Ecosystems and Biomes

• Ecology pertains to relationships between biotic and abiotic aspects of an environment.
• Ecosystem ecology studies how larger-scale organisms interact within their setting to cycle energy and matter.
• Ecosystems and communities have dynamic equilibrium, where fluctuations are normal, but factors generally stay within a range that supports the survival and success of living organisms.
• Ecologists study various scales of the environment.
• The biosphere refers to the living part of Earth as a whole, including the hydrosphere, lithosphere, and atmosphere.
• Biomes are regions of Earth with characteristic temperatures, precipitation levels, and biotic communities, either aquatic or terrestrial.
• An ecosystem is a smaller region containing a somewhat defined group of biotic and abiotic factors.
• A community refers to a group of interacting populations of organisms.
• Population is a group of organisms of the same species found in the same place at the same time.
• An organism is an individual member of a species.

Ecosystem Terminology

• Organisms possess different roles in their communities and ecosystems.
• Roles are generally defined by diet.
• A niche is an organism's role and habitat.

Diet Types

• Autotrophs make their own nutrients, supporting all other organisms in the community.
• Photoautotrophs produce food through photosynthesis.
• Chemoautotrophs use heat and inorganic molecules to make food through chemosynthesis.
• Heterotrophs must consume other organisms to meet their needs.

Trophic Levels

• Troph refers to 'feeder'.
• The trophic level is an organism's position in its food chain/web, based on what it eats or what eats it.
• Producers are autotrophs, forming the base of the food chain/web.
• Consumers are heterotrophs.
• Primary consumers, also known as herbivores, eat autotrophs.
• Secondary consumers, also known as carnivores, eat primary consumers.
• Tertiary consumers eat secondary consumers and may be apex predators.
• Quaternary consumers may exist but only in ecosystems with lots of energy, that is, apex predators.
• Detritivores eat dead or decaying material and help to recycle waste in ecosystems, such as cockroaches and millipedes.
• Decomposers are like detritivores but break down material outside their bodies; for example, fungi secrete enzymes onto material and then absorb small molecules.
• Omnivores feed on two or more trophic levels and can eat both animals and plants.

Ecological Models

• Models are demonstrations of how the systems work.
• Ecologists use models to track the flow of matter and energy from the abiotic environment through organisms in a system.
• Models act as simplified versions of the natural world.

Food Chains

• Food chains are the simplest ecological model.
• They illustrate one organism at each trophic level, starting with producers.
• Arrows in food chains indicate the flow of matter and energy.
• Removing an organism in a food chain would have an affect on the others.
• Food chain length is limited due to the second law of thermodynamics.
• Some energy is wasted at every transfer from one trophic level to the next.
• This energy is 'lost' through chemical bonds in waste products and used by the organism for survival activities like finding resources or escaping predators.
• Food chains are helpful and need to be interpreted, but they are missing some ecosystem elements.

Food Webs

• Include a larger number of organisms.
• They are also more accurate because they illustrate more relationships but can be harder to interpret and work with.
• Tracking energy and matter transferred in an ecosystem allows identification of change consequences made to the environment.
• Biomagnification occurs when environmental toxins become concentrated higher up in a food chain.
• Biomagnification is not to be confused with bioaccumulation, which refers to the buildup of a contaminant in one individual over time.

Feeding the Planet

• Feeding the world poses challenges as global populations continue to rise.
• As countries become more industrialized, the trend is toward including more meat in diets.
• In terms of energy efficiency, more people could be fed on a plant-based diet or by eating insects.

Ecological Pyramids

• Are used to show the relative amounts of material/energy at each trophic level.
• The dimensions of each part of the pyramid are proportional to the amount of material/energy at that level.
• The 3 pyramid types measure numbers, biomass, and energy.

Pyramid of Numbers

• Represent the number of all organisms at each trophic level (may include multiple species).
• A pyramid of numbers may also be inverted or spindle-shaped due to how the food chain is built and the size of the base organism.
• One single large producer can support an entire food chain.
• Numerous parasites can also live on a single host, in some instances.

Pyramid of Biomass

• Shows the dry mass of materials present in each trophic level.
• May be inverted, and is common in aquatic environments where producers and primary consumers are small.
• Algae and zooplankton biomass distribution represent an inverted aquatic ecosystem.

Pyramid of Energy

• Pyramid of energy demonstrates amount of chemical energy present at each trophic level, typically in kJ or kcal.
• It always acts as an upright pyramid because illustrates the limit for there is also energy transfer from one level to the next.

10% Rule

• Only 10% of the energy in one trophic level makes it to the next.
• You can calculate how much energy from one level transfers to the next by multiplying the energy in the first level by 0.10 to find the energy in the next level.
• The remaining energy's fate is usage by organisms within the level to survive.
• This energy is lost from organisms in the form of chemical bonds (CO2 they breathe out, in urine, or in feces).
• This energy also radiates out in the form of heat.

Ecological Feedback and Trophic Cascades

• Bodies have numerous feedback and regulatory systems to maintain health and equilibrium.
• Ecological feedback refers to a system where populations stay at the size that the environment can support, also known as its' carrying capacity.
• Healthy feedback systems maintain moisture, energy, and nutrient levels that fluctuate but still support the community.
• Biodiversity is present in healthy ecosystems, supporting as many trophic levels as possible.

Trophic Cascades

• Trophic cascades occur when an organism is removed from an ecosystem.
• Wolves from Yellowstone demonstrate cascading effects when removed because they stabilize everything below as a keystone species.
• Otters from the north pacific demonstrate cascades when removed, as sea-urchin populations exploded and ate all the kelp.
• Kelp forests are a critical habitat for many ocean species.
• Ecosystem engineers are animals that modify the habitat in a way that supports other organisms in the ecosystem.
• Beavers turn rivers into rich wetlands that provide habitat for other organisms; these wetlands also filter water and enrich soil.
• Elephants prevent trees from taking over in grasslands and create channels for water in the rainy season.
• Trophic cascades can cause major problems in disturbed ecosystems but also point to the most effective solutions.
• Reintroduction of a keystone species or ecosystem engineer can restore ecosystems.

Nutrient Cycling In Terrestrial Ecosystems

• Are founded on the productivity of primary producers.
• Energy transfer in the system happens from the amount of light converted into organic matter.
• Matter, energy, and nutrients pass up the chain as consumers eat the producers.
• Plants absorb nutrients in the soil and assimilate them.

Soil Composition

• Soil is the literal base of terrestrial ecosystems.
• It contains the substrate for rooting and acts as storage reservoir for nutrient needs.
• The litter, or the top layer, is made of organic matter such as dead leaves, grasses, and feces.
• Decomposers and detritivores occupy this layer, breaking down materials and making them more accessible to plants.
• Topsoil consists of small rocks and partially decomposed organic matter known as humus, and is typically rich and dark in nutrients.
• Subsoil contains more rock and less organic matter.
• Bedrock is solid rock marking the end of the soil layer.
• It is often impermeable, so water can sit above this layer in a reservoir.
• Soil quality influences plant community diversity and ecosystem productivity which dictates the diversity of the animal community.
• It provides organic molecules that heterotrophs feed on.
• Creating micro-habitats that animals can specialize in.
• More diverse plant communities correlate to more niches available in the ecosystem.

Forest Structure

• The forest floor acts as home to:
• Decomposing matter
• Decomposers and detritivores
• Small organisms that rely on decomposing matter
• Large organisms that cannot climb
• The forest floor is cool, moist, and has plants adapted to low light conditions.
• The understory consists of trunks of taller trees, shrubs, and partially shade-tolerant plants.
• The understory is cooler than other layers, has some sunlight, but free of wind.
• The canopy is where the bulk of the leaves from trees are located.
• The canopy has lots of fruit and light, but getting water may be challenging, but offers an ideal habitat for climbing animals.
• The emergent layer consists of extra tall portions of trees and is windy but has intense sunlight reaching the organisms.

Nutrient Cycles

• Nutrients move through ecosystems via absorption in producers to the consumption and assimilation in consumers and through abiotic processes.
• Some nutrients have large reservoirs (storage) in the biosphere.
• Abiotic processes, like the hydrologic cycle, help to move some of these nutrients around.

The Hydrologic Cycle

• Precipitation which includes rain or snow.
• Condensation which is the formation of clouds.
• Evaporation is water changing from a liquid to a gas.
• Transpiration is evaporation from plant's stomata.
• Percolation is the moment of water through soil.
• Leaching refers to the movement of the water which dissolves nutrients.
• A watershed is an area of land that supplies water for a river or body of water.
• The water table refers to the level of ground water under the layer of soil.
• Runoff/overland flow happens when soil is saturated and water flows over the top and enters bodies of water.

Nitrogen Cycle

• N is critical for plant growth and acts as an component of chlorophyll and is required to synthesize amino acids and proteins.
• The largest storage area is N2 gas in the atmosphere, but cannot be used by organisms in this form
• Plants can absorb nitrates (NO3-), ammonia (NH3), ammonium (NH4+), & sometimes nitrites (NO2).
• Plants & animals can also assimilate organic forms of nitrogen, such as amino acids
• Atmospheric nitrogen gas must be fixed into bio-available forms

Terminology for the Nitrogen Cycle

• Nitrogen Fixation involves converting N2 gas into biologically available nitrogen.
• Lightning can provide the energy to bind N to the O in the atmosphere
• Nitrifying bacteria can also fix N
• Nitrification forms nitrates from other nitrogen sources.
• Nitrifying bacteria can covert inorganic nitrogen into nitrates through an aerobic reaction, and are often on the nodules of plant roots.
• Denitrification is an anaerobic process.
• The nitrification middle step of this process forms nitrites from nitrates and the end of the process forms N2 gas which is no longer bioavailable.
• Not directly beneficial to living organisms.
• Ammonification is the formation of ammonia from other nitrogen sources like urine or feces or decomposing organic matter (proteins).
• There is no P stored in the atmosphere, but it's main reservoir is in sedimentary rock
• P is biologically available in the form of phosphate (PO₄³⁻), which is found in cell membranes, nucleic acids, and is calcium phosphate (in bones & shells)
• The two interacting cycles that move phosphorous are a short cycle where P moves around in a food chain.
• The long cycle involves geologic activity.
• Animal waste is a source of P, and is is easily absorbed and assimilated by the soil.
• Another source of P is from the broken-down shells of marine animals.
• Weathering refers to the process lichen use by secreting enzymes onto the surface of rock to liberate nutrients.
• The nutrient that is in the least supply is the one that dictates the the productivity in the system.
• Phosphorous has is commonly the most limiting nutrient in aquatic environments.

Eutrophication

• P is a common component of fertilizer and detergents.
• Contamination of water bodies with P leads to eutrophication.
• Physical factors affecting aquatic ecosystems, such as depth which determines the amount of light that will reach the soil. Deeper bodies of water will have aphotic (lightless) zones, where photosynthetic organisms cannot rely on the organisms in their food chain.
• Shallow waters are called photic zones and may be highly productive due to the levels of light they get.
• Turbidity refers to, and is caused by dirt + silt + phytoplankton + or algae that cloud the water in which decomposition outpaces photosynthesis in turbid settings.

Indicators of Water Clarity

• Water clarity can be measured using a secchi disk.
• Soil refers to regions that have light where aquatic plants can root into and obtain nutrients.
• These soil types provide a greater diversity of habitats.
• The benthic zone acts as the soil region.
• While the benthos describes the organisms that live in this zone.
• The littoral zone refers to where light reaches the soil, and only open water it is then called the limnetic zone, or profundal zone.
• Flow rate, riffles + rapids stir up the flow of water. which may pose choppy habitats in where organisms may struggle to live but also increases the total of dissolved gasses.

Water Temperature

• Cooler waters have contain more dissolved gasses that lead to more nutrient rich and productive habitats.
• In warmer waters organisms may have more favor in organism's bodies, nut nutrients become fastly easily depleted. Density - water is most dense most densely located at 4°c, because of what they come a come as separated layers.
• Water at 0°C (ice) is less dense than the less cool water, so it floats allowing for if that allows.

Lakes in Temperate Zones

• These lakes are considered stratified because because of the temperature and density.
• The specific Layers are separated between specific temperatures known as temperatures that known which are separated by the thermocline, which means that nutrients are on the the is the bottom of the top, where in water is the water and is separated by a layer, of which are also are the layers in the

Chemical Factors in Aquatic Ecosystems

• N & P will runoff into aquatic ecosystems and result in eutrophication.
• Organisms that die, is reduced in depth, causing more decomposers and which make the water and oxygen level to be become shallow.
• Deep lakes are call oligotrophic + rich in oxygen + few algae, but as eutrophication over time with access fertilization and blocking sunlight.
• With the levels like run in ocean, the ph is influenced through geologic surroundings and sulfur compounds.
• There is a Narrow in pH that leads to Narrow life, due to tissues being damaged.
• Certain levels like and motion of the water, it dissolves different, temperature, amount, levels, by how much and by how much the, amount oxygen, amounts and levels of ocean and water, this helps to regulate the levels of oxygen.

Indicators of Water Health

• Coliform Bacteria act as health with containing waters due to high amounts of feces water because due to waters and, and waterways and waters what helps to and is in order to is, in the animals is the and due to health by organisms indicators is the health of the organisms indicators indicators coliform is where the large amount of feces comes due where the of water is, and the that is the waterways. _ Aquatic Invertebrates help to tell.

This quiz covers ecosystems and biomes, including energy flow, trophic levels, and the roles of different organisms. Test your understanding of ecological concepts.