The biological process by which new individuals are formed.

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Is every part of a virus important for replication?

Is every component of a virus absolutely essential for its infection and replication in a host cell? Or can you just have parts of it to cause infection?
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150 views

Why isn't Rh disease present in other mammals?

I have read about Rhesus D Hemolytic Disease of the Newborn, sometimes called "Rh disease". It's rare, but it can happen when an Rh+ baby is conceived by an Rh- mother. This raises many questions. I ...
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106 views

Why do some women have menstruation-like spotting throughout their pregnancy?

An interesting question that was asked during a lecture about human reproduction: what is the biological mechanism behind some pregnant women getting monthly spotting that they mistake for a regular ...
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1answer
44 views

Are there any studies on the fertility levels of humans/mammals as a function of their stay at Antarctica?

Wikipedia, and Space.SE seem to indicate humans become infertile in space due to the increased exposure to cosmic rays. Knowing as we do that Antarctica is holey, and subject to increased radiation ...
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1answer
65 views

Productive turnover and generations in the fruit fly

I was reading about the Lenski experiments on the evolution of E. coli bacterium and Dr. Elders's experiments on the evolution of the guppy. These two experiments absolutely fascinated me, and seemed ...
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4answers
2k 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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3answers
207 views

Could a sperm be altered to contain a female's genetics?

while discussing with a friend a while back on the likelihood a Funtari (a woman with both fully developed and functioning sets of genitalia) existing in real life we got into a discussion of weather ...
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1answer
37 views

If hermaphrodite C. elegans can reproduce with females?

C. elegans can self fertilize, or they can mate with males. But are they able to mate with females? Or is there some kind of morphological barrier that prevents that?
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2answers
166 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 ...
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2k views

Cell life: division for immortality or reproduction with aging

Are the two cells that are derived from one cell, ‘twin sisters’ or a ‘mother and a daughter’? In other words, can a cell really be divided to live an "immortal" life or is cell reproduction the ...
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2answers
299 views

Are identical twins exactly the same?

http://www.scientificamerican.com/article.cfm?id=identical-twins-genes-are-not-identical According to this article some identical twins show differences with respect to their copy number variants. ...
3
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1answer
105 views

is it necessary that every theca of an angiospermic anther must contain two microsporangia

i basically don't know the procedure or sequence of steps involved in the formation of anthers but i have read it somewhere it is formed from the dedifferentiation of shoot apical meristem of the ...
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1answer
63 views

Alternating Ovulation

I have often heard that right and left ovaries alternate in releasing ovum. Is it always true? What controls this rhythm? Is it simply because the other ovary is unresponsive to LH or FSH? If so, ...
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1answer
138 views

Are any organisms known to use meiosis I to create non-identical offspring asexually?

So, there are numerous species of animals who use parthenogenesis, but to my knowledge the reproduction is clonal. That is, the offspring are identical to the mother. Are there any documented cases ...
3
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1answer
68 views

What is the purpose of segments in citrus fruit?

What is the purpose of segments in citrus fruit? In my experience, each segment usually contains from zero to two seeds. I may have seen more but only rarely, if I remember correctly. What is the ...
3
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1answer
96 views

Would ovoviparous to viviparous mutation have been gradual? How would that work?

It seems unlikely that an ovoviparous ancestor of mammals long ago could have had a viviparous offspring in a sharp one-generation dividing line, but what would be the gradual steps between egg birth ...
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2answers
47 views

Can genetically engineering the DNA of a human zygote, make it a twin of another human in entirety?

My question is simple. If I wanted to make an exact twin of an individual, will genetically engineering the DNA of the zygote to match with the individual suffice?
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1answer
54 views

Which is better against genetic mutations? Asexual or Sexual Reproduction?

In terms of genetics, which type of reproduction is better against adverse mutations? I understand a bit of Muller's Ratchet—in which asexual organisms accumulate a number of deleterious mutations in ...
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1answer
149 views

Advantages of bisexual reproduction over asexual one toward species promotion? [duplicate]

Are there any advantages of bisexual reproduction over asexual one towards species conservation and promotion? Do animals that have two or more sexes have more chances to reproduce? Does anybody had a ...
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2answers
136 views

How far into a pregnancy is it before visible signs of it is apparent and risk of physical trauma increases

I'm doing research for a series I'm writing. in it the main character is pregnant however goes off to fight a criminal organization who have been killing her friends and i want her appearance to show ...
3
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1answer
26 views

Mutation in axillary buds of trees overcoming self-incompatability?

I seem to recall from either reading or lecture that there have been instances of trees that are self-incompatible accumulating enough mutations in an axillary bud that the resulting branch was able ...
3
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1answer
87 views

Predictable microchimerism

I read in New Scientist recently that microchimerism occurs between previously born siblings and grandparents, not just the mother. Do we know which parts of the genome are likely to be transferred? ...
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1answer
44 views

Incestual Reproduction in Animals

I'm quite curious on how animals view incestual pairings. Given there are enough mates around, i have quite observed that most females (subjects are dogs, cats, pigeons and chickens) would go choose ...
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1answer
53 views

Confusion regarding seedless grape and the normal process of germination

In general, does seedless grape by definition contains seed or is the seed small enough that the process of ingestion creates the illusion that there is no seed? If the latter is true, is the ...
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1answer
172 views

Meiosis vs. Mitosis

Meiosis is a type of cell division that reduces the chromosome number from 2n to n to make gametes viable for reproduction in humans. I know that during meiosis, there is independent assortment and ...
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1answer
389 views

Are there records of monozygotic twins in which one experiences androgen insensitivity syndrome

I have given my high school biology students the thought experiment of "What would happen if a researcher induced twinning of a female zygote and then replaced one of the X Chromosomes with a copy of ...
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38 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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195 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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30 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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26 views

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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2answers
147 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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1answer
168 views

Is it really detrimental to humans as a species to reproduce with one's own first cousin?

Tired of hearing of these urban legends and popular opinions, I ask this question here to see if there really is scientific merit to this belief. My questions is, is it really "harmful" for a person ...
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2answers
308 views

How to know if a woman is fertile without actually making her pregnant?

How to know if a human female is fertile (can give birth to child in future) without making her pregnant? Any signs, tests?
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2answers
217 views

Why are animal births not taken as seriously as human births?

When humans give birth, more than often medical assistance is needed. Others gather around and frantically look for any way to help. But when an animal gives birth, it is usually seen as a moment ...
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92 views

Evolution after the development of sexual reproduction

My understanding of evolution is that genetic mutation occurs in individual members of a species, and they become a new species. Isn't a definition of species a group of genetically similar organisms ...
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302 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 ...
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1answer
101 views

Which process is needed to complete male reproductive development?

In order to properly complete male reproductive development: ...
2
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1answer
96 views

Two-fold cost of sex and r/K selection theory

This article cites a bunch of articles (I haven't been through them) that the effect of the two-fold cost of sex is "reduced" in stable environment or in K-selected environment. It says: [..] the ...
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1answer
43 views

maximum # of generations possible in a population of cannibalistic rats

Assume a sufficiently large population of rats (to allow genetic variation and facilitate inbreeding) in a place with abundant water, sunlight, shelter but no food. For how many generations can this ...
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1answer
148 views

Scrotal temperature and vascularization

The testes (at least in human males) are vascular organs, the vascularization extending even o the interstitial spaces of the seminiferous tubules. The function of the scrotal sac, is to isolate the ...
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1answer
58 views

Reduction of size in diatoms due to asexual reproduction

From this we can see that diatoms reduce their size after asexual reproduction. This would ultimately lead to nonviable small size. Is there any mechanism to avoid this ?
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2answers
108 views

Stay young by reinserting own DNA from years ago?

As far as I know, the DNA sequence becomes shorter every time a cell divides. A shorter sequence results in information loss and aging characteristics. As a countermeasure, shouldn't one stay young ...
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1answer
478 views

Has the age at which menopause occurs changed throughout history?

I was reading recently that the age of menarche has decreased in the last 150 years, and was wondering if the age of menopause in humans has also changed recently? Would there be selective pressure ...
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1answer
77 views

Are there any organisms with larva more advanced than adult form?

Usually adult organisms are more sophisticated than corresponding larva, i. e. frogs, mosquitoes, fish. Are there species where the opposite is true?
2
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1answer
66 views

Evolution from Mating types to different sexes

Imagine a lineage of multicellular organisms that had mating types and evolved their mating types into sexes. What are the possible mechanisms that might have brought this lineage to evolve sexes from ...
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0answers
39 views

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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1answer
39 views

What is the name of this type of inflorescence?

I was having a look at a rhizophora plant (from the mangrove family), and I got curious about its inflorescence. I can't make out what kind of inflorescence it is. Here is a photo of the ...
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1answer
66 views

Do chickens always lay eggs?

http://de.wikipedia.org/wiki/Hühnerei says it takes up to 24 h for a chicken to produce an egg. Is that dependent on the chickens nutrition, i.e., if it does not get enough food or the wrong kind, ...
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1answer
37 views

Surrogacy Post Fertilization

The wikipedia page on surrogacy highlights two main forms of surrogacy: Traditional Surrogacy and Gestational Surrogacy. Traditional surrogacy inseminates the surrogate mother with sperm, while ...
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1answer
1k views

In what animal species is the sex ratio skewed in favour of the fertile female?

Ants have something like a single fertile female to several males. The same applies to bees, and larger animals - elephants too. Is the sex ratio universally skewed in favour of the female? What ...