[removed]

> Most of the time the answer to such more general questions is because it works and isn't a deadly disadvantage.

I didn't really think about this but yeah, it makes a lot of sense.

> Also male and female isn't answered with a simple XX or XY chromosome pair. There are species of frogs where in the north XX are female and XY are male, but in the south XX are male and XY are female and in the middle 50-50 chance. Sex isn't determined by only one chromosome. It's far more complicated and can differ between species.

Learning something new everyday it is!

As I recall from school, all reproduction is asexual or sexual. But it gets complex because asexually reproducing bacterium are able to laterally transfer genetic material. And then there are viruses out there incorporating themselves into genomes. And so it appears to me that the very basis of reproduction has and-ifs and it just gets more sophisticated from there.

For example, environmental factors are able to affect genetic expression as you observe with reptiles.

However, if you take a planaria (flatworm) and mechanically split it in the proper manner, you can get two individuals.

And then we toss in hermaphrodism: plants don't stop and go ahead and fertilize themselves because their genetics provides for two sets of sexual organs. The angiosperms have been very successful at an evolutionary level as we are able to witness by so much green.

>Why do some animals have sex determination which is not genetically determined?

So your Q is about "environmental sex determination" and the mechanism is genetic. The organisms have the genetic ability to express all sexual phenotypes and the egg of a reptile makes a genetic decision to express a certain set of genes based on an environmental cue if hot or cold. It's just a game time decision.

https://en.m.wikipedia.org/wiki/Environmental_sex_determination

[removed]

[removed]

The question should be, what benefit does a determined sex have. Being a hermaphrodite doubles you're chances in a partner.

My guess is, the more complex the organism the harder a sex change is, so it's only beneficial in certain circumstances. Snails for example move very slowly and their senses aren't the best, so it's good if you can make children with every other individual of your species that you meet.

Sex change can often be found in fish, ocean is vast and it can be dangerous to venture out of your part of the reef, so it's great if one of your buddies can become a female when your original female dies. Or you're a male moray eel and never get to make little morays because your the runt of the reef, your genes would be lost, but at the end of your life you become a female and bam youre genes get to live on.

Then you have species with no need for sex, prospering with only female members.

Also male and female isn't answered with a simple XX or XY chromosome pair. There are species of frogs where in the north XX are female and XY are male, but in the south XX are male and XY are female and in the middle 50-50 chance. Sex isn't determined by only one chromosome. It's far more complicated and can differ between species.

Most of the time the answer to such more general questions is because it works and isn't a deadly disadvantage. To get a more specific answer you'll have to look at a more specific scenario (aka a specific species or environment).

Temperature-based determination existed before genetic one. Mammals, birds, and some other animals including many insects evolved genetic determination because the temperature of their egg was too stable to serve as a random way to assign sex. If the eggs have varying temperatures, temperature-based sex determination is the simplest way.

Hermaphrodism existed before non-hermaphrodite species. When sex was first evolved in the first eucharyote, they evolved into hermaphrodite species. Male and female sexes evolved later. Most likely because male animals were more successful at forcing their mate to do the female role which is more energy demanding, so they could breed more.

[removed]

Specific heat capacity refers to the heat capacity per mass. As you can probably imagine, it is not always useful to talk about the total heat capacity, e.g., if you want to characterize not an object, but a type of material. There is also molar heat capacity, which is the heat capacity per 1 mol particles and which is directly connected to the specific heat capacity through the molar mass of a material.

For specific impulse, it is about momentum change (which is force) per ejected unit of mass. So that isn't necessarily comparable to specific heat capacity because it does not just depend on the material that is ejected but rather by the exit velocity of the ejected material. In this case, you might also consider the volume-specific impulse, which gives you the force per ejected unit of volume, as you have limited space in a rocket.

Interesting, thanks.

The Y Chromosome is mostly non-coding DNA. We know that it has been losing genes for millions of years. The reason it shrinks while others don't is that it has no duplicate partner to repair itself from, like every other chromosome has including the X chromosome, though X only has a partner in women. We also know that it has been lost in other mammals. Some of them found alternative ways to keep producing males. We don't know for sure, but it is a reasonable hypothesis that others did not and went extinct.

[removed]

[removed]

[removed]

[removed]

[removed]

I see why mycologists claim there are thousands of unidentified species of fungi. It makes sense that many variants would occur.

Today, hybridization is recognized as pretty common, and many hybrids are fertile. It also is considered an important evolutionary process, which shaped the evolution of many organisms, including humans. The previous belief that hybridization is rare and is an "evolutionary dead-end" is long gone.

Speciation isn't one and done, it's a shift in the average of a whole population, so this would be part of it but definitely not the norm

Evolution is a complicated thing and hybridisation shouldn't be brushed off. It's quite common in more closely related animals, which leads to different results than random mutation. It's likely what you said was taught to you at one time but evolution is one of those things that's always overly simplified and it annoys most biologists I know.

[removed]

[removed]

[removed]

[removed]

[removed]