U2 ECOLOGY

What is the first law of thermodynamics

Law of conservation of energy

• Energy can be transformed but not created or destroyed

What is the second law of thermodynamics

• Energy transformations in ecosystems are inherently inefficient

• When energy is transformed it must be degraded into a less useful form such as heat

Examples:

• Only 10% of energy is transferred to the next trophic level

  • 90% is lost as heat during metabolic process

• Organisms break down glucose to release energy but not all is converted into usable energy for cellular activities

  • Some are lost as heat

Describe photosynthesis and cellular respiration flow diagram

Answer these about photosynthesis and cellular respiration

• Where does it occur

• Primary energy source

• Reactants

• Products

Photosynthesis

• Occurs in chloroplast

• Primary energy is sun

• Reactants are CO2 and H20

• Products are glucose and oxygen

Cellular respiration

• Occurs in cytoplasm and mitochondrion

• Primary energy is glucose

• Reactants are glucose and oxygen

• Products are CO2 and H20

What are the similarities between photosynthesis and aerobic cellular respiration

• Involves the electron transport chain

• Need for organism’s survival

• Involves gas exchange

What is cellular respiration

• Organisms break down glucose to release stored chemical energy for cellular activities

• Provides energy for growth, repair and maintenance

• Essential to sustain life process

What are autotrophs

• First tropic level

• Primary source of energy and organic matter

  • Releases oxygen and absorb CO2

• Absorbs water and releases into the atmosphere through transportation

• Habitat for animals

• I.e. Trees, seaweed, purple bacteria

Name all trophic levels

What are included into decomposers

• Saprotrophs

  • Secret enzymes onto dead materials

  • Break it down then absorb dissolved nutrients

  • Fungi on a log/Bacteria in soil

• Detritivores

  • They ingest chunks of dead material and digest inside their gut

  • Earthworms, milipedes

Formula to calculate energy efficiency

What is Net productivity

• Amount of biomass remaining after losses from cellular respiration

• For producers (plants)

  • Energy left over after the plant used some of captured energy for its own respiration

• For consumers (animals)

  • Energy left over after animal used to eat and respirate

What is the gross productivity

• Total gain in biomass over a specific period

• For producers (plants)

  • Amount of energy captured from sunlight and converted into chemical energy through photosynthesis

• In consumers

  • Total amount of energy obtained from ingestion of food

Net productivity formula

NP = GP-RESPIRATION LOSS

What is bioaccumulation

• Build up of non biodegradable pollutants in an organism or trophic level over time

• Pollutants absorbed faster than they are metabolised / excreted

• E.g. Fish in contaminated waters accumulate mercury in their tissues

What is biomagnification

• Non-biodegradable pollutants accumulating

  • Higher concentrations in predator’s body

• Pollutants accumulate in organisms across trophic levels due to inefficient metabolism and excretion

• Example:

  • Plankton absorb pollutants from water → accumulate in their tissue and fish eat plankton → larger predator

HL What are the types of autotrophs

Autotrophs can synthesize their own carbon compounds

• Photoautotrophs

  • Use light energy to drive process of photosynthesis

  • Plants, algae

• Chemoautotrophs

  • Energy from oxidation of inorganic molecules

  • Sulfur bacteria in deep sea hydrothermal vents

HL What are the heterotrophs

Cannot synthesize their own carbon compounds from inorganic sources

• Herbivores

  • Deer, rabits - grass

• Carnivores

  • Lions, sharks -eats others

• Omnivores

  • Plants and animals

• Detritivores

  • Dead organic matter

• Saprotrophs

  • Decompose matter by secreting digestive enzymes and absorbing the resulting nutrients

HL Explain what chemoautotrophs are

• Use inorganic chemical reactions as an external energy source

• H2S, NH3, Fe2+ to produce organic molecules

HL What is gross secondary productivity

GSP = Food eaten - poop

HL Formula for ecological efficiency (slide 128, 2.2)

Explan the variability in ecological efficiency

However it is not a constant and can significantly vary due to:

• Ecosystem types

  • Aquatic: 10%-20%

  • Terrestrial 5-10%

• Trophic levels

  • Plants → herbivores are higher than transfer between higher levels bc of metabolic processes and heat

HL What is entropy

• The measure of amount of disorder or randomness in a system

• It increases as biomass passes through ecosystems

HL Explain carbon stores in the lithosphere

• Fossil fuels

  • coal, oil and natural gas

  • Formed from remains of ancient plants

  • Stored for hundreds of miliions of years until extracted by humans

• Limestone in the form of calcium carbonate

  • Accumulation of shell,coral, fecal debris or percipitation from seawater

  • Residence time of hundreds of millions of years

HL Explain coal formation

• Partially decomposed plant matter, primarily from ancient forests and swamps

• Millions of years of plant debris in wetlands

• Burial under sediments → physical and chemical transformations →. peat

  • Increased temp and pressure = peat into brown → soft → hard coal

HL Oil and natural gas formation

• Partially decomposed algae and planktons

• Settle on ocean floor → mixed with sediments = organic rich mud

• Also buried under temp and pressure = chem change = liquid oil and gaseous hydrocarbons (natural gas)

• Migrate through rocks until trapped by impermeable rock layers = reservoir

HL Reef building coals

• Corals and shellfish create calcium carbonate skeletons → turns into limestone after long periods

• Becomes a significant carbon reservoir

HL Methane formation

• Makes up a small part of atmospheric gases but traps heat 28x better than co2

• Remains in atmosphere for 10 years until oxidised to co2 and h2o

HL Methanogensis + impacts of methane

• Methane (CH4) from organic matter by methanogenic bacteria

• Occurs in anaerobic (oxygen free) environments like swamps, rice paddies

• Converts dead organic matter into methane gas

Impacts

• Produced in cows and sheep’s stomach during digestion

  • Increased demand of food = more methane

  • Rice in water flooded fields = more methanogen populations = more production

HL Nitrogen cycle + flow diagram

• Atmosphere 78% nitrogen gas → not directly usable by most organisms

• Major component of amino acids and backbone of proteins and DNA

HL Name inorganic and organic nitrogen stores 2 each

Inorganic

• Atmosphere as N2 gas

• Soil holds it in gas form

  • Can’t be directly used by plants or animals

• Ocean: Decomposing matter → ammonia → NO3 → NO2

Organic

• Plants and animals

• Stored in proteins

• Transferred from producers to consumers through food chain

  • used to create new tissues and cells

HL Name nitrogen transfers and transformations 2 each

Transfers

• Moves through atmosphere, soil, living organisms

• Uptake of nitrogen compounds by plant roots

Transformations

• Conversion of N2 to NH3

• Ammonia + water = NH4+ taken up by plants

HL What are nitrogen fixing bacteria + mutualistic relationship with legume roots

• Free living but some forms mutualistic relationship with legume roots

• Benefits

  • Bacteria fix nitrogen → converts nitrogen in a way where the plant can absorb = advantage in nitrogen limited environments

  • Plant provides glucose + safe home in nodules

HL What is dentrification ( a part of the nitrogen cycle)

• Does the opposite

  • Bacteria in low oxygen conditions convert N2 or water into nitrogen fas → return to atmosphere as part of nitrogen cycle

• Bacteria cant use CO2 for respiration so use N2 as alternative

• Stealing their nitrogen supply = lose a key nutrient needed for growth = can suffocate roots = can kill plants

HL What are insectivorous plants

• In waterlogged , anaerobic soils some plants adapt by capturing insects

• E.g. Sundews

• Digests insects and use them as nitrogen source

HL Name two human impacts on nitrogen cycle

• Aquaculture

  • Fish farms use fertilizers and antibiotics

  • Pollutes surrounding water bodies → affects nitrogen cycle

• Livestock ranching

  • Livestock waste releases large amount of ammonia (indirectly causes dentrification

    • Enters soil and water systems through leaching, groundwater flow and runoff

    • Extra nitrogen being dumped into the cycle in the wrong place and amount

HL What is the haber process

• Increased food production by creating ammonia rich fertilizers

• Using nitrogen from atmosphere and hydrogen from methane (natural gas) → reacting it at high temp to create ammonia

  

HL Haber process pros and cons 2 each

Pros

• Increase crop yields

  • Consistency

• Econ growth

  • More jobs in the fertiliser industry

Cons

• Increase crop yields

  • Over reliance = soil nutrient imbalance

• Econ growth

  • Econ benefits not evenly distributed

HL 3 ways to mitigate impacts on nitrogen cycle

• Efficient use

  • Application techniques to minimise runoff to reduce pollution

• Prevent nitrogen depletion

  • Mixed cropping, crop rotation

• Reduce nitrogen emissions from industrial emissions

True or false: CO2 is converted into organic compounds like glucose which are used to build plant tissues

True

What is carbon sequestration

• The process where carbon accumulates over time through carbon sequestration

• Capturing gaseous and atmospheric co2 → storing in solid / liquid form

• Healthy carbon sequestering ecosystems support diverse plant and animal species

Carbon sinks vs stores

• Stores

  • Ocean, soil, atmosphere, living organisms

  • Anything that holds carbon

• Sinks

  • Actively absorbing more carbon than it releases

  • Trees → absorb more than they respirate

All sinks are stores but other way round doesnt work

Flow diagram of global carbon cycle

Name 2 organic carbon stores + briefly on how it works

• Crude oil and natural gas (fossil fuels)

  • Formed from remains of plants millions of years ago

  • Carbon in the form of hydrocarbons → release co2 when burned

• Plants

  • Photosynthesis

Name 2 inorganic carbon stores + briefly on how it works

• Atmosphere

  • CO2

  • Traps heat cuz its a greenhouse gas

• Soil

  • In form of carbonates

    • Calcium carbonate

Describe the formation of fossil fuels

• Dead plants and microorganisms accumulate in sediment layers

• Buried under high temp and pressure

• Undergoes chem and physical transformation = transforms into fossil fuels (coal, oil, natural gas)

Describe 2 carbon flows

• Photosynthesis

  • Absorb co2 → convert into organic compounds using energy from sunlight → stores carbon in plant biomass

• Defecation

  • Some carbon is excreted as waste

  • Process returns carbon to soil → used by decomposers or soil

SLIDE 2.3.8