Ecosystems and global change

Primary productivity

The rate that solar energy is captured and converted into chemical bonds by photosynthesis

Photosynthesis

6CO₂+6H₂O + E(sunlight) → C₆H₁₂O₆ + 6O₂

• Organisms use this energy for

  • Cellular respiration

  • growth

  • reproduction

Energy Path story

• GPP (Energy created through photosynthesis)

• Respiration (Tree uses some energy)

• NPP (Energy left in oranges (GPP-Respiration)

• GSP (Energy turtle gets from fruit)

• Egested energy (Turtle poops peals)

• Assimilated energy (Turtle uses it to live)

• NSP (Energy left for reproduction)

Ecology Efficiency

The percentage of chemical energy transferred from on trophic level to the next

• NSP/NPP

• 5-20% average at around 10$

Terrestrial energy pyramid

• Energy becomes increasingly scares as it moves up through successive trophic levels

• The number of top carnivores provides an estimate of the health of an ecosystem

• No more than 4 or 5 trophic levels

Standing stock biomass

The total weight of living organism within a defined area

Aquatic energy pyramids

• The relative amount of energy at each trophic level is inversely related to the amount of standing stock biomass.

Phystoplankton as primary producers

• They have an extremely high reproductive rate

• so small population is ok

Bottom-Up control

When the abundance of producers determines the abundance of organisms

Top-down control

When the abundance of high level consumers determines the abundance of organism

DDT

• 1950s

• A synthetic insecticide that kills insect borne human diseases

• Damages liver, reproductive system, and causes cancer

Biological Amplification

• Fat soluble poisons accumulate in zooplankton

• When fish consume they get even more in their tissue and so on

Rachel Carson

• Silent Spring (1962)

• She exposes the dangers of biological amplification of industrial chemicals like DDT 

Global nutrient cycles

Atmospheric nitrogen is converted into fixed nitrates by lightening and nitrogen fixing bacteria.

• N₂ into NO₃^-

• Fixed nitrogen is used by plants and its also converted back into N₂ and into N₂O (a greenhouse gas)

Human impact on global nutrient cycle

modern industry and agriculture increased the rate of nitrogen fixation. 

• This has led to eutrophication and oxygen depletion 

• Increased N₂O

Eutrophication

• Too much nitrogen that leads to oxygen depletion

Carbon cycle 

1. Atmospheric CO₂ is captures by photosynthesis and tuned into glucose and bioavailable forms of carbon 

2. Plant biomass decompose or become fossil fuels

3. Respiration increases released CO₂

4. Humans have altered this cycle by burning fossil fuels and releasing too much CO₂

Climate change

• Okjokull glacier (first to fully melt)

• Increase in temperature cause by too much CO₂ methane (CH₄) and nitrous oxide in the atmosphere (N₂O)

Greenhouse Gas effect

1. Solar radiation warms earths surface and greenhouse gasses

2. The surface emits infra-red radiation (heat)

3. Water vapor increases (is a greenhouse gas)

4. Carbon dioxide, methane, and nitrous oxide act as glass and hold in that heat

Triple threat for the ocean

• The ocean absorbs 90% of the heat

• It absorbs 25% of the CO₂

• So the ocean is warmer, has less oxygen, and is more acidic