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 does oogenesis have to begin in foetal stage itself?
In males, spermatogenesis begins after puberty and they retain this ability throughout their life time. However, in females, oogenesis begins and ends in the foetal stage itself and the female is ...
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Is the germ line epithelium involved in oogenesis?
Oogonia are the germinal epithelium cells, meaning that they come from the germ line epithelium, right? But in one website, they say that the germ line epithelium is not involved in gamete production ...
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Intersexual competition regarding energy investiture of offspring
A while ago I remembered reading about a species that had evolved so that the male sperm cells promoted the energy investiture of the female in this offspring upon fertilisation. Since this was a r-...
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Do wolves mate with siblings?
I have just watched a "documentary" on a female wolf raising her cubs in the Alps. I found various aspects of the programme less than convincing, but one in particular puzzled me. The alpha ...
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Why do humans have sex for recreational purposes? [closed]
It never made sense to me why human beings crave sex other than for reproducing. It controls our society. It causes heartache, jealousy, anger, low self-esteem etc. Sometimes humans will have sex ...
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For animals with separate hermaphrodite and non-hermaphrodite populations which is more common, female + herm or male + herm?
I think the question already says it all. I know there exist animals that have both herm and female populations and other's with herm and male populations, I'm not personally aware of any animal that ...
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Can offspring be less genetically similar to the parent than more distant relatives?
I'd be interested in answers about any sexually reproducing species, but for simplicity I'm going to focus on humans in this question.
If the parents are very genetically different (i.e. the number of ...
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Are there any other types of sex systems besides 2-sex system and the hermaphroditic system? [duplicate]
For example, 3-sex system or even more.
Would a 3-sex system be too chaotic?
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Can a species stabilize with non-Fisherian (e.g. 3:1) female:male ratio?
A (possibly naive) idea that could make it possible is if the male genes contribution is inversely proportional to the female:male stability ratio.
For example, if there's a population of 300 females ...
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why are dizygotic twins genetically dissimilar
I am a high school student and I am a little confused in a topic related to dizygotic twins, I get to know that dizygotic twins are genetically dissimilar because they are formed as a result of two ...
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Why isn't the ovum reabsorbed into the body (like sperms) if it is not fertilised?
I have read that when sperms are not ejaculated out of the body, they are broken down and reabsorbed. Why can't the ovum be reabsorbed into the body instead of shedding it out during menstruation.
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Do some animals have a tolerance to the negative effects of inbreeding?
Are some animals more or less tolerant to inbreeding? By tolerant I mean do they have a genetic mechanism that allows them to inbreed and corrects for issues introduced through this? When I started ...
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Is human zygote unicellular or multicellular [closed]
Is the human zygote which is formed by fusion of sperm and egg a unicellular structure? Bcz at some places the 2 celled stage which is formed due to cleavage has been labelled as the zygote. So is the ...
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Check simple human fetus answers
Based on this image and questions, could someone please check my answers?
Question 1: At which one of the following points will the blood passing the point be more oxygenated after birth than before ...
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Does lack of adaptations for sperm competition necessarily shows the species are monogamous/serially monogamous/polygynous?
On the one hand adaptations for sperm competition, such as large testes, mate guarding, etc. are used to support that female in species are promiscuous.
On the other hand we know multiple eusocial ...
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Is there any evidence for sperm parameters being connected to fitness of the offspring produced by that sperm?
In most (if not all) sexually procreating species the amount of offsprings a male can produce is limited not by the amount of sperm he can produce, but by the amount of eggs his sperm can fertilize (...
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Reproduction in animals
Humans have acquired knowledge about their environment through many observations. Today, humans have wide variety of resources to gain knowledge about reproduction in human beings and other ...
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What are these structures inside a cut open Allamanda blanchetti?
As suggested by @tyersome in my previous question on the same topic which I posted yesterday, I have cut open few flowers of Allamanda blanchetti
in order to observe if any reproductive structures ...
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Allamanda blanchetti fertilization mechanism
Here is an Allamanda blanchetti flower in my garden.
My question is based on the observation that the flower seems to be devoid of any reproductive structures, i.e., Stamen or Carpel, so how does it ...
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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 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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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