Dissolved Oxygen and Aquatic Primary Productivity
In light of depiction of low Mesozoic oxygen levels, Peter Ward addressed a controversial issue regarding how dinosaurs breathed. Birds have an air sac breathing system with an inflexible septate lung, which is highly superior to the mammalian . At 1600 meters elevation, today’s birds are about twice as efficient at extracting atmospheric oxygen as mammals are. Flying is the most aerobically demanding activity on Earth and a bird’s air-sac breathing system is a primary reason why they can fly, and is an energetic feat far beyond what any mammal can accomplish. The high-performance respiration that birds possess is also why they live far longer than similarly sized mammals, but is . When a mammal breathes, it inhales oxygenated air and exhales carbon dioxide, but it is not a very efficient system, as fresh and depleted air mix in the lungs. The , on the other hand, passes fresh oxygenated air along the lungs with each breath. One might say that birds constantly inhale. can . Since birds evolved from dinosaurs, and indeed dinosaurs, just when this innovation developed is of great interest to paleobiologists. If the early Mesozoic were the low-oxygen times that GEOCARBSULF depicts, then the air sac system would have been a logical adaptation to oxygen-poor air.
The relationship between pH, oxygen and photosynthesis ..
The germinating peas will use cellular respiration more than the non-germinating peas and therefore consume more oxygen, but the chloroplasts may produce some O2 through photosynthesis.
This graph shows that the germinating peas had high rates of respiration than the non-germinating peas, temperature being irrelevant in this context.
People are usually surprised to hear that grass is a relatively recent plant innovation. and only became common in the late Cretaceous, along with flowering plants. With grass, some , and grazers have been plentiful Cenozoic herbivores. According to , carbon dioxide levels have been falling nearly continuously for the past 150-100 million years. Not only has that decline progressively cooled Earth to the point where we live in an ice age today, but is currently considered the key reason why complex life may become extinct on Earth in several hundred million years. In the Oligocene, between 32 mya and 25 mya some plants developed a during photosynthesis known as . It allowed plants to adapt to reduced atmospheric carbon dioxide levels. C4 plants became in the Miocene, and grasses are today’s most common C4 plants and . The rest of Earth’s photosynthesizers use or , which is a water-conserving process used in arid biomes.
Use of Oxygen Electrode in Measurements of Photosynthesis and ..
A free radical is an atom, molecule, or ion with an unpaired valence electron or an unfilled shell, and thus seeks to capture an electron. The used to create ATP in a mitochondrion leaks electrons, which creates free radicals, which will take that electron from wherever they can get it. creates some of the most dangerous free radicals, particularly the . The more hydroxyl radicals created, the more damage inflicted on neighboring molecules. Another free radical created by that electron leakage is , which can be neutralized by , but there is no avoiding the damage produced by the hydroxyl radical. Those kinds of free radicals are called (“ROS”). ROS are not universally deleterious to life processes, but if their production spins out of control, the oxidative stress inflicted by the ROS can cripple biological structures. ROS damage can cause programmed cell death, called , which is a maintenance process for complex life. Antioxidants are one way that organisms defend against oxidative stress, and is a standard antioxidant. Antioxidants usually serve multiple purposes in cellular chemistry, and antioxidant supplements generally do not work as advertised. They not only do not target the reactions that might be beneficial to prevent, but they can interfere with reactions that are necessary for life processes. Antioxidant supplements are blunt instruments that can cause more harm than good.
Dissolved Oxygen and Water Temperature.
About 1 bya, began to decline and microbial photosynthesizers , probably due to predation pressure from , which are eukaryotes. Eating stromatolites may reflect the of , although grazing is really just a form of predation. The difference between grazing and predation is the prey. If the prey is an (it fixes its own carbon, by using energy from either or ), it is called grazing, and if the prey got its carbon from eating autotrophs (such creatures are called ), then it is called . There are other categories of life-form consumption, such as and (eating dead organisms), and there are many instances of . For complex life, the symbiosis between the and its cellular host was the most important one ever.