Section 2: Terrestrial Ecology
ECOSYSTEMS:
4 Intermingling Regions: Atmosphere, Hydrosphere, Lithosphere and Biosphere
Biotic is all the living organisms (biosphere)
Abiotic is everything else including soil, water, rocks, air, etc. (atmosphere, lithosphere, hydrosphere)
Trophic Levels:
Autotrophs - use sunlight to make sugar
1. Producers → the photosynthetic organisms that bring energy into the food chain via the sun
Heterotrophs - have to find food
2. Primary consumer → Organisms that eat producers; herbivores (grazers such as cows, insects, etc)
3. Secondaryconsumer → organisms that eat primary consumers; carnivores
4. Tertiary consumer --> organisms that eat carnivores (mosquitos, fish, etc)
Ten Percent Rule:
10% of the usable energy is transferred to the next trophic level. Reason: 90% of the usable energy is lost as heat during the organisms lifetime
(2nd law of Thermodynamics), not all biomass is digested & absorbed, predators expend energy to catch prey.
Relationships of Organisms in Ecosystems
Species Richness: # of different species in a given area (high species richness is in Costa Rica, low in the Arctic)
Species evenness: how close in numbers each species is in a given area (high species richness would be lots of individuals from lots of different species, low would be a lot of two species but only a few from other species)
Mutualism: symbiotic relationship where both organisms benefit.
Commensalism: symbiotic relationship where one organism benefits & the other is unaffected.
Parasitism: relationship in which one organism (the parasite) obtains nutrients at the expense of the host.
Keystone Species: species whose role in an ecosystem is more important than others.
Indicator Species: species that serve as early warnings that an ecosystem is being damaged.
Remediation is treating hazardous material to reduce or eliminate harm to human or environmental health.
Restoration/Reclamation is returning a disturbed site to a more-or-less natural condition.
Mitigation is when you lessen the negative impact of something you have to do. Like digging for oil using methods that disturb the land the least.
Krill is a keystone species. Look at all the animals that eat it!!
Insect lives in fishes mouth. Bad for fish, good for insect parasite until fish dies
Mutualism, good for moth and good for plant
Predator and Prey:
* Eating is just a transfer of energy.
Cycles
Nitrogen Cycle: Nitrogen is almost 80% of the air. It is turned into usable nitrogen by nitrogen-fixing bacteria in the soil. It goes into plants and animals and is returned as waste or when they decompose, turning into ammonia (ammonification) and then into nitrate ions (nitrification).
Human Alteration of Cycle:
1. Humans adding Nitrogen to crops as fertilizers. These runoff into the hydrosphere and cause Eutrophication of water bodies
2. Burning fossil fuels releases N into the atmosphere causing acid rain
* Nitrogen Fixation: because atmospheric N cannot be used directly by plants, it must first be converted into ammonia by bacteria.
* Ammonification: decomposers covert organic waste into ammonia.
* Nitrification: ammonia is converted to nitrate ions (NO3-).
* Assimilation: inorganic N is converted into organic molecules such as DNA, amino acids & proteins in an organism.
* Denitrification: bacteria convert ammonia back into N2 (gas).
Carbon Cycle: This balance is being altered by human release of fossil fuel burning
Human Alteration of Carbon Cycle:
1. Deforestation reduces the amount of CO2 that can be taken out of the atmosphere
2. Burning fossil fuels puts CO2 into the atmosphere
Sulfur Cycle: S is a micronutrient needed for some proteins; usually found in rocks
Human alteration:
1.Sulfur released into atmosphere as S02 which turns to H2SO4 through coal burning causing acid rain
Phosphorus cycle: very slow cycle
phosphorus does not exist as a gas; released by weathering of phosphate rocks, it is a major limiting factor for plant growth.
Human alteration:
1. Humans mine Phosphorus (mining has its own problems)
2. Adding fertilizers rich in Phosphorus runs off and causes Eutrophication