Biomass transfer through an ecosystem

Question 1

What is the source of energy for organisms? How is it transferred

Answer 1

• the sun
• light energy to chemical energy in plants and other photosynthetic organisms
• chemical energy transferred to other non-photosynthetic organisms as food

Question 2

What is a trophic level?

Answer 2

• each stage in a food chain

Question 3

What are the different types of organisms in each trophic level?

Answer 3

• first trophic level
  
  • always a producer
  • organisms that converts light energy to chemical energy
• subsequent trophic levels are all consumers
  
  • obtain eenergy by feeding on other organisms

Question 4

What are the different types of consumers?

Answer 4

• primary consumer
  
  • animals that eats a producer
• labelled successively after this

Question 5

Why do food chains rarely have more than 4 consumers

Answer 5

• there isn’t sufficient biomass and stored energy to support any further organisms

Question 6

What are decomposers and why are they important?

Answer 6

• important components of food webs
• break down dead organisms
• release nutrients back into the ecosystem

Question 7

What do the levels of pyramid in a food chain represent

Answer 7

number of organisms at each trophic level

primary always at bottom

Question 8

What is biomass?

Answer 8

• mass of living material present in a particular place or in a particular organism
• important measure in the study of food chains and food webs as it can be equated to energy content

Question 9

How is biomass calculateD? What are its units?

Answer 9

• multiply biomass present in each organism by the total number of organisms in that trophic level
• g m^-2
  
  • ^​or g m^-3 in areas for water

Question 10

How is biomass measured?

Answer 10

• mass of fresh material
• water content must be discounted
  
  • unrelaible as water content varies
    
    • unless large samples are used
• calculate dry mass

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Question 11

How is dry mass measured and waht are its problem?

Answer 11

• organisms killed
• placed in oven a 80 degress until water has evaporated
  
  • 2 identical mass reading

Question 12

Why does biomass decrease at ach trophic level?

Answer 12

• when animals eat, small proportion of food ingested is converted to new tissue
• it is only this part of the biomass which is available for the next trophic level to eat - same with energy

Question 13

What is ecological efficiency?

Answer 13

• the efficiency with which biomass or energy is transferred from one trophic level to the next is ecological efficiency

Question 14

Why do producers only convert 1-3% of the light energy they receive to chemical energy and hence biomass?

Answer 14

• not all of the solar energy available is used for photosyntheis
  
  • 90% reflected
  • some transmitted through leaf
  • some is unusable wavelength
• limiting factors for photosyntesis
• energy ‘lost’ as it is used for photosynthetic reactions

Question 15

What is gross production?

Answer 15

• the total solar energy that plants convert to organic matter is called the gross productions
  
  • plants use 20-50% OF THis energy in respiration
  • remaining is converted to biomass
• tyhis is the energy available to the next trophic level and is known as the net production

Question 16

Why do consumers at each level convert at most 10% of the biomass in their own organic tissue becae?

Answer 16

• not all the organism is eaten
• some energy transferred to the environment as metabolic heat,
  
  • result of movement and respiration
• some parts of the organsm are indigestible
  
  • egested as faeces
• some energy lost from the animal in excretory materials such as urine

Question 17

What is the equation for ecological efficiency?

Answer 17

energy or biomass available after transfer / energy or biomasws available before the transfer x 100