The biological process by which new individuals are formed.

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Relationship between lifespan and reproductive age?

I remember reading a while ago that there is a "general rule" in biology between an animals lifespan and when they reach reproductive age. In other words, an organism that reaches sexual maturity ...
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Do only one or both pairs of homologous chromatids exchange genetic material during the process of crossing over?

To be specific: Assume chromosomes A and B are homologous. They've both replicated into A1, A2 and B1, B2 and have formed a tetrad at the equator (synapsis). Most textbooks show either A1 and B1 OR A2 ...
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How is excess semen removed if ejaculation does not occur?

There are some attempts to answer the question that I found via cursory Google search, but none of them were appropriately sourced. This site claims that they are "recycled like blood cells", but ...
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Is there a mechanism by which mammals lose interest in a partner after mating?

I'm reading the book called "Cupid's poison arrow", which revolves around a rather simple assumption: most mammals, including humans have a genetic program that is responsible for ever increasing ...
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28 views

How only one follicle develops into graffian follicle?

I've studied that one out of many follicle develops into mature or graffian follicle. The fact which confuses me is that, since all follicles are in same ovary, close to each other with equal supply ...
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52 views

Negative association between habitat quality and reproductive success in birds

I'm looking for bird studies that have found either a negative correlation or no correlation between habitat quality and reproductive success. Or in other words, bird studies that have found that ...
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117 views

Mating types in fungi (and somatogamy)

I would have some related questions about the mating types of fungi. Does a single spore generate a mycelium possessing only one mating type? If it does not in general, do Ascomycota and ...
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512 views

Do Asian women have more difficult births than Europeans?

I recently heard a claim that Asians in general have more difficult births than Europeans. Is this true? I have found a few studies(1,2) on the effect of ethnicity on birth outcomes but they seem to ...
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23 views

Breeding Southern Right Whales Genetics

I don't know much about biology. I just like watching David Attenborough videos and this made me curious. I just watched this video about breeding Southern Right Whales, and these two quotes puzzled ...
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118 views

How long does conception take?

I know that conception is a multi-step process. A sperm fuses with an egg. Its contents diffuse into the cytoplasm. Dad's DNA is transported to the nucleus. Proteins are gradually made from Dad's DNA....
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43 views

Expected reproduction rate of a dandelion and/or fern

I am working a basic mathematical/computer simulation of an ecosystem, and I need to know the birth rate of each organism in my simulation. However, I could not find any data for how often a small, ...
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105 views

Is the number of stamens always 9 for geranium?

We are studing in class the reproduction of plants. We start the lesson by observing some components of flowers, it was the Géranium. First of all we start counting the number of sepals , petals and ...
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41 views

Division of Polar Body

The first polar body formed after meiosis-I is completed in oocyte, may or may not divide. Why is the statement that "it may or may not divide"? Is it random ?
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A program for cell motility assessment with a batch process function?

Cell motility assessment is a branch of experimental biology or medical science. One example could be an assessment of treatment effects on sperm motility of an animal. The standard procedure involves ...
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72 views

Why does it take many sperm for one sperm to fertilize an egg?

Hundreds of acrosomes must undergo exocytosis to digest holes in the zona pellucida. This is one case that does not bear out the adage, “The early bird catches the worm.” A sperm that comes along ...
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29 views

Founders of Cnidarian colony

I know that colonial Cnidaria enlarge their colony by the means of asexual reproduction and sexual and asexual reproduction can originate individuals that will be part of other colonies. Nevertheless,...
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Ancestral states of sex determination system

Most (maybe all?) species that reproduce sexually have either genders (anisogamy) or mating types (isogamy). There exist today many different type of sexual determination system. There is a whole ...
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31 views

Is there a database of pollen-seed distances across plant species?

I was enjoying Richard Smith's excellent answer to this question, and wondered: If you consider the pollen/seed distribution range to be plant locomotion, is there a database that compares these ...
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41 views

Why is sex pleasure giving activity but not childbirth?

Asking from an evolutionary viewpoint. Sex is a pleasure giving activity so that it encourages reproduction and spreading of genes. But childbirth ,the most crucial part of the reproductive process, ...
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14 views

What drives male fish to spray their milt?

In mammals the sexdrive of the males is because the intercourse provides a satisfaction where after, the sperm is ejaculated into the female. However, the male sperm doesn't enter the female fish but ...
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15 views

what is the natural way of rose to propagate by its vegetative cells?

I have read that rose reproduces sexually. But I have also heard that it can propagate by its vegetative cells (vegetative cells in its root). Is this correct? If yes, can I know how does it propagate ...
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25 views

Zygote Implantation and Pregnancy Detection

In a normal pregnancy, the embryo (blastocyst) implants between 8-9 days after ovulation. My understanding is that it is able to implant because the fertilized embryo produces a hormone that triggers ...
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69 views

How often does parthenogenesis in mammals happen?

Probably everyone knows that mammals can't produce viable offspring by parthenogenesis. But there are reports of human chimeras (see: a human parthenogenetic chimaera) and it's known for mice to ...
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43 views

Big cat in heat for months?

In this documentary about a lioness and a leopard the leopard is in heat for months. https://www.youtube.com/watch?v=MGqmylkOuKw Usually a big cat would be in heat for 5 days and then not in heat ...
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104 views

How many mitotic divisions do haploid cells undergo before fertilization?

Background This question is about human physiology and gametogenesis. A spermatozoid is not necessarily the direct "offspring" of diploid cell. Stated differently, a spermatozoid cell can be the ...
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from an ageing reproductive stem cell's DNA to baby's “brand new” somatic cells' DNA

On the one hand, somatic cells's DNA age as life goes on, mitosis after mitosis, and that is reflected into reduced telomeres. On the other hand, during life, reproductive stem cells must age too. ...
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32 views

Location of embryo development in angiosperms

What floral organ does the development of the embryos of angiosperms occurs in? Is it the ovary? The pollen tube grows down through the style and double fertilization occurs and the embryo begins to ...
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54 views

Hot water bath and Infertility

From here: Effect of temperature. Sperm cells will not mature at core body temperature in most mammals (spermatogenic DNA polymerase b and recombinase activities exhibit unique temperature optima)...
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437 views

How does proximal centriole of human sperm function?

I've read that the human's unfertilized oocyte ( stuck at metaphase 2 of meiosis ) lacks centrioles and that it completes meiosis 2 after fertilization as sperm gives its proximal centriole. Then what ...
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31 views

Creating Sperm via cell culture adaptation

I am wondering if it is theoretically possible to create "artificial sperm" via cell culture adaptation. That is at very high level, can you replace the genes of one sperm cell with those of another ...
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30 views

recombinant gametes

Suppose you are able to observe under a microscope the total number of meiotic divisions occurring in one gonad of a given individual and to outnumber exactly the crossovers between two given loci ...
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84 views

Why does the ovum prefers to be arrested at metaphase 2 of meosis before fertilization? What is the possible advantage of this process?

Why does the human ovum prefers to be arrested at metaphase 2 of meosis before fertilization? What is the possible advantage of this process??Please help me with it.
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136 views

Why aren't antheridia and archegonia touching?

Antheridia and archegonia are the two male and female gametangia, respectively, and they are found in bryophytes. To cause fertilization, usually a thin film of water must be present for the sperm ...
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13 views

What did William Harvey discover from experimenting with deer?

On his wikipedia page, I read the following: In particular, Charles' hunting expeditions gave Harvey access to many deer carcasses; it was upon them that Harvey made many observations and ...
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Function of prostate gland and seminal vesicles

Multiple sources (my textbook, internet, videos) have been confusing me as they state various things. Which structure produces most of the semen and produces carbohydrates for the sperm; the seminal ...
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Is the bulbourethral (Cowper) gland turned on during puberty or is it on at birth?

I am trying to find information about the bulbourethral (Cowper) gland and if it gets turned on during puberty or not. I tried asking several other online sites and they said they couldn't help. I don'...
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44 views

What is effect of sperm in blood?

Staphylococcus aureus, Streptococcus pyogenes, and Clostridium perfringens all produce hyaluronidase. Each of these bacteria are pathogens (use hyaluronidase as a virulence factor to destroy the ...
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Does the spermatogonia divide to form primary spermatocyte or grow into primary spermatocyte?

I have two contrasting sources. One says that a spermatogonia 'divides' into two primary spermatocytes. The other says that there are two types of spermatogonia, one of which 'grows' into a primary ...
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38 views

How many children could Hunter-Gatherer support?

Hunter-Gatherers, to my knowledge, have to cover a fair amount of ground in order to be able to live off the land. This ought to have a placed a limitation on the number of children that they could ...
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45 views

Why do earthworms cross-fertilise being hermaphrodite

Although the earthworms are hermaphrodites, they dont di self fertilisation but crossfertilisation. What is the logical reason behind them doing it?
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284 views

When does meiosis occur in flowering plants?

At what point in the development of a flower does meiosis occur?
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Nature vs Nurture in Rooster mating dance: Are roosters lame dancers because they never learned any better?

I've seen, read about, or heard several avian courtship dances, flights, songs, and other rituals. They are general very impressive, fancy, and beautiful. Roosters, by comparison, are quite lame. The ...
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Why do four spermatids have different genomes?

It's been a while since my last class in genetics, so I've forgot most of it. However, I found myself studying human reproduction and I've the following doubt concerning spermatogenesis: the process ...