Exam 4 Part 4/5

Trophic structures

What is the primary energy source for life on Earth?

Sunlight.

What percentage of sunlight is typically absorbed by primary producers?

Approximately 1%.

Describe the nutrient cycle in terms of system type.

The nutrient cycle is a closed system.

What is the First Law of Thermodynamics?

Energy cannot be created or destroyed; it can only change form.

What are organisms that capture sunlight energy called?

Autotrophs or producers.

Define 'trophic levels'.

Levels in a food chain organized by the flow of energy.

Who are primary consumers in a food chain?

Organisms that consume plants and are always at the second trophic level.

What is Gross Primary Productivity (GPP)?

The overall rate of energy captured by primary producers from the sun. (the amount of energy actually absorbed by the plant form the sun)

How does Net Primary Productivity (NPP) relate to Gross Primary Productivity (GPP)?

NPP is always lower than GPP because it accounts for energy used for metabolism and maintenance.

Why are energy transfers between trophic levels considered inefficient?

Energy is lost as heat and only about 10% is transferred to the next level.

What do decomposers do in an ecosystem?

They break down large organic molecules into smaller ones that can be reabsorbed. Decompose nutrients on a molecular level

What are trophic cascades? (think domino affect)

Changes in abundance of organisms at one trophic level that can influence energy flow at multiple trophic levels.

What is a keystone species?

A species that regulates the population of other species in an ecosystem.

How does aquatic ecosystem biomass pyramid differ from terrestrial ecosystems?

Aquatic ecosystems can have an inverted biomass pyramid because primary producers have little biomass but high productivity.

What role do detritivores play in an ecosystem?

They consume detritus and excrete nutrients, helping to recycle materials.

What happens to most of the light energy from the sun that is not absorbed by plants?

It is either reflected, absorbed by other materials, or passes through the plant.

Why might people choose a vegan diet for environmental reasons?

To reduce the amount of plant biomass needed to produce meat, which is less efficient.

Tertiary consumers in the trophic leveling are what type of spices?

Usually carnivores apex predators but can also be omnivores

All non-producers/other organisms are ….

heterotrophs and get energy by consuming other organisms

Autotrophs are the

producers (always found at the bottom of the food chain)

Heterotrophs are the

Consumers, get energy from consuming other organisms this includes herbivores, carnivores, omnivores, detritivores (feed on dead organic material), and decomposers (decompose dead organic material)

In a food web, an herbivore can best be described as a: 

Primary consumer

Drawing a food web for an entire population isn’t going to work especially as the species age what happens to their diet?

The diet of an individual changes with age making a food web hard to layout, as each period of life brings new species to consume ( think of the red herring example, or of a baby human into and adult)

How do plants survive from the 1% of the light energy they absorb? what process do they use?

60% of the 1% that comes down and gets absorbed goes to cellular respiration, yet it requires energy for this process (Makes ATP out of light energy)

The NPP is the remainder, what’s leftover from the GPP, so this makes the NPP always higher or lower then the GPP?

Always lower. Were subtracting from the amount of energy used by the organism to survive.

what is the fate of all organisms?

All organisms are either consumed or enter the detritus pool

In most ecosystems, most NPP become?

Detritus without passing through a heterotroph, straight from the producers

Which biome is the most productive in NPP?

On land: Tropical rain forest, tropical seasonal forest, and temperate evergreen forest

In water: The algae beds and reefs, Swamps and wetlands, and estuary (freshwater inflow from rivers into the open sea)

where can energy go in the system?

Energy is used up (or escapes as heat) moving from level to level

with each level increase the consumer gets how much from the level below?

~10% percent goes to the next trophic level!

Why is there less biomass at high trophic levels?

Fewer organisms = less biomass at higher trophic levels (inefficient transfer of energy)

Because of Energy; disturbance; ecosystem size; etc, how many trophic levels are there usually in an ecosystem?

Consequently, food chains tend to have < 5 trophic levels.

Ecological Efficiency

Describes the efficiency with which energy is transferred from one trophic level to the next. but a transfer among trophic levels is very inefficient

Biomass pyramid measures not over time but…

productivity of ecosystem

what is the formula to solve for a biomass pyramid?

Productivity / Consumer (Primary, secondary, Tertiary) = proportion of productivity * 100 because its a percentage

Could an energy pyramid ever be inverted?

The Energy Pyramid cannot be inverted! Because there won't be enough energy to give to the primary consumers and so forth as energy is lost between trophic levels.

what is standing biomass?

Consumers life the fish live for years and they accumulate the biomass.

Why do aquatic ecosystems have an inverted biomass pyramid when compared to terrestrial ecosystems? 

•  Primary producers have little biomass in aquatic systems.

• Despite having a low biomass their efficiency and productivity rate help make up for it, being able to support biomasses of consumers higher up the food chain.

Can a biomass pyramid be inverted?

The Biomass Pyramid can be inverted!

Example of Deer and Wolves in a trophic cascade how does the change in abundance of wolves effect the ecosystem?

With less wolves more deer come and start to overpopulate, these deer eat the understory of the forest making the ecosystem less efficient and healthy as when the understory was present.