I was being overly simplistic. It's a measurement of the rate at which work is done, not the measurement of work itself

This question seems to miss the understanding that horsepower is a measure of work done- that is, some amount of mass multiplied by some amount of distance all divided by some amount of time. (Horsepower a a unit is kinda weird like most US customary units, so you would have to pay around with the numbers a bunch to get mass, distance, and time out of the force, rotational speed, and constant that make up this particular unit)

In an application where your work gets done at a slow speed and doesn't need to change that speed significantly or quickly like towing or farming, a better unit of measurement to use would be in units of force. How much force can this machine apply to this load. For things that rotate, the force is torque.

Horsepower is calculated from torque and rpm. The equation is (torque × rpm)/5252. If all the torque needed is generated at a very low rpm, as is the case with large diesel engines, the horsepower is going to come out small.

Crabs have gills under their shell near their legs. They have an appendage that pushes water over them called a scaphognathite and can seal the water inside the shell with articulating plates to keep the gills wet. When they are out of the water and blowing bubbles out of what looks like their mouth, that's the result of them breathing with their gills. As long as they can keep finding more oxygenated water, aquatic crabs can stay out of the water for a surpassing long time, like a day or two. Land crabs have a weird lung gills hybrid organ but they're adapted to land life and just seek out water to keep that organ wet. Coconut crabs are a type of hermit crab that can't swim and will drown in about an hour if they are swept away or fall into water

I'm pretty sure this has been asked recently. Lungs are designed specifically to exchange gas with blood. They've got a huge amount of surface area to do this. Mammals have alveoli, and other vertebrates have parts that function similarly but the structures can be different. The big thing here is that the air sacs can expand when a breath is inhaled and there are a bunch of capillaries lining the air sacs that exchange gas through the cells in the air sacs. Gills don't really expand like that. They're flexible but they don't increase in volume nearly to the degree that lungs can. Gills are also very delicate and are dependent on the surrounding water for structural support. They can't do their job if the water isn't supporting them. They still perform gas exchange, but in the case of gills, the gas comes from the oxygen dissolved into the water. This also means that there has to be gas dissolved in the water or the fish will die from oxygen deprivation.

One of the things that determines whether a drug is available over the counter versus behind the counter or by prescription isn't just the potential for harm in case of overdose, but the potential for abuse and the potential for affecting public health. For example, if everyone could just grab amoxicillin whenever they want, we'd probably end up with a bunch of strains of medication resistant bacteria because a lot of people would take it every time they got symptoms that felt like being sick and wouldn't take enough for a long enough time to kill off all the bacteria exposed to the drug. Epinephrine has potential to be abused as a stimulant.

2 of the 3 biggest advances in power in automotive engines today compared to those of the mid 20th century are efficiency changes. Fuel injection has gotten better, whether compared to earlier fuel injection or to carburetors. It can atomize fuel into smaller, more uniform particles and disperse them with more precision during the proper part of the cycle. Stronger, lighter materials and lubricants with less friction have become standard, losing less power to parasitic power loss, and the third thing is less efficiency related, but tighter tolerances, more precise control of fuel delivery and valve timing, and stronger materials have led to the compression ratio of a regular passenger vehicle today exceeding that of performance cars back in the previous century, while staying on the same grade of fuel.