d. What is the difference between food chains and food webs?

Question

i. A food web is a complex network of interconnected food chains
showing the multiple pathways through which energy and nutrients
flow in an ecosystem.
ii. Food webs illustrate the complexity and interdependence of
organisms within an ecosystem.
iii. They help show the impact of changes in one part of the ecosystem
on the __________________.
● Example: Grass is eaten by both grasshoppers and
rabbits; grasshoppers are eaten by frogs and birds;
rabbits are eaten by foxes and _____________.
5. Energy Pyramids Reveal the Inefficiency of Food Chains
a. Living organisms, including carnivores and herbivores, can convert only
_________ % of what they consume into their own mass.
i. The remaining _____% is diverted to what?
b. In understanding the flow of energy in an ecosystem, it is important to
define the biomass of the given area. What does biomass refer to?
c. The relative shape of the pyramid can also vary depending on the
ecosystem. Do the producers or do the top consumers impact the shape
of the pyramid more? Why?
why is meat considered a luxury in terms of energy
ii. Three inputs are needed for photosynthesis to occur. Explain where
each of these inputs comes from and what it will be used for in
photosynthesis:
● Light energy:
● Water:
● Carbon dioxide:
3Phelan, What is Life, 5e, 2021,© W. H. Freeman and Company

Answer 1

Sure! Let's break down the information step by step:

Food Chains vs. Food Webs

1. Food Chain: A simplified linear sequence showing how energy and nutrients pass from one organism to another in a specific path.
2. Food Web:
   • (i) A food web is a complex network of interconnected food chains showing the multiple pathways through which energy and nutrients flow in an ecosystem.
   • (ii) Food webs illustrate the complexity and interdependence of organisms within an ecosystem.
   • (iii) They help show the impact of changes in one part of the ecosystem on the entire ecosystem or other species within it.
   • Example: Grass is eaten by both grasshoppers and rabbits; grasshoppers are eaten by frogs and birds; rabbits are eaten by foxes and humans (or another predator).

Energy Pyramids and Their Efficiency

1. Energy Conversion:
   • a. Living organisms, including carnivores and herbivores, can convert only 10% of what they consume into their own mass.
   • i. The remaining 90% is diverted to what? Metabolic processes, heat loss, and waste.
2. Biomass Definition: Biomass refers to the total mass of living matter within a given area or volume. It includes all the organic material of living organisms in that space and is crucial in understanding the flow of energy in an ecosystem.
3. Impact on Pyramid Shape: The shape of the energy pyramid can vary depending on the ecosystem; typically, producers impact the shape more because they form the base of the pyramid and have more biomass than the top consumers. This is due to the 10% rule, where only a small portion of energy transfers to higher trophic levels.
4. Meat as Luxury: Meat is considered a luxury in terms of energy because it takes significantly more energy and resources (like land and water) to raise livestock compared to producing plant-based food sources. Thus, for the same amount of energy consumed in the form of meat, many more resources are needed.

Inputs for Photosynthesis

i. Photosynthesis Inputs:

• Light Energy:
  • Comes from the sun and is used to energize the electrons involved in the photosynthesis process.
• Water:
  • Taken up by the roots from the soil. It is used as a reactant in the light-dependent reactions, contributing to oxygen production and providing electrons.
• Carbon Dioxide:
  • Sourced from the air through plant stomata, it is used in the Calvin cycle to produce glucose and other carbohydrates.

Feel free to ask if you have more questions on this topic or any other!