Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

Energy Transfer in Ecosystems

•

An ecosystem includes all the organisms living in a particular area and all the nonliving (abiotic) conditions
...

• Ultimate source of energy is sunlight which is converted into chemical energy by
plants
...
They trap energy in the bonds of carbohydrate
molecules
...
Primary consumers directly
eat producers
...
Tertiary consumers
(predators, scavengers or parasites) eat secondary consumer
...


Saprobionts – Decomposers that break down complex materials into simple ones
...
They break down organic
molecules into inorganic molecules and release minerals and elements in a form that
plants can absorb
...
Obtaining nutrients from dead
organic matter using extracellular digestion is known as saprobiotic nutrition
...
g
...


Herbivore – Animal that eats plants and therefore is the primary consumer
...


Ombnivore – Animals that eats both plants and animals
...


Food Chain – Describes a feeding relationship and energy transfer
...
The arrows represent the direction of energy flow
...
Usually 4-5 trophic levels as
insufficient energy is available to support large enough breeding population at trophic
levels higher than these
...

Shows how energy is transferred through an ecosystem
...
Strong interaction (heavy lines) could represent an
exclusive predator prey relationship
...




















Biomass
• Dry mass is the mass of the organism when water is removed
...

• Biomass is the total mass of living material in a specific are at a given time
...
(grams per square meter g
m ) Volume is measure in grams per cubic metre (g m )
...

(bomb Calorimetry)
• The bomb is surrounded by w water bath and the heat of combustion causes small
temperature rise in this water
...
Weigh a sample of dry material and then burn it in pure oxygen within a sealed
chamber (bomb)
2
...

• Most of the sun’s energy is not converted because:
1
...

2
...

3
...

4
...


Gross Primary Production (GPP) – chemical energy stored in plant biomass in a given
area or volume
...
E
...
kJ ha year
(kilojoules per hectare per year)
...


Net Primary Production (NPP) – chemical energy store in plant biomass after
respiratory losses to the environment have been taken into account
...

• Usually less than 10% of NPP in plants can be used by primary consumers for
growth
...

• Low percentage due to:
1
...

2
...

3
...
g
...
Energy losses occur as heat from respiration and lost to the environment
...
Get rid of food chains that don’t involve humans, energy losses will be reduced and
the NPP of the crop will increase – get rid of pests using pesticides
...
Herbicides kill weeds which removes direct
competition with the crop for energy from the Sun
...

2
...
Parasites live in or lay their
eggs on a pest insect, they either kill the insect or reduce its ability to function
...
g
...
Pathogenic bacteria and viruses kill pests
...
g
...

3
...
Combined
effect of using both can reduce pest numbers even more so NPP is increased even
more
...
Movement is restricted so less energy is used in muscle contraction
...
Environment kept warm in order to reduce heat loss from the body
...
Controlled feeding so the animals receive the optimum amount and type of food for
maximum growth with no wastage
...
Exclusion of predators so no loss of organisms in the food web
...

• More food can be produced in a shorter space of time often at a lower cost
...











Nutrient Cycles
• The nutrient is taken up by producers as simple inorganic molecules and
incorporates the nutrient into complex organic molecules
...

• When producers and consumers die their complex molecules are broken down by
saprobiotic microorganisms making sure the nutrients are released for reuse
...

• The fungi are made up of long, thin strands called hyphae which connect to the
plants roots
...
g
...
Also increases uptake of water
by the plant enabling the plant to better resit drought
...
g
...














The Nitrogen Cycle
• 78% of the atmosphere is nitrogen but few organisms can require nitrogen gas
directly
...

• Other ways in which nitrogen gets into an ecosystem are by lightning (fixes
atmospheric nitrogen) or artificial fertilisers which are produced from atmospheric
nitrogen on an industrial scale in the Haber Process
...

• Nitrogen compounds form dead organisms and animal waste (urine – from the
breakdown of excess amino acids and faeces – from proteins, nucleic acids and
vitamins) are turned into ammonia by saprobionts which goes on the form
ammonium ions in the soil
...



Nitrification
• Ammonium ions in the soil are changed into nitrogen compounds that can be used
by plants (nitrates)
• Oxidation reactions so releases energy and carried out by free living soil
microorganisms
...

• Nitrifying bacteria (Nitrobacter) change nitrates into nitrites
...


Nitrogen Fixation
• Where nitrogen gas in the atmosphere is turned into nitrogen containing
compounds
...
Nitrogen rich compounds are released from
them when they decay
...
g
...
They obtain carbohydrates from
the plant and the plant acquires amino acids from the bacteria
...
Fewer aerobic nitrifying and nitrogen fixing bacteria are found
...


























































The Phosphorus Cycle
• Phosphorus is used by plants and animals to make biological molecules e
...

phospholipids, DNA and ATP
...

1
...
The ions
are absorbed by the plants through the roots
...
Phosphate ions are transferred through the food chain as animals eat the plants and
are in turn eaten by other animals
...
Phosphate ions are lost from animals in waste products during excretion
...
Once dead saprobionts break down the organic compounds (decomposition)
releasing phosphate ions into the soil for assimilation by plants
...

5
...
g
...

6
...

































Need for Fertilisers
• Crops take in minerals from the soil as they grow and use them to build their own
tissues
...

• Phosphates and nitrates are lost when animals or animal products are removed
from the land
...

When they are moved for slaughter the nutrients aren’t replaced through their
remains or waste products
...

• Using fertilisers changes the balance of nutrients in the soil – too much of a
particular nutrient can cause crops and other plants to die
...
g
...


Artificial (inorganic) Fertilisers – contain pure chemicals e
...
ammonium nitrate as
powders or pellets
...
Always contain nitrogen, phosphorus and potassium
...

• Nitrogen is essential component of amino acids, ATP, and nucleotides in DNA
...
This increases the rate of photosynthesis and improves crop
productivity
...
These out compete other species which die as a result
...
g
...


Leaching
• Can be when more fertiliser is applied than the plants need or are able to use at a
particular time it leads to fertilisers leaching into waterways
...

• More likely to occur if the fertiliser is applied just before heavy rainfall
...

• In natural fertilisers the nitrogen and phosphorus are still contained in organic
molecules that need to be decomposed by microorganisms before they can be
absorbed by plants
...


•

Leaching of phosphates is less likely than leaching of nitrates as phosphates are less
soluble in water than nitrates
...
Leaching
can cause eutrophication
...

• Natural process that occurs mostly in freshwater lakes and lower reaches od rivers
...
In most leaks and rivers nitrate ion concentration is naturally low so it is the limiting
factor
...
As nitrate ion concentration increases as a result of leaching it is no longer the
limiting factor for the growth of plants and algal growth (algal bloom)
3
...

4
...

5
...

6
...

7
...

8
...
these organisms die due
to oxygen starvation
...
Without aerobic organisms there is less competition for the anaerobic organisms
whose population now rise
...
The anaerobic organisms further decompose dead material releasing more nitrates
and some toxic wastes such as hydrogen sulphide which makes the water putrid

---