Questions tagged [sexual-reproduction]

Reproduction involving two morphologically distinct gametes, such as sperm and egg, where offspring inherit genes from two parents.

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Why do the two sexes have different reproductive costs and capabilities?

Is there an evolutionary explanation that shows why the reproductive costs are mostly on the female sex? And therefore, why do males can potentially have more offspring? Does that happen to create ...
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Is it true that recanalisation of the vas deferens, if any, tends to happen soon after a vasectomy (less than 1 year), and if so, why?

https://doi.org/10.1016/s0140-6736(00)02436-3 "How reliable is a vasectomy? Long-term follow-up of vasectomised men": Most episodes of recanalisation are believed to happen soon after ...
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Flatworms sexual reproduction; one must be the mother and the other the father?

I watched this. I wonder if both of these flatworms ever end up pregnant. Earthworms are simultaneous hermaphrodites, meaning worms have both male and female reproductive organs, just like flatworms. ...
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What causes the sound of climaxing bees?

I just saw the funniest video of bumblebees(?) having sex. (mirror) As they were getting it on, there seemed to be an almost audible 'moaning' coming from the pair. From what I presume it was a sexual ...
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Why does inbreed produce a higher percentage of abnormal babies? [closed]

The babies of close (say, brother and sister, or cousin and niece) family members have a higher chance of being born with an abnormality than babies from non-family related men and women. Why?
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Why do human females have periods?

Why do human women have periods when most animals don't? It is known that the unfertilized egg needs to be shed from the uterus. But why shed the whole endometrium? Why didn't evolution put ...
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1answer
95 views

Polyandry in birds

The WP article on Bateman's principle states “Until recently, most bird species were believed to be sexually monogamous. DNA paternity testing, however, has shown that in nearly 90% of bird species, ...
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If species are reproductively isolated, then how are interspecific hybridisations carried out?

during fertilisation there is compatibility test done so that both sperms and eggs are of same species. the zona pellucida of egg bears sperm specific receptor proteins(ZP3 receptor proteins) which ...
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Sperm formation - Frequent Ejaculations

I have visited various authenticated websites and other materials and learnt that a complete sperm development takes approximately 64 days. My doubts : If sperm truly takes 64 days to develop, how ...
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Recommended books and articles on the origin and evolution of sexual reproduction? [closed]

I'm interested in learning about the origin and evolution of life on Earth. In particular, one topic that puzzles me a lot as a layman is the evolution of sexual reproduction, since the DNA mutations ...
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Exact meaning of the term “clutch”

When reading a Wikipedia article to do with chickens, I have come across the term "clutch", but I was not able to entirely figure out what this word means. I was wondering whether the term clutch can ...
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Does antibodies get produced in female body against sperms?

Our immune system produces antibodies against any foreign particles entering our body.In female body sperms are a foreign particle .Does females produce antibodies or some sort of chemical resistance ...
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What is the developmental and health outcome of an XY individual with an SRY addition on their X chromosome?

I know that "XX male" syndrome occurs through various means, including the addition of an SRY gene in one of the X chromosomes. The developmental and health outcomes of such individuals can be ...
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What is the weight of a single human sperm (spermatozoon) compared to a single human egg

While the difference in dimension is well covered, I have been unable to find the mass measurements of each.
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34 views

In human embryology, what starts ovum cell division?

Maybe I am not using the correct search keywords in Google, but I cannot seem to find anything beyond basic information taught in schools about fertilisation of the egg by the sperm. After the sperm ...
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Why is there such a long interval between ages of sexual maturity and of reproduction in female chimpanzees?

There seems to be some disagreement on the ages at which female chimpanzees typically reach sexual maturity and when they typically first give birth, but regardless, different sources seem to agree ...
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How does antagnostic coevolution work in ducks?

I recently learned that in ducks, the penis and vagina have coevolved: the vagina of the female ducks gets dead-end sacs and clockwise coils; the penis of male ducks become longest and its morphology ...
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What's the difference between male and female?

As long as we only look at humans the differences are clear: males have chromosomes XY, produce sperm and don't get pregnant. Females have chromosomes XX, produce egg cells and bear babies. But when ...
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Sex and human's sexual urge.

Why is it necessary for humans to feel pleasure while having sex? Why is it that other animals don't need to experience it? Is it evolutionary ? Why do we mate for pleasure when it's so energy wasting/...
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1answer
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Why spermatogenesis is an independent process while formation of ovum is dependent on fertilization by sperm?

At the time of ovulation,secondary oocyte is arrested at Metaphase II and goes into the fallopian tube.If fertilization occurs, sperm binds with secondary oocyte and releases Anaphase promoting factor ...
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Sexual Reproduction in Humans

Is the human egg cell (ova) considered motile? We know that is is not actively motile but it is transferred via the fallopian tube to the uterus. Does that make it motile?
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If a woman was fertilized with her own DNA, would it be her clone?

Several questions: 1) Can human DNA fertilize an egg, without having been naturally packaged in a sperm cell? 2) If a female had her ovum fertilized with her own DNA, would the fetus be her clone? ...
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Polyploidy, or why plants of different species can produce fertile offspring hybrids more frequently than animals?

This site says: Plants hybridize much more frequently and successfully than animals do. [...] Chromosomal doubling (polyploidy) occurs more frequently in plants and facilitates the fertility of the ...
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Limitations of the Self-Incompatibility Mechanism in Plants

For a given plant species, how many types of S-loci exists to prevent self-pollination? I would like to know how often a plant stops fertilization process by other plants, thinking the pollens belong ...
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Evolution of the haplo-diplontic life cycle

From wikipedia > Biological Life Cycle: haplontic life cycle - the haploid stage is multicellular and the diploid stage is a single cell, meiosis is "zygotic". diplontic life cycle - the diploid ...
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No. of meiotic divisions to produce specific no. of seeds

If I want to produce 100 seeds. Then the no. of meiotic divisions is 125 which can be calculated by the formula x + x / 4. x = no. of seeds produced. How is this formula derived?
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In men, why do over 80% of sperm have abnormal form? [duplicate]

Here is the percentage of normal forms among fertile mens according to the centile (Source: Cooper et al. 2010): 2.5: 3% 5 (below this is Teratozoospermia): 4% 10: 5.5% 25: 9% 50 (median): 15% 75: ...
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How does better sperm result in more viable offspring?

Quoting wikipedia: Greater choice and variety of mates increases a female's chance to produce more viable offspring. This led me to the question: "How sperm parameters are connected with entity ...
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185 views

Are Males the main evolutionary tool for production of genetic variation necessary for evolution?

What I'm saying here is just a personal reflection, that might turn to be gravely erroneous, actually I'm asking that because I didn't see it presented elsewhere. Evolution is propelled by two ...
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Can threat to survival increase mutation rates in germline cells?

Can stress that is related to a threat of survival of a population of animals or plants in some environment, like due to hunger, thirst, fear from predators, etc..; results in an increase in average ...
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Is Mutation Theory still “valid” for complex organisms?

I'm afraid like most people I suffer from having learned "A History of Evolution" in school, rather than cutting to the chase and learning the actual "up to date" version of the subject. (Imagine if ...
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How does DNA still work after recombination?

If you take two computer programs and randomly swapped pieces from each of them. The result is not going to work. It will just be garbage. If you take two novels and randomly swapped chapters the ...
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What are the (statistically) normal pH levels in the most-outer part of human sexual organs?

What are the (statistically) normal pH values of the outer skin/epidermis of human sex organs (groin/crotch) in the male and female? e.g male testes, female vulva, male glans, the enveloping epiderm, ...
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What are the advantages of sexual reproduction over asexual reproduction? [closed]

What are the advantages of sexual reproduction over asexual reproduction? How does variation influence ecological and evolutionary success?
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Spermatozoa and sperms

Does spermatozoa and sperm have different meaning?If they are same why do wikipedia have 2webpages ? But most websites mention them as the same thing.I am confused .Thank you in advance
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How does acetylcholine (aCh) cause erection?

I have read this article on physiology of erection : Activation of cholinergic receptors on the endothelial cell by acetylcholine or stretching of the endothelial cells as a result of increased ...
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In what fluid does the sperm swim in the oviduct?

We know that after sexual intercourse, sperm enters the female body and continues to pass through the oviduct by swimming. "Swimming" implies the presence of fluid. I want to know what that fluid is ...
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Where does female ejaculate actually originate from?

It's common knowledge that it's released via the urethra, but where does it originate? If it doesn't come from a part of the clitoris, then why is the clitoral glans called the clitoral glans? How ...
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Is dandelion a sporophyte or gametophyte?

My text book claims all land plants undergo alternation of generation. However, I don't see how it could be with dandelion. The flower head gets pollinated and then turn back on itself. After a while ...
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Evolution of sexual reproduction from asexual

How exactly did asexually reproducing organisms evolve into sexually reproducing ones? Why was it considered more favourable?
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In bacterial conjugation, how do F+/F- cells detect each other?

I've just learnt about bacterial conjugation and while it is interesting info about early sexual activity in microbes, one aspect confuses me and doesnt seem to be mentioned in the material I read: ...
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What animal has the longest juvenile period?

I just heard the following complaint from a comedienne. Humans are the only animal that is completely useless for the first twenty five years of life. Obviously this is just a joke but it is true ...
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Among primates, is it true that homosexual behavior is extremely unnatural and uncommon?

I was recently reading a book published by some anonymous biologist known as Lynn Saxon, in which she appears to want to refute Christopher Ryan's thesis in Sex at Dawn that prior to the invent of ...
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why has evolution favored sexual reproduction using two mates over sexual reproduction using three mates?

Many animals species require two members — a male and a female — to sexually reproduce. Why has nature (or the process of evolution) chosen to favor the form of sexual reproduction which requires two ...
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How do the chromosomes arrange themselves after fertilization in humans?

In human reproduction the male produces sperm containing 23 chromosomes and the female has the oovum containing 23 chromosomes , so after fertilization the zygote contains 46 chromosomes. What I want ...
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Spermatogenesis question

I found this diagram in my textbook regarding the process of spermatogenesis. But, I doubt if the labelling done is correct or not. Especially, I can't figure out any difference between the cells ...
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Can any animal ejaculate at will without physical contact?

Note: In this question, I'm asking about animals that have a penis that functions very similarly to humans. I've read some animals have dramatically different methods of copulation and physiologies, ...
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Is it Theoretically Possible to Create a Male clone from the donor Cell of a Female?

I understand that Dolly the Sheep was created without the presence of a sperm cell. Instead, nucleus DNA from somatic cells of adult sheep were used. Since Dolly was female, i am assuming that the ...
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How diverse are the sperm cells of an individual male due to random mutations?

Due to the sheer number of sperm cells in an individual and the rate of mutations, are they likely to be incredibly diverse and encompass most of what we see across our species? For instance would it ...
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Do reproductive organs function before puberty?

Testis means one of the two male reproductive glands that produce spermatozoa and secrete androgens. Ovary means one of usually two organs that produce oocytes and secrete oestrogen and progesterone. ...