Transfers of energy and matter Details

Question 1

Types of systems(in ecology)

Answer 1

-Open systems
-Closed systems

Question 2

The principal source of energy in most ecosystems is sunlight(T/F)

Answer 2

True

Question 3

How does energy pass to ecosystems where little or no light penetrates?

Answer 3

-Some energy may pass to these ecosystems in dead organic matter transferred from other ecosystems, which can be digested by saprotrophs
-Inorganic chemical reactions(chemosynthesis) is also used by chemoautotrophs as a source of energy

Question 4

Producers use an external energy source to make all the carbon compounds that they require from simple inorganic substances like carbon dioxide(T/F)

Answer 4

True

Question 5

In food webs, arrows indicate the direction of transfer of energy and biomass(T/F)

Answer 5

True

Question 6

Processes by which dead organic matter can be generated

Answer 6

-Death of whole organisms
-Defecation
-Shedding of leaves, skin cells, haris, arthropod exoskeletons(i.e. moulting) and other unwanted body parts

Question 7

Dead organic matter contains chemical energy in carbon compounds(T/F)

Answer 7

True

Question 8

Some dead organic matter is eaten by animals such as vultures and earthworms, but large amounts are digested by saprotrophs(T/F)

Answer 8

True

Question 9

How do saprotrophs digest dead organic matter?

Answer 9

-Saprotrophs secrete digestive enzymes into the dead organic matter and digest it externally
-They then absorb the products of digestion

Question 10

Main groups of saprotrophs

Answer 10

-Bacteria
-Fungi

Question 11

Why are saprotrophs known as decomposers?

Answer 11

They break down insoluble macromolecules in dead organic matter into small, soluble molecules and ions(and in doing so, cause the gradual breakdown of solid structures)

Question 12

Importance of decomposers

Answer 12

-Without extracellular digestion carried out by decomposers, dead organic matter would build up year by year
-Ions such as ammonium(NH₄⁺) would not be released into the environment, so other organisms that absorb them would lose their supply.

Question 13

Decomposers are the waste disposers and recyclers of ecosystems(T/F)

Answer 13

True

Question 14

Purpose of amino acids

Answer 14

-Protein synthesis
-Photosynthesis(for producers)

Question 15

Purpose of sugars

Answer 15

Energy supply
Synthesis of polysaccharides

Question 16

Purpose of fatty acids

Answer 16

-Energy supply
-Construction of membranes

Question 17

Purpose of organic bases

Answer 17

Synthesis of nucleic acids during DNA replication and transcription

Question 18

Autotrophs make all the carbon compounds they need themselves, using carbon dioxide(CO₂) or hydrogen carbonate(HCO₃⁻) as a carbon source(T/F)

Answer 18

True

Question 19

A reduction reaction inside autotrophic cells converts the simple inorganic carbon sources into an initial carbon compound(i.e. carbon fixation).
The initial carbon compound produced by carbon fixation is then built up into a wide variety of other carbon compounds by anabolic reactions.(T/F)

Answer 19

True

Question 20

Carbon fixation and anabolic reactions require an external energy source(T/F)

Answer 20

True

Question 21

Possible sources of external energy(for carbon fixation)

Answer 21

-Light
-Inorganic chemical reactions

Question 22

Types of autotrophs

Answer 22

-Photoautotrophs
-Chemoautotrophs

Question 23

How chemoautotrophs synthesize carbon compounds

Answer 23

-A substrate in a reduced state(e.g. sulfur, hydrogen, hydrogen sulfide, ammonia, etc.) is absorbed and then oxidized.
-Oxidation reactions release energy
-Chemoautotrophs use the energy from the oxidation reaction to synthesize carbon compounds

Question 24

Examples of chemoautotrophs

Answer 24

Some bacteria and archaea species

Question 25

How heterotrophs synthesize carbon compounds

Answer 25

They digest carbon compounds that were part of another organism and then use the products of digestion to build the large complex carbon compounds they need (E.g. Guanacos digest proteins in the leaves of tara bushes, breaking them down to amino acids. They then use these amino acids to synthesize the proteins that they need)

Question 26

Why must large compounds(e.g. proteins, polysaccharides, nucleic acids) be broken down before they are absorbed?

Answer 26

Assimilation requires absorption of carbon compounds into cells, so the molecules must be small and soluble enough to pass across cell membranes

Question 27

Subdivisions of heterotrophs

Answer 27

-Saprotrophs -Consumers

Question 28

How do unicellular organisms ingest food?

Answer 28

-They take the food into their cells by endocytosis, and then digest it inside phagocytic vacuoles -They absorb products of digestion from the vacuoles into their cytoplasm

Question 29

Uses of energy(in the form of ATP) in organisms

Answer 29

-Anabolic reactions to synthesize molecules(e.g. triglycerides, nucleic acids) -Active transport to generate concentration gradients -Movement(both of structures in cells and of whole organisms) -Maintaining constant body temperature(for mammals and birds)

Question 30

Carbon compounds such as carbohydrates and lipids are oxiized to release energy and this energy is used to phosphorylate ADP, producing ATP(T/F)

Answer 30

True

Question 31

In both autotrophs and heterotrophs, ATP is produced by cell respiration(T/F)

Answer 31

True

Question 32

Pyramids of energy show the amount of energy gained per year by each trophic level in an ecosystem(T/F)

Answer 32

True

Question 33

Unit for energy in pyramids of energy

Answer 33

kJ m⁻² yr⁻¹(or kilojoules per square meter per year)

Question 34

Decomposers are NOT part of food chains(T/F)

Answer 34

True

Question 35

Main forms of energy loss from food chains

Answer 35

-Incomplete consumption(some organisms are never consumed and eventually die; the energy in dead organisms passes to saprotrophs which are not part of the food chain) -Incomplete digestion(not all substances, like cellulose or boes, are digested; indigestible material is egested in faeces and the energy passes to saprotrophs) -Cell respiration(carbon compounds that have been oxidized in respiration cannot pass to the next trophic level and the energy that they contained is lost from the food chain)

Question 36

A smaller amount of energy flows to each successive trophic level because there are smaller amounts of energy-containing subtances like carbohydrates and proteins(T/F)

Answer 36

True

Question 37

How autotrophs and heterotrophs generate heat

Answer 37

-When energy is released by oxidizing substrates in cell respiration, some of the energy is converted to heat -When the ATP is used within cells, more of the energy is converted to heat

Question 38

Why can energy not be recycled?

Answer 38

Ultimately, all of the energy that enters food chains is transferred into heat and lost to the abiotic environment

Question 39

Matter can be recycled, but energy CANNOT be(T/F)

Answer 39

True

Question 40

Why are food chains limited in length?

Answer 40

So much energy is lost between each trophic level and the next; after only a few stages,not enough remains to support another trophic level.

Question 41

Why do animals in higher trophic levels no thave to eat more food to gain enough energy(even though energy decreases with each trophic level)?

Answer 41

Their prey contains large amounts of energy per unit mass(there is just not much prey available sometimes)

Question 42

Both autotrophs and heterotrophs produce biomass by growth and respiration(T/F)

Answer 42

True

Question 43

What mainly determines a biome's capacity to accumulate biomass?

Answer 43

The rate of photosynthesis

Question 44

Unit of measurement for primary/secondary production

Answer 44

gC m⁻² yr⁻¹(or grams of carbon accumulated per square metre of ecosystem per year)

Question 45

Heterotrophs obtain carbon compounds from organisms in a lower trophic level and use them in metabolic processes, resulting in an increase in biomass(T/F)

Answer 45

True

Question 46

Why is net production always lower than gross production?

Answer 46

Cell respiration results in a loss of carbon compounds and therefore biomass in every trophic level

Question 47

Why is primary production always lower than secondary production?

Answer 47

Cell respiration results in a loss of carbon compounds and therefore biomass in the producers

Question 48

Main types of carbon fluxes(due to living organisms)

Answer 48

-Photosynthesis -Feeding -Respiration

Question 49

The carbon cycle

Answer 49

Question 50

Why are ecosystems open systems?

Answer 50

Both matter and energy can enter or exit

Question 51

Examples of carbon sinks

Answer 51

-Growing forests -Waterlogged habitats(e.g. swamps) where anaerobic conditions prevent decomposition of dead organic matter by saprotrophs, so peat containing carbon accumulates

Question 52

Examples of carbon sources

Answer 52

-Volcanoes -Forest fires -Animal respiration

Question 53

What does the Keeling Curve show

Answer 53

It shows a graph of the atmospheric carbon dioxide concentrations that have been measured at Mauna Loa Observatory in Hawaii since 1959

Question 54

Trends shown by the Keeling Curve

Answer 54

-CO₂ concentration increases between October and May and then falls from May to October -The graph of carbon dioxide concentrations for one year shows that the increase is not completely reversed by the decrease, so the concentration at the end of the year is higher

Question 55

Why does the CO₂ concentration increase between October and May and then fall from May to October(in the Keeling Curve)?

Answer 55

There is relatively more photosynthesis during summer in the northern hemisphere(when most plants are in their growth season), and relatively more respiration during norhtern hemisphere winter

Question 56

Why is there a net increase in CO₂ concentration at the end of each year(in the Keeling Curve)?

Answer 56

Anthropogenic factors(e.g. burning of fossil fuels, deforestation)

Question 57

How are autotrophs and heterotrophs dependent on each other for supplies of oxygen and carbon dioxide?

Answer 57

-Autotrophs split water molecules during photosynthesis and release energy from them into the atmosphere -Heterotrophs absorb oxygen produced in photosynthesis and use it to oxidize carbon compounds, producing carbon dioxide and releasing it into the atmosphere -Autotrophs absorb the carbon dioxide and use it in photosynthesis

Question 58

Autotrophs obtain all the elements they need as inorganic nutrients from the abiotic environment(T/F)

Answer 58

True

Question 59

Heterotrophs obtain the elements they need as part of the carbon compounds in their food, **but** they do also obtain other elements as inorganic nutrients from the abiotic environment(e.g. sodium, potassium, calcium, etc.)(T/F)

Answer 59

True

Question 60

How come no element has ran out, despite the quantities of each element being finite on Earth?

Answer 60

-Elements can be endlessly recycled -They are absorbed from the abiotic environment as inorgaic ions or molecules, used within living organisms and then returned to the abiotic environment with the atomic structure unchanged -In many cases, an element is passed down from organism to organism before it is released back into the abiotic environment

Question 61

Why are decomposers important for recycling chemical elements?

Answer 61

They break down the carbon compounds containing the chemical elements; for example, they release nitrogen from proteins in the form of ammonia

Question 62

The details of recycling vary from element to element(e.g. the carbon cycle is different from the nitrogen cycle)(T/F)

Answer 62

True

Question 63

Features of pyramids of energy

Answer 63

-Shows how muc energy is retained in each trophic level -Always decreases in size as the trophic level gets higher -Measured in kilojoules per metre squared per year(kJ m⁻² yr⁻¹)

Question 64

Features of pyramids of biomass

Answer 64

-Shows the total biomass at each trophic level -Doesn't always decrease in size as the trophic levels get higher -Measured in kilograms per metre squared(kg/m²)