1.4 (C, D) Ecological energetics & Nutrient recycling

How do food chains work?

All energy from sunlight

Transferred to chemical energy by photosynthesising organisms

Energy passes as chemical energy in food between other organisms

What is the role of producers (herbivores)?

Make complex organic molecules using simple inorganic molecules

What are photo & chemoauotrophs?

Photoautotrophs- Most are green plants using light energy to photosynthesise

Chemoautotrophs- Eg- nitrifying bacteria. Use chemical energy from inorganic substances

What are heterotrophs?

Obtain energy by feeding on other organisms

What is the role of consumers? (Carnivores)

Primary- Consumers (herbivores) feed on producers

Secondary- Consumers (carnivores) feed on primary consumers

Tertiary- Consumers feed on secondary consumers

Quaternary- Consumers feed on tertiary consumers

What is the role of detritivores?

Involved with decay & decomposition

Eat:

• Dead plants

• Dead animals

• Animal waste

eg: earthworms and woodlice

What is the role of decomposers?

Complete the breakdown of dead plants, animals & animal waste

Lysotrophic nutrition: secrete enzymes on the dead material, enzymes hydrolyse the large molecules into small molecules & then they absorb the small molecules

eg: bacteria & fungi

Recall the trophic levels

insert diagram from pg 1 of booklet

What is Net Primary Production?

The rate at which plants accumulate the products of photosynthesis, as new plant biomass

What is Gross Primary Production?

The rate at which plants convert sunlight energy into chemical energy in organic molecules during the process of photosynthesis

How to calculate NPP

insert formula from og 3

What are pyramids of numbers?

Shows the number of each organism showing the order of the food chain

Length of bar proportional to numbers present

What are the drawbacks of pyramids of numbers?

• Organism size not considered- pyramids can be strangely shaped

• Difficult to accurately represent numbers to scale

Define biomass

The total mass of plants & animals present of a particular trophic level in a habitat

What are pyramids of biomass?

Organisms dried out & dry mass is used. Because of this, a small sample is used

Overcomes problem of trying to compare numbers when the organisms are of very different sizes

What are drawbacks to pyramids of biomass?

• Almost impossible to measure biomass of all individuals on a tropic level

• Sample taken- not representative

• Time of sample may affect biomass

What are pyramids of energy?

Compares the mount of energy stored at each trophic level in a habitat over a given period of time

Always pyramid shaped

What are the drawback of pyramids of energy?

Hard to collect necessary data because measurements need to be made over a time period

Why is not all solar radiation absorbed by the leaf?

• Waxy cuticle reflecting

• Used to evaporate water from leaf surface

• Energy lost as heat (light energy →chemical energy)

• Transmit through leaf & not strike any chloroplasts

Around 1% used in photosynthesis

Why isn’t all energy stored in plants used by primary consumers?

• Not all plant eaten (eg roots left)

• Difficult to digest (eg cellulose)

• Energy lost in excretory products

• Consumer uses energy for respiration to make ATP so also heat loss

• Some plant parts enter decomposer food chain

Only up to 10% of chemical energy in organic molecules used by primary consumers

Why are carnivores more efficient at transferring energy into new cell materials?

• Faeces contains less indigestible material

• No mutualistic organisms in digestive system (that use up energy from food)

Secondary consumers & above can be up to 20% efficient

Why is additional energy input needed to achieve higher productivity in farms?

Food- Fuel farmers carrying out physical work

Fossil fuels- Fuel machinery for crops & transport

Use of fertilisers on farms

Increases primary productivity as less nutrients in soil due to harvesting

How is efficiency of energy conversion increased in farms?

Confinement-

• less energy used for muscle contraction

• Warm conditions- less energy lost as heat

• Improves respiration:production ratio

Feed-

• High energy foods (eg siliage)

• High protein foods (eg soya meal)

• More digestible- less energy lost through indigestibility

Name the processes adding CO2 into the atmosphere

• Respiration

• Combustion

• Decomposition

Name the process removing CO2 from the atmosphere

Photosynthesis

Draw the carbon cycle

insert image from bgooklet

What is the role of decomposers?

Break down nitrogenous molecules in dead organisms & animal waste & release ammonia or ammonium into the soil/water

eg saprobiotic microorganisms

AMMONIFICAITON

What is the role of nitrifying bacteria?

Convert ammonia/ammonium ions into nitrate ions

AMMONIA → NITRITE IONS → NITRATE IONS

Ammonia is oxidised

NITRIFICATION

What is the role of nitrogen fixing bacteria?

Convert unreactive nitrogen gas into a more reactive form 9eg ammonia)

Occurs when lightning passes & through the bacteria

Some bacteria live in the soil & some species form mutualistic relationships with plants. eg legumes has this bacteria in their root nodules

What is denitrification?

Denitrifying bacteria convert nitrates into nitrogen gas.

Reduces soil fertility

Anaerobic- thrive in waterlogged soils or compacted soil.

Draw a diagram of the nitrogen cycle

insert picture