Energy Flux Flashcards
Explain photosynthesis
It is the process by which green plants and certain other organisms transform light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism’s activities. During photosynthesis in green plants, light energy is captured ad used to convert water, carbon dioxide, and minerals into oxygen and energy-rich organic compounds.
What is chloroplast?
It is a structure within the cells of plants and green algae that is the site of photosynthesis, the process by which light energy is converted to chemical energy, resulting in the production of oxygen and energy-rich organic compounds.
Define biomass.
The biomass is the mass of living biological organisms in a given area or ecosystem at a given time. Biomass can refer to species biomass, which is the mass of one or more species, or to community biomass, which is the mass of all species in the community. It can include microorganisms, plants or animals. The mass can be expressed as the average mass per unit area, or as the total mass in the community.
What are GPP and NPP?
Gross primary productivity (GPP) is the rate at which an ecosystem’s producers (usually plants) convert solar energy into chemical energy as biomass found in their tissues. It is usually measured in terms of energy production per unit area over a given time span, such as kilocalories per square meter per year (kcal/m2/yr).
Net primary productivity (NPP) is the rate at which producers use photosynthesis to produce and store chemical energy minus the rate at which they use some of this stored chemical energy through aerobic respiration. In other words, NPP =GPP -R, where R is energy used in respiration. NPP measures how fast producers can provide the chemical energy stored in their tissue that is potentially available to other organisms (consumers) in an ecosystem.
Autochthonous vs Allochthonous
Autochthonous: organic matter produced by photosynthesis within the ecosystem’s boundaries.
Allochthonous: organic matter imported from outside the ecosystem’s boundaries
How does NPP change in different ecosystems?
On land, NPP generally decreases from the equator toward the poles because the amount of solar radiation available to terrestrial plant producers is highest at the equator and lowest at the poles.
In the ocean, the highest NPP is found in estuaries where high inputs of plant nutrients flow from nutrient-laden rivers, which also stir up nutrients in bottom sediments. Because of the lack of nutrients, the open ocean has a low NPP, except at occasional areas where an upwelling (water moving up from the
depths toward the surface) brings nutrients in bottom sediments to the surface.
In general, terrestrial ecosystems are more productive than the aquatic ones: this is because in oceans there is an extinction of light in the depths. In the ocean, just a few superficial layers are able to produce photosynthetic processes.
Most productive biomes in the oceans are the temperate ones.
Most productive biomes on land are tropical rainforest and savannas.
What factors limit primary production in terrestrial ecosystems?
Terrestrial primary production varies considerably across the surface of the Earth and among different ecosystem types. Terrestrial primary production, both NPP and GPP, vary from north to south (or latitudinally) due to gradients in plant community composition, growing season length, precipitation, temperature, and solar radiation.
Limiting factors:
Resources: solar radiation, CO2, Water, soil nutrients
Condition: temperature
What factors limit primary production in aquatic ecosystems?
In aquatic ecosystems, primary productivity is driven by the availability of nutrients and light and, to a lesser extent, by temperature and other factors. Iron is a limiting nutrient in 30% of the ocean, it comes from wind-blown particulate matter and is very insolubile in sea-water.
The highest production is along continental shelves and in areas of upwelling (brings nutrient rich water to the surface). Main, open ocean has low nutrient availability and therefore low primary productivity. Nutrient renewal in the open ocean comes from vertical mixing, which is often blocked in tropical oceans by permanent thermocline.
Explain bottom-up and top-down effects.
The bottom-up effect means that a lower trophic level in the biological network affects the community structure of higher trophic levels by means of resource restriction. (hence the influence of physical and chemical abiotic factors on primary producers and up).
The top-down effect refers to a higher trophic level influences the community structure of a lower trophic level through predation. (hence the influence of consumers or biotic factors, on lower levels).
What is a trophic pyramid?
Trophic pyramid, also called an energy pyramid, showing the progression of food energy. The pyramid base contains producers, organisms that make their own food from inorganic substances. All other organisms in the pyramid are consumers. The consumers at each level feed on organisms from the level below and are themselves consumed by organisms at the level above. Most of the food energy that enters a trophic level is “lost” as heat when it is used by organisms to power the normal activities of life. Thus, the higher the trophic level on the pyramid, the lower the amount of available energy.
Explain trophic cascade in lakes.
The concept of cascading trophic interactions predicts that an increase in piscivore biomass in lakes will result in decreased planktivorous fish biomass, increased herbivorous zooplankton biomass, and decreased phytoplankton biomass.
- Large fish feed on smaller fish and invertebrates
- Large fish therefore influence zooplankton, and large zooplankton (eaten by planktivorous fish) dominate the zooplankton.
- This reduces phytoplankton biomass and the rate of primary production
Why are aquatic and terrestrial systems different?
Aquatic systems are: discrete, homogeneous habitats, with rapid prey population dynamics relative to predator dynamics. Common prey are uniformly edible. Systems are simple and trophically stratified.
Terrestrial systems are: fuzzy, heterogeneous habitats with variable prey population dynamics. Common prey is not uniformly edible. Complex systems with weak and diffuse species interactions.
HOWEVER: terrestrial agricultural systems are similar to aquatic systems.
What are the main components (players) in an ecosystem?
Autotrophs: photoautotrophs or primary consumers + chemoautotrophs
Herbivores, carnivores and omnivores : consumers
Decomposers
Organic sink
Atmosphere, minerals and water
Solar energy
What is the distribution of dead organic matter in biomes?
Deserts: the lack of moisture means that minerals are trapped inside the soil particles. This means there are very few minerals to support plant growth. Dry conditions are the worst for bacteria.
Tropical forests: because precipitation in tropical rainforest regions exceeds evapotranspiration at almost all times, a nearly permanent surplus of water exists in the soil and moves downward through the soil into streams and rivers in valley floors. Through this process nutrients are leached out of the soil, leaving it relatively infertile.
Temperate forests: The soil in temperate forests are thick and fertile as the forest floor is covered by trees and there is a vast wildlife. It’s covered with the dead parts of plants and animals and, the decomposers act on the dead and decaying matter and turn it into useful nutrients or organic manure. Thus the humus collection is more and the soil is more fertile.
Tundra: The soil in the Arctic is largely permafrost or soil that remains frozen year-round, leaving only a thin surface layer of thawed soil in summer for plant roots to grow in. Tundra soil is also scarce in many of the nutrients that plants need to grow.
How does energy enter the ecosystem?
All energy in ecosystems comes from the sun. Producers, such as plants, algae and cyanobacteria use the energy from sunlight to make organic matter from carbon dioxide and water. This established the beginning of energy flow through almost all food webs.
