I have no education on this beyond high school biology, but I recently ended up on the Cleveland Clinic page for the thymus, which read:

“Your thymus is a small gland in the lymphatic system that makes and trains special white blood cells called T-cells. The T-cells help your immune system fight disease and infection. Your thymus gland produces most of your T-cells before birth. The rest are made in childhood and you’ll have all the T-cells you need for life by the time you hit puberty.”

This has left me puzzled. Don’t these guys live in your bloodstream? If I donate blood do I just permanently have fewer T-cells now? Surely that can’t be the case, or losing any amount of blood would irreparably damage your immune system, but I don’t have enough knowledge to understand why.

Iirc, I learned that grapefruits can block certain enzymes in medicine,and the reason it's cautioned against eating grapefruit with most medicine is because it can cause a buildup of it. So if grapefruit causes it, would it be because grapefruit has a particular chemical that other citrus fruits don't? Or is it that citrus fruits do interfere, just not as much as grapefruit? Because if it interfered at the same strength grapefruit does, I'd assume the warning on medicines would be akin to "don't take with citrus products" instead of grapefruit specifically.

Seems strange how photons can cause such a fast reaction

So let's say hypothetically sound does go through the medium... Does it mean that the Temperature of the medium itself will increase due to the fact that sound is an energy wave? (Btw thx guys for your insights...) P.S I'm a 10 th grader so Im new to this kind of topic but still curious

I’ve heard a lot of things about Norovirus. Only bleach kills it. It only takes a few particles to become infected. It lives on surfaces for two weeks. Immunity only lasts two months. You shed virus for weeks after infection.

If all of this is true, how come it isn’t a LOT more widespread? I’ve read it infects about 5-10% of the population annually. I got norovirus or something like it twice last spring from my son who got it at school. Before that, I think I MIGHT have had it once in my life when I was a kid. But if all of the above is true, you’d expect to get it a lot more often.

If Enceladus is confirmed to have water below it's oceans, with confirmed vapour spews then why is NASA going to the more skeptical Europa with it's Europa clipper mission? Why is Europa more likely to have life compared to Enceladus?

Whenever you watch documentaries or read about the late Cretaceous it is always said that the dinosaurs were declining before the impact. Sometimes this is framed as the beginning of a minor extinction event, other times the implication is that the dinosaurs would have vanished with or without the asteroid. But it is never elaborated on. However looking on the surface it looks like the dinosaurs were just fine. Archosaurs still filled almost all megafauna niches on earth. Dinosaurs were still THE dominant land vertebrates and were even starting to encroach on aerial and aquatic niches. From what I'm seeing, the dinosaurs in the late Cretaceous were even more dominant, diverse and abundant than at other times of the Mesozoic. I don't see why the dinosaurs couldn't have kept this success up until today had the asteroid never hit. Does anyone know what is meant by this "decline"?

I live in western Maryland, so we have a lot of waterfowl in the summer and spring. I have always been taught that they fly south for the winter and that's why we don't see them in the colder months.

Last week, we had a day that was unusually warm, about 60-65 degrees, and I was surprised to see that there were ducks in the pond near my house. This confused me, since it seems like it would take them a very long time to fly back up north, and we only had the warm weather for a day. I've seen this before, but I guess I've never thought too hard about it.

A lot of "little information is a dangerous thing" here. I know that all* eukaryotes have mitochondrion in their cells. Mitochondrion use aerobic respiration to create ATP. So what are plants using these processes for.

Plus how did they evolve in an oxygen poor early Earth?

Obviously I could be totally wrong on my above assumptions e.g. they need oxygen to produce ATP etc

Edit: Thanks for all the answers even though this post is was at 0 votes.

There are insects that continuously inbreed with their siblings, and mouse colonies or all of Australia’s rabbits are started by just a few individuals. How have they avoided accumulating Habsburg-level inbreeding issues?

Wouldn’t mammalian meat be more biologically available and suitable for a human’s body, since we are also mammals?

Are there, or have there ever been any humans that could reproduce both as a male and as a female? And if not, have there at least been any that had both types of sex cells, sperm and eggs?

There are plenty of people with some sort of intersex traits. I know that there is usually a strong push towards full of one or the other, so I wouldnt be TOO surprised if its truly never happened. Still, my bet would be that there has been.

My understanding is that mammal lungs are fairly delicate by necessity. But according to NOAA sperm whales can dive to 10000ft, doesn't that mean that the volume of their lungs is 1/300 that at the surface? How is this possible without damaging the lungs? Is it simply having a highly specialized surfactant or are there other structural changes protecting the lungs? NOAA also says the can stay down for 60 minutes, it doesn't seem like significant gas exchange would occur at that volume, at least relative to the metabolic needs of such a large animal. Are they just relying on the O2 saturation they achieved at the surface to function for that long? Is that how it works when we hold our breath?

Sorry for the run-on question

I totally get wearing masks at the store and 6-8 ft social distancing, but I just saw a linus tech tips video of two people in a 50 sqft room standing next to each other with Razer masks on.
so like, how much of a difference did it actually make?

I was trying to search on reddit the answer to this question, assuming the question has been asked before. And I was surprised to read that many answered the question by saying that there was no scientific evidence, that animals always show irratic behavior with the slightest disturbance in their proximity, that animals would only be alerted due to P-waves at most a few minutes to an hour earlier than humans.

I found that highly weird, since there seems to be plenty of evidence at least very indicative of animals having advanced 'knowledge' of natural events like earthquakes many hours before it happens, in some cases even days.

See this article below for example:

https://www.bbc.com/future/article/20220211-the-animals-that-predict-disasters

So why do animals know and humans don't? [or do we?]

Proxima Centauri B is so much further away, and Hubble imaged Pluto better than a spec of light, so why not Eris?

Do they have to crack the plates? Drill them open? Saw them out and replace them?

I really can't imagine it would be easy.

I'm currently studying for my embryology exam and there's one thing during I can't understand.

One of the first thing the embryo does when arriving int the uterus is nesting in the endometrium. A this point the embryo is under the simple epithelia of the endometrium.

But once the embryo turns into a foetus and start to get bigger how does this small layer contain the foetus ? There must be a point where the foetus break the epithelia to develop in the womb cavity where he has a place to grow and from where he'll be able to get out during child birth ?

Does all visible light travel at the same speed? Or does the (wavelength? frequency?) change the speed at which light will travel. So like purple light vs red light. What about something like radio waves vs gamma?