PRODUCTIVITY OR HOW FAST AN ORGANISM GROWS

1
PRODUCTIVITY OR HOW FAST AN ORGANISM GROWS
2
ENERGY ENTERS THE ECOSYSTEM AS SUNLIGHT

• Only 1-2 of the light energy falling on a tree
  is captured and turned into chemical energy by
  PHOTOSYNTHESIS
• The rest is reflected, or just warms up the tree
  as it is absorbed

3
Gross productivity is a measure of total energy
captured

• It is measured in joules (J)
• It is the energy captured or assimilated by an
  organism
• for a plant, it is the sunlight actually fixed
  by the leaves during photosynthesis

Energy is stored in leaf as sugars and starches,
which later are used to form flowers, fruits,
seeds,
4
(No Transcript)
5
Gross Productivity

• GP
• The total energy gain in biomass per unit time.
• GPP Photosynthesis in primary producers
• GSP Adsorption in consumers

6
Net primary productivity

• Plants have to use some of the energy they
  capture to keep themselves growing
• they move water and stored chemicals around
• they make hormones and enzymes to control their
  metabolism
• they make flowers, fruits, new leaves and stems
• the energy left over after they have used what
  they need is called the net productivity
• the energy used by the plant for essential tasks
  is called respiration energy, and eventually it
  is released to the environment as heat

7
Net Productivity

• NP
• The gain in energy or biomass per unit time
  remaining after allowing for respiratory losses
  (R)

8
Net and Gross Primary Productivity

• Gross primary productivity and net primary
  productivity are not the same
• The plants produce biomass over time and then
  loose some of it due to respiration.
• Does this make sense?
• NPP GPP - R

9
So how are gross primary and net primary
productivity related ?

• Net productivity Gross productivity -
  Respiration Energy
• or using symbols
• NPP GPP R
• The productivity of a plant is called PRIMARY
  PRODUCTIVITY because plants are the first or
  primary organisms in the food web

10
Chart of Net Primary Productivity for biomes
11
Secondary Productivity
12
Gross secondary productivity

• Gross secondary productivity refers to the
  production of biomass over time by consumers.
• It is also called assimilation

13
NSP
14
Gross Secondary Productivity

• Animals must eat other organisms to obtain
  energy, unlike plants which photosynthesise
• Animals may eat plants or animals or both
• Not all the energy in food is absorbed
  (assimilated) into an animals body
• Unassimilated food is ejected as faeces or
  droppings
• gross secondary productivity food assimilated
• gross productivity food eaten - energy in faeces

15
Net Secondary Productivity

• Gross secondary productivity
• Energy eaten - energy in faeces
• As well as keeping themselves alive, animals must
  use energy to move and keep warm - plants need
  rather less energy- but in the end it, as in
  plants, it all turns to heat
• Net secondary productivity (NSP)
• food eaten - faeces - respiration energy
• so NSP GSP- R (just like plants)

?
16
Net and gross productivity in the food web

• In a food web diagram, you can usually assume
  that
• the energy input into an organism represents the
  Gross Productivity (GP)
• the energy output from that organism to the next
  trophic level represents the Net Productivity
• the difference between GP and NP R (respiration
  energy ) and/or loss to decomposers

?
17
Remember only 10 of biomass is transferred
between trophic levels
18
Pyramid of Biomass Review
19
Pyramid of Productivity
20
Energy flow through an ecosystem
21
Use the food web from the slide before

• Draw a complete food web for the ecosystem
• the sun
• named primary producers (at least 2)
• named primary consumers (at least 3)
• named secondary consumers (at least 2)
• named decomposers (at least 2)
• respiration energy loss
• On your diagram use arrows to show direction of
  energy flow

22

• Complete this energy flow diagram
• label GPP, NPP and R for the primary producer
• add arrows to show missing energy pathways (3 in
  total)
• fill in the blank box to explain why some
  sunlight is not fixed by plant

23

• Draw your own energy flow diagram, rather like
  the one on the previous slide to show energy
  flows through one of the animals named in your
  food web. You should include the following
  labels
• energy lost in faeces
• food ingested
• respiration loss, R
• GSP, NSP
• arrows showing energy moving to carnivores and
  decomposers