It can be helpful at this juncture to grasp the cumulative impact of , inventing , inventing , inventing that made possible, and inventing . Pound-for-pound, the complex organisms that began to dominate Earth’s ecosphere during the Cambrian Period consumed energy about 100,000 times as fast as the Sun produced it. Life on Earth is an incredibly energy-intensive phenomenon, powered by sunlight. In the end, only so much sunlight reaches Earth, and it has always been life’s primary limiting variable. Photosynthesis became more efficient, aerobic respiration was an order-of-magnitude leap in energy efficiency, the oxygenation of the atmosphere and oceans allowed animals to colonize land and ocean sediments and even fly, and life’s colonization of land allowed for a . Life could exploit new niches and even help create them, but the key innovations and pioneering were achieved long ago. If humanity attains the , new niches will arise, even of the , but all other creatures living on Earth have constraints, primarily energy constraints, which produce very real limits. Life on Earth has largely been a for several hundred million years, but the Cambrian Explosion was one of those halcyonic times when animal life had its greatest expansion, not built on the bones of a mass extinction so much as blazing new trails.
All animals, , use aerobic respiration today, and early animals (, which are called metazoans today) may have also used aerobic respiration. Before the rise of eukaryotes, the dominant life forms, bacteria and archaea, had many chemical pathways to generate energy as they farmed that potential electron energy from a myriad of substances, such as , and photosynthesizers got their donor electrons from hydrogen sulfide, hydrogen, , , and other chemicals. If there is potential energy in electron bonds, bacteria and archaea will often find ways to harvest it. Many archaean and bacterial species thrive in harsh environments that would quickly kill any complex life, and those hardy organisms are called . In harsh environments, those organisms can go dormant for millennia and , waiting for appropriate conditions (usually related to available energy). In some environments, it can .
Function and Equation for Respiration
1. Click on the following links and use the information provided to write a definition of cellular respiration in your own words.2. Identify which living things carry out the process of respiration.3. Write the chemical equation for cellular respiration. Label the reactants and products. Where have you seen something like this equation before? Explain.4. How does the equation for cellular respiration compare with the equation for photosynthesis?5. What is ATP? Why is it an important product of cellular respiration?6. Using the same link from #5, write the chemical equation for the breakdown of ATP. Does the reaction release energy (exothermic) or absorb energy (endothermic)? Support your answer.7. Write the equation for the synthesis of ATP. Does the reaction release energy (exothermic) or absorb energy (endothermic)? Support your answer.
Use the following link to answer questions 8-10:
8. What is the main site of respiration in the cell?9. Make a sketch of the respiration organelle and label its parts.10. What energy molecules are produced in this respiration organelle?11. What is the difference between aerobic and anaerobic cellular respiration?12. Click on the �Cellular respiration� link and scroll down to fermentation. What is lactic acid fermentation? Where does it occur?13. What does a build up of lactic acid cause?14. What is alcoholic fermentation?15. In what industry is alcoholic fermentation important?16. Which produces the larger amount of energy � aerobic or anaerobic respiration? Support your answer with information from the reading.
17. Write a summary of cellular respiration. In your response:
Perhaps a few hundred million years after the first mitochondrion appeared, as the oceanic oxygen content, at least on the surface, increased as a result of oxygenic photosynthesis, those complex cells learned to use oxygen instead of hydrogen. It is difficult to overstate the importance of learning to use oxygen in respiration, called . Before the appearance of aerobic respiration, life generated energy via and . Because oxygen , aerobic respiration generates, on average, about per cycle as fermentation and anaerobic respiration do (although some types of anaerobic respiration can get ). The suite of complex life on Earth today would not have been possible without the energy provided by oxygenic respiration. At minimum, nothing could have flown, and any animal life that might have evolved would have never left the oceans because the atmosphere would not have been breathable. With the advent of aerobic respiration, became possible, as it is several times as efficient as anaerobic respiration and fermentation (about 40% as compared to less than 10%). Today’s food chains of several levels would be constrained to about two in the absence of oxygen. Some scientists have and oxygen and respiration in eukaryote evolution. is controversial.