Energy Transfer and Nutrient Cycle Flashcards
(35 cards)
1
Q
Define biomass
A
Chemical energy stored in plants
2
Q
Define dry mass and outline how you measure it
A
- Mass of the organism w/ water removed
- Sample of organism is dried in oven. Sample is weighed at regular intervals. Once mass is constant, water is fully removed
- Unit: kg m-2
- Mass of C present usually takes 50% of dry mass
3
Q
Outline how you can estimate the amount of chemical energy stored in biomass
A
- Sample of dry biomass is burnt + energy released is used to heat known vol of water (calorimeter)
- Change in temp of water is used to calculate chemical energy of dry mass
4
Q
Define gross primary production (GPP)
A
Total amount of chemical energy converted from light energy by plants
5
Q
Define respiratory loss (R)
A
50% of GPP is lost to env as heat when plants respire
6
Q
Define net primary production (NPP)
A
- Energy available to plant for growth + reproduction
- Energy available to organisms at next stage of food chain
7
Q
What is it called when primary production is expressed as a rate?
A
Primary productivity
8
Q
Net primary production equation
A
NPP = GPP - Respiratory loss
9
Q
What percentage of chemical energy stored in consumers’ food is not transferred to the next trophic level?
A
90% of total available energy is lost
10
Q
Give examples of how energy is lost
A
- Not all the food is eaten eg. bones
- Egested as faeces
- Respiration
- Excretion of urine
11
Q
Net production of consumer equation
A
N = I - (F+R)
- N = Net production
- I = chem energy in ingested food
- F = chem energy lost in faces + urine
- R = energy lost during respiration
12
Q
What does food chains and food webs show
A
- How energy is transferred through an ecosystem
- Food chain: simple lines, each stage = trophic level
- Food web: Lots of food chains that overlap
13
Q
Define decomposers
A
Break down dead or undigested material, allowing nutrients to be recycled
14
Q
Outline how farmers simplify food webs to reduce energy loss to non-humans
A
- Reduce pests using chemical pesticides:
- Insecticides kill insects
- Herbicides kill weeds removing direct competion
- Biological agents also reduce no. pests:
- Paracites kill insect or reduce ability to function
- Pathogenic bacteria + viruses
15
Q
Outline how farmers reduce respiratory losses w/i humanfood chain
A
- Controlling conditions so energy is used for growth + less lost in respiration:
- Movement is restricted
- Indoors + kept warm so less energy is lost by generating body heat
16
Q
Define a natural ecosystem
A
Ecosystem that hasn’t been changed by human activity
17
Q
Define saprobionts and outline what they do
A
- Feed on remains of dead plants and animals and on their waste products
- Secrete enzymes + digest food externally, then absorb nutrients they need - extracellular digestion
18
Q
Outline how fungi form symbiotic relationships (mycorrhizae) w/ roots of plants
A
- Fungi made up of long, thin strands called hypae, which connect to plant’s roots
- Hypae inc SA of plant’s root system, helping plant to absorb ions from soil, also inc uptake of water
- In turn fungi obtain organic compound from plant
19
Q
Why do plants and animals need nitrogen?
A
To make protein and nucleic acids
20
Q
What are the 4 different processes in the nitrogen cycle?
A
- Nitrogen fixation
- Ammonification
- Nitrification
- Denitrification
21
Q
Outline what happens during nitrogen fixation
A
- N gas from atm is turned into nitrogen-containing bacteria
- Carried out by bacteria (rhizobium) which turn N into ammonia, going on to form ammonium ions that can be used by plants
- Rhizobium: found inside root nodules of leguminous plants
- Form mutualistic releationship w/ plants: provide plants w/ N compounds + plants provide carbs
22
Q
Outline what happens during ammonification
A
- N compounds from dead organism are turned into ammonia by saprobionts, forming ammonium ions
- Animal waste (faeces + urine) also contains N compounds + so go through the same process
23
Q
Outline what happens during nitrification
A
- Ammonium ions in soil change into nitrogen compounds that can be used by plants
- Nitrifying bacteria change ammonium ions into nitrites
- Other nitrifying bacteria change nitrites to nitrates
24
Q
Outline what happens during denitrification
A
- Nitrates in soil are converted into N gas by denitrifying bacteria - use nitrates for respiration
- Happens under anaerobic respiration eg. waterlogged soil
25
Why do plants and animals need phosphorus?
To make **phospholipids**, **DNA** and **ATP**
26
Outline the phosphorus cycle
* **Phosphate ion**s in **rocks** are **released** in soil by **weathering**
* Ions **taken in** by **plants** through **roots**. **Mycorrhizae inc rate** ions can be **assimilated** (absorbed + used to make complex ions)
* Ions **transferred** through **food chain**
* **Lost** from animals in **waste**
* When **plants + animals die**, **saprobionts break down organic compound**, releasing ions into soil for assimilation by plants. Also release in **urine** + **faeces**
* **Weathering** of rocks release ions in **seas**, **lakes** + **rivers** - taken in by **aquatic producers** (algae) + passed to **birds**
* **Waste** product of **sea bird** (**guano**) contains **high proportion** of **ions** + **return** to **soil** - **natural fertilisers**
27
Describe how mineral ions are lost from the env
* **Crops** **take in minerals** to make **new tissue**, when **harvested** they're **removed** from field - **decomposers** **unable** to **return minerals** to soil
* **Animals** that **eat** the **grass** and **take in** the **nutrients** are **removed** from land - unable to **replace** **nutrients** through **remains** or **waste**
28
Why are fertilisers added to soils?
**Replace lost nutrients**, **more energy** from ecosystem used for growth, **inc efficiency** of energy transfer
29
What are artificial fertilisers?
* **Inorganic**
* Contain **pure chemicals** as powders/pellets
30
What are natural fertilisers?
* **Organic matter**
* **Manure**, **composted veg**, **crop residue** + **sewage sludge**
31
Describe the process of leaching when using fertilisers
* When **water soluble compounds** in soil are **washed away** into **ponds/rivers**
* Can lead to **eutrophication**
* More likely to occur if fertiliser applied **before heavy rainfall**
* **Inorganic** fertilisers: **relatively soluble**, **excess** minerals **not used** up immediately **more likely** to leach
* **Organic** fertilisers: organic molecules **need** to be **decomposed** before being absorbed so more **controlled** + **less leaching**
* **Phosphate less soluble** than nitrates so **less leaching**
32
Nitrate from fertiliser applied to crops may enter ponds and lakes. Explain how nitrate may cause the death of fish in fresh water (5)
* **Stimulate rapid growth** of **algae**
* **Block light reaching plants** below
* Plants die bc **unable** to **phototsynthesise**
* **Saprobionts** feed on dead plant matter, **inc no. bacteria reduce O2 conc** in water by carrying out **aerobic respiration**
* Fish die bc **not enough oxygen** to **respire**
33
Upwelling often results in high primary productivity in coastal waters.
Explain why some of the most productive fishing areas are found in coastal waters (2)
* **Nutrients used** by **algae/plants** for **growth**
* **More food** = **fish produce more**
34
Describe the role of microorganisms in producing nitrates from the remains of dead organisms (3)
* **Saprobionts** break down **remains** into **ammonia**
* **Ammonia/ammonium ions** into **nitrite** then into **nitrate**
* By **nitrifying bacteria**
35
Denitrification requires anaerobic conditions. Ploughing aerates the soil. Explain how ploughing would affect the fertility of the soil (2)
* **Fertility inc** bc **more nitrates** are **formed**
* **Less/no denitrification**
