18 votes
Accepted

Is blood regarded as an organ?

Blood is considered a type of connective tissue (sometimes). However, an organ is formed of multiple different tissues. Thus, blood is a tissue, not an organ.
  • 2,395
14 votes
Accepted

What is the definition of "Natural Selection"?

Official definition Is there an official definition of natural selection that is adopted by biologists nowadays? and what is that definition exactly? I don't think there is such a concept as an "...
  • 67.8k
11 votes
Accepted

Was Darwin aware of the difficulties behind the concept of species?

The whole point of Darwin's theory was that transition from one species to another is extremely slow and gradual. There are plenty of quotes in "Origin of Species" stating this, and also affirming ...
  • 421
9 votes
Accepted

Can domestic breeding be considered evolution?

Yes, selective breeding results in evolution. Definitions of evolution I don't understand why you say that for 3 of the definitions you found, selective breeding would not be considered as evolution....
  • 67.8k
8 votes
Accepted

Are 'homeothermic' and 'endothermic' synonymous?

[D]o homeothermic and poikilothermic have the same meaning as endothermic and ectothermic respectively[?] No. Once you are referring to the source of the heat, while the other time you are referring ...
  • 67.8k
8 votes

What is the difference between a cytokine, a hormone and a protein hormone?

Parts of the answer are in the text that you provide yourself. But I shall try to add where i can. What do each of these three terms [hormone, cytokine and protein hormone] mean and how are they ...
  • 533
8 votes

What is the definition of "Natural Selection"?

I've adapted your definitions to another process that I think will be less controversial to you. Eating is the intake of food by taking into the mouth, chewing, and swallowing. Eating, the process ...
  • 39.3k
6 votes

Is blood regarded as an organ?

While organs are generally considered to have a single, specified function (or perhaps a group of closely-related functions), blood (the fluid inside the vessels, not the vessels themselves) has many ...
  • 15.1k
6 votes
Accepted

What is a tardigrade "in tun form"?

From Illinois Wesleyan University: One way in which tardigrades have adapted to various types of environments, has been to reversibly suspend their metabolism. This state is known as ...
  • 51.8k
6 votes

Evolution as a directed graph exploration?

But in order to find shortest path, which is known well from algorithmic theory, you have to be as broad as possible. You try to explore as many vertices, as possible, which means you're creating ...
  • 3,210
6 votes

About the definition of ketogenic amino acid

The fundamental 'problem' with acetyl-CoA is that it cannot be converted to glucose via the tricarboxylic acid (TCA) cycle: a two-carbon compound (acetyl-CoA) enters the TCA cycle, but two carbons are ...
  • 4,658
5 votes

Do apes and humans share 99% of DNA or 99% of genes? What is the difference?

Most of the answers here focus on the difference between the concepts of 'DNA' and 'genes' very well. However, the sequence identity between humans and chimpanzees is not covered as rigorously and ...
  • 2,878
5 votes

What is the definition of a mutation?

Good question! The term mutation can be used with two different meanings. Each definition can further be split into two different more detailed definitions. The reason for this slight mess is mainly ...
  • 67.8k
5 votes
Accepted

Introgression vs admixture

The difference is referring to the directionality of gene flow. We talk about genetic introgression when there is some gene flow from one population (say, population A) to the other (say, population ...
  • 67.8k
5 votes
Accepted

Is studying chemical and physical properties of chemical substances that make up organisms really a task of molecular biology?

If you look at the Google ngram for the term ‘Molecular Biology’ you will see that it first appears just before 1960, and it is relevant that the Journal of Molecular Biology was founded in 1959. It ...
  • 23.1k
4 votes
Accepted

What does pseudo-irreversible mean?

it seems to mean persistent or long-lived. Is that correct...? Yes, it's correct, but how persistent the effect is is related to the rate of dissociation or rate of turnover of the receptor. It is ...
4 votes
Accepted

Problem with an analogy (Cell Membrane)

Osmosis is the diffusion of water. Pinocytosis is the endocytosis of liquid/water.
4 votes

Can domestic breeding be considered evolution?

The answer is "yes". Evolution is defined as a change in heritable characteristics of a population over generations, and to me, there is no reason not to define domestic animals as populations. The ...
  • 272
4 votes

Evolution as a directed graph exploration?

Your theory is based on many false assumptions. Evolution becomes nothing but a finding a shortest path in that unbelievably huge directed graph. What makes you think that evolution followed the ...
  • 421
4 votes
Accepted

What do the column labels in this table mean?

F(1,22) is the result of an F-test with degrees of freedom 1 and 22, in this context most likely this is an F-test in the context of ANOVA; for the meaning of those degrees of freedom I would suggest ...
  • 39.3k
3 votes
Accepted

Can an exotic species be also endemic?

I think this partially depends on the timeframe. Endemism is usually divided into paleoendemism and neoendemism (see e.g. Kier er al in PNAS for use of both terms). Here, neoendemism is referring to ...
3 votes

What is the philosophical definition of life?

There is no difference along the lines of philosophy vs. science. However, there are broader and narrower definitions in biology. The broadest I know of is "a self-replicating, chemical system (...
  • 13.7k
3 votes

What is the philosophical definition of life?

They ask different questions. Philosophy may ask what is life, is there a purpose behind it, etc. Biology asks how does it work, chemistry what are the chemical reactions that drive it, physics maybe ...
3 votes

What is a gene transcript, how is it different from an allele?

No. A gene is a unit of the genome stored in the form of DNA. It can be transcribed into mRNA (the transcript) to be used as a template in protein synthesis. A gene can come in many different ...
  • 556
3 votes

What is the definition for vitamins?

Generally speaking, bulk essential nutrients (e.g. amino acids, fatty acids) are used stoichiometrically to form macro cellular structures and are 'baked in' to the structures or compounds they are ...
  • 116
3 votes

What is the definition of a mutation?

What I was taught by people in genomics is that "variation" is preferred for an allele that was not private to just one individual or family, but was found in pretty much unrelated individuals, while "...
  • 5,070
3 votes
Accepted

What is Environmental Robustness? Is it different from plasticity?

I think robustness and plasticity are different concepts, although related to each other. I would define plasticity as the property of a system to adapt to external changes. As defined in the ...
  • 1,720
3 votes

What is the difference between abiogenesis and spontaneous generation?

What truly differentiates abiogenesis from spontaneous generation? There are three differences. Frequency Abiogenesis occurs very infrequently. Perhaps only once in all of earth's 4.5 billion year ...
  • 2,896
3 votes
Accepted

Usage of "lineage" over "species"

Lineages have many levels, it is like using the word groups in some ways, they are stacked inside each other like the worlds biggest branching Russian nesting doll. All vertebrates is a lineage, all ...
  • 13.7k

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