The biological process by which new individuals are formed.

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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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29 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
24 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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42 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
34 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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1answer
16 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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28 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 ...
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1answer
155 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 ...
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55 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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1answer
101 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 ...
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1answer
47 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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19 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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98 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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24 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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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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3answers
130 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 ...
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18 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)?
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66 views

Lyonization vs Genetic Imprinting

Lyonization is the process in which there is inactivation of an X chromosome in females. This process is implicated in mosaic forms of turner's syndrome (in this case the altered ...
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73 views

Why are there no artificial wombs yet?

If the conditions within the womb are mimicked, and proper amniotic fluid with constantly recycling nutrients is maintained, is it not possible to obtain an artificial womb? Is there anything missing? ...
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56 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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57 views

How does a baby retain a blood group different from it's mother, in her womb?

It's a well-established fact that blood group is decided by genotype. But, when a new child starts it's journey in the womb, then the mother's blood (along with it's agglutinins and agglutinogens) ...
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39 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 ...
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1answer
139 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 ...
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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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1answer
68 views

What are some difficulties animals had to overcome to reproduce on land?

This is for AP Biology, but the assigned textbook chapter doesn't contain any information about the question. What are some difficulties animals had to overcome to reproduce on land? Some ...
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1answer
50 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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162 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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1answer
66 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
241 views

What is the difference between embryology and developmental biology?

The question is quite explanatory in it self, I used to think that both are same but then find somewhere that embryology is a part of developmental biology, can somebody please elucidate?
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1answer
45 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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1answer
44 views

Are there multicellular isogamous species?

Are there multicellular isogamous species? Seeking through the examples of wikipedia I would tend to think that there are no multicellular isogamous species.
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46 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
63 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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1answer
352 views

Can ovulation and menstruation occur simultaneously?

Is that possible that ovulation happens in the time of actual menstrual haemorrhage in human females - let say in a case that woman has 21 day cycle and her menstrual period is 7 days? If yes, does ...
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1answer
34 views

Which C. elegans would be appropriate for general study?

Would wild type N2 be best or Dyp-11? I know they're different, but I just want to observe the worms to see life stages, movement, etc. Dyp-11 seems like it would be easy to see but N2 is the wild ...
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32 views

Regarding inherited fertility in animals

If an animal is fertile does it follow that both its parents of the same species (not necessarily the same species of the offspring)? Was it Mayer who said a fertile male and fertile female of two ...
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40 views

Meiosis I or II [closed]

Suppose an organism has 8 chromosomes. When the female and male organisms mate, how many chromosomes will the mother contribute to the offspring? Why?
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1answer
103 views

Which process is needed to complete male reproductive development?

In order to properly complete male reproductive development: ...
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61 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
6k views

Do bacteria die of old age?

I know that the cells of mammals at least stop dividing when they are old, and then die a programmed cell death. Then other cells have to replace them. But in a bacterial colony, each cell ...
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792 views

Negative role of Placenta

How can a placenta turn hostile to the mother or fetus ? What are the abnormalities found during placental delivery ?
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1answer
402 views

Alfred Jost's rabbit experiment: how did he actually do it?

I was watching a Crash Course on Biology YouTube video by Hank Green: Great Glands - Your Endocrine System. Hank humorously describes a sex determination experiment by Alfred Jost as follows ...
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1answer
81 views

Waste generation by embryo [closed]

How does an embryo produce waste products even when its organ systems are not developed fully ? How does the placenta identify or differentiate waste materials from embryo ? Which organelle or ...
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1answer
164 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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2answers
189 views

How do taenia form a species?

I know that there are many hermaphrodite animals and plants. But many of them seem to still exchange genes by mating with another member of their species. I now happened to read the Wikipedia ...
6
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1answer
87 views

Gender and age-specific mutation rate in plants

Background General concept According to Cochran and Harpending (2013), mothers transmits on average a number $x$ of new mutations to their offspring. This number $x$ is independent of the age of the ...
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1answer
42 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
276 views

How can Taenia solium (tapeworm) lay 35,000 eggs per proglottid?

As far as I know TAENIA SOLIUM is an acoelomate which basically means that the space between the alimentary canal and the gut is completely filled [or] occupied by the mesoderm and they do not have ...
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1answer
59 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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42 views

Is asexual and sexual reproduction a universal feature of Bryozoans?

I found some clues that most, if not all, bryozoans can reproduce and multiply by asexual and sexual means, for example: Thomsen & Hakansson 1995: "Sexual Versus Asexual Dispersal in Clonal ...