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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42
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1answer
7k views

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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2answers
4k views

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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5answers
3k views

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 ...
10
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4answers
984 views

Can sexual reproduction create new genetic information?

Is there a small chance that in sexual reproduction a new allele forms in the off-spring that was not present in either of the parents, or are the alleles in the offspring always from at least one of ...
10
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1answer
2k views

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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2answers
520 views

Do males ever produce the offspring?

Are there any non-asexual species in which the male of the species produces the offspring? If so, why are they considered male and not female?
8
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2answers
1k views

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 ...
8
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3answers
2k views

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 ...
8
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3answers
29k views

What is the function of the polar bodies produced during oogenesis?

Why are polar bodies produced during oogenesis in human females? I read that polar bodies are produced during meiosis so that the oogonium (or gamete mother cell) can be converted into a haploid ...
7
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1answer
465 views

What is most ancestral: isogamy or anisogamy?

Sexual reproduction can be feasible with anisogamy (gametes of different sizes i.e. genders) or isogamy (gametes of same size i.e. mating types) or with undifferentiated gametes (i.e. true random ...
6
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2answers
319 views

Can diploidy evolve in absence of sexual reproduction?

Theoretical question Can diploidy (or polyploidy) evolve from a haploid lineage in the absence of sexual reproduction ? For what theoretical reason? How can such evolution take place? Empirical ...
6
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1answer
411 views

Why are mice with a single X chromosome and no Y chromosome males?

I was searching online and I read this article Mice can be male without Y chromosome and this is a part of it: The experiments demonstrate that there are multiple ways to make males, says Richard ...
6
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1answer
154 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 ...
6
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1answer
5k views

What happens to tube nucleus of the pollen tube after fertilisation?

Background: Pollen tube contains a vegetative cell and a generative cell. The vegetative cell contains the tube nucleus, and the generative cell contains two male gametes. The two male gametes fuse ...
6
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1answer
259 views

Conjugation in bacteria

I was studying about conjugation in bacteria, I have a doubt. In conjugation F- cell transforms into F+ cell when there is a formation of sex pilli in between the two. The doubt is if the F- cells ...
5
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2answers
436 views

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 ...
5
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1answer
130 views

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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0answers
356 views

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, ...
4
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2answers
29k views

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?
4
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1answer
206 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 ...
4
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1answer
94 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 ...
4
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1answer
120 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 ...
4
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1answer
845 views

Why is pollen used as a dietary supplement?

Sporopollenin is the hardest biological substance and can't be degraded by any know enzyme (my school textbook). Then why is pollen used as a dietary supplement if it can't be digested? Also, pollen ...
4
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2answers
104 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 ...
3
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1answer
171 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 ...
3
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2answers
70 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 ...
3
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3answers
981 views

Evolution of sexual reproduction from asexual

How exactly did asexually reproducing organisms evolve into sexually reproducing ones? Why was it considered more favourable?
3
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0answers
266 views

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: ...
2
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1answer
77 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 ...
2
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1answer
1k views

Is Parthenogenesis known as Sexual reproduction or Asexual reproduction?

I have seen that in some books refer to Parthenogenesis as sexual and in others as asexual. The ones that say it's a form of sexual reproduction,they focus on the fact that meios has happened in the ...
2
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1answer
30 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 ...
2
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1answer
118 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 ...
2
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1answer
204 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 ...
2
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1answer
65 views

How many plants arise from a polyembryonic seed? [closed]

When I asked this question to my teacher she said that she doesn't know. So I wanted to know? Is there any use of polyembrony in plants?
2
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1answer
89 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 ...
2
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0answers
58 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 ...
2
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0answers
132 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) ...
2
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0answers
223 views

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/...
2
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0answers
337 views

Where does new blood comes from when penis get erected? [duplicate]

In Humans, During sexual arousal in males, his penis will get erected with blood. Where does this new blood coming to fill his penis which is required for erection ?
2
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0answers
435 views

Motile egg cells

According to the Wikipedia article on anisogamy, some types of this form of sexual reproduction involve motile egg cells, i.e. they're capable of movement under their own power, just like sperm cells. ...
2
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0answers
82 views

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 ...
2
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0answers
30 views

Extremely Scientific Sexual Education Material?

I'm trying to prepare material for 'the talk' about sex and reproduction. I know there's plenty of great books and resources out there for young readers, which I'll use to start with, but I'm also ...
2
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0answers
85 views

Does increased calorie intake cause increase in libido in humans?

I'm interested in the effect of increased calorie intake on sex hormones and chosen mating strategy in humans. I'm aware that humans have a dual mating strategy - somewhere between pair bond and ...
2
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2answers
13k views

Difference between inbreeding and interbreeding

Is inbreeding the same as interbreeding? On this site interbreeding is defined as (http://www.thefreedictionary.com/interbreeding): To breed with another kind or species; hybridize. To breed ...
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1answer
718 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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2answers
183 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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1answer
1k views

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
1k views

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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1answer
378 views

How can a haploid plant be bisexual?

According to Wikipedia: Meiosis is a specialized type of cell division that reduces the chromosome number by half. This process occurs in all sexually reproducing single-celled and multicellular ...
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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 ...