C 4.2 Transfer of energy & matter

Question 1

What is a closed system and open system

Answer 1

Closed system – Energy can enter or leave, but chemical resources stay the same and cannot be added or removed.

Open system – Both energy and chemical resources can enter or leave the system freely.

Question 2

How are Heterotrophs using sunlight

Answer 2

Heterotrophs use the sunlight indirectly as they are feeding on autorophs and are therefore still dependent on it.

Question 3

What happens to enviroments that don’t recive sunlight

Provide a example

Answer 3

Life in those ecosystems is usually adapted to the decreased amount of energy they have available

For example sunlight in a cave- The Mexican blind cavefish:

Since vision is useless in total darkness, these fish have evolved to be blind, conserving energy that would otherwise be used for developing and maintaining eyes.

Question 4

How do organisms survive in caves with little to no sunlight?

Answer 4

Organisms must adapt to darkness and limited food.
Streams bring dead organic matter, providing energy for cave ecosystems.

Question 5

What about gaves with no influx of dead organic matter

Answer 5

Some caves, like Movile Cave (Romania), receive no organic influx.

Chemoautotrophic bacteria generate energy using chemical reactions with sulfides, methane, iron, and magnesium instead of sunlight.

Question 6

how does light affect underwater producers?

Answer 6

Light must pass through water to reach producers.

Transmission is not 100%, meaning less light reaches deeper areas.

Shorter wavelengths (blue light) penetrate deeper, while longer wavelengths (red, orange) are absorbed quickly.

Question 7

How does Light availabity affect aquatic animals

Answer 7

Light availability affects aquatic photosynthesis, limiting producers to shallow depths

Question 8

How does sunlight impact different ecosystems?

give the example of each ecosystem

Answer 8

Sunlight is the primary energy source for most ecosystems.

Producers (cyanobacteria, plants, algae) convert sunlight into energy via photosynthesis.

forests: Most sunlight is absorbed by the canopy, leaving the forest floor shady.

Deserts: High sunlight but few producers, so little energy is captured.

Oceans & Freshwater: Light penetration is limited; shorter wavelengths (blue/violet) reach deeper.

Coastal waters: Often intense, reducing light availability for photosynthesis.

Key Idea: Sunlight availability determines ecosystem productivity and energy flow.

Question 9

In what form does energy enter and flows as in a food chain?

Answer 9

Energy enters as light, flows as nutrients through the food chains and usually leaves as heat.

Question 10

How does chemical energy transfer between organisms in a food chain?

Answer 10

Chemical energy passes to a consumer as it feeds on a Organsim that was in the previsous stage of the food chain

Question 11

Examples of recycled nutrients

Answer 11

include carbon, nitrogen and phosphorus.

Question 12

What is a example of biotic and abiotic factors within an environment

Answer 12

The recycling of nutrients

Nutrients are absorbed from the environment,

used by living organisms

and then returned to the environment.

This process can be conceptualized as a cycle.

Question 13

How does energy transfer through a food chain?

Answer 13

Sunlight provides energy to drive the food chain.

Producers (plants) convert light energy into chemical energy through photosynthesis.

Primary consumers (herbivores) eat producers to obtain energy.

Secondary consumers (carnivores) eat primary consumers for energy.

Tertiary consumers may eat secondary consumers, forming longer food chains.

Decomposers (fungi & bacteria) break down dead organisms and waste, recycling nutrients.

Question 14

Example Food Chain (Monte Desert, South America):

Answer 14

🌿 Tara shrub (Senna arnottiana) → 🦙 Guanaco (Lama guanicoe) → 🐆 Puma (Puma concolor)

Question 15

How to build a food web

Answer 15

Building a Food Web:

Identify species in an ecosystem using techniques like sweep nets and beating sticks to collect invertebrates.

Use tools (e.g., Insect This, iNaturalist) to classify organisms and determine feeding relationships.

Question 16

How do decomposers obtain energy

Answer 16

Decomposers are supplied with energy from carbon compounds in dead organic matter

Question 17

what types of organic matter do decomposers break down?

give examples

Answer 17

Animal waste – Faeces, urine, and other excretions.

Dead plants – Fallen leaves, wood, bark, and decaying roots.

Animal remains – Dead bodies, bones, and tissues.

Shed exoskeletons – Molted shells from insects, reptiles, and crustaceans.

Organic debris – Fruit, seeds, and other plant material.

Question 18

How do decomposers obtain energy and recycle nutrients?

Example

Answer 18

Decomposers (saprotrophs) secrete digestive enzymes onto dead organic matter.

They break down insoluble carbon compounds into simpler, soluble ones.

Examples of organic matter broken down: exoskeletons, fallen leaves, feces, and dead organisms.

Fungi & bacteria absorb digestion products like sugars and amino acids.

This process prevents dead organic matter from accumulating and recycles nutrients into the ecosystem.

Question 19

What are consumers and detrivores?

Answer 19

Both types of heterotrophy

Cosnumers- Ingests organic matter which is living or recently killed

detrivores- They ingest non living organic matter

Question 20

What do all organisms need

Answer 20

All organisms need carbon-containing compounds

Question 21

Examples of the need for variety of carbon compounds

Answer 21

amino acids for the syntheisis of proteins

sugar for energy supply and synthesis of polysaccharides

Fatty acids for energy supply and for constructing membranes

Organic bases for synthesizing nucleic acids during DNA replication and transcription

Steroids and many other groups of carbon compounds

Question 22

How do autotrophs produce their own carbon compounds?

Answer 22

Autotrophs synthesize their own carbon compounds using carbon dioxide (CO₂) or hydrogen carbonate (HCO₃⁻).

They also require nitrate, phosphate, and other inorganic substances for essential nutrients.

Energy for this process comes from external sources:

Light energy (used by photoautotrophs, e.g., plants, algae).

Chemical reactions (used by chemoautotrophs, e.g., some bacteria).
Autotrophs support ecosystems by providing energy and organic compounds for consumers.

✅ Key Idea: Autotrophs are the foundation of food chains, converting inorganic molecules into organic matter using light or chemical energy.

Question 23

Why do autotrophs need energy, and how do they obtain it?

Answer 23

Autotrophs synthesize carbon compounds using simple inorganic substances.

They require energy for carbon fixation (converting CO₂ into organic molecules).

Energy is also needed for anabolic reactions that build macromolecules like proteins, lipids, and carbohydrates.

Question 24

What are the two types of autotrophs based on their energy source?

Answer 24

Photoautotrophs use light energy for photosynthesis (e.g., plants, algae, cyanobacteria).

Chemoautotrophs obtain energy from oxidizing inorganic substances (e.g., sulfur, hydrogen sulfide, iron, ammonia).

Both use this energy to synthesize carbon compounds from CO₂ or HCO₃⁻.

Question 25

How do chemoautotrophs obtain energy, and why are oxidation reactions important?

Answer 25

Chemoautotrophs use oxidation reactions to release energy. They oxidize reduced inorganic substances like sulfur, hydrogen sulfide, iron, ammonia, and hydrogen. This energy is used to synthesize carbon compounds (e.g., glucose, amino acids). Example: Iron-oxidizing bacteria extract energy from iron compounds.

Question 26

What are heterotrophs, and how do they obtain carbon compounds?

Answer 26

Heterotrophs obtain carbon compounds by consuming other organisms. They cannot synthesize organic molecules from inorganic substances like autotrophs. Examples: Animals, fungi, and most bacteria. They depend on producers or other consumers for carbon-based nutrients.

Question 27

How do heterotrophs break down and use carbon compounds? How can it occur explain assimilation

Answer 27

Digestion breaks down complex molecules like proteins and nucleic acids. Can occur internally (e.g., animals) or externally (e.g., fungi, decomposers). assimilation: After digestion, nutrients like amino acids, monosaccharides, and fatty acids are absorbed and used to build new macromolecules.

Question 28

What are the two main types of heterotrophs, and how do they differ? (how they digest) (what do they consume) (what they produce as a result)

Answer 28

Consumers (e.g., animals): Digest food internally using a digestive system. Consume living or recently dead organic matter. Products of digestion: Amino acids, sugars, fatty acids. Saprotrophs (e.g., fungi, bacteria): Digest food externally by secreting enzymes onto dead material. Absorb the broken-down nutrients. Consume dead and decaying matter. Products of digestion: Amino acids, sugars, fatty acids (similar to consumers).

Question 29

How do autotrophs and heterotrophs release energy? and explain cellular respirartion

Answer 29

through cell respiration Cell respiration releases energy by breaking down carbon compounds, supplying ATP to all living organisms.

Question 30

What cellular activities require ATP?

Answer 30

Macromolecule Synthesis – Builds DNA, RNA, proteins, and other large molecules. Active Transport – Pumps molecules or ions across cell membranes. Movement of Cell Structures – Moves chromosomes, vesicles, and muscle fibers. Temperature Regulation – Maintains body heat in birds and mammals.

Question 31

What waste products are released in cell respiration?

Answer 31

Carbon dioxide (CO₂) – Produced when breaking down carbohydrates & fats. Water (H₂O) – Formed as a byproduct of respiration. Heat – Released energy that cannot be reused and dissipates into the environment.

Question 32

How is ATP produced in cell respiration, and why is it necessary?

Answer 32

All cells produce ATP through cell respiration. Carbohydrates and lipids are oxidized, releasing energy. This energy is used in endothermic reactions to form ATP. ATP stores chemical energy in a usable form for the cell.

Question 33

Why is energy transfer in cell respiration not 100% efficient?

Answer 33

Some energy from respiration is always lost as heat, making energy transfer inefficient.

Question 34

Why can some organisms belong to multiple trophic levels in different food chains?

Answer 34

Many organisms have varied diets and may belong to multiple trophic levels in different food chains.

Question 35

What does an energy pyramid represent?

Answer 35

Energy pyramids illustrate the decreasing energy transfer across trophic levels.

Question 36

What are the steps to build an energy pyramid?

Answer 36

Use Energy Values – Each trophic level's energy (in kJ/m²/year) should be calculated. Start with Producers – Place primary producers (e.g., plants) at the base of the pyramid. Stack Consumers – Arrange primary, secondary, and tertiary consumers above in decreasing order. Draw to Scale – Bar lengths should be proportional to the energy values. Label the Pyramid – Include units (kJ/m²/year) and trophic level names.

Question 37

Why does energy decrease at higher trophic levels? Reasons for Energy Loss:

Answer 37

Respiration & Heat Loss – Organisms use energy for metabolism. Movement & Activity – Energy is used for movement and biological processes. Waste – Not all food is digested or absorbed. Inefficiency of Energy Transfer – Only about 10% of energy is passed to the next level.

Question 38

Why is there less energy available at each successive trophic level?

Answer 38

Cell Respiration – Energy is lost as heat during metabolism.

Question 39

What are ways that the energy is not transferred to the next trophic level?

Answer 39

Not ingested – Some organisms or parts are not eaten. Not digested – Some materials cannot be broken down (e.g., fiber). Excreted – Unused energy leaves as waste (e.g., feces). Respired – Used in metabolism, lost as heat.

Question 40

Why are decomposers important in energy transformations?

Answer 40

Break down dead organisms, feces, and organic matter. Release nutrients back into the ecosystem. Convert trapped energy in waste into usable forms for other organisms.

Question 41

What is incomplete consumption, and how does it affect energy transfer in food chains? example

Answer 41

Not all parts of an organism are eaten by the next trophic level. example: Predators do not consume bones or hair, and locusts may eat only parts of plants. The energy in uneaten parts is lost from the food chain. Instead, it passes to decomposers and detritivores like fungi and earthworms.

Question 42

What is incomplete digestion, and how does it cause energy loss in a food chain? example/process

Answer 42

Not all ingested food is fully digested and absorbed by organisms. Example: Some animals cannot digest tough plant fibers like cellulose. Undigested material is egested as faeces. The energy in faeces does not pass along the food chain. Instead, it is used by saprotrophs and detritivores (e.g., fungi, earthworms).

Question 43

How does cell respiration contribute to energy loss in food chains?

Answer 43

Carbohydrates, proteins, and other organic molecules are oxidized in cell respiration to release energy. The products of respiration, carbon dioxide and water, cannot pass energy to the next trophic level. Only carbon compounds that are not oxidized in respiration can be transferred to the next trophic level. Less energy is available at each successive trophic level.

Question 44

How is heat lost to the environment?

Answer 44

due to conversion of chemical energy to heat in cell respiration. Heat energy is unusable to organisms and is lost from ecosystems Heat resulting from cell respiration makes living things warmer. This heat passes from hotter to cooler bodies and is eventually lost to the abiotic environment

Question 45

What happens to energy as it flows through the food chain?

Answer 45

Energy can be converted from one form to another. Energy enters ecosystems in the form of sunlight. It is transformed into chemical energy by photosynthesis. Chemical energy flows along food chains and to decomposers. Ultimately all of this energy is transformed into heat.

Question 46

The second law of thermodynamics states

Answer 46

that energy transformations are never 100% efficient.

Question 47

Why is heat lost to the environment in both autotrophs and heterotrophs during cell respiration?

Answer 47

Energy transfers are not 100% efficient. Some energy is lost as heat when ATP is produced in cell respiration. Additional heat is generated when ATP is used in cellular processes. Heat energy cannot be converted back into usable forms and is eventually lost to the environment. Birds and mammals may generate extra heat to maintain a constant body temperature.

Question 48

The number of trophic levels is limited by

Answer 48

how much energy enters the ecosystem. If the energy is low at the start of the food chain, then energy will be quickly lost making the chain very short. Abundant energy at the start can sustain multiple trophic levels

Question 49

Why is not all energy stored in autotrophs consumed by herbivorous heterotrophs?

Answer 49

Some plant material is not consumed by herbivores. Energy in dead organic matter is lost as heat after decomposition. Only chemical energy in carbohydrates and carbon compounds that are not used in cell respiration is available to the next trophic level.

Question 50

Why are organisms in a trophic level not entirely consumed by the next trophic level?

Answer 50

Herbivores do not eat all parts of plants (e.g., some plants are partially consumed). Predators do not consume certain materials like bones, hair, or other indigestible parts. Energy in uneaten material is passed to saprotrophs or detritivores instead of the next trophic level.

Question 51

What happens to energy in undigested and egested food?

Answer 51

Some parts of food are indigestible (e.g., cellulose in plants). These indigestible parts are egested as feces. Energy in feces does not pass through the food chain but instead goes to saprotrophs or detritivores.

Question 52

what is Biomass

Answer 52

Biomass is the total mass of a group of organisms within one trophic level. It consists of the cells and tissues of those organisms, including the carbohydrates and other carbon compounds that they contain.

Question 53

Why do apex predators like orcas and bluefin tuna consume food from lower trophic levels?

Answer 53

here is not enough energy available after passing through four or five trophic levels. Most energy flows through only two or three levels before reaching apex predators.

Question 54

How does sunlight affect biomass in ecosystems?

Answer 54

Greater sunlight increases plant biomass, leading to more energy at the base of the food chain. More biomass supports a greater number of organisms at higher trophic levels.

Question 55

What are some ways biomass is lost in a food chain?

Answer 55

Carbon dioxide is lost during cellular respiration water is lost via transpiration and evaporation waste products such as urea are excreted.

Question 56

Why does biomass decrease at each successive trophic level, but the energy content per unit mass remains unchanged?

Answer 56

At each successive trophic level, the total biomass decreases because not all consumed material is converted into body mass—some is lost through respiration, waste (feces), and other metabolic processes. However, the energy content per unit of biomass remains the same because the chemical energy stored in carbon compounds (such as carbohydrates, proteins, and lipids) remains constant per gram of tissue.

Question 57

What is Primary productivity: the 2 types

Answer 57

Gross primary productivity (GPP) Net primary productivity

Question 58

What is Gross primary productivity

Answer 58

is the total biomass of carbon compounds made in plants by photosynthesis

Question 59

What is Net primary productivity

Answer 59

is GPP minus the biomass lost due to respiration of the plant and which is available to consumers. NPP=GPP−Respiration Loss (R)

Question 60

What is Secondary productivity

Answer 60

is the accumulation of carbon compounds in biomass by animals and other heterotrophs through ingestion of sugars and amino acids from food followed by being built up into macromolecules (assimilation) Organic matter being built up by consumers

Question 61

What is Primary productivity

Answer 61

the accumulation of carbon compounds in biomass by autotrophs; accumulation of biomass occurs when autotrophs grow and reproduce. Organic matter being built up by Producers

Question 62

How is primary production measured?

Answer 62

Primary production is measured in mass (of carbon) per unit area per unit time, typically in g m⁻² yr⁻¹.

Question 63

What factors influence Net Primary Productivity

Answer 63

Sunlight availability (amount of solar radiation) Rainfall (precipitation levels) Temperature (higher temperatures increase enzyme activity in photosynthesis) Soil nutrients (nutrient availability affects plant growth)

Question 64

Why is there less biomass on the secondary production?

Answer 64

Because carbon compounds are used in cellular respiration where they are converted into CO2 and water therefore secondary production is lower than primary production

Question 65

What consequence does that have on the secondary production when compared to primary production?

Answer 65

Differences in production are reflected in farm yields. Production of crops per unit area is always much higher than production of meat and other animal products.

Question 66

What are Carbon sinks with examples

Answer 66

are natural systems that absorb and store carbon dioxide (CO₂) from the atmosphere. CO2 from plant respiration CO2 from aquatic plant respiration

Question 67

What are Carbon sources with examples

Answer 67

systems or processes that release carbon dioxide (CO₂) into the atmosphere, CO2 from the atmosphere moves into autotrophs for photosynthesis CO2 from the atmosphere or water moves into autotrophs for photosynthesis

Question 68

What are the main processes that recycle carbon in ecosystems?

Answer 68

photosynthesis, feeding, respiration, decomposition, and combustion.

Question 69

How does photosynthesis contribute to the carbon cycle?

Answer 69

ants and algae absorb carbon dioxide (CO₂) from the atmosphere and use it to produce glucose through photosynthesis, storing carbon in their biomass.

Question 70

How do animals obtain carbon?

Answer 70

Animals consume plants and other organisms, absorbing carbon in the form of carbohydrates, proteins, and fats. This carbon becomes part of their biomass.

Question 71

How is carbon returned to the atmosphere?

Answer 71

Cellular respiration in plants, animals, and decomposers breaks down glucose, releasing CO₂ back into the atmosphere.

Question 72

How do decomposers contribute to the carbon cycle?

Answer 72

acteria and fungi break down dead waste, releasing carbon dioxide into the atmosphere through respiration.

Question 73

How does human activity impact the carbon cycle?

Answer 73

Burning fossil fuels and biomass releases large amounts of CO₂ into the atmosphere, increasing carbon levels and contributing to climate change.

Question 74

Carbon cycle restricted to Photosynthesis, Feeding and Respiration

Answer 74

☀️ Sunlight  ⬇️ (used by plants) 🌿 Plants (Autotrophs) perform Photosynthesis  🌱 Take in CO₂ from the atmosphere  🌱 Convert CO₂ into glucose (C₆H₁₂O₆)  🌱 Release O₂ (oxygen) into the atmosphere  ⬇️ (Energy stored in plants) 🐄 Animals (Heterotrophs) eat plants (Feeding)  🍃 Ingest glucose and other organic molecules  ⬇️ (Use glucose for energy) 🐄 Animals & Plants perform Cellular Respiration  💨 Release CO₂ back into the atmosphere  🔥 Break down glucose for ATP energy  💨 Exhale CO₂, which is used by plants again 🔁 Cycle repeats!

Question 75

How to know if the ecosystem is acting as a carbon sink or source

Answer 75

If photosynthesis exceeds respiration, there is net uptake. The ecosystem is acting as a carbon sink. If respiration exceeds photosynthesis, there is net release. The ecosystem is acting as a carbon source.

Question 76

What causes the release of carbon dioxide into the atmosphere during combustion?

Answer 76

The combustion of biomass, peat, coal, oil, and natural gas releases carbon dioxide (CO₂) into the atmosphere.

Question 77

What are the natural and human causes of carbon dioxide release through combustion, and what is its impact on the environment?

Answer 77

Natural causes: Lightning strikes can ignite wildfires, leading to natural combustion. Human activities: Burning fossil fuels and biomass greatly increases CO₂ emissions. Impact: These carbon sinks formed at different times in Earth's history, but their combustion today contributes significantly to climate change.