3.5 Energy and ecosystems Flashcards
define photoautotrophs
produces
use light energy to synthesise their own food
how do plants synthesise their own organic compounds
from atmospheric, aquatic CO2
most sugars used as respiratory substrate
rest used to make biological molecules = forms plant biomass
define heterotrophs
cannot synthesise their own energy
obtain it from autotrophs/ other hetertrophs
act as consumers
how can biomass be measured
- mass of carbon
- dry mass of tissue per given area
method to measure biomass
- sample of organism dried in oven at low temp , to avoid combustion
2.sample reweighed at regular intervals - mass constant = all water removed
4.mass of carbon = 50% of dry mass
5
why is dry mass used
more representative
water content of sample varies
what is calorimetry used for
to estimate chemical energy stored in dry biomass
method for calorimetry
- sample of dry biomass burnt
- energy released used to heat known vol of water
- change in temp of water used to calculate chemical energy
define GPP
gross primary production
-chemical energy store in plant biomass in a given area in a given time
define NPP
net primary production
- chemical energy store in plant biomass after respiratory losses
- GPP - R
- available for plant growth and reproduction
- available to other trophic levels
formula for net production of consumers
N = I - (F + R)
rates of productivity units
kJ ha–1 year–1
why is per unit area used
different environments vary in size
standardises results so
environments can be compared
why is per year used
more representative
as it takes into account effect of seasonal variation
on biomass
so environments can be compared
describe inefficient energy transfer between sun–>producer
- wrong wavelength of light
- light strikes non-photosynthetic region
- light reflected
- lost as heat
describe inefficient energy transfer producer–>primary consumer–>secondary consumer etc
- respiratory loses
- lost as heat
- not all plant/animal eatern
- some food not digested
farming practices to increase energy transfer efficiency; crops
simplifying food webs to reduce energy/biomass loss
- herbicides->killweeds/less competition/more energy to create biomass
- fungicides->reduce fungal infections/more energy to create biomass
- pesticides->reduce loss of biomass from crops
fertilisers
farming practices to increase energy transfer efficiency ; livestock
reduce respiratory losses within human food chain
-restrict movement
-keep warm
slaughter animal while young- most of energy used for growth
selective breeding to produce breeds with higher growth rates
antibiotics - prevent loss of energy due to pathogens
role of saprobionts in recycling chemical elements
- feed on dead plants/animals + their waste products + break down organic molecules
- secrete enzymes for extracellular digestion
role of mycorrhizae in recycling chemical elements
- symbiotic relationship between fungi + roots of plants = mycorrhizae
- fungi act as extension of plant =hyphae=increase sf area = ^ rate of absorption of water/nutrients
- mutualistic relationship- plants produces fungi with carbohydrates
state the stages of the nitrogen cycle
ammonificiation
nitrification
nitrogen fixation
denitrification
what happens in ammonification
- nitrogen containing compounds from dead organism/waste broken down
- converted to ammonia ->ammonium ions in soil
- by saprobionts
what happens in nitrification
ammonium ions–>nitrites–>nitrates
two stage oxidation reaction
by nitrifying bacteria ( need o2)`
nitrates absorbed via active transport
why do farmers aerate their soil
increase o2->more nitrifying bacteria, less denitrifying–>maximise nitrogen availability
