population biology - What's in a Name: Statistical Genetics

Mendel published his results 1866 but they were rediscovered only in 1900. The Hardy-Weinberg model is an application of Mendel's rules to a population that is not under selection forces. So the one builds on the other, and Hardy-Weinberg is a simplification model-wise, and Mendel's rules are not detailed enough either. It's the same relation as with a physical law like gravitation and a mathematical model of its consequences applied on many entities, like models of a solar system's gravitational behaviour.

botany - Why do some fruits have a much wider range of acceptable sizes than others?

Pumpkins, squashes in general, grow on vines, while apples grow on trees. Vines are fast growing and trees are not. Zucchini can be quite large; cucumbers, too. Pears, plums, peaches and other tree fruits do have a reduced variation in fruit size. While I do not know the answer to your question, my background in plant biology tells me that this is an important part of the reason. For example, a watermelon or pumpkin rests on the earth, but a tree fruit hangs. If that fruit is too heavy it falls from the ground before it is ripe - before the seeds are fully differentiated that is. So, while "evolution" might be an answer, it is important to discuss what aspects are at play.

I think it has to do with vine vs tree, and how the fruit is attached and hangs/lays.

zoology - Effect of spaying on the female cat organism and health

From the standpoint of the skeletal system, spaying is definitely not good for her health. Removal of the ovaries mimics what happens at menopause, when circulating estrogen levels fall. Estrogen is necessary for maintenance of bone mineralization. Without estrogen, bones start to demineralize (the same process that happens in human females after menopause, leading to osteoporosis).

Then again, some animals, if they do not get pregnant, will cycle indefinitely until they get anemic and die. Ferrets are an example. So it's better to have these spayed.

evolution - Do large animals often evolve into smaller animals?

Your question brings up several important issues with regards to the evolution of body size. The rationale for concluding that the ancestral mammal had a small body size is that all of the taxa in that area of the tree tend to be small. In contrast, if all of those taxa had been cow-sized, then the most parsimonious conclusion would be that the ancestral mammal was cow-sized.

Identification of ancestors is difficult

Identification of a fossil species as the most recent common ancestor of a pair of sister taxa is exceedingly difficult. The way that different species are diagnosed in fossils in by their unique derived characteristics (autapomorphies). So if a fossil is found with no autapomorphies, then it is plausibly an ancestor (i.e., at the split between two sister taxa). Some would argue that if you don't find any autapomorphies, then you just haven't looked closely enough.

Cope's Rule

The idea that lineages tend to evolve toward larger body size is known as Cope's Rule, named for the paleontologist Edward Drinker Cope. The success of Cope's Rule has been highly variable, with some lineages following and others not (Polly, 1998).

Some clades following Cope's Rule

Some clades not following Cope's Rule

Note that many results depend on the methods used.

Evidence from experimental evolution

Several studies have addressed body size evolution in vertebrates both directly and indirectly. MacArthur (1944a, 1944b) directly selected for large and small body mass in laboratory mice. Within 8 generations, mean body masses had increased or decreased by over 50%. Even when body mass is not directly selected upon, mass can change in a correlated way. Selection for high levels of voluntary activity has led to an approximately 25% reduction in body mass.

Based on these studies, evolution of body size (larger or smaller) is certainly possible within relatively few generations.

pathology - Why are some bodily fluids more of an infection risk than others?

This is just about where the pathogens can be found that are dangerous to people.

Vomit is highly acidic and less accommodating to microbe growth. Similarly saliva has many immune components in it as well as digestive enzymes that keep most microorganisms down.

Urine and CSF are actually quite sterile as they come from environments that are highly filtered - the kidney is an osmotic processor that essentially is a molecular filter and does not allow cells to pass, the spine is highly insulated from the blood and other direct exposure to microorganisms.

Compare that with the 'dangerous' list and you have organs that are open to human pathogens. Venerial disease like HPV is so common that what - about 1 in 5 people under a certain age carry it. That is a pretty high expectation of a biohazard. most infections and viruses are blood bourne - influenza, cold, as well as any bacterial infections.

Feces is always a dangerous thing to handle as the digestive tract is rich in nutrients and essentially directly open to external bacteria and fungi. (and its not acidified like the stomach). Also parasites like tape worms and other multicelled animals! yum!

Diarrhea is often caused by an infection of some sort, so its just more likely a hazard, but feces is always a place where you might find a pathogen.

This is not to say that the 'safe' list is totally safe. Its just less likely to bear disease causing agents.

zoology - Can all mammals swim?

With respect to the giraffe claim, this article seems relevant:

D. M. Henderson, D. Naish, Predicting the buoyancy, equilibrium and potential swimming ability of giraffes by computational analysis, J Theoretical Biology 265 (2010) 151-159.

It cites several non-"random person on the internet" claims that giraffes cannot swim:

It is generally thought that giraffes cannot swim, but relevant
observations are few. Shortridge (1934) and Goodwin (1954) state that
giraffes were poor waders and unable to swim. Crandall (1964)
discussed a case where a captive giraffe escaped from a carrying
crate, ran to the end of a jetty, and fell into the water. The animal
reportedly sank without making any attempt to swim. MacClintock (1973,
p. 54) stated ‘Giraffes cannot swim. Rivers are barriers they do not
cross’. Wood (1982, p. 20) noted that ‘Because of its extraordinarily
anatomical shape the giraffe is one of the very few mammals that
cannot swim – even in an emergency! Deep rivers are an impassable
barrier to them, and they will avoid large expanses of water like the
plague’.

They then go on to show that a model giraffe could plausibly swim, writing: "For practical and ethical reasons we are unable to use live giraffes..."

They conclude:

In summary, the results and speculations of this study show that it is
not impossible that a giraffe could propel itself in water, but in
terms of energy efficiency relative to that of the horse, it would
appear that the costs of aquatic locomotion might be too high. It is
reasonable to expect that giraffes would be hesitant to enter water
knowing that they would be at a decided disadvantage compared to being
on solid ground.