The biological process by which new individuals are formed.

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Can sexual selection operate in temperature dependent sex determining organisms?

Or more broadly, are distinct forms of genetic inheritance (ie. sex chromosomes) needed for sexual selection? My thinking was that since there are no sex determining loci, there could not be linkage ...
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5 views

Cure for high anti TPO levels to attain pregnancy successfully [migrated]

Can a person with high anti tpo levels be treated to have successful pregnancy ? Does intralipid infusion help in this process ? Does prednisone help in this process ?
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1answer
24 views

Why can't gametes of one species fuse with that of the other species?

I have read that gametes of one species cannot fuse with that of another? For example the sperm of a dog can't fuse with the ova of a cat or a horse?
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3answers
71 views

Why didn't humans evolve to reproduce identical twins all the time?

According to the selfish gene theory, it seems like because identical twins sometimes get produced, a mutation to a gene that says, "if you have an identical twin, be fully altruistic towards them" ...
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38 views

How do you explain the seasonal variation in the number of the oogenic cells? [closed]

First, I don't know what is seasonal variation. Could you explain it as well?
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1answer
26 views

Albinism inheritance problem: what are the father's alleles if he got an albino kid?

Albinism is caused by a recessive gen "c". A normal man marries an albino woman. The first son happened to be albino. What are the possible phenotypes of the parents? What is the chance that ...
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2answers
88 views

The selective pressure of contraceptives

Does it seem probable that the existence of contraceptives (which has reduced human reproduction to below survival-level in many populations) will be a completely new selective pressure on human ...
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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 ...
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4answers
3k views

Can the third sex be categorized as Male or Female?

Hijra are people who have a penis (not sure if sexually active) but look much like a female (perhaps for some feminine biological property). Wikipedia says they are "physiological males who have ...
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28 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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0answers
15 views

About binary fission in amoeba [closed]

We know that amoeba reproduces by binary fission. Then does it mean that it never dies but keeps regenerating? In other words and more generally, does reproduction by fission by unicellular organisms ...
9
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1answer
78 views

What bacteria do unborn babies contain?

This Scientific American article states that "[human] infestation [by bacteria] begins at birth". This would suggest that unborn babies are free from any bacteria. However, if the mother catches a ...
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0answers
47 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 ...
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2answers
81 views

Why do we produce so many sperm?

So apparently we produce roughly 300 million sperm daily. Is there a reason why this is necessary? Wouldn't a much smaller (but still large) number be sufficient? Like, one million?
3
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1answer
39 views

What is the simplest autotrophic cell?

Very simple cells, such as Nanoarchaeum equitans, require a host to provide certain essential ingredients for life. Complex life-forms (like humans) require a whole ...
9
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0answers
59 views

How is centriole number maintained during meiosis?

I've found a website (Pearson's BioCoach) that claims centrioles duplicate in Prophase II. Is this accurate? Does it depend on the species in question? Looking at three textbook illustrations of ...
3
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0answers
35 views

Can two members of the same sex have a biological baby? [duplicate]

I imagine that this would work using a similar technique to dolly the sheep. For two females, the nucleus of an egg would be placed in a sperm which has had its nucleus removed. The 'female' sperm ...
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2answers
2k views

How was birth control realized in ancient days? [closed]

In ancient days, there were no birth control methods like condoms or contraceptive pills available. How did they control pregnancy?
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22 views

How does the Platypus grow before it eats?

From this fascinating documentary on monotremes it is mentioned that the Platypus is born less than 1 cm in length, but has doubled its size by day three when it begins to nurse. How does the animal ...
6
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1answer
129 views

Isogametes and oogametes

I have found the following definitions of different types of gametes: isogametes: gametes looking and behaving the same; heterogametes: gametes different in size or in behaviour; oogametes: gametes ...
9
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1answer
261 views

Why does the sex of the parent species determines the species of a hybrid offspring

I've read a little about hybrid animals, and have been amazed by the fact that the sex of the parent species determine the species of the offspring, in some hybrids. A male horse and a female donkey ...
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0answers
29 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, ...
5
votes
1answer
94 views

Can androgen-insensitive genetic-males get pregnant?

According to the linked report, people with androgen insensitivity syndrome appear as male, but have both feminine and masculine outer genitalia. However, I was not able to find out whether their ...
3
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0answers
50 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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0answers
35 views

The Human Menstrual Cycle [duplicate]

1) What happens in the ovary and in the bloodstream that brings about this change in the uterus? 2) Why does the level of FSH decrease and remain at a relatively low level during the luteal phase of ...
6
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1answer
96 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 ...
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2answers
357 views

Have we ever observed two drosophila lineages that evolved reproductive isolation in labs?

Background The standard definition of species refers to the concept of reproductive isolation. If two lineages are found to be reproductively isolated, then we consider these two lineages to belong ...
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1answer
22 views

How the pattern of fertilization path is determined before the cell division to form the blastocyst? Is it individually specific?

After sperm meets ovum,the inactive nucleus starts following a particular path inside the zygote rather chase a path.This path is biologically known as fertilization path (as mentioned in an article ...
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2answers
58 views

If the haploid prothallium of a fern fertilizes itself into a diploid sporophyte, does this make all ferns clones?

From what I understand in the alternation of generations in ferns, mature spores germinate into a haploid prothallium. But how does this gametophyte produce recombinant gametes if it itself develops ...
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5answers
621 views

Does any animal species have two sexes and more genders?

Does it exist any animal species that have two sexes and a kind of different internal diversification in two genders or more? I mean no something like different-task-based diversity but something ...
4
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3answers
176 views

Gametes of two different species

I always wondered why gametes from two different species dont fuse together to form an offspring. eg a donkey (sperm) and a female dog (egg) I know this is not possible but I'm just curious.
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0answers
48 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 GĂ©ranium. First of all we start counting the number of sepals , petals and ...
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1answer
31 views

What is the developmental basis of the placental sac?

The placental sac is the organ that provides nutrients to the embryo from the mother. My question is that, since this obviously involves a lot of complexity, where does the sac originate from ...
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0answers
49 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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1answer
40 views

Which monkey species features two distinct male phenotypes?

I remember coming across a popular science article years ago about a monkey species which featured two male genotypes: the first were good looking males who acquired social status (as alphas or betas) ...
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2answers
63 views

Do the eggs for larger litters come from the same meiosis events, or different ones?

There are some species of animals that give birth to more than one pup at a time. In these species, are the fertilized eggs all from one or a limited group of meiosis processes, or are they from ...
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1answer
24 views

Can yeast in a primary fermentation of wine be used as a source of yeast for new fermentation?

So if I were to pitch bread yeast, and get to primary fermentation, which as I understand it, is the point at which regular cellular respiration can no longer continue due to a lack of oxygen , which ...
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0answers
33 views

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 ...
6
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1answer
131 views

Why do women live longer than men?

According to Wikipedia and many other sources, women live substancially longer than men (over 5 years in the U.S.). Men can reproduce for much longer than women. So longer living men would have the ...
5
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1answer
225 views

What is the maximum number of babies a human woman can have?

I know you could divide the female fertility period (~40 years, right?) by 9 months which would give something like ~50 kids (with no multiple kids per pregnancy). The limiting factor in this ...
2
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1answer
52 views

Do all kind of unicellular asexual reproductions let mutations happen, resulting in evolution?

I know about fission, an unicellular asexual reproduction method, where the mother cell splits into two daughter cells. Does this kind of asexual reproductions let mutations happen, leading to much ...
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24 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 ...
7
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1answer
278 views

Cytoplasmic determinants - protostomes and deuterostomes

Cytoplasmic determinants are spread unevenly in the egg, and so when embryo starts forming (cells start dividing), the determinants are also unequally divided between cell. This unequal distribution ...
2
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1answer
80 views

Role of Calcium and Magnesium in capacitation/acrosome reaction

During the acrosome reaction, the activation enzyme present in the sperm dissolves the corona radiata and zona pellucida enabling the sperm to reach the plasma membrane of the egg. Also calcium and ...
5
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2answers
130 views

Do changes in an organism's cell modify the genetic information it uses for reproduction?

What I'm actually interested about is whether a modification in one cell during the life of an asexually reproducing organism affects its genetic information? Which cell's genetic information is used ...
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25 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. ...
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3answers
329 views

When is the second polar body extruded from the egg nucleus?

When does the second polar body gets expelled from the egg nucleus during oogenesis ? I know that it occurs after the entry of the sperm into the secondary oocyte but does it occur before the ...
12
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2answers
323 views

Why, specifically, does each generation, on average, improve upon the design of the species rather than degrade it?

In every non-life example I can envision, a copy of a copy is always a degraded or less pure version of the original unless some outside influence acts to correct the copy back toward the ideal ...
6
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1answer
1k views

How does a sperm cell die?

What causes an animal sperm cell to die? Does it die somehow from being outside its original environment? I've studied the Wikipedia page on sperm and I see a lot of information on what makes up a ...
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19 views

Can medications or drugs damage oocytes? [closed]

Some drugs are teratogens, but can any drugs cause DNA damage to oocytes before ovulation or conception (eg chemotherapy drugs)?