ESS Topic 2 Case Studies

Biotic Examples

Biotic Examples

- Predation - Fox & Rabbit
- Mutualism - Coral, between animals & algae
- Herbivory - Rabbit & lettuce
- Parasitism - ticks & dogs
- Disease - evergreen robber frog & amphibian disease
- Competition - pigeons & crows

Amazon Rainforest Ecosystem

- The largest biodiversity on Earth
- World's biggest rainforest
- 16,000 tree species and 390 billion individual trees
- 2.5 million species of insects

Carbon Cycle

Transfer processes in carbon cycle:
• herbivores feeding on producers
• carnivores feeding on herbivores
• decomposers feeding on dead organic matter
• CO2 from atmosphere dissolves in rainwater & oceans.
Transformation processes in carbon cycle:
• photosynthesis transforms CO2 + H2O => glucose using sunlight energy trapped by chlorophyll
• respiration transforms glucose => CO2 + H2O+ energy
• combustion transforms biomass => CO2 + H2O
• biomineralization transforms CO2 => calcium carbonate in shellfish & coral
• fossil fuels made from sedimentation of organic matter, incomplete decay & pressure

Nitrogen Cycle

Transfer processes in nitrogen cycle:
• herbivores feeding on producers
• carnivores feeding on herbivores
• decomposers feeding on dead organic matter
• plants absorbing nitrates through their roots

Transformation processes in nitrogen cycle involve four different types of bacteria:
• nitrogen-fixing bacteria transform N gas in the atmosphere into ammonium ions
• nitrogen-fixing bacteria include bacteria that live in the soil and other bacteria that live in plant root nodules
• nitrifying bacteria transform ammonium ions into nitrite & then nitrate
• denitrifying bacteria transform nitrates into N
• decomposers break down organic N into ammonia (deamination)
• producers convert inorganic materials into organic matter
• producers use N from nitrates to make amino acids then protein
• decomposers convert organic storage into inorganic matter
• decomposers transform protein and amino acids into ammonium ions

Impacts of human activities on carbon and nitrogen cycle

- In both, combustion of forest and fossil fuels increases conc of oxides in atmosphere
- In both, deforestation & agriculture leads to decomposition, also releasing oxides
- In carbon, CO2 is released by respiration, NOs are released into soil water by nitrification
- CO2 impacts global warming at a bigger degree than NO
- Both oxides acidify water, NO may cause acidify soil & acid deposition
- Deforestation removes organic storages of both, reduces C absorption from atmosphere & inorganic N storages in soil
- Use of inorganic fertilisers increase N in soil, run off cause N in aquatic systems
- Herbicide might kill organisms, reducing both organic storages
- Extraction of fossil fuels transfers C storages to Earth's surface

Succession - Sand Dunes

- Migration - sand grains move inland until they meet an obstruction, small infant dune is formed.
- Colonisation - plant seeds and spores carried by the wind land on embryo dune, harsh conditions and bare ground, highly tolerant plants, sand continues to accumulate.
- Establishment - vegetation cover becomes more continuous with only a few small patches of bare sand, marram grass develops
- Competition - number of new species slows down, few signs of bare sand, soil has become deeper
- Stabilisation - woody plants, some vegetation, birch trees
- Climax - shading by taller vegetation, lower species diversities, no new species added to the community, vegetation in equilibrium with environment

Zonation - Mountain Environment

- Bottom - lots of vegetation, low altitude, fertile soil, high biodiversity
- Middle - less vegetation, higher altitude, less fertile soil, some biodiversity
- Top - no vegetation, high altitude, infertile soil, minimal biodiversity