Ecosystems / Organisms

Symbiosis

Symbiosis

close, long-term interactions between individuals of two different species.

• mutualism

• commensalism

• parasitism.

Mutualism

two organisms of different species provide each other with resources or services, and both organisms benefit.

• + / +

Commensalism

one organism benefits, and the other organism is not significantly affected

• + / ?

Parasitism

one organism—the parasite—benefits by living and feeding on another organism—the host—who is harmed but not immediately killed

• + / -

Population

group of organisms of one species that interbreed and live in the same place at the same time

Community

interacting group of various species in a common location

Ecosystem

a particular location on Earth with interacting biotic (living) and abiotic (nonliving) components

Biome

geographic region that is characterized by a certain climate and diverse presence of plants and animals

Littoral Zone (lake)

Top, near-shore layer of a lake

• Shallow

• Plentiful sunlight and nutrient inputs from the surrounding land

• Supports a wide variety of plants and animals.

Limnetic / Open-Water Zone (lake)

Sunlit surface layer

• Where most photosynthesis takes place

• Starts away from shore, just past the littoral zone, extends to the depth penetrated by sunlight

• Supports phytoplankton and zooplankton, along with freshwater fish

Profundal / Deep-Water Zone (lake)

Deep, open-water layer

• Too dark for photosynthesis

• Cooler water, less dissolved oxygen than the shallower zones

• Supports fish adapted to these cooler waters

Benthic Zone (lake)

Soil, soil organisms at the bottom of the lake

• Decomposers

• Low oxygen

Three Zones of Rivers

• Source

  • water at high elevations collects from precipitation and snowmelt

  • cold, fast moving

  • high DO content, low nutrient content

• Transition

  • wider + slower moving

  • less DO, more sediment

  • warmer, more nutrient rich (supports wide variety of organisms)

• Floodplain

  • More sediment, even less DO

  • Supports greatest variety of organisms

Generalist vs Specialist

Generalist:

• species with a broad niche that is easily adaptable to many environmental conditions

Specialist:

• narrow niche with incredibly specific needs in order to survive

Carbon vs Carbon Dioxide

Carbon

• An essential element that forms the base of all organic matter, including the bodies of living organisms, and is a key component of fossil fuels.

Carbon Dioxide

• A compound in the atmosphere that is taken in by photosynthetic organisms to make organic molecules and is later released back into the atmosphere through processes such as respiration and decomposition

Photosynthesis

The process by which energy from sunlight is used to transform carbon dioxide from the atmosphere into the organic matter that fuels food webs

Cellular Respiration

The process by which living organisms break down organic compounds to produce usable energy, releasing carbon dioxide into the atmosphere as a by-product

Biogeochemical Cycles

Earth is a closed system: matter cannot be created or destroyed (law of conservation of mass). Instead, matter moves through the earth in biogeochemical cycles.

Carbon Cycle

Carbon Sinks

Natural or artificial reservoirs that absorb and store carbon dioxide from the atmosphere, helping to mitigate climate change

Largest Reservoir of Nitrogen on Earth?

Atmosphere - nitrogen gas makes up 78%

• However, plants and animals cannot directly use this nitrogen gas. To get the forms of nitrogen they need, these organisms rely on the nitrogen cycle

Steps of the Nitrogen Cycle

Nitrogen fixation: During this step, atmospheric nitrogen gas is fixed, or converted into a form that can be used by plants and animals:

• Lightning! Forms nitrate, falls to surface as precipitation

• In soil: nitrogen-fixing bacteria

Ammonification:

• As dead organisms and waste decompose, ammonia and ammonium ions are returned to the environment through ammonification.

• This process is carried out by certain bacteria and fungi.

Nitrification:

• groups of nitrifying bacteria convert the products of ammonification into nitrites and then nitrates.

Denitrification:

• Denitrifying bacteria convert nitrites and nitrates back into nitrogen gas, returning nitrogen to the atmosphere

Phosphorus

Essential nutrient for living organisms

• Often the limiting nutrient in ecosystems. This means that phosphorus is the nutrient in shortest supply, so it puts a limit on plant growth.

  • Plants use it quickly, natural phosphorus replenishes slowly

Steps of the Phosphorus Cycle

• Largest reservoirs are buried in rock and deep ocean sediments. Weathering of these sediments releases phosphate ions.

• Ions leach into surface water and soils

  • In soil, taken up by plants and can then move up the food chain.

• May stay inside organisms or released as waste.

• As bodies and waste break down, phosphorus returns to the environment compacted into layers of soil and rock.

How do humans affect the phosphorus cycle?

By using animal waste and phosphate sediments to make fertilizer, detergent, and other products.

• When these products are released into the environment they can enter aquatic ecosystems as runoff. This can accelerate plant growth in these ecosystems, leading to harmful algal blooms.

Water on Earth

Of the water on Earth, 97.5% is salt water. Of the remaining water, over 99% is in the form of underground water or ice. Less than 1% of fresh water is found in lakes, rivers, and other available surface forms.

• Most water on Earth does not cycle rapidly.

Steps of the Hydrologic Cycle

• Driving force: the sun’s energy

  • The sun warms the ocean surface, other surface water

  • Liquid water evaporates, ice sublimes—turn directly from a solid to a gas.

  • Water moves into the atmosphere in the form of water vapor.

• Precipitation

  • Water vapor in the atmosphere condenses into clouds and eventually falls as precipitation, rain or snow

• Upon reaching the surface, it may evaporate again, flow over the surface, infiltrate into the soil, or percolate into the ground (forming groundwater)

  • Water in upper levels of soil may be taken up by plants through the roots

  • Most water that enters a plant's body will be lost back to the atmosphere in a process called transpiration.

    • Water enters through the roots, travels upwards through vascular tubes made out of dead cells, and evaporates through pores called stomata found in the leaves.