Edexcel A level Biology B Student Book 2 ActiveBook
- Biology notes that will help international a level students prepare for their unit 4 exam.
- Consist of Chapter 5B: Ecology.
- 90% types notes with the other 10% being hand written usually in tables. - Useful tools to help learn and memorise them like emojis, diagrams, tables and shortcuts.
, 1) Ecological productivity
• Organisms that carry out photosynthesis or convert light energy into chemical
energy are known as producers
Primary productivity refers to the rate at which producers do this
• GPP (gross primary productivity) = rate at which chemical energy is converted into
carbohydrates during photosynthesis
90% of the energy originally converted
• NPP (net primary productivity) is the by the plant will not be stored as new
GPP - plant respiratory losses. It can plant biomass and will not be available to
be defined as the rate at which energy be passed on to the primary consumers
is stored in plant biomass
NPP is important as it represents the energy available to organisms at higher
trophic levels (= position of organism in a food chain) in the ecosystem
plant respiratory loss= carbohydrates
NPP = GPP - R used up by the plant that are not stored as
plant biomass
2) Energy and biomass transfers
1. Producers such as plants convert light energy chemical energy
2. This chemical energy stored in plant biomass is passed to primary consumers
3. The primary consumers digest the plant tissues chemical energy is transfered
to the tissues of the primary consumer
4. The secondary consumer ingests the primary consumer and the chemical energy
is passed on to the former and so on on top of the food chain
When it dies, the chemical energy decomposers
represent
transfer of
energy from
one trophic
level to the next
, Energy loss in a food chain
Energy is lost to the environment at every trophic level by several ways:
Producers
• Light passes through the leaves or is reflected away
• Light hits non-photosynthetic parts of plant
• Certain wavelength are absorbed (not all of them)
• Plants release energy during respiration, some of which is lost to the enviroment as
heat
Consumers
• When a consumer ingest another organism, not all the chemical energy in the
consumer’s food is transferred to the consumer’s biomass because
Not every part of the food organism is eaten so energy lost to the environment
Consumers can’t digest all the food so energy is lost through feaces
Lost in the form of heat when consumer respire
Excretion
• The energy loss at each level limits the maximum length of food chains
• Net productivity is
the rate at which
energy is converted
into biomass in the
body of the
consumer (= energy
received - energy
losses)
Energy efficiency = net productivity
X 100
energy received
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