Ecological Energetics and Trophic Levels

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Questions and Answers

What is the definition of biomass?

The mass of inedible organic materials in an ecosystem.

The energy used to create new heterotrophic biomass.

The energy lost during the transfer from one trophic level to the next.

The total mass of all organisms in an ecosystem at a specific time. (correct)

What percentage of energy is typically transferred from one trophic level to the next?

10% (correct)

30%

50%

90%

Which factor contributes to the low energy transfer from sunlight to producers?

Use of light for photosynthesis.

Chlorophyll absorption efficiency.

High wavelengths absorbed.

Evaporation of water. (correct)

Which of these is a way that energy is transferred from primary consumers to decomposers?

Excretion. Signup and view all the answers

What impact does the inedibility of certain plant parts have on energy transfer?

Limits energy access for primary consumers. Signup and view all the answers

How is the efficiency of photosynthesis calculated?

GPP divided by total energy striking the plant multiplied by 100. Signup and view all the answers

Why is the energy efficiency between secondary and tertiary consumers greater compared to producers and primary consumers?

More energy is converted into biomass in higher trophic levels. Signup and view all the answers

Which statement best describes secondary production?

Energy used to create new animal biomass. Signup and view all the answers

What is the primary role of electron carriers in the thylakoid membrane?

To pump hydrogen ions into the thylakoid space Signup and view all the answers

What happens to RuBP levels when carbon dioxide levels decrease?

RuBP levels initially rise, then remain constant Signup and view all the answers

What is GALP primarily used for after its production?

Regeneration of RuBP and glucose synthesis Signup and view all the answers

What percentage of radiant energy is captured by green plants?

1-5% Signup and view all the answers

How does energy loss occur between trophic levels?

Due to inedible body parts and energy loss to decomposers Signup and view all the answers

What is the relationship between gross primary productivity (GPP) and net primary productivity (NPP)?

NPP = GPP - plant respiration Signup and view all the answers

What factor causes GALP levels to not accumulate in chloroplasts during photosynthesis?

GALP is continuously utilized for regeneration of RuBP and glucose synthesis Signup and view all the answers

What occurs to GP levels when carbon dioxide availability decreases?

GP levels drop and then stabilize at a lower level Signup and view all the answers

What is a plagioclimax?

A climax community that is artificially stopped by human interference. Signup and view all the answers

Which statement best describes secondary succession?

It starts in soil that already contains seeds and organic matter. Signup and view all the answers

Which of the following is NOT a typical trend observed during biological succession?

Decrease in species diversity. Signup and view all the answers

How does a regularly mown grassy field affect ecological succession?

It halts the progression of succession to climax communities. Signup and view all the answers

What effect do trees have on the habitat for small birds as succession progresses?

They create additional nesting sites and cover. Signup and view all the answers

What happens to oxygen availability in water when temperatures rise or water flow decreases?

Oxygen availability drops. Signup and view all the answers

How does soil pH influence microbial activity?

Low altitude soils have higher pH levels and support many microbes. Signup and view all the answers

Why does species diversity tend to increase in mixed woodlands?

They offer a variety of food sources and niches. Signup and view all the answers

What impact does pH alteration have on enzyme function?

It may change the shape of the active site and inhibit metabolism. Signup and view all the answers

What typically happens to the population density of birds when shrubs are replaced by pine trees?

It drops initially but increases again in mixed woodlands. Signup and view all the answers

What is the main reason for faster secondary succession compared to primary succession?

Soil is already present with organic material. Signup and view all the answers

What effect does altitude have on environmental conditions?

Wind speed and rainfall generally increase with altitude. Signup and view all the answers

Which statement correctly defines intraspecific competition?

Competition between members of the same species for shared resources. Signup and view all the answers

What is the primary role of decomposers in the ecosystem?

They help break down litter into organic matter. Signup and view all the answers

What characteristic of steep slopes affects water retention?

Water drains more readily from steep slopes. Signup and view all the answers

Which of the following describes a factor affecting the survival of organisms in soil?

Increased waterlogged conditions significantly reduce oxygen availability. Signup and view all the answers

What effect does temperature increase have on plant species survival?

Some species may die if temperatures exceed their optimum range. Signup and view all the answers

How does increased carbon dioxide impact plant growth?

It enhances photosynthesis and overall plant growth. Signup and view all the answers

What is a likely consequence of changes in plant distribution due to global warming?

Loss of habitat may decrease animal species numbers. Signup and view all the answers

How do changes in rainfall patterns due to global warming affect organisms?

Some species may perish if they cannot adapt to new rainfall conditions. Signup and view all the answers

What happens to animal metabolic reactions when temperatures are below the optimum?

Metabolic reactions slow down, leading to reduced growth. Signup and view all the answers

Which of the following is a possible impact of global warming on herbivores?

Reduction in numbers due to decreased food supply. Signup and view all the answers

If global temperatures keep increasing, what is a possible effect on enzyme activity?

Enzyme activity may decline if temperatures rise too high. Signup and view all the answers

What is a potential outcome for species unable to adapt to increased desertification from global warming?

Possible extinction or forced migration to suitable areas. Signup and view all the answers

Study Notes

Energy Flow Through an Ecosystem

Energy flow through an ecosystem is called ecological energetics
Green plants capture 1-5% of radiant energy from the sun
Energy ultimately comes from the sun
Captured energy is converted to chemical energy and flows through the ecosystem

Trophic Levels

Level at which an organism feeds in a food chain
Energy is lost between trophic levels due to inedible body parts and decomposers
Not enough energy to sustain many trophic levels
GPP decreases as energy is lost

Biomass

Biological material from living or recently living organisms
Mass of living biological organisms in a given area or ecosystem at a given time (Kg/hectare)

Secondary Production

Formation of heterotrophic biomass through time
Energy used to make new animal biomass

Measurement of Biomass

Measurement of biomass in a grassland over a year is more useful than on a particular day
NPP varies over short periods of time
Whole year gives an average value of NPP
Biomass includes all inedible organic materials

Transfer of Energy

Energy is lost as it passes from one trophic level to the next
Only 10% is stored to make new biomass
10% is transferred to the next trophic level
Plants respire using products of photosynthesis
𝑁𝑃𝑃 = 𝐺𝑃𝑃 − 𝑟𝑒𝑠𝑝𝑖𝑟𝑎𝑡𝑖𝑜𝑛 𝑏𝑦 𝑝𝑙𝑎𝑛𝑡𝑠
Not all plant material is edible
90% of energy is lost during transfer

The Fate of Light Energy

Light is reflected back into space
Light energy reflected from leaves
Light energy is used in evaporating water
Light energy is missing chloroplast/passing through the leaf
Incorrect wavelength of light

Percentage Efficiency of Photosynthesis

Percentage eﬃciency of photosynthesis is calculated by dividing GPP by the total amount of energy striking the plant multiplied by 100

Why energy efficiency between secondary and tertiary consumers is greater than that between producers and primary consumers

In plants some parts are inedible
Animals cannot digest cellulose or lignin
More plant material goes to decomposers than consumers
Plant material is less energy-rich

Ways in which energy is transferred from primary consumers to decomposers

Death/dead remains, excretion, egestion, moulting of fur

Oxygen Availability

When water is cold or fast flowing there is enough dissolved oxygen
Organisms that need oxygen for survival can exist
As temperature of water rises, or water becomes still the oxygen content drops
Mostly anaerobic organisms survive in low oxygen environments
In terrestrial habitats, spaces between soil particles contain air, and there is plenty of oxygen for plant roots
In waterlogged soil, air spaces are filled with water and oxygen availability is very low
Plants with special adaptations (aerial roots) to obtain oxygen can survive

Edaphic Factors

Factors related to the structure of the soil
Soil structure and mineral content affect the survival of various populations
Soil pH

Soil pH

Measure of hydrogen ion concentration in aqueous solution
Indicates the level of acidity or alkalinity
Low altitudes have high pH (4.5-8) and support many microbes
Microbes help to break down litter into humus
Higher altitude have low pH (3-6.5)
Fewer microbes survive and fungi help to form humus

pH and Growth of Organisms

pH affects enzymes and enzymes affect metabolism
Due to change in pH the shape of the active site is altered by the ionisation of the R groups
This affects metabolism as substrates cannot fit into the active site

Topographic Factors

Aspect (slope):- angle of the sun on a south facing slope is greater; receive more sunlight and are warmer
Inclination (steepness):- water drains more readily from steep slopes
Altitude (height):- at higher altitude the temperature is lower, the wind speed is greater and there is more rainfall

Biotic Factors

Involve all those factors that are living
Competitors
Predators
Decomposers
Population Density
Disease

Competition

Organisms compete with each other for various available resources
Animals compete for food, water, shelter, mate and nesting sites
Two types of competition- interspecific competition and intraspecific competition

Intraspecific Competition

Competition between members of the same species within the same niche for a limited source
If the territory is small or relatively little food available intraspecific competition occurs

Succession

A directional change in the species structure of an ecological community over time.
Succession starts with a pioneer community in an environment
Occurs when organisms modify the environment and make conditions more favorable for other species
Eventually, the environment and community reach a stable climax community
May be primary or secondary

Primary Succession

Occurs in an environment with no previous life
Starts with bare rock or sand
Pioneer species such as lichens and mosses colonize
Gradually, soil develops and other organisms can live there
Climax community is reached when the environment is stable

Secondary Succession

Occurs in an environment where previous life has been cleared
Starts with soil already present
Occurs faster than primary succession
Pioneer species are often fast-growing plants
Climax community is reached when the environment is stable
Some organisms may remain from the previous community

Trends of Succession

Kind of plants and animals change continuously
Increasing biomass and decomposing plant and animal material.
Species diversity increases.
A progressive reduction in net community production.
Increase in community respiration.

Mixed Woodland and Biodiversity

Diﬀerent food items are available.
Provide many niches.
Provide many nesting places and shelter.
Species diversity increases.

Secondary Succession (Continued)

This type of succession happens on land that has been cleared of all the plants, but where the soil remains, e.g., after a forest ﬁre or where a forest has been cut down by humans
The sequence of events is similar to that seen in primary succession
The numbers of plants and animals present right from the beginning of this succession is much higher because the soil is already formed and contains seeds, roots, and small organisms.

Which type of succession would occur faster?

Secondary succession occurs faster because the soil is already present.
Seeds or roots of earlier plants might be still existing in the soil.
They can grow quickly into new plants when enough water and sunlight is available.

Describe the eﬀect of change in the plant community on the number of species of small birds. GIVE REASONS

Increased number of species as succession progresses / number of species increases from grassland to woodland
Grassland is open habitat, but trees provide more cover
Birds easily spotted by predators in grass / converse for trees and shrubs
Trees provide roosting / nesting sites
Mixed woodland provides greater variety of food to support more species.
Trees provide more niches for species

Global Warming

Due to global warming, earth’s mean surface temperature is increasing
Loss of existing species in places where the temperature is not ideal for them to survive
Changes in distribution of plant species.
Changes in rainfall patterns and growing seasons
Temperature may become too hot for some species and this may affect enzyme activity.
Increased carbon dioxide results in more photosynthesis / GPP/ NPP / biomass

Effects of Global Warming on Plant Species Affect Animal Species

If the temperature increases above the optimum temperature some of the plant species may die
Reduction of herbivore because of reduction in food supply
Results in a reduction of predator or secondary consumers.
A change in distribution of plants could result in a change in distribution of herbivores.
Loss of habitat decreasing the numbers of animal species
Loss of shelter provides more food for predators, so the predator would increase in number

Effect of Increased Temperature for Animals from Global Warming

Global warming increases the earth’s mean surface temperature
When the temperature increases up to optimum temperature metabolic reactions speed up
So, the rate of growth increases and the life cycle becomes faster.
Above optimum temperature, metabolic reactions fall
So, their rate of growth falls and life cycle slows down

Global Warming Causes Other Types of Climate Change

Global rainfall patterns and the timing of seasonal cycles aﬀect plants and animals.
Changing Rainfall Patterns
Due to Global warming some areas will get more rain, others will get less rain
Changing rainfall patterns will affect the development and life cycles of some organisms
Changing rainfall patterns will also affect the distribution of some species, e.g., deserts could increase in area because of decreases in rainfall
So, species that are not adapted to live in deserts will have to move to new areas or they will die out.

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Description

Explore the flow of energy through ecosystems, the concept of trophic levels, and the measurement of biomass. Understand how energy transformation occurs from green plants to higher trophic levels and the implications for biological productivity. This quiz offers insights into ecological energetics and the dynamics of living organisms in their environments.