Exam 2 Knowledge Check

An invasive species of insect enters an ecosystem and begins to quickly reproduce. The increased offspring lead to even more reproduction, which result in still more offspring the following year. This eventually creates exponential growth. What is the name of this example?

a. A positive feedback loop

b. A negative feedback loop

c. Dynamic equilibrium

d. Homeostasis

An invasive species of insect enters an ecosystem and begins to quickly reproduce. The increased offspring lead to even more reproduction, which result in still more offspring the following year. This eventually creates exponential growth. What is the name of this example?

a. A positive feedback loop

b. A negative feedback loop

c. Dynamic equilibrium

d. Homeostasis

a. A positive feedback loop

In eutrophication, what organism directly consumes oxygen, leading to hypoxia?

a. Phytoplankton

b. Zooplankton

c. Bacterial decomposers

d. Large aquatic plants

c. Bacterial decomposers

Which of these ecosystems would you expect to have the greatest net primary productivity?

a. A savanna

b. A tundra

c. Cultivated farmland

d. An estuary

d. An estuary

What is the first step in developing an ecological model (without observation)?

a. Gathering data

b. Forming hypotheses

c. Predicting relationships in nature

d. Constructing the ecological model

b. Forming hypotheses

A system stabilized by negative feedback, with opposing processes offsetting each other, is said to be in ________.

a. environmental balance

b. dynamic equilibrium

c. normal balance

d. static control

e. harmonic resonance

b. dynamic equilibrium

The eutrophication that has taken place in Chesapeake Bay, the Gulf of Mexico, and other locations appears to be due to ________.

a. pesticide use along the waterways

b. heavy metals dumped in the sewage

c. excess nutrients from fertilizers

d. global warming from human use of fossil fuels

e. weather alone, because it is only obvious in the summer

c. excess nutrients from fertilizers

Which of these would decrease the rate of evaporation in an ecosystem?

a. Creation of a reservoir behind a dam

b. Replanting a forest, decreasing soil exposure

c. An increase in wind

d. An increase in global surface temperatures

b. Replanting a forest, decreasing soil exposure

What is the largest reservoir of carbon?

a. The oceans

b. The atmosphere

c. Living organisms

d. Sediments

d. Sediments

The Haber-Bosch process has reduced a bottleneck and greatly enhanced the availability of what nutrient?

a. Carbon

b. Nitrogen

c. Phosphorus

d. Water

b. Nitrogen

All of the following are considered Earth's structural spheres except the ________.

a. hydrosphere

b. lithosphere

c. atmosphere

d. geosphere

e. biosphere

d. geosphere

In an aquatic ecosystem experiencing eutrophication, levels of dissolved macronutrients ________ and dissolved oxygen levels ________.

a. decrease; decrease

b. increase; increase

c. decrease; increase

d. increase; decease

e. remain stable; increase

d. increase; decease

What conclusions can be drawn from the data shown in the figure?

a. Automobiles do not contribute to nutrient pollution in Chesapeake Bay.

b. Repairing broken septic systems will probably result in a large decrease in phosphorus pollution entering Chesapeake Bay.

c. Full protection of Chesapeake Bay will require consideration of activities within the bay's airshed and not just the bay's watershed.

d. Wastewater treatment plants do not contribute significantly to nutrient pollution in Chesapeake Bay.

e. Agriculture accounts for 98% of the nitrogen and phosphorus entering Chesapeake Bay.

c. Full protection of Chesapeake Bay will require consideration of activities within the bay's airshed and not just the bay's watershed.

The precipitation that flows over land and enters waterways is ________.

a. evaporation

b. flux

c. transpiration

d. moisture

e. runoff

e. runoff.

Nitrogen and phosphorus pollution in the Chesapeake Bay causes phytoplankton numbers to increase, which ultimately leads to the process called __________.

a. photosynthesis

b. eutrophication

c. nitrogen fixation

d. carbon fixation

b. eutrophication

The entire area of land that a river drains is called its __________.

a. dead zone

b. watershed

c. wetland

d. Phytoplankton

b. watershed

Which of the following best characterizes the factors that have contributed to the dead zone in the waters of the Chesapeake Bay for the past few decades?

a. the farm practices around the Chesapeake Bay

b. fertilizer runoff from farms, animal manure, and stormwater runoff in the watersheds surrounding the Chesapeake Bay

c. gasoline spillage from the refineries

d. increasing oil spills in the Chesapeake Bay

b. fertilizer runoff from farms, animal manure, and stormwater runoff in the watersheds surrounding the Chesapeake Bay

What does the term emergent properties describe?

a. the characteristics of emerging vegetation, such as the forb called fireweed

b. the particular timing and season of emergence of flowers in the spring, as long as timing of the emergence of flowers is not being changed by global climate change

c. the particular timing and season of emergence of organisms from dormancy

d. characteristics that are not evident in the system's individual components but are evident only by looking at the whole operating system

d. Characteristics that are not evident in the system's individual components but are evident only by looking at the whole operating system.

A contributing factor to the process of eutrophication is __________.

a. nitrogen and phosphate pollution

b. lack of nutrients

c. acid rain

d. stable populations

a. Nitrogen and phosphate pollution.

Ecotones are the ________.

a. areas between territories of organisms

b. interactive behaviors leading to communication

c. sounds that animal communities make in ecosystems

d. studies of specific biomes by ecologists

e. transitional zones between ecosystems

e. transitional zones between ecosystems.

Biodiversity is partially influenced by net primary productivity (NPP). Where can the highest terrestrial rates of NPP be found?

a. tropical rainforests

b. deserts

c. polar regions

d. deciduous forests

e. tundra

a. tropical rainforests.

Nitrogen and phosphorus are referred to as macronutrients because ________.

a. they are needed to manufacture large biomolecules

b. they are required in large amounts for organisms to survive

c. they are larger than other nutrients needed by plants

d. they are needed by large organisms

e. their cycles have larger reservoirs than those of micronutrients

b. They are required in large amounts for organisms to survive.

The two largest pools of the carbon cycle, in order, are ________.

a. fertilizers and the atmosphere

b. sedimentary rock and plants

c. sedimentary rock and oceans

d. oceans and respiration

e. freshwater streams and plants

c. Sedimentary rock and oceans.

Ecological modeling can help us ________ ecosystem services.

a. create many new

b. decrease the cost of maintaining

c. control the growth of

d. replace destroyed

e. understand

e. understand

Examples of micronutrients include ________.

a. carbohydrates and lipids

b. phosphorus

c. DNA and RNA

d. iron and zinc

e. nitrogen and carbon

d. iron and zinc

Scientists use simplified representations called ________ to understand large, complex systems and make predictions about them.

a. models

b. GIS

c. metapopulation

d. patches

e. Sources

a. models

Recent research suggests that ________ is now the key limiting factor in phytoplankton growth in the Gulf of Mexico.

a. oil pollution

b. temperature

c. phosphorus

d. nitrogen

e. sunlight

c. phosphorus

A metapopulation is __________.

a. a population that is undergoing exponential growth

b. a population that spans two biomes

c. a really big population

d. a network of separate populations with some interbreeding between them

d. a network of separate populations with some interbreeding between them

Which of the following statements about dead zones is correct?

a. Dead zones occur in terrestrial ecosystems.

b. Dead zones occur in the Arctic tundra.

c. Dead zones, once they exist, are permanent.

d. Dead zones are reversible if nutrient pollution input to a system is reduced.

d. Dead zones are reversible if nutrient pollution input to a system is reduced

Nitrifying bacteria convert _____ to _____.

a. nitrogen gas ... ammonium

b. nitrogen gas ... nitrates

c. ammonium ... nitrites

d. nitrates ... nitrogen gas

e. ammonium ... nitrogen gas

c. ammonium ... nitrites

_____ removes nitrogen from the atmosphere.

a. Denitrification

b. Nitrification

c. Mineralization

d. Nitrogen fixation

e. Assimilation

d. Nitrogen fixation

Assimilation is indicated by the letter(s) _____

The figure shows the nitrogen cycle. Each letter indicates the definite process of this cycle. Letter A indicates the process of uptake of nitrates by the plants. Letter B marks the transformation of ammonium into nitrites by bacteria. Letter C marks the synthesis of ammonium by the decomposers. Letter D marks the transformation of nitrogen of atmosphere to ammonium by bacteria. Letter E marks the single cell organisms, which take part in the nitrogen cycle and are located in the root nodules. (Credit: harrisonko18)

a. A

b. D and E

c. C and D

d. C

e. B

a. A

Nitrogen-fixing bacteria is(are) indicated by the letter(s) _____.

The figure shows the nitrogen cycle. Each letter indicates the definite process of this cycle. Letter A indicates the process of uptake of nitrates by the plants. Letter B marks the transformation of ammonium into nitrites by bacteria. Letter C marks the synthesis of ammonium by the decomposers. Letter D marks the transformation of nitrogen of atmosphere to ammonium by bacteria. Letter E marks the single cell organisms, which take part in the nitrogen cycle and are located in the root nodules. (Credit: harrisonko18)

a. D and E

b. A and B

c. A

d. C and D

e. B and C

a. D and E

Nitrification is indicated by the letter(s) _____

The figure shows the nitrogen cycle. Each letter indicates the definite process of this cycle. Letter A indicates the process of uptake of nitrates by the plants. Letter B marks the transformation of ammonium into nitrites by bacteria. Letter C marks the synthesis of ammonium by the decomposers. Letter D marks the transformation of nitrogen of atmosphere to ammonium by bacteria. Letter E marks the single cell organisms, which take part in the nitrogen cycle and are located in the root nodules. (Credit: harrisonko18)

a. B and E

b. A

c. B and C

d. D and E

e. B

e. B

Denitrifying bacteria convert _____ to _____.

a. nitrogen gas ... nitrites

b. nitrogen gas ... ammonium

c. ammonium ... nitrogen gas

d. nitrogen gas ... nitrates

e. nitrates ... nitrogen gas

e. nitrates ... nitrogen gas

Which one of these is a nitrate?

a. NO3 -

b. SH

c. NO2 -

d. NH4 -

e. NH2

a. NO3 -

Which one of these is a nitrite?

a. NO3 -

b. NO2 -

c. PO4 -

d. NH2

e. NH4 -

b. NO2 -

An organism gets carbon by using carbon dioxide in the atmosphere to make sugar molecules. This organism is a

a. decomposer.

b. primary consumer.

c. higher-level consumer.

d. producer.

e. None of the above

d. producer

Which organisms play a role in returning carbon to the atmosphere?

a. Producers only.

b. Decomposers only.

c. Producers, consumers, and decomposers.

d. Consumers only.

e. Consumers and decomposers, but not producers.

c. Producers, consumers, and decomposers

Every carbon atom in the organic molecules that make up your body MUST recently have been part of

a. a primary consumer.

b. a producer.

c. a sugar molecule made in one of your chloroplasts.

d. a higher-level consumer.

e. a decomposer.

b. a producer

Imagine following a single carbon atom through the carbon cycle. Which of the following is a possible path for the carbon atom to take?

a. The atmosphere; a plant; an herbivore; another plant; then back to the atmosphere.

b. The atmosphere; a decomposer; a higher-level consumer; then back to the atmosphere.

c. The atmosphere; a decomposer; then back to the atmosphere.

d. The atmosphere; a plant; a higher-level consumer; then back to the atmosphere.

e. The atmosphere, a plant, a herbivore, a decomposer, then back to the atmosphere

e. The atmosphere, a plant, a herbivore, a decomposer, then back to the atmosphere

Which process or processes return carbon to the atmosphere?

a. Photosynthesis only

b. Cellular respiration and the breakdown of large organic molecules into smaller organic molecules

c. Breakdown of large organic molecules into smaller organic molecules

d. Cellular respiration and photosynthesis

e. Cellular respiration only

e. Cellular respiration only

The majority of Earth's fresh water exists ________.

a. in the atmosphere

b. in freshwater lakes, streams, and rivers

c. in the oceans

d. in the form of ice

e. in groundwater

d. in the form of ice

The first essential step in changing atmospheric nitrogen into more usable NH3 is called ________.

a. biogeochemical cycling

b. denitrification

c. nitrogen fixation

d. nitrification

e. ammonification

c. nitrogen fixation

Nitrogen fixation is a process that makes nitrogen available to plants and is carried out by ________.

a. mutualistic and free-living bacteria

b. nitrogen gas dissolving in fresh water and in the ocean

c. parasitic bacteria

d. plants during photosynthesis

e. volcanic eruptions

a. Mutualistic and free-living bacteria.

Humans have dramatically altered the rate of nitrogen fixation into forms usable by autotrophs by ________.

a. increasing the erosion of farmlands through poor agricultural practices

b. burning of fossil fuels to meet our energy needs

c. producing synthetic fertilizers and applying them to crops, lawns, and parks

d. selectively removing leguminous plants

e. using antibiotics to reduce the numbers of denitrifying bacteria

c. producing synthetic fertilizers and applying them to crops, lawns, and parks

By damming rivers and creating reservoirs, we are ________.

a. decreasing evaporation

b. increasing transportation

c. decreasing transpiration

d. increasing evaporation

e. increasing transpiration while decreasing evaporation

d. increasing evaporation

Which organelle in plant cells is primarily responsible for photosynthesis?

a. Mitochondria

b. Nucleus

c. Golgi apparatus

d. Chloroplast

d. Chloroplast

What is the primary pigment responsible for capturing light energy during photosynthesis?

a. Chlorophyll

b. Carotenoids

c. Xanthophylls

d. Anthocyanins

a. Chlorophyll

What is the smallest unit?

a. Atom

b. Element

c. Proton

d. Neutron

e. Electron

e. Electron

It loses 2 electrons and then it is stable due to the 8 on the next shell to the inside.

a. Sodium, with one electron in the outside shell and 8 in the shell just to the inside of that.

b. Carbon has four electrons in the valence shell.

c. Oxygen has 6 electrons in the outermost shell.

d. Carbon has two electrons in the outermost shell and 8 in the shell just to the inside of that.

d. Carbon has two electrons in the outermost shell and 8 in the shell just to the inside of that.

It tends to pick up four electrons by sharing with other atoms to make a total of 8.

a. Sodium, with one electron in the outside shell and 8 in the shell just to the inside of that.

b. Carbon has four electrons in the valence shell.

c. Oxygen has 6 electrons in the outermost shell.

d. Carbon has two electrons in the outermost shell and 8 in the shell just to the inside of that.

b. Carbon has four electrons in the valence shell.

It tends to lose one electron and then its outer shell goes away and it is left with 8 in its new outside shell.

a. Sodium, with one electron in the outside shell and 8 in the shell just to the inside of that.

b. Carbon has four electrons in the valence shell.

c. Oxygen has 6 electrons in the outermost shell.

d. Carbon has two electrons in the outermost shell and 8 in the shell just to the inside of that.

a. Sodium, with one electron in the outside shell and 8 in the shell just to the inside of that.

It picks up 2 electrons by sharing with other atoms.

a. Sodium, with one electron in the outside shell and 8 in the shell just to the inside of that.

b. Carbon has four electrons in the valence shell.

c. Oxygen has 6 electrons in the outermost shell.

d. Carbon has two electrons in the outermost shell and 8 in the shell just to the inside of that.

c. Oxygen has 6 electrons in the outermost shell.

One atom gives away an electron and another accepts it. They are held together by their opposite charges.

a. Hydrogen bond

b. Ionic bond

c. Covalent bond

b. Ionic bond

A strong bond that holds together molecules found in cells, such as glucose, protein, and DNA, in which electrons are shared.

a. Hydrogen bond

b. Ionic Bond

c. Covalent bond

c. Covalent bond

Forms between the negative end of one polar molecule and the positive end of another, such as in water. This kind of bond does not form a new compound.

a. Hydrogen bond

b. Ionic Bond

c. Covalent bond

a. Hydrogen bond

What is the atomic number of an atom that has 6 protons, 6 neutrons, and 6 electrons?

a. 18

b. 12

c. 6

d. 0

e. -1

c. 6

Which of these refers to atoms with the same atomic number but different atomic masses?

a. These atoms are isotopes.

b. These atoms have different numbers of electrons.

c. These atoms are isomers.

d. These atoms have different numbers of protons.

e. These atoms are different elements.

a. These atoms are isotopes.

Fluorine's atomic number is 9 and its atomic mass is 19. How many neutrons does fluorine have?

a. 10

b. 19

c. 9

d. 81

e. 28

a. 10

An uncharged atom of boron has an atomic number of 5 and an atomic mass of 11. How many protons does boron have?

a. 6

b. 11

c. 5

d. 0

e. 16

c. 5

________ is defined as the number of protons plus the number of neutrons.

a. Mass number

b. Ionic number

c. Atomic number

d. Nuclear number

e. Isotopic number

a. Mass number

An atom has 2 electrons, 3 protons, and 3 neutrons. What is the atom's mass number?

a. 5

b. 8

c. 6

d. 3

e. Cannot be determined from the information given

c. 6

All of the following are compounds except ________.

a. oxygen gas

b. methane

c. table salt

d. glucose

e. water

a. oxygen gas

The law of conservation matter states that ________.

a. matter can be created but not destroyed

b. matter is a renewable resource

c. matter is a nonrenewable resource

d. matter cannot be created or destroyed

e. matter can be destroyed but not created

d. matter cannot be created or destroyed

Nitrogen is the most abundant element found in ________.

a. animals

b. plants

c. the air

d. oceans

e. Earth's crust

c. the air

The second law of thermodynamics states that energy ________.

a. becomes more ordered in the absence of counteracting forces

b. is easily created

c. becomes matter

d. does not change

e. becomes less ordered in the absence of counteracting forces

e. becomes less ordered in the absence of counteracting forces

Charged atoms that form molecules are held together by __________.

a. covalent bonds

b. hydrogen bonds

c. ionic bonds

d. neutron bonds

c. ionic bonds

Which of the following sequences is arranged in proper order from smaller units to the largest units?

a. organism, atom, molecule, neutron

b. neutron, atom, organism, molecule

c. proton, element, molecule, organism

d. molecule, atom, neutron, electron

c. proton, element, molecule, organism

In an atom, which of the following components is located in the nucleus?

a. Neutrons

b. Ions

c. Electrons

d. Protons

a. Neutrons

d. Protons

An atom has 2 electrons, 3 protons, and 3 neutrons. What is the atom's charge?

a. +1

b. +3

c. -2

d. +8

e. -1

a. +1

Radioisotopes __________.

a. are atoms with differing numbers of protons

b. emit only radio waves

c. emit radiation as they decay into more stable atoms

d. are charged atom

c. emit radiation as they decay into more stable atoms

Which of the following reactions represents cellular respiration?

a. water + carbon dioxide + energy → sugar + oxygen + water

b. nitrogen + oxygen + sugar → methane + carbon dioxide

c. sugar + carbon dioxide + energy → water + oxygen

d. sugar + oxygen → water + carbon dioxide + energy

e. water + carbon dioxide → sugar + oxygen + water + energy

d. sugar + oxygen → water + carbon dioxide + energy

Many organisms that undergo chemosynthesis use ________ instead of ________ to fuel the processes that convert carbon dioxide into sugars.

a. sunlight; sulfuric acid

b. hydrogen sulfide (H2S); sunlight

c. sunlight; carbohydrates

d. energy; sunlight

e. sunlight; water

b. hydrogen sulfide (H2S); sunlight

River water stored behind a dam is best described as a form of ________.

a. entropy

b. chemical energy

c. kinetic energy

d. potential energy

e. thermodynamics

d. potential energy

During photosynthesis within plants, ________.

a. sugars and carbon dioxide are produced

b. carbon dioxide and oxygen are produced

c. oxygen and carbon dioxide are consumed

d. water and carbon dioxide are consumed

e. the high-quality energy from sugar is converted to heat and light

d. water and carbon dioxide are consumed

When you burn a log in your fireplace, you are converting ________.

a. electromagnetic to chemical

b. thermal to electromagnetic energy

c. proteins to amino acids

d. chemical to thermal energy

e. chemical to nuclear energy

d. chemical to thermal energy

According to the first law of thermodynamics, the total amount of energy in the universe __________.

a. is constantly decreasing

b. is constantly increasing

c. is lost to entropy

d. remains constant

d. remains constant

The process of __________ generates the oxygen that we breathe and the food that we eat.

a. chlorophyllization

b. chemosynthesis

c. respiration

d. photosynthesis

d. photosynthesis

Which of the statements below is the best description of energy?

a. Entropy is another name for energy.

b. Energy is the food we eat.

c. Energy is the ability to do work.

d. Energy can be created and destroyed.

c. Energy is the ability to do work.

In most ecosystems, the original source of energy for the living things in the system is __________.

a. the primary producer

b. glucose

c. the heterotroph

d. the sun

d. the sun

Which of the following is an example of kinetic energy?

a. a rock falling from a cliff

b. the energy held in bonds between atoms

c. a rock at the top of a cliff

d. the energy held in food

a. a rock falling from a cliff

Which of the following statements regarding energy is true?

a. Producers create energy.

b. The total energy in the universe is decreasing.

c. Living systems tend to move toward disorder.

d. Heterotrophs destroy energy when they eat food.

c. Living systems tend to move toward disorder.

The second law of thermodynamics states that __________.

a. the total energy in the universe is increasing with time

b. all of the food energy eaten by an organism can be used by that organism

c. the energy in the universe is constant

d. in any transformation, some of the original energy is converted to heat or light and the system becomes more disordered

d. in any transformation, some of the original energy is converted to heat or light and the system becomes more disordered

Which of the following represent the reactants (ingredients) necessary for cellular respiration?

a. hydrogen sulfide, carbon dioxide, water

b. carbon dioxide, water, and oxygen

c. glucose and oxygen

d. starch, enzymes

c. glucose and oxygen

The energy source for chemosynthesis in the ocean vent community is __________.

a. hydrogen sulfide

b. carbon dioxide

c. water

d. glucose

a. hydrogen sulfide

Which of the following are the reactants (ingredients) needed for photosynthesis to occur?

a. plant seeds, water, and soil

b. glucose, oxygen, and sunlight energy

c. sunlight, plants, and oxygen

d. carbon dioxide, water, and sunlight energy

d. carbon dioxide, water, and sunlight energy

Which of the following statements best describes the role of autotrophic, or self-feeding, organisms in ecosystems?

a. Without heterotrophs, there would be no autotrophs.

b. They produce their own inorganic molecules, which can be broken down for energy.

c. They consume other organisms for energy.

d. They produce their own organic molecules, which can be broken down for energy.

d. They produce their own organic molecules, which can be broken down for energy.

What is the primary purpose of cellular respiration in cells?

a. Energy production

b. Waste elimination

c. DNA replication

d. Protein synthesis

a. Energy production

During cellular respiration, what is the primary source of the carbon atoms that end up as carbon dioxide (CO2)?

a. Oxygen (O2)

b. Glucose (C6H12O6)

c. Water (H2O)

d. Pyruvate

b. Glucose (C6H12O6)

Which type of organisms can perform cellular respiration?

a. Only animals

b. Only plants

c. Both plants and animals

d. None of the above

c. Both plants and animals

Fires release the carbon stored in plants, so measuring the extent and severity of forest fires around the globe is an important ingredient in understanding the carbon cycle.

A. True

B. False

A. True

Which one of these increases the level of carbon dioxide in our atmosphere?

A. Cutting down trees

B. Transportation

C. Energy

D. All of the above

D. All of the above

Why do levels of carbon dioxide in the atmosphere fall during the summer in the Northern Hemisphere?

A. More people live at high latitudes in the Northern Hemisphere and they burn less fossil fuel and wood for heating in the summer.

B. People in the Northern Hemisphere drive more in the summer, thus releasing more carbon dioxide into the air.

C. The Northern Hemisphere is covered by a significant amount of vegetation. During the summer this vegetation takes up more carbon dioxide, and during the winter, when it decays, it releases more carbon dioxide.

C. The Northern Hemisphere is covered by a significant amount of vegetation. During the summer this vegetation takes up more carbon dioxide, and during the winter, when it decays, it releases more carbon dioxide.

Plants use carbon dioxide and water to make their own food through the process of photosynthesis. When they are performing photosynthesis, plants reflect light strongly in which of the following wavelengths?

A. Near-infrared

B. Visible

C. Ultraviolet

D. All of the above

A. Near-infrared

Plants on land have taken in approximately half of the carbon dioxide that humans have put into the atmosphere over the last several decades.

A. True

B. False

B. False

Carbon dioxide (CO2) is:

A. Natural

B. Caused by human activities

C. Both

C. Both

Carbon dioxide is not the only carbon-containing compound in the atmosphere researchers are studying. What else are scientists looking at?

A. Black carbon (soot)

B. Carbon monoxide

C. Methane

D. All of the above

D. All of the above

People have been concerned about the rise in carbon dioxide in our atmosphere, the result of human activity, since what period of time?

A. 18th century

B. 19th century

C. 20th century

D. 21st century

B. 19th century

What role does the ocean play in the carbon cycle?

A. It is a major source of carbon dioxide regionally.

B. It is a major absorber (sink) of carbon dioxide globally.

C. Both a and b

D. Neither a nor b

C. Both a and b

What is the smallest unit that still has all of the elements chemical properties?

(a) Atom

(b) Molecules

(c) Compound

(d) Proteins

(a) Atom