
• the producer converts nutrients into complex organic molecules
• producer is eaten by primary consumer and nutrient is passed on
• this then passes on along the food chain when the primary consumer is eaten
• when producers and consumers die the saprobiontic microorganisms e.g. decomposers break down the complex molecules into the nutrients original form and retaken up by producers

Question 17

How are nitrate ions absorbed into the roots of plants

Answer 17

active transport

Question 18

What is the ammonification stage of the nitrogen cycle

Answer 18

ammonification - the release of ammonia from organic nitrogen containing compounds e.g. proteins and nucleic acids from faeces and dead produces/consumers, and forming ammonium in the soil

Question 19

What is the nitrification stage of the nitrogen cycle

Answer 19

the conversion of ammonium into nitrate ions by nitrifying bacteria, in a 2 step process:
1 - oxidation of ammonium ions into nitrite ions NO2-
2 - oxidation of nitrite ions into nitrate ions NO3-

Question 20

What is the nitrogen fixation stage of the nitrogen cycle and what are the 2 types of nitrogen-fixing bacteria

Answer 20

this is where nitrogen gas is converted into nitrogen containing compounds which can occur naturally when lightening passes through the atmosphere

can also be carried out by:
-free-living nitrogen-fixing bacteria, they reduce nitrogen gas to ammonia which they use to make amino acids, and release nitrogen rich compounds when they decay

-mutualistic nitrogen-fixing bacteria, they obtain carbohydrates from the roots in return of supplying amino acids to the plant

Question 21

What is the denitrification stage of the nitrogen cycle

Answer 21

when there is a low oxygen level anaerobic denitrifying bacteria convert nitrates in the soil into nitrogen gas, reducing the nitrogen containing compounds for plants thus the soil must be kept well aerated

Question 22

What conditions do nitrifying bacteria require and how can it be obtained

Answer 22

they require oxygen to carry out the reaction thus air pockets in the soil are needed, which can be resolved by ploughing and a good drainage system to avoid air pockets filling with water

Question 23

What are saprobionts

Answer 23

they secrete enzymes which break down starch into glucose molecules and break dow ammonia into amino acids

Question 24

What is the phosphorus cycle

Answer 24

• geographical uplifting of rocks cause sedimentary rocks to surface
• weathering and erosion of rocks help phosphate ions be able to be absorbed by plants
• the phosphate ions are passed on to the animals which feed on the plants
• excess phosphate ions are excreted as waste products
• when plants and animals die, decomposers e.g. bacteria/fungi break them down releasing the phosphate ions into the soil
• some phosphate ions remain in bones/shells
• phosphate ions released by decomposition/dissolved out of rocks are transported into lakes where they reform sedimentary rock

Question 25

What are the roles of mycorrhizae

Answer 25

they are types of fungi with a mutualistic relationship with the plant which attach the the roots of plants which act as extensions which increase the surface area for the to absorb water and minerals, and in return gain organic compounds e.g. sugars and amino acids

Question 26

What are natural organic fertilisers

Answer 26

consist of dead and decaying remains of plants and animals as well as waste products e.g. manure

Question 27

What are artificial inorganic fertilisers

Answer 27

a blended mix of minerals needed for a specific crop which has been converted from deposits mined from rocks e.g. nitrogen, phosphorus and potassium

Question 28

What are the effects of using nitrogen containing fertilisers

Answer 28

• reduced species diversity - as the soil favours the growth of rapidly growing species and out compete other plants
• leaching - pollution of water sources
• eutrophication - as a result of leaching

Question 29

What is eutrophication

Answer 29

• due to leaching, lakes now have an increase in nitrogen concentration and the plants and algae increase growth
• the growth of algae causes the surface of the lakes to become densely populated with algae, called algal bloom
• this prevents light from penetrating lower into the water
• under water plants begin to die causing oxygen levels in the water to decrease
• saprobionts start to decompose the plants
• oxygen becomes the limiting factor and organisms e.g. fish cannot respire aerobically
• population of anaerobic organisms increase and decompose dead material and release toxic wastes e.g. hydrogen sulphide making the water putrid