125 votes
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Do bacteria die of old age?

This is a interesting question and for a long time it was thought that they do not age. In the meantime there are some new papers which say that bacteria do indeed age. Aging can be defined as the ...
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42 votes
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What's the difference between male and female?

Sexes (male and female) are generally defined in terms of Anisogamy, which means that there are size differences between the gametes (i.e. the reproductive cells that fuse at fertilization). The sex ...
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42 votes
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Why do human females have periods?

Short answer Shedding or reabsorbing the endometrial lining is energetically advantageous to the female.The advantage of shedding over re-absorption may be that sperm-born pathogens are removed from ...
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27 votes
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Cells of umbilical cord - mom's or son's?

Cells of umbilical cord - mom's or son's? Answer: Son's. The interface you are looking for is in the placenta. https://en.wikipedia.org/wiki/Placenta Formally the fetal side of the placenta is ...
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22 votes

Why do we have more male infants born?

Note: This is based on literature searches I've done a while ago out of general curiosity. I'm in no way an expert on human reproduction. First, I'm not sure if you are asking about evolutionary ...
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22 votes
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Can an organism exist as a single cell but come together as multi-cellular during certain times?

Welcome to Biology StackExchange. Am I remembering this incorrectly? No, you're remembering it correctly. I think you're talking about slime molds. You'll find more information on the wiki page ...
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21 votes
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Have we ever observed two drosophila lineages that evolved reproductive isolation in labs?

Rice and Salt$^1$ bred fruit flies for 35 generations and from one line of flies created two groups that were isolated from each other reproductively. They could not interbreed because they no longer ...
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  • 2,759
21 votes
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Can a human be made with ovum but without sperm?

Nice question! It is actually very difficult to do so because humans, obviously, are far more complex than some animal species which naturally show parthenogenesis. Just to mention, there are female-...
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17 votes

Do males ever produce the offspring?

Yes the males of a group of bony fish Syngnathidae can bear offsprings or as you say produce offsprings. This group includes Seahorses and Pipefishes. In some species the male have either a brood ...
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  • 8,754
14 votes
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How does a sperm cell die?

So most cells require growth factors and survival factors to stay alive in an organism. Cells which stop receiving survival factors, such as sperm, undergo a process of programmed cell death (PCD) ...
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12 votes
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How was birth control realized in ancient days?

The need for birth control has been a concept for thousands of years and remains an important issue for men and women today, the need for contraception helped humans to achieve control over our ...
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  • 1,874
12 votes
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Can androgen-insensitive genetic-males get pregnant?

Short answer People with androgen insensitivity syndrome do not have a functional uterus and cannot bear a child. Background Androgen-insensitive genetic males may develop female genitalia and ...
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11 votes

Why asexual reproduction?

When you say, why don't we see more sexually reproducing species than asexual, I presume you are referring to bacteria, protists, archaea, some fungi, etc. Most multicellular organisims do reproduce ...
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11 votes
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How does a fetus retain a blood group different from its mother?

The maternal and fetal blood circulation systems are completely separate. The embryo's blood cells start developing at around week 5 gestational age (3 weeks after conception), the same way any other ...
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  • 2,227
10 votes

Does our eyeball increase in size as we grow?

First of all, I should quote the sentence from the MOST reliable ophthalmology sourcing in the world - American Academy of Ophthalmology: Section 11 - "Lens and Cataract" "The equatorial diameter of ...
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  • 5,620
10 votes

Have we ever observed two drosophila lineages that evolved reproductive isolation in labs?

Diane Dodd's experiments on Drosophila pseudoobscura would be another example of lab-based speciation. http://www.jstor.org/stable/2409365?__redirected To summarise - four populations each adapted ...
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9 votes

Could a sperm be altered to contain a female's genetics?

You might be interested in this article. In this study they created haploid ES cells from artificially activating an unfertilized oocyte and growing the haploid cells. These cells, when introduced in ...
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9 votes

Why do we have more male infants born?

There is an article in the Journal of Popular Science from 1885. However, I do know there is at least one more recent article floating around some where since I read it. At the moment, I can't find it ...
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9 votes
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Can females be recreated from male DNA?

Short answer Technologically yes, but practically no, because there would be no surrogate mother available to bring the artificial XX zygote to term. Background Theoretically a cell with two male Xs ...
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9 votes
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How do traits with no negative effects get "weeded out" via evolution?

Oops I wrote a lot! This is almost a very brief introduction to some concepts of population genetics. A little bit of terminology first Locus A locus (plur. loci) is a position on a chromosome. ...
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9 votes
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How did the orchids evolve to support pseudocopulation when they do not have any organ for vision to see how insects look like?

Evolution does not work based on an organism (or designer) "seeing" a problem and seeking a solution. Evolution via natural selection works when members of a population that have a certain heritable ...
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9 votes
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A study has found that cell phones cause infertility, is this something to worry about or is the study flawed?

The study is basically worthless. First, the study was not constructed to test this hypothesis, so it's just something interesting that may point to future studies. It does not provide sufficient ...
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9 votes

Why do OX5034 GM mosquitos require the presence of tetracycline to survive? What does the drug do in this case?

They don't go into any detail on the sites you link to and I don't have time to look into patents, but from the context it sounds like they may be using a tetracycline repressible promoter. This is ...
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  • 5,203
9 votes

In life history theory, does trade-off between reproduction and growth and maintenance imply longer health span for a sexually inactive organism?

I am not sure if life span could be extended in such circumstances but the probability of survival could probably increase, given the high metabolic costs of growing and raising offspring. I work ...
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8 votes
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What is this Sacrificial Reproductive Strategy Called?

It is called Semelparity. From wikipedia: Semelparity and iteroparity refer to the reproductive strategy of an organism. A species is considered semelparous if it is characterized by a single ...
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8 votes

Why are female not competitive for reproduction like males?

As @Dexter said, there are examples of species where female compete for the access to the males but most often it is the other way around; males compete for the access to the females. The reason for ...
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8 votes
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Why are mice with a single X chromosome and no Y chromosome males?

Almost all mammals (including mice and humans) have two sexes where the males have a Y chromosome and an X chromosome (whereas females have two X and no Y chromosomes). This is not the only way ...
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  • 8,718
8 votes
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What wasp like insect breeds in clay pots with dead spiders?

It's some sort of potter wasp/mason wasp (Eumeninae). The spiders are paralyzed and brought there as food for its larvae. Here is an example of an opened nest I found on Bugguide.net that looks ...
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  • 2,049
8 votes
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If a mother had a child with her own son, could a paternity test yield positive result for the son's father?

Let's approach some different methods of distinguishing parents: 1: The Y chromosome. These are passed down from father to son. Therefore, if the baby is male, its Y chromosome will be the same as ...
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