120 votes
Accepted

Are male and female brains physically different from birth?

Short answer Yes, men and women's brains are different before birth. Background First off, learning effects versus genetic differences is the familiar nature versus nurture issue. Several genes on ...
user avatar
  • 51k
72 votes
Accepted

Why does a coconut have exactly three "holes"?

The three "holes" are the result of the 3 carpels in coconut flowers, and three carpels is typical of the family Arecaceae (Palms). The "holes" are actually germination pores, where one is usually ...
user avatar
67 votes
Accepted

How does a baby deer stand the day it's born?

If you compare placental mammals in how much time they need to start walking, you'll see that deer are no exception. Humans are an exception. Hypothesis of Obstetrical Dilemma The hypothesis of ...
user avatar
  • 67.5k
63 votes
Accepted

Can brain cells move?

The question is relatively broad and one should take into account that the brain not only consists of neurons, but also glial cells (supportive cells) and pre-mitotic neuronal stem cells. Furthermore, ...
user avatar
  • 51k
40 votes
Accepted

How long before robin no longer needs the nest on my porch?

According to Cornell's All About Birds website, you will have to wait about a month for the nest to be cleared. The egg incubation period is 12–14 days. Following hatching, the nestlings will remain ...
user avatar
34 votes

How does a baby deer stand the day it's born?

Deer are hardly unique in this, The young of horses, cows, and I suspect most grazing species are able to walk soon after birth. The reason, of course, is evolutionary: flight is the species ...
user avatar
  • 3,603
24 votes
Accepted

Is female the default sex in humans?

Summary: The idea that primary sexual determination defaults to female was proposed several decades ago and is primarily based on the observation that, in the absence of Sry, ovarian development ...
user avatar
  • 17.5k
22 votes
Accepted

Why do plants fruit?

Seeds are spread by many mechanisms Wind dispersal: When air currents used to spread seeds. Often these plants have evolved features to facilitate wind catching, for example dandelions. Aka, ...
user avatar
  • 16k
14 votes

Why does a fetus drink and urinate into the amniotic fluid?

In utero, the growing little human is getting ready to be an independently functioning individual. While it is everything but that, it must be able to obtain fluids and nutrients through its mother's ...
user avatar
  • 51k
12 votes

How does an embryo know where to grow limbs etc

You may want to look into "Evolutionary - Developmental Biology", which deals with how an embryo develops into a grown organism. Thus, by combinatorial specifying the identity of particular body ...
user avatar
  • 6,487
12 votes

Is fluoride toxic, and how worried should I be about it?

First of all: Yes, fluoride is toxic, but the toxicity depends largely on the form (soluble vs. unsoluble, which fluoride salt etc.) occurs. It also depends on the environment since insoluble salts ...
user avatar
  • 49.1k
11 votes
Accepted

What is the biological age of grafted plants?

In my experience (in common with the experience of everyone I've talked to who could be considered an expert on the subject), taking old wood and using that as a scion when grafting new trees ...
user avatar
  • 3,677
11 votes

Can brain cells move?

To add to Christiaan's answer, I'll mention one striking example of long-distance neuronal migration in the adult mammalian brain: the so-called Rostral Migratory Stream found in rodents, in rabbits ...
user avatar
  • 1,277
10 votes

Does our eyeball increase in size as we grow?

First of all, I should quote the sentence from the MOST reliable ophthalmology sourcing in the world - American Academy of Ophthalmology: Section 11 - "Lens and Cataract" "The equatorial diameter of ...
user avatar
  • 5,620
10 votes
Accepted

Do babies resemble their father?

Resemblance between parent and offspring is certainly true. Some traits are more obvious than others, for example skin colour would be very obvious. As babies mature they will gradually begin to look ...
user avatar
  • 16k
9 votes
Accepted

Are there specific features of birds that cats/small predators are attracted to?

Not all cat predatory behavior is innate. Researchers found that cats predatory behavior for birds vs. mice depends to a significant degree on training by the mother: if the mother taught predatory ...
user avatar
9 votes
Accepted

Why are certain baby (water)fowl yellow?

Wild ducklings, like these baby Mallard ducks, are in fact typically only partly yellow: Photo by TheBrockenInaGlory via Wikimedia Commons, used under the CC-By-SA 3.0 license. While I'm no expert, ...
user avatar
9 votes

How does a baby deer stand the day it's born?

That you use the word "learn" in your question leads me to think that you're under a common misconception that people have about biology. It can seem self-evident to us that certain skills, for ...
user avatar
  • 1,389
8 votes

Are fish and reptilian scales homologous?

No, fish scales are dermal (= formed in derma) bones like skull roof bones. Scales in reptiles are formed by epidermis and are made primarily of protein (from keratinocytes), being similar in ...
user avatar
  • 2,889
8 votes
Accepted

Is there any scientific evidence that a human has ever grown a third set of teeth?

There are legitimate case reports in credited journals of hyperdontia, or the condition of having supernumerary teeth. Such cases are often associated with congenital syndromes-- cleft lip and palate, ...
user avatar
  • 1,634
8 votes

Could we slow down life?

Short answer: Changing something (instead of everything) yes. There are several studies on the impact of environmental factors on life span. Of course it depends from organism to organism. Diet ...
user avatar
  • 3,008
8 votes
Accepted

How do neurons find each other?

Q: We know neurons can organize into very complex networks, but how? The answer is your first guess: Neurons find other target neurons with specific chemical signals. Q: What are the names of said ...
user avatar
8 votes

Are male and female brains physically different from birth?

One point of view you rarely see is the perspective of sex differences from an evolutionary standpoint. Never mind that this is the reason why the differences exist in the first place if they do at ...
user avatar
8 votes
Accepted

What animal has the longest juvenile period?

As you indicate in your question, the average age of sexual maturity is probably the best way to approach this, since immaturity is usually how juveniles are defined. Age of puberty is also different ...
user avatar
8 votes
Accepted

Are there any known consequences of the right-handedness of the DNA double helix?

The short answer is no, there currently aren't any visible macroscopic asymmetries in some organisms traceable to DNA's handedness. The long answer is still no, but I want to clarify that this "no" ...
user avatar
  • 96
7 votes

Does our eyeball increase in size as we grow?

No. In fact the lens of the eye, which is nearly optically perfect in humans, does not change or grow after it is fully formed around week 26 of gestation. Interestingly this is why one of the cues ...
user avatar
  • 27.4k
7 votes
Accepted

which exact mechanism triggers the first cell differentiation after n divisions?

The first differentiation in human embryogenesis is from early blastomeres into trophoblast, which forms the outer layer of the blastocyst, and inner cell mass (ICM). It may be unsurprising then that ...
user avatar
  • 17.5k

Only top scored, non community-wiki answers of a minimum length are eligible