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A thread for scientific nerdiness

I love this idea!!!! I've got something for y'all:

We, animals, go through a pretty straightforward life cycle. We spend our lives as diploid -- having two copies (one from mom, one from dad) of each chromosome. We start out as a zygote, then we become an adult, and the adult will produce either 4 sperm per single gamete-making cell or 1 egg and 3 mini-cells (not usable for us), through meiosis -- which means the gametes are haploid (aka, only have one copy of each chromosome). Then those come together to form a brand new diploid zygote.

Science jargon!

Plants are freakier. Plants go through a diploid life cycle as well, but it's when they reproduce that everything gets weird.

First of all, many plants are hermaphrodites -- a completely separate gender (most animals are naturally hermaphrodites as well, such as worms (annelidas) and mollusks; that is different from fish who change gender throughout their life cycle, because they will go from male to female, never becoming hermaphrodites). Some plants are male, or female -- but some species have all three genders. Marijuana is a classic example of this -- the males only have male flowers, the females only have female flowers, and the hermaphrodites have both and/or their flowers contain both female and male parts. Weeping willow trees have two genders, either male or female. Lots of perrenial yard flowers are pure hermaphrodites -- their species only has one gender.

Pine cones are very gendered, by the way.

((((Fun fact: 300 million years ago, there were no flowers! That includes any species of grass. There were only mosses, ferns, and cycads, conifers, and certain kinds of pines. Before pine trees and conifers took over, there used to be "tree ferns" -- taller than any tree you'll see today (except giant redwoods)! They lasted longer than any species on Earth ever has; yep, no matter what you look at that's alive, it probably wasn't as successful as tree-ferns! Except moss, lol

But it gets cooler! An adult plant (I'm sticking with flowering plants, but all plants have this life cycle) flowers, and goes through meiosis -- that is, the diploid (two copies of genome) forms a haploid (half the genome) cell through meiosis, similar to animals. BUT THEY DON'T PRODUCE GAMETES YET, unlike animals. Male parts produce microspores, often called pollen.

Pollen is the male offspring of the flowering plant. It is genetically different from its parent, and it is called a gametophyte. It's parent is called a sporophyte, because it produces the gametophyte. This is called an alternation of generation -- that's because plants don't reproduce straight forward the way we do. They create an entirely new generation that does it for them!

What an energy/drama saver!

Female plant parts produce the gametophyte called a macrospore. Just like in animals (like us), meiosis produces 4 pollen cells per one gametophyte-making cell. The plant releases these, to an pollinator or the wind or water if aquatic or marine.

The female megaspore is accompanied by 3 cells that in animals are useless. But in plants, the three cells act as a placenta of sorts, and are genetically distinct just like the megaspore. They will help bring nutrients from the flowering plant to the zygote later.

Pollen lands on a flower or other part where a megaspore, and then the pollen begins to grow a tube, and it begins to create sperm. The sperm will meet the egg of the megaspore, and then fertilization happens and the zygote is created!

So, this means that any seed pod you've ever seen is a grandma, a mom, and a grandchild all nurtured in the same place by the mom and grandma, AND assisted by three aunts.

All plants on land do this.

In moss it gets weirder. You can see that the first generation has green leaves and lasts years and years. But if you look closely, you'll see the second generation, which looks totally different -- no leaves, just a long brown stalk that holds the third generation, which will grow leaves.

Isn't that wild?
Then those come together to form a brand new diploid zygote

Actually, not all animals are diploid. Some insects, most notably the Hymenoptera (bees, wasps, ants, etc.), are haplodiploid. So assuming that nothing goes wrong, females will develop from fertilized eggs and are fully diploid, but males develop from unfertilized eggs and are haploid. Reproductive females can control the sex of their offspring by controlling the release of stored sperm and choosing whether or not to fertilize their eggs. Interestingly, males of most hymenopteran species, with the exception of the Xyelidae, will duplicate the DNA content in their alary muscles, which allows for an increased metabolic rate in those tissues and more efficient flight. So they are born haploid but ultimately become a mix of haploid and diploid.
A new fact! Leaving it as a different post on purpose (trying not to overload you, but this stuff is way too cool to keep to myself).


But luckily slightly easier to understand than plants.

So, humans and other animals go through their entire lives with two copies of each chromosome, unless they are only gametes, pre-fertilization.

Plants have alternating generations: the first generation has both copies of each chromosome throughout their lives. But the next generation -- the ones that produce gametes -- go through their entire lives with only half the genome (one copy of each chromosome). Then the third generation, like the first, has two copies of each chromosome.

But fungi go through their entire life like the gamete-producers of plants -- totally haploid (one copy of each chromosome).

Also, though fungi are way more related to us than to plants, they do not produce sperm nor egg. They therefore don't have female or male genders -- which is why their "genders" are referred to as "mating types." but many species have THOUSANDS of mating types/genders! They are some of the weirdest, most alien life on Earth. :D

Fungi start as a zygote within a tiny spore. Once ready, the fungi hatches from the spore and grows out of it -- its body is called a hypha.

The hypha grows and eats whatever (sometimes not even organic stuff -- some fungi use nuclear waste as food, by using the same pigment that keeps us from getting sunburns!). Then, it might meet another hypha.

If the hypha are different mating types (as in, they are compatible somehow and are not the same gender (a way to avoid hooking up with siblings or other family)), then they will fuse their bodies together, but only where they met. (They stay separate elsewhere.) So romantic.

They do share nutrients and food sources, and they even communicate to each other for years (they are unlikely to ever let go of one another, and for ones that do scientists aren't sure what triggers it), but they do not fuse their cell nuclei. That's right -- both hypha are still genetically distinct, even when fusing their bodies!

And they stay haploid (only one copy of each chromosome).

The hyphae will grow together for a while, until conditions are right to consider reproduction. Then, the hyphae will begin to grow toward the soil surface (scientists are still trying to find out how they know which way is "up," because even if the fungi are put sideways they will grow sideways to the surface anyway) and they will form a mushroom.

It is in the mushroom that the two hyphae will actually engage in sexual reproduction. They will finally fuse a nucleus, creating a diploid (two copies of each chromosome) cell, which will then go through meiosis, and then produce spores that are haploid like the adults (only one copy of each chromosome).

Isn't that weird?

Fungi fun facts!!
Fungi not only form relationships with their own species, but will sometimes "befriend" other species -- particularly plants.

It is thought that fungi may have coaxed plants onto land 320 million years ago (or so, I'm a bit bad at dates) and that plants "invented" roots in order to have relationships with fungi, who were gifting nutrients to plants. They still do this.

In forest environments, fungi will have relationships with thousands of plants. One in Michigan is considered the largest organism on Earth, and it has connections to entire forest systems.

Fungi in systems like this will often help trees communicate directly to one another through their roots, transfer "sugar gifts" to less fortunate trees or other plants, and support plants through hard times such as droughts.

In Chernobyl, there is a chilling example of fungi like this making due with what humans caused.

One species impressed scientists by taking radioactive molecules from young trees in Chernobyl and transferring it. The trees still got radiation and frequently radiation poisoning, but they could grow. The fungus was depositing the radioactive substances below the soil.

Another of the SAME species figured out something else. Scientists noticed a field with only some grass that was very radioactive-resustant and assumed that this species of fungus was absent here. They were wrong. It turned out that the fungus was concentrating radioactive particles and then poisoning things that tried to grow there after some time, including insects. The fungus then eventually got the nutrients from the dead organisms.

Weird stuff!

In the human gut, some species of fungi help us digest food.

Also, we use fungal toxins such as penicillin to aid our own immune systems. We're sort of borrowing from the immune system of another organism. But! This is also why bacteria can evolve to ignore antibiotics so quickly -- they have already been exploded to these toxins in the wild, thanks to interactions of fungus outside of our worlds.
Actually, not all animals are diploid. Some insects, most notably the Hymenoptera (bees, wasps, ants,...
And some, like frogs, can be polyploid
I didn't know about the polyploid :o

And now that you mention it, I remember playing with C. elegans and it was a hermaphrodite species -- but if the babies only had half the genome, they became male. Definitely an exception!

Life is cool
Did you know that if all life on earth, and every single piece of matter dissapeared, except for nematode worms, we could still make out the surface features of the planet, the position of every single car, building plane. Even the shape of animals could be seen, even identified by the parasitic nematodes on their body... every single thing on the planet would appear ghostlike

Nematodes are 80% of all biomass on Earth, despite being less than a third of a hairs width long...
More fun facts about insect mating:

Fruit flies males may enjoy sex, but I doubt that male honeybees do. After initiating copulation, which lasts only a few seconds, male honeybees become paralyzed and flip backwards. Then the pressure of the hemolymph in their abdomens during ejaculation actually ruptures their endophallus, sometimes audibly, and blows the male backwards away from the female. The bursting of their copulatory organs is inevitably fatal, usually within a few minutes. Aren't you glad you don't suffer terminal penis explosion when you have sex?
More fun facts about insect mating:

Fruit flies males may enjoy sex, but I doubt that male honeybees...
I mean I think deep sea angler fish have it worse...
The male is about 50-70% smaller than the female. It has no digestory tract, it is in fact a living pair of male genitalia. The males only role in life is to reproduce (it has about 2 weeks to do this before it starves)...unfortunately this is both extremely painful for it and also its last act on earth. The male finds a female and bites into it. The males mouth and most internal organs then dissolve or fuse into the females blood circulation (at this point, the male is effectivley dead). The female is left with the husk of the male attached to her plus the still living male genitalia. The female then uses these genitalia to make babies, which in some species EAT THEIR WAY OUT of the womb...and she has a reminder of every male she has mated with...there genitals still fused to her..

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