Questions tagged [reproduction]

The biological process by which new individuals are formed.

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9
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2answers
2k views

Do hormone drugs affect whether a person feels sexual attraction to males or females?

I know that ingesting testosterone and other hormonal drugs may stimulate libido and increase sexual desire. But I wonder, if a man ingests female hormones such as estrogen, will he experience sexual ...
9
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2answers
42k views

Can the mating of a couple with Rhesus positive and negative blood types result in miscarriage?

Can the combination of $+ve$ and $-ve$ blood groups of a couple be a cause of miscarriage in pregnancy?
4
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2answers
299 views

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?
3
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1answer
129 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 ...
3
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1answer
994 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 ...
5
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2answers
6k views

The probability of indirect human fertilization?

What is the probability of conception in situations when sperm isn't directly ejaculated into the woman's vagina, like: The man's or the woman's hands come into contact with sperm, for example when ...
32
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6answers
18k views

Why are not all species hermaphrodites?

If a hermaphrodite animal (like slug, snail, etc) finds a partner they can mate immediately. If another animal with "normal" reproduction (lets say a mouse) finds a partner they can only mate if they ...
9
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1answer
600 views

What evolutionary pressures pushed Galápagos tortoises to mature so slowly and live so long?

I read that they take up to 40 years (in the wild) to reach the age of reproduction and are thought to live over 100 years, with one in captivity reaching over 170 years. Can someone explain in ...
3
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1answer
3k 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 ...
3
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1answer
72 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 ...
6
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1answer
1k views

Why did mammals evolve to have two testes?

What makes mammals tend to evolve to have two testes?
13
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2answers
2k views

Do twins “run in the family”?

My wife and I recently found out that we are going to have twins and so nearly everyone asks if we have a family history of twins. Now I know that the answer for me is that it doesn't matter—as ...
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5answers
22k 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 ...
11
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1answer
1k 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 ...
7
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1answer
4k views

Do egg laying animals experience a pregnancy?

Does a female animal that lays eggs experience a pregnancy-like period of time, where she will feel and behave differently as if she were fertilized and her body is prepared to lay a fertile egg, not ...
6
votes
1answer
147 views

Macromolecule levels in daughter cells after fission

When a prokaryote undergoes binary fission, how are the non-DNA macromolecules distributed between the two daughter cells? This is motivated by comments on a previous question and a G+ discussion. I ...
9
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1answer
3k views

A timeline of the odds for survival for fertilized eggs and fetuses

I'm looking for data to build a timeline of the odds for survival of a fertilized egg, i.e., What are the odds it'll last a week? What are the odds it'll last a month? 2 months? (and so on until)...
3
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1answer
104 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? ...
6
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2answers
260 views

What are possible health risks to women having large numbers of children?

What is the possible health issue the women would face in this record? The record for most children born to a single couple belongs to the first wife of Feodor Vassilyev of Russia. In 27 ...
7
votes
1answer
7k views

Is ovum + ovum fertilization possible for human?

In humans is it possible to fertilize a ovum with another ovum from the same female subject? I already found some works in which the ovum is fertilized by a somatic cell (see e.g. this ), but I am ...
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1answer
118 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?
10
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1answer
882 views

Is sexual reproduction outside the same biological family possible? Has it ever occured successfully?

Are there any examples of two species taxonomically classified in different biological families that have successfully hybridized and produced viable offspring? If not, is there an example of where ...
6
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1answer
162 views

Reproduction and defecation

In mammals and birds the external reproductive organs and waste removal organs see to be the same. Is this always the case with other animals such as insects etc...? Are there any good reasons for it?
4
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1answer
93 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 ...
4
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4answers
799 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.
1
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1answer
770 views

What animals stop other members of their species from mating and why?

(In particular primates) I know chimps do. Powerful alpha males chimp would beat up omega males that they caught mating. I know gorillas do. Powerful alpha males gorillas would beat up omega males ...
7
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1answer
909 views

Is it purely the nervous system causing vaginal lubrication (arousal)?

My girlfriend was watching some documentary on TLC about a paralyzed woman getting pregnant. I believe that woman still has some feeling, as she spoke about feeling the effects of a bladder ...
6
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1answer
358 views

Effect of spaying on the female cat organism and health

Veterinarians often recommend spaying a female cat if the owner does not want her to have kittens. What does biology know about the effect of spaying on female cats' organism and health (apart from ...
11
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3answers
3k views

Species with reproduction barriers that can both reproduce with a third species

To start with, I do not have a sound knowledge in biology or any formal education in the area. I was told that one of the definition of a species is a reproductive barrier, which means that if two ...
7
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1answer
1k views

When do most mammals mate?

Is one part of the day more prevalent then other when it comes to mammal animals mating? Is there an aggregating study that has been done to see if these living beings in nature mate mostly during day ...
6
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2answers
1k views

How are the gene sequences of individual sperm and egg cells “randomized”?

What I mean by "randomized" is, in the place where an egg cell or sperm cell is made, what is the mechanism by which each one is not made identically? Though I am a layman, I'm pretty sure that if the ...
19
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3answers
621 views

Are human fetuses more likely to be male? [duplicate]

Question: From a physiological point of view, when sex is determined in a human fetus, is it equally likely to be male or female? Studies in this area typically measure age at birth, where the data ...
19
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2answers
8k views

Why do some mammals not have testes in a scrotum?

Coming from an evolutionary approach, Is the only purpose of a scrotum to regulate the temperature of the testes? Knowing all mammals are warm blooded, shouldn't all mammals have testes in a scrotum?...

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