The biological process by which new individuals are formed.

learn more… | top users | synonyms

1
vote
1answer
25 views

Effect of the health of the male parent at the time of conceiving

Does it matter at all in determining the traits of a baby what the current health of the father is? For example, let's say I got diabetes at the age of 40 because of the poor lifestyle choices. Will ...
4
votes
3answers
60 views

Does the genetic material the sperm carries affect it's physical properties

Basically, what I'm asking is, is the actual sperm cell built from the blueprint in the DNA of the man or is it itself also a consequence of the DNA it carries? I'd like to know a few more things ...
4
votes
3answers
99 views

Does our eyeball increase in size as we grow?

Does the size of the eye increase as we develop from the stage the complete eye first forms to infancy and then to adulthood ?
2
votes
1answer
43 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 ...
6
votes
2answers
82 views

Why did women historically have such a high mortality rate during birth?

Historically women had a relatively high chance of dying while giving birth. At first thought it seems to me that this would be a disadvantage for the species for the obvious reason that a dead ...
6
votes
1answer
811 views

Why is fructose not glucose the main energy source of sperm?

The seminal fluid contains fructose as the main energy source for the sperm and not glucose. Why is fructose and not glucose the primary energy source for these sperm, since glucose is the ...
1
vote
1answer
44 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, ...
15
votes
5answers
2k 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 ...
0
votes
1answer
22 views

Fertilization of an egg by two sperm

What happens when two sperm fertilize an egg? This can be either naturally or by experiment.
1
vote
1answer
24 views

Mutated Sperm - What happens?

I saw on TV that not all sperm are the same. Some have mutations like 2 and 3 tails? There were other mutations as well. If one of these mutated sperm actually fertilized an egg, would the embryo ...
3
votes
1answer
70 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 ...
1
vote
1answer
30 views

Bacterial Conjugation/Horizontal Gene Transfer — how does the plasmid exchange work?

So according to a PPT I'm reading, bacterial conjugation works by the two bacteria joining pili and exchanging plasmids. So how exactly do the plasmids get across the gap? If I understand this ...
1
vote
1answer
25 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 ...
7
votes
0answers
30 views

Beginning of the urogenital system

Are any invertebrate nephridia (proto/meta) homologous with vertebrate kidneys in the sense that embryologically they also begin together with the genital system? When did the embryologic association ...
3
votes
2answers
103 views

Asexual reproduction and Telomeres

Many eukaryotic organisms like yeasts, hydras , planarias, plants etc reproduce asexually. Replication of End of linear DNA pose a limit to the number of cell divisions. My question : Do asexually ...
2
votes
0answers
57 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 ...
1
vote
1answer
28 views

Book on yeast reproduction, evolution and on the use of yeast as model organism

I am looking for a good book in: Yeast reproduction mating types Recombination mating type determination mechanism Yeast evolution Yeast as model organism and its use in experimental biology It ...
2
votes
2answers
116 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 ...
1
vote
0answers
19 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 ...
2
votes
1answer
32 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 ?
2
votes
1answer
32 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 ...
6
votes
1answer
154 views

Regulation in plants bearing cleistogamous and chasmogamous flowers

In most plants bearing cleistogamous flowers, chasmogamous flowers are also borne by the plants. For example, Viola, Oxalis and Commelina contain both these kinds of flowers.( I am unaware of a ...
2
votes
2answers
82 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 ...
3
votes
4answers
824 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 ...
1
vote
1answer
73 views

Why do some animals and fungi prefer asexual reproduction?

Animals like Sponges and Hydra and fungi like Yeast and Mushroom can reproduce both asexually and sexually. However, they only reproduce sexually if the 'circumstances' are 'bad'. Is there a specific ...
5
votes
0answers
62 views

Neuroendocrinal mechanism of parturition

My book reads, "The fetus signals that it is mature by secreting certain hormones that diffuse across the placenta into mother's blood and cause the secretion of oxytocin from her posterior ...
4
votes
1answer
98 views

Causes of monozygotic twins

Twins could be monzygotic i.e. identical twins and dizygotic i.e. non-identical twins.Well, monozygotic twins occur when a single egg is fertilized to form a zygote which later divide into separate ...
0
votes
1answer
141 views

Need of X or Y chromosome protein after meiosis

After meiosis each spermatid get either the X chromosome or the Y chromosome. I know that the 4 spermatids formed from 1 spermatogonia are connected by cytoplasm and so the proteins made by X or Y ...
1
vote
0answers
30 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.
1
vote
1answer
37 views

Terms related to megasporogenesis

Well, I am not able to understand the exact difference between megasporocyte and archesporium. Also I'm not quite able to get, how or precisely from where do these arise? Please help.
2
votes
2answers
216 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?
6
votes
1answer
110 views

Why does the chance of having a baby with Down's syndrome increase with the age of the mother?

Down's syndrome occurs when either the egg or the sperm cell contain on extra chromosome 21. To my understanding, women are born with all the egg cells in place already, so there's no further cell ...
4
votes
0answers
48 views

Why isn't RH disease present in other mammals?

Basically, I have read about RH disease, Its rare but it can happen when an RH + baby is conceived by an RH - mother. This raises many questions. I have heard this problem only happens with humans, ...
2
votes
2answers
109 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 ...
3
votes
2answers
108 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 ...
3
votes
2answers
94 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 ...
2
votes
0answers
49 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 ...
2
votes
1answer
77 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 ...
8
votes
1answer
139 views

Why does the gender 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 gender of the parent species determine the species of the offspring, in some hybrids. A male horse and a female ...
1
vote
1answer
121 views

Is there a human form of estrus?

Now I just learn that estrus is a trait in all mammals except Humans. So does it occur significantly in Humans? Of course I'm aware of the cliched "horny", "aroused" etc., but is it a biological ...
8
votes
1answer
284 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 ...
8
votes
1answer
225 views

Could humans and chimpanzees hybridize?

In some cases two species can hybridize. For example, Tigers and lions can hybridize to produce "Ligers". Would it also be possible for humans and chimpanzees (or any other species) to hybridize ? ...
3
votes
1answer
51 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, ...
4
votes
0answers
96 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 ...
0
votes
1answer
52 views

Male behaviour during breeding season

The mountain blue bird build nests to attract females and exhibit aggression towards other males during breeding season. Which of the following is likely to give the birds maximal evolutionary ...
4
votes
3answers
328 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 ...
0
votes
1answer
62 views

The probability of indirect human fertilization (follow-up)

This question is a follow-up to this one. I've been wondering how small that probability is. As we all know, "safe" sex, that is (correctly) using a condom and all that, isn't perfectly safe. So, in ...
1
vote
0answers
16 views

Division of Polar Body

The first polar body formed after meiosisI is completed in oocyte may or may not divide. Why it may or may not divide ? Is it random ?
3
votes
2answers
100 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. ...
4
votes
1answer
70 views

Why is there sperm mitochondrial suicide?

The mitochondria in the sperm are digested upon entry into the egg, making mDNA inheritance exclusively female. What is the advantage of this? Wouldn't some male mDNA be beneficial because of the ...