Earth's Changing Cycles

A hypothesis is

An idea to explain why something is the way it is and falsifiable

A tipping point is

A point that if passed will lead a system to fundamentally change the way it functions and is hard to predict

A statement is scientific if

Someone can disprove it and it agrees with the evidence

Albedo

Is defined as the proportion of incident sunlight or radiation that is reflected by a surface and is higher for ice than for water which leads to increased melting of ice

Color images of Earth from space show significant amounts of green due mainly to which biomolecule?

Chlorophyll

Biogeochemical systems are hard to model and predict because

They contain main different components, they can contain both linear and non-linear relationships, they can be impacted by rare events that are hard to study and capture in models due to their rareness, and the models we build based upon how the system functions today may not hold true in the future

Homeostasis is achieved via

Negative feedbacks in a system

It has been stated that we are living in the Anthropocene. For this to be true, geologists argue that human activity needs to be creating such a drastic change that our activity will show up in future geological records. Which of the following can be considered evidence of the Anthropocene?

Current extinction rates are greater than long-term averages, atmospheric carbon dioxide levels are rising at a rate not seen for 66 million years, plastics are long lived and near-ubiquitous in the environment, and burning of fossil fuels and biomass has deposited a layer of black carbon in sediments and on glaciers

The Earth is

An open system, but for many purposes we can consider it closed as material fluxes in and out are small

Carbon dioxide concentrations in the atmosphere are currently

Higher than they have been in the last 400 thousand years or more, oscillate with the seasons from slightly higher in a hemisphere’s winter to lower in a hemisphere’s summer but still increasing year on year at present, and contributing to global warming

The Earth has been described as a Goldilocks planet, why?

Because it is not too hot, not too cold, just right for life as we know it to thrive

Tipping points in the Earth system include

Changes to thermohaline circulation, sea-ice loss, permafrost organic carbon thaw, and Amazon rainforest dieback

Levels of carbon dioxide in the atmosphere have increased from about 280 ppm to over 400 ppm in the last one hundred years or so. This level and rate of change is

Unprecedented in the last 400 thousand years or more of Earth’s history, and occurring at such a fast rate that it is unclear how the Earth system will react and whether the lifeforms the Earth supports will be able to adapt to their changing world

Which of the following are types of autotrophy?

Photosynthesis and chemosynthesis

Which of the following are synonyms?

Autotrophy and primary production and photosynthesis and photoautotrophy

Humans and other heterotrophs

Can make greater use of net primary production if they consume organisms lower down the food chain and rely on primary producers to generate usable potential energy in the form of organic matter

Organic and inorganic forms of C are important components of life, climate, and biogeochemical cycles. Which of the following are organic compounds?

Glucose, chlorophyll, enzymes, and DNA

Steady state models or representations of biogeochemical systems usually include

Boxes or pools and arrows representing flows or fluxes

The First Law of Thermodynamics

States that matter is neither created nor destroyed

The Second Law of Thermodynamics

Results in losses of useful energy as we move up a food chain

In a first order reaction

The reaction rate is directly proportional to the concentration of one of the reactants and the reaction rate slows over time, while the half-life remains constant

An enzyme is

A biological catalyst that can greatly accelerate reaction rates and a protein

Enzymes are critical to the rates of many important biogeochemical reactions observed on Earth. Which of the following statements are true

The loss of a substrate in an enzyme mediated reaction often follows Michaelis-Menten kinetics and decreases in concentration following 1st order kinetics and enzymes ARE NOT perfect catalysts as they denature (degrade) over time meaning organisms need to make new ones

Net ecosystem productivity is

Calculated as: gross primary production minus ecosystem respiration and a way of calculating how much carbon an ecosystem is accumulating (storing) or losing

Primary production in the ocean is limited by

Nutrients such as nitrate and phosphate and sunlight

The following are examples of events that can change (disturb) or have changed (disturbed) local or global biogeochemical cycles and ecosystems

The industrial revolution, the evolution of oxygenic photosynthesis, and forest fires

Why are food chains pyramid-shaped (narrower at the top)

Useful energy is lost on moving up each trophic level and the efficiency of carbon transfer up the food chain is less than 100% and typically between 1 and 10%

Your ecological efficiency will be greatest and carbon footprint smallest if you eat a diet of only

Primary producers

Acid rain

Will be less damaging to natural waters in landscapes that contain limestone and is a decrease in the pH of rain water below natural, CO2 equilibrated levels

Acid rain can have various negative impacts on vegetation, aquatic life and human health. Acid rain results from emissions of primary pollutants that then form acids (secondary pollutants). Which are the correct pairings of the main primary and secondary (acid) pollutants involved in producing acid rain

Sulfur dioxide and sulfuric acid and nitrogen dioxide and nitric acid

Acid rain occurs when emissions of gases such as sulfur dioxide and nitric oxide dissolve into rain water. Which of the following statements about acid rain are true

Acid rain can cause a loss of nutrients from surface soils and reduce plant productivity and acid rain has a lower pH than "natural" rain

The loss of large wild land mammals (megafauna) after the emergence of humans on Earth is

An example of competition from a new species reducing the range of pre-existing species and likely to show up in the future geologic record as one marker of the Anthropocene

The stratospheric ozone layer

Protects us and other life forms on Earth from damaging UV light and is formed by a process that begins with the photolysis of molecular oxygen

The ozone hole

Became a major environmental concern in the 1980s and was due to the release of CFCs to the atmosphere and isn't literally a hole, but a thinning or "depletion" of ozone above the south pole.

Humans are reliant upon primary production for sustenance. How have natural levels of primary productivity been enhanced to yield greater amounts of food?

By mining phosphorous rich rocks to use as fertilizers, by increased irrigation to remove water limitation in some regions, and by the advent of a new chemical reaction - the Haber process - to increase nitrogen fertilizer production

Approximately how much of the current global population is supported by the production of synthetic nitrogen fertilizers?

Half

Which of the following are true about main vs. trace gases in the atmosphere?

Main gases occur at higher concentrations and are less sensitive to perturbation (change) and trace gases occur at very low concentrations and are more sensitive to perturbation (change)

Available nitrogen can be used directly by plants and other organisms. Which are forms of available nitrogen

Ammonia (NH3), nitrate (NO3-), nitrite (NO2-), and ammonium (NH4+)

Elements such as C, N and P are required in certain ratios by different organisms and, therefore, in whole ecosystems. What is the scientific term for these elemental ratios?

Stoichiometry

Elements that are essential for life but in small quantities are called

Trace elements or micronutrients

Which of the following denote ecosystems that have too much nitrate or phosphate

Eutrophic

Which of the following can limit net ecosystem production on land

Available nitrogen, rainfall (water), and sunlight (irradiation)

If a chemical species (e.g. nitrate, phosphate) is at low concentration in the surface ocean and high concentration in the deep ocean, it is

Very likely to be a nutrient required for marine life

Black carbon is

Often used to refer to the most burnt, aromatic compounds produced by fire, any form of organic material altered by fire or heat, and untoasted bread

Methane hydrates hold massive amounts of methane, but even if released this methane may not cause too much warming as it will probably be

Oxidized to carbon dioxide before it reaches the atmosphere (carbon dioxide having an 84 times lower global warming potential at the 20 year horizon)

Methane is

Produced in anoxic environments by anaerobic microbes, produced by natural and anthropogenic fires, a greenhouse gas, and an energy source in oxic environments

Methane is mainly produced where?

Anoxic environments

Permafrost is

A soil layer that is permanently frozen, even in summer and a mammoth (massive) and vulnerable (i.e. may be released as climate warms) store of global organic carbon

Refractory soil carbon

Is the soil carbon that turns over slowest and includes humic acids and black carbon

Permafrost soils have the potential to drive a major increase in global CO2 and temperature if they thaw. If permafrost starts to thaw at a rapid rate, this could result in a what?

Tipping point

The following are part of the black carbon pool

Condensed aromatics formed at high temperature and lightly charred wood

When might ice burn

When it is a methane hydrate

Which of the following are natural sources of methane

Wetlands and termites

It will be warmer at the end of the century than it was at the start. How much warmer is uncertain. Which of the following is responsible for the greatest amount of uncertainty in predictions of future global temperatures?

Uncertainty about future human emissions

The world is warming. As an approximate rule based upon historical data and IPCC projections

The world will warm due to continued emissions of carbon dioxide following an approximately linear relationship (i.e. for every Petagram of CO2 emitted, we can expect a fixed amount of warming)

Climate change is happening and will continue throughout the century. How extreme climate change will be by 2100 depends mainly upon

Human choices and how they translate to carbon dioxide emissions

Presenting climate data in terms of anomalies

Plots the amount of change relative to a specified time point and allows the amount of change predicted by different models to be more readily compared

The performance of Global Climate Models (GCMs) is continuing to improve due to

Increased spatial resolution of input data and models, improvements in our biogeochemical understanding of the Earth system, increased model sophistication both for individual components of the Earth system and by combining many components of the Earth system into models, and increased temporal resolution of input data and models

Tipping points in the Earth system

Are best treated as interrelated processes that could lead to a domino effect

Climate change will cause

Variable changes in temperature for different places on Earth and increased likelihood of flooding in some places and increased likelihood of drought in others

Geoengineering includes Carbon Dioxide Reduction technologies. Which of the following are true about CDRs?

Many CDR technologies may buy us time (they are impermanent) but leave future generations to deal with climate change and current CDR technologies may help offset some future emissions, but we still need to reduce emissions to prevent severe climate change

Which of the following gases are greenhouse gases

Carbon dioxide and methane

The energy that comes from the combustion of natural gas (methane) comes from

Potential energy in chemical bonds

Human activity has increased the global cycling of nitrogen and phosphorous. Which of the following is true

By the mid-1900s, human activities had increased phosphorous cycling by approximately 4 times pre-industrial rates and by the mid-1900s, human activities had approximately doubled global rates of nitrogen cycling compared to pre-industrial rates

Which of the following can fix nitrogen either on their own or through symbiosis with another organism?

Legumes such as peas and beans and bacteria called diazotrophs

Nitrification and denitrification are

Processes that can generate nitrous oxide and part of the nitrogen cycle in the ocean and on the land

Which wavelengths of light are emitted from the Earth's surface (i.e. are emitted by a black body of the average temperature of Earth

Infrared wavelengths (i.e. thermal radiation)

What was the main driver of global temperature during the last 400,000 years up until the industrial revolution?

Changes in insolation, plus feedbacks to ice cover and biogeochemical cycling

Which wavelengths of light can reach the Earth's surface from the sun most efficiently (i.e. are not strongly absorbed by the atmosphere

Visible and radio

Upwelling and downwelling (the sinking of cold and/or salty water) drive the following

The global flow of water around the oceans basins (thermohaline cicrculation) and primary production by phytoplankton along some coastlines

Why is nitrogen often a limiting nutrient despite making up 98% of the atmosphere

Many organisms can only use available forms of nitrogen such as NO3 (nitrate) and NH4 (ammonia)

All the carbon on Earth

Has been reused again and again and again passing through the air, us, all the other organisms that now share our planet, and those that were a part of our planetary ancestry and was formed in the heart of a dying star

Aromatic compounds give freshwaters their often brown color. They are

A type of cyclic (ring) molecule and photoreactive

Natural processes have offset (i.e. removed from the atmosphere) about 2/3rds of the anthropogenic CO2 added to the atmosphere, reducing the climate change experienced to date. This natural offset is predicted to become less efficient in the future, such that we will experience more warming per unit of CO2 emitted in the future. Which of the following are expected to lead to a reduction in this offset in the future

A reduction in the efficiency of the land carbon sink due to a combination of factors, including the saturation of photosynthetic enzymes as carbon dioxide continues to increase in the atmosphere (i.e. a reduction in the CO2 fertilization effect), and reduction in the efficiency of the ocean solubility (physical) pump

Soils accumulate organic carbon

At highest rates in the years to decades after a major disturbance (e.g. a disturbance similar to those we discussed as triggering a primary succession) and very slowly if the soils are already well developed (1000s of years old) and have not been disturbed recently

The ocean and components of the land carbon cycle have absorbed some of the carbon dioxide emitted by human activity. Are the natural biogeochemical cycles likely to act as a natural savior and remove all the greenhouse gases we are adding to the atmosphere?

No. If we want to reduce future climate change, we need to act

The higher northern latitudes (greater than 50 degrees N) hold a large proportion of the worlds soil carbon. These latitudes hold more soil carbon than tropical latitudes and equivalent southern hemisphere latitudes because

Higher northern latitudes have a greater proportion of the global land mass than equivalent southern hemisphere latitudes and conditions for soil carbon accumulation are favorable at higher, colder latitudes than in the tropics

Which of the following has increased the amount of anthropogenic carbon stored on land?

Nitrogen fertilization, carbon dioxide fertilization, and forest regrowth

Why do we need to consider biogeochemical processes when trying to predict future climate change

Positive natural feedbacks may increase the strength of anthropogenic warming and negative natural feedbacks may decrease the strength of anthropogenic warming

Which of the following is relevant to the physical (aka solubility) pump?

Cold water is denser than warm water and cold water can absorb more gas than warm water

Which of the following is true of phytoplankton

Are an important part of the "soft" biological carbon pump which is driven by the sinking of organic matter to depth in the ocean where it is later respired to CO2 (most of it) or buried at the sea floor (small amount) and they are the microscopic plants of the sea and fix approximately as much oxygen through photosynthesis as the trees on land

Which of the following are relatively short-term (less than 1000 years) natural processes that remove anthropogenic carbon dioxide from the atmosphere?

Ocean invasion: Seawater buffer and land uptake: Photosynthesis minus respiration

The following is true

Primary production on land is often limited by water availability and primary production in the ocean often occurs 10s to 100 meters below the sea surface

The human population is growing by just over 1% per year. At this rate the population will double about every 60 years. Resource pessimists and resource optimists have different views on the feedbacks that occur between natural resource utilization, population growth, environmental degradation and carrying capacity. Which of the following views is likely to be held by a Resource Optimist

We will invent new technologies capable of offsetting the pressure we place on the natural environment and humans are exceptional to the extent that our population will never be limited by the carrying capacity of the local and/or global environment

The biological carbon pump increases the efficiency with which the oceans can absorb carbon dioxide. Which of the following are relevant to the soft (organic) component of the biological carbon pump?

Phytoplankton grow near the surface of the ocean where they can fix carbon dioxide and sinking particulate organic matter (dead plankton, fecal pellets, etc.) is converted to carbon dioxide at depth in the ocean

Soil organic carbon residence time increases with

Decreasing temperature and decreasing precipitation

Microbes are important to small scale and global scale biogeochemical cycles because they

Exist in large numbers and have a high surface are:volume ratio

If you measure the concentration of a reactant it is reduced at a constant rate no matter its concentration it is following -------- order kinetics

Zero

Life is a highly ordered process. How is an organism able to create order (reduce entropy) within itself despite the 2nd law of thermodynamics

Life uses organized, useful energy to move materials via non-spontaneous flows, but in doing so releases less useful, higher entropy energy and as an organism creates order within itself, it increases entropy in its environment to a greater degree. Thus, total entropy actually increases in the universe as organisms use useful energy

Heat flow from the Earth's interior powers the movement of the continents over geological time and drives spectacular events like volcanic eruptions. The amount of energy reaching the Earth's surface from the interior each year is

Greater than all the energy generated per year by industrial processes and less than 1% of the energy reaching the Earth's surface from the sun each year

Carbon is

A major component of the current and past climate system, the currency of the industrial revolution and our current society, the currency of life, and the building block of life

Carbon, oxygen, nitrogen and phosphorous are

Four of the main elements that together drive Earth's biogeochemical cycles and produced during the death of stars

Black carbon aerosols

Absorb light and heat, contributing to global warming

Which of the following are pools of soil organic matter

Semi-refractory organic carbon with a slow turnover (centuries), refractory organic carbon with a passive (near-zero) turnover (millenia), and labile organic carbon with a fast turnover (decades)

The loss of large wild land mammals (megafauna) after the emergence of humans in Earth is

Likely to show up in the future geologic record as one marker of the Anthropocene and an example of competition from a new species reducing the REALIZED niche of the existing species

Why did wood (tree rings) formed in the 1950's appear old based upon radiocarbon dating?

Burning of fossil fuels diluted the radiocarbon signal of atmospheric carbon dioxide and this radiocarbon depleted carbon was then incorporated in to trees by photosynthesis

Stoichiometry describes

The ratios of chemical elements found in an organism and the ratios of chemical elements found in an ecosystem

Carbon isotopes can tell us about the source and apparent age of organic carbon, including black carbon. Which of the following is true about C isotopes?

Radiocarbon (14C) data indicate that black carbon in the oceans is \~20,000 and stable carbon (13C) isotope data indicate that black carbon in the oceans is not derived from trees on land

Urbanization is

Altering local, regional, and global hydrologic and carbon cycles and described as the most forceful form of land-use change

Humans are now an urban species, with more people living in urban systems than rural ones. Which of the following are true?

The carbon cycle in highly urbanized areas such as Boston is dominated by anthropogenic C emissions, the degree of urbanization between nations and globally can be hard to assess given differences in how “urban” is defined by different countries, and although cities cover limited land area people living in cities are responsible for most C emissions