19.1 Energy Flow (Cambridge (CIE) O Level Biology): Flashcards
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What is the principal source of energy input to biological systems?
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Cards in this collection (46)
What is the principal source of energy input to biological systems?
The Sun
Which process uses the Sun's energy to make food in plants?
Photosynthesis
All energy transfers on Earth can be traced back to the .
All energy transfers on Earth can be traced back to the Sun.
True or False?
All life on Earth depends, directly or indirectly, on photosynthesis.
True.
Solar energy powers photosynthesis, which provides the energy that all living things ultimately rely on.
Roughly how much of the Sun's energy entering the atmosphere reaches the Earth's surface?
About half
Define photosynthesis.
The process by which plants use light energy to make glucose from carbon dioxide and water.
In what form does energy from the Sun reach plants?
As light energy
Energy is eventually transferred from living organisms to the environment as .
Energy is eventually transferred from living organisms to the environment as heat.
True or False?
Energy is recycled endlessly between organisms and the Sun.
False.
Energy flows through organisms and is eventually lost to the environment as heat; it is not recycled.
What two forms of energy flow through living organisms?
Energy flows as:
light energy from the Sun
chemical energy stored in organisms
Define producer.
An organism that makes its own food using energy from sunlight, e.g. a green plant.
Define decomposer.
An organism that feeds on dead or decaying matter by breaking it down.
What does a food chain show?
The transfer of energy from one organism to the next, starting with a producer.
What is the source of all energy in a food chain?
Light energy from the Sun
What do the arrows in a food chain represent?
The transfer of energy from one organism to the next
Energy is transferred from one organism to the next in a food chain by (eating).
Energy is transferred from one organism to the next in a food chain by ingestion (eating).
Define food web.
A network of interconnected food chains.
Why are food webs a more realistic representation than food chains?
Because most animals do not rely on just one type of food source.
What name is given to a herbivore that feeds on producers?
A primary consumer
True or False?
A secondary consumer is a carnivore that eats primary consumers.
True.
Secondary consumers are carnivores that feed on the primary consumers (herbivores).
A food web shows the of organisms, i.e. how a change in one population affects others.
A food web shows the interdependence of organisms, i.e. how a change in one population affects others.
True or False?
If the earthworms that feed on grass decrease, the grass population would also decrease.
False.
The grass population would increase, because fewer species would be feeding on it.
Define trophic level.
The position of an organism in a food chain, web or pyramid.
In what form does energy flow from the Sun to producers?
As light energy
How do producers change the light energy they receive?
They convert light energy into chemical energy.
True or False?
Energy flow through a food chain is a cyclical process, with energy being recycled.
False.
Energy flow is non-cyclical; once energy reaches the top of a chain it is lost to the environment, not recycled.
Unlike energy, the chemical that organisms are made from are repeatedly recycled.
Unlike energy, the chemical elements that organisms are made from are repeatedly recycled.
What is a primary consumer?
A herbivore that feeds on producers.
Why is only some of an organism's energy passed on to the next trophic level?
Only the energy made into new cells stays with the organism to be eaten; the rest is used or lost.
In what main ways is energy lost at each trophic level?
Energy is mainly lost through:
movement
heat
waste products (urine)
undigested waste (faeces)
Energy is lost as heat mainly in and birds, which keep a constant body temperature.
Energy is lost as heat mainly in mammals and birds, which keep a constant body temperature.
Why are food chains rarely more than five organisms long?
Because so much energy is lost at each trophic level that too little remains to support further levels.
True or False?
It is more energy efficient for humans to eat crop plants than livestock fed on those crops.
True.
Energy is lost from the animals, so less energy is available to humans than if they ate the crops directly.
Of the chains wheat to cow to human, or wheat to human, which gives humans more energy?
wheat to human, because no energy is lost through the cow.
What does a pyramid of numbers show?
How many organisms there are at each trophic level of a food chain.
What does the width of each bar in a pyramid of numbers represent?
The number of organisms at that trophic level.
True or False?
A pyramid of numbers is always pyramid-shaped.
False.
A pyramid of numbers can be other shapes, because one large organism can support many smaller ones.
In any ecological pyramid, the are always placed at the bottom.
In any ecological pyramid, the producers are always placed at the bottom.
Why might a pyramid of numbers not be pyramid-shaped?
Because one large organism (e.g. an oak tree) can contain enough energy to support many smaller organisms.
Define biomass.
The dry mass of living material (the mass of organisms not including their water).
True or False?
A pyramid of biomass is always pyramid-shaped.
True.
Biomass must decrease as you move up a food chain, so the pyramid always narrows towards the top.
A pyramid of biomass is drawn using the mass of organisms, which excludes water.
A pyramid of biomass is drawn using the dry mass of organisms, which excludes water.
Why must biomass decrease at each level going up a food chain?
Because a smaller mass of food cannot support a larger mass of consumers above it.
Why is a pyramid of biomass a better representation than a pyramid of numbers?
It shows the actual quantity of plant or animal material at each level, so it always forms a true pyramid.
What does a pyramid of energy show?
How much energy is passed on at each trophic level.
A pyramid of shows how much energy is passed on at each trophic level.
A pyramid of energy shows how much energy is passed on at each trophic level.
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