4.2 Energy flow Flashcards
For most biological communities, what is their initial source of energy?
Sunlight
How can living organisms harvest sunlight energy?
Photosynthesis
What 3 groups of autotrophs carry out photosynthesis? What are they often referred to as?
Plants, eukaryotic algae (e.g. seaweed), and cyanobacteria
Often referred to by ecologists as producers
Why are heterotrophs indrectly dependent on light energy?
- They use carbon compounds in their food as a source of energy
- In most ecosystems all oe almost all enrgy in the carbon compounds will originally have been harvested by photosynthesis in producers
How does the amount of energy supplied to ecosystems in sunlight vary around the world?
Sahara dessert: high sunlight intensity but less producers = less energy becomes available to organisms
Redwood forests of california: less sunlight intensity but more producers = more energy becomes available to organismss
What is light energy converted into in carbon compounds by photosynthesis?
Chemical energy
How does light energy get converted into chemical energy?
Producers absorb sunlight using chlorophyll and other photosunthetic pigments. This converts the light energy to chemical energy, which is used to make carbohydrates, lipids and all the other carbon compiunds in producers
How do producers release energy from their carbon compounds?
By cell respiration and then use it for cell activities
What is the energy released as when producers release energy through cell respiration and cell activities?
lost to the environment as waste heat
What part of producers are available to heterotrophs?
Carbon compoinds in cells and tissues of producers
How does chemical energy in carbon compounds flow through food chains?
By feeding
What is a food chain?
A sequence of organisms, each of which feeds on the previous one.
* usually 2-5 organisms in a food chain
What organisms are always first in a food chain? second? third?
Producers <- primary consumers <- secondary consumers <- tertiary and so on
What does the arrow in a food chain indicate?
the direction of energy flow
How is energy released by in living organisms and what does it convert to?
Energy released by respiration is used in living organisms and converted to heat
What cell activities in living organisms need energy for?
- Synthesizing large molecules like DNA, RNA and proteins
- Pumping mplecules or ions across membranes by active transport
- Moving things around inside the cell, such as chromosomes or vesicles, or in muscle cells the protein fibres that cause muscle contraction
What supplies energy for cell activites? Where is the energy produced?
ATP
* each cell produces its own ATP supply
How do all cells produce ATP?
By cell respiration
What is the process of cells producing ATP by cell respiration?
- Carbon compounds (carbohydrates and lipids) are oxidized
- These oxidation reactions are exothermic
- The energy released is used in endothermic reactions to make ATP
So cell respiration transfers chemical energy from glucose and other carbon compounds to ATP
What does the second law of thermodynamics state?
Energy transformations are never 100% efficient.
* Not all of the erngy from the oxidation of carbon compounds in cell respiration is transferred to ATP.
* The remainder is converted to heat
What are 4 energy conversions living organisms can perform?
- Light energy to chemical energy in photosynthesis
- Chemical energy to kinetic energy in muscle contraction
- Chemical energy to electrical energy in nerve cells
- Chemical energy to heat energy in heat-generating adipose tissue
According to the laws of thermodynamics in physics, where does heat pass from?
Heat passes from hotter to cooler bodies, so heat produced in living organisms is all eventually lost to the abiotic environment
* The heat remains in the ecosystme for a while, but is ultimately lost
What is biomass?
Biomass is the total mass of a group of organisms
What is included in biomass?
it consists of the cells and tissues of those organisms, including the carbohydrates and other carbon compounds that they contain
Why does biomass have energy?
Because carbon compounds have chemical energy
How can ecologist measure how much energy is added per year by groups of organisms?
Ecologist can measure how much energy is added per year by groups of organisms to their biomass
What is the trend found by measuring how much energy is added per year by groups of organisms to their biomass?
The energy added to biomass by each successive trophic level is less
* and secondary consumers the amount of energy is always less per year per square meter of ecosystem done in primary consumers
What is the reason for this trend?
(the energy attitude biomass by each successive trophic level is less)
The loss of energy between trophic levels
What is the reason for this trend?
(the energy attitude biomass by each successive trophic level is less)
The loss of energy between trophic levels
What is the only energy available to organisms in the next trophic level?
Chemical energy in carbohydrates and other common carbon compounds that have not been used up in cell respiration
* The rest is lost by heat
What is the only energy available to organisms in the next trophic level?
Chemical energy in carbohydrates and other common carbon compounds that have not been used up in cell respiration
* The rest is lost by heat
How may organisms in a trophic level not entirely consumed by organisms in the next trophic level?
Undigestable material
* predators may not eat material from the bodies of the prey such as bones or hair
How may organisms in a trophic level not entirely consumed by organisms in the next trophic level?
Uneaten material & indigestible materials
What happens to the energy in uneaten materials?
Energy and uneaten material passes to saprotrophs or detritivores rather than passing to organisms in the next trophic level
What happens to materials that are indigestible?
It is egested in feces. Energy and feces does not pass all along the food chain and instead passes to saprotrophs or detritivores
Because of what losses do only a small proportion of the energy in the biomass of organisms in one trophic level become part of the biomass of organisms in the next trophic level?
- Loss from heat
- Loss from uneaten materials
- Loss from indigestible material -> egested as feces
How much energy is transferred to the next trophic level?
10%
For what reason is the number of trophic levels in a food chain restricted?
The fact that there is less and less energy available to each successive trophic level
Why does biomass also diminish along food chains?
Due to loss of carbon dioxide and water from respiration and loss from the food chain of uneaten or undigested parts of organisms.
* the biomass of higher trophic levels is therefore usually smaller than that of lower levels
* there is generally a higher biomass of producers, the lowest trophic level of all, turn off any other trophic level
How can the amount of energy converted to new biomass by each trophic level be represented?
Pyramid of energy
How can the amount of energy converted to new biomass by each trophic level be represented?
Pyramid of energy
What does each horizontal bar represent in a pyramid of energy?
Each trophic level
How should a pyramid of energy be represented?
- The bars should be labeled producers at the bottom
- Each bar is a representation of the amount of energy
- Amount of energy should be per unit area per year
- The pyramid should be stepped, not triangular
