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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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1answer
32 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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31 views

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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47 views

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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54 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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44 views

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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131 views

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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Human children with sex abnormalities due to food packaging and river pollutants?

Some news sites are highly vocal about transgender news articles, and also sometimes report hormonal issues due to pollution, like sex-changes in fish and low sperm counts in men. Is there any ...
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230 views

Why are (some) human men sexually attracted to female breasts?

Many human men are sexually attracted to female breasts. Is there an evolutionary reason for this?
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173 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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1answer
83 views

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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83 views

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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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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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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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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146 views

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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177 views

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 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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125 views

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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420 views

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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1answer
96 views

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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1answer
1k views

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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1answer
128 views

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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2answers
106 views

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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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. ...
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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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211 views

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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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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160 views

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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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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2answers
76 views

When does genetic randomization happen?

When two parents (regardless of species) reproduce in sexual reproduction each offspring is generally a random combination of genetic traits from each parent. Their developed traits then depend on the ...
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1answer
3k views

Hardy-Weinberg sex linked formula

The "big five" assumptions are the ones listed in the main text. However, the basic formulation of Hardy-Weinberg equilibrium also relies on a few other assumptions; Allele and genotype frequencies ...
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Why are male gametes and female gametes not equally sized

Why is it that male gametes are smaller and produced in larger quantities than female gametes that are large and lesser in number. Why aren't the gametes equally sized, or their sizes the other way ...
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2answers
524 views

How does sexual reproduction generate more genetic variation?

I'm curious as to why sexual reproduction generates genetic variation. For me, the term genetic variation is a little ambiguous. The way I understand it, it's the number of alleles at a locus in a ...
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100 views

At what level of relation does inbreeding become dangerous?

Inbreeding within first cousins appears to have an established history of dangers, and anything closer than that relationship also. However, how distantly related do two individuals have to be for ...
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2answers
149 views

How do biologists determine the parents of a child

I am not well-versed in biology so this question might be wrong. As far as I understand meiosis, two germ line cells with 23 chromosomes each (one cell from the father and another from the mother) ...
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62 views

Number of alleles' variations in a mushroom that has over 20,000 sexes

I am trying to understand the mating behavior of a particular species of fungi known as Schizophyllum commune, or the split-gill. I found a blog post that explains the mechanisms that define the ...
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1answer
100 views

A stem cell method for creating artificial wombs?

1) Grow the endometrium using stem cells (It has already been done (Cambridge, 2017)) 2) Attach the embryo to it and allow the placenta to grow. In 2003, there was a researcher at Columbia who did ...
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85 views

Organisms that do not wish to reproduce [duplicate]

Are there any organisms that do not want to reproduce? As humans, there are people who do not want to reproduce with the opposite sex. Do any other organisms replicate this behavior? Also, why does ...
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975 views

Location of male and female reproductive organs in fern (prothallus)

I can't seem to find an authoritative answer to this anywhere else online. Basically, my school text-book says the antheridium (male organ) is located on the lower surface of the fern prothallus and ...
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1answer
211 views

Sexual reproduction in organisms with 1 parent

An organism that carries out sexual reproduction with itself, for example a flower with both the anther and stigma, does it actually contain 2 sets of genes in order to produce genetically ...
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415 views

How Excessive masturbation can make a person unfit for army? [closed]

Recently I saw this news trending, I never heard single disadvantage regarding masturbation. But China Army considering it has danger for army. So How Excessive masturbation can make a person unfit ...
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Why can't two different genetically species reproduce to give a viable offspring?

What is the reason that only organisms belong to same species can produce a viable and reproductively healthy offspring but organisms of two different species cannot?
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478 views

Variations in asexual reproduction

It has always been said that sexual reproduction produces offsprings which are superior to their parents, due to the variations which they acquire causing them to survive better in their environment. ...
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134 views

Role of neuraminidase in preventing polyspermy in humans

Neuraminidase is a hydrolytic enzyme present in the acrosome of human sperm. It removes neuraminic acid (salic acid) from glycoproteins. I have read in a book that due to this reason it (the enzyme) ...
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1answer
773 views

Does sperm weight causes sex ratio?

Chromosome X in female sperm is heavier than male Y chromosome. Does it causes difference in fertility of sperm and heavier female sperm is unable to fertilize better than male sperm? This is given ...
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121 views

How is it possible for monosomies to occur?

I was taught in biology class that a cell dies if it doesn't have at least one copy of a chromosome "type". If this is the case, that means that: Zygotes without a copy of a specific chromosome (for ...
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213 views

Is there a theoretical maximum on the number of sexes a given species can have?

Background: To the best of my knowledge, most sexually-reproducing species of organism have two sexes, although there are also sexually-reproducing species of organism (flatworms come to mind) which ...