43
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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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27
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Crossbreeding mouse and chinchilla
"Chinchilla" is both a separate rodent, and also a name for a Mus musculus mouse coat color/pattern. Here it's used in the latter context. You may be more familiar with the word "agouti&...
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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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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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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
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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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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
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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
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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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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
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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
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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
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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8
votes
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What animal has the longest juvenile period?
As you indicate in your question, the average age of sexual maturity is probably the best way to approach this, since immaturity is usually how juveniles are defined. Age of puberty is also different ...
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7
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Why are female not competitive for reproduction like males?
Actually there are lot of examples in which females are competing for mating which also have evolutionary consequences. It is also widely spread in nature. This competition may arise at cellular, ...
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Pregnancy from two parents with incompatible blood types, can it lead to complications?
The rhesus factor (the + / - part of the blood group) can cause complications with pregnancy under certain conditions and lead to the so called Rh disease:
If the mother is rhesus negative and the ...
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How many primary oocytes in human female body at birth?
Short answer: The developmental process starts from oogonia as follows:
Oogonia(7million) in the foetus develops into primary oocyte(2million) in the foetus prior to gestation which again develops ...
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Do hermaphrodites have more nerve fibers in their puendal nerve?
Short answer
The genitals of true intersex individuals are not duplicated. Instead, their external genital features are hybrid structures. In turn, it's not a matter of duplicated neural innervations.
...
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7
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Minimum age to reproduce
The youngest fathers recorded were 11 years old (see wikipedia >
List of youngest birth fathers).
The youngest mother recorded is L. Medina was 5 years, 7 months and 21 days old when giving birth, ...
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7
votes
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Very frequent multiple births in humans
Risk factors for dizygotic twinning are related to multiple follicular development, and include maternal family history, ethnicity, geography, maternal parity, maternal age, and, of course, use of ...
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votes
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Sperm formation - Frequent Ejaculations
The arithmetic of human sperm
A young, healthy man produces about 1000 sperms every second, which comes to about 90 million per day [1]. These sperms are stored in the epididymis and ductus deferens ...
- 1,297
7
votes
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Is being able to interbreed and produce fertile offspring a transitive relation in biology?
The ring species conundrum
As commented above, in essence this is the classic case study of ring species, and reading up on it will completely answer your question. A case of ring species is ...
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6
votes
Do only one or both pairs of homologous chromatids exchange genetic material during the process of crossing over?
Yes, it is perfectly possible for both pairs of non-sister chromatids to cross over in a single tetrad. The "standard textbook" depiction is a simplification, true tetrads can sometimes be very ...
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6
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Why do chickens continuously lay unfertilized eggs?
Chickens are domesticated Red Jungle Fowl. In the wild, Red Jungle Fowl live in flocks with one rooster for every few hens (where "few" is probably less than five in the wild, though in zoos flocks ...
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