Tag Info

Hot answers tagged

13

Yes, plants! Plants are autotrophs. While Animals and fungi are heterotrophs. Have a look to the wikipedia articles. In short, autotrophs organisms are organisms that synthesize their own compounds from inorganic compounds. Heterotrophs organisms are organisms that synthesize their own compounds from organic compounds. Therefore, any multicellular plants ...


6

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 derivation to hair, feather and nails. On the other hand, in reptiles one must differentiate between scales and osteoderms (= scutes). Scutes are widespread among ...


6

The answer by Remi.B is excellent, I'll just attempt an explanation by way of gene networks: In genetics we see new genes "linking" to the older genome by regulation pathways and by being "fit" only in the context of the existing genome. This has the effect of making the older genes indispensable. Change them and you rupture the whole mesh. If you want to ...


4

You can have a look to the most basal branches and you may get a pretty good idea of what those early plants looked like. What we call plants is what we call plantae or Archaeplastida in Latin. This clade contains the red algae and the green algae. Within the green algae are the land plants. In the land plants are the embryophyta which contain all what you ...


3

Selection is a mechanism of evolution which favours specific forms of traits over others, this can cause the spread of beneficial mutations through a population. Natural selection is the spread of beneficial traits/genes through populations as a result of the natural variance in their effect on reproductive output (a function of life history traits like ...


3

Organisms on Earth did not evolve in a homogenous environment. A critical part of speciation (when you go from a single species into two or more) is a reproductive barrier. This can be a literal, physical barrier - mountain range appears between two populations, valley in the middle of habitat floods and isolates the two halves of the population, a small ...


2

You can't predict the evolution of anything because evolution is driven solely by the environment. It is the environment that squeezes species into to specific forms. We have has a much say in our shape and form as a whirlpool does and for the same reasons, both humans and whirlpools result form powerful outside forces. In order to have shot at even making ...


2

You are right in the sense the evolutionary biology doesn't try to explain the origin of life as it is not within its scope. Other fields of biology investigate the question of origin of life (abiogenesis). Now, there is a very important difference between spontaneous generation and evolution. Life originated at some point and the through repetitive ...


2

I don't think it is a clever thing to group all types of decussation and look for a general explanations. I would tend to think that different decussation have different explanations. It is like asking what are the hypothesis to explain evolution of body size. There is no general answer to that but only a list of case specific impact of different factors on ...


2

This just got too big for a comment and I think might actually qualify as an answer. Can you give me a source for what you're reading? According to this, which matches the definitions you are using, K=(Nu)/N=u where K is the substitution rate, u is the mutation rate in the population, Nu is the individual mutation rate, and N is the population size. I went ...


2

I don't fully understand how your model works I don't fully understand how you model your population. Is it a standard $oop$ (object-oriented programming) where you simulate each individual? Or is it a simulation where you already use some mathematical model? You could eventually copy-paste your code. it is probably not very long, right? What language did ...


2

First, you need to recognise the difference between Natural selection and Artificial selection. As a basic definition, you can say that in natural selection, selection is done on fitness (overall, long-term success of reproduction) and is determined by the complete living environment of the species. In artificial selection, selection is done by humans on a ...


2

Here is a more morphologic, less genetic answer: According to this article, the 2 sets of paired appandages (shoulder and pelvic) was set in stone when agnathans transitioned into gnathostomes (ie. when the first vertebrate organisms began to evolve jaws, an anatomic change that allows for classification of different stages of history found in the fossil ...


2

From Conner and Hartl's A primer of ecological genetics: "Any variance in reproductive success among individuals greater than random expectations, a commonplace concurrence in natural populations, reduces effective population size." So yes, selection does reduce the effective population size and for the reason you suggest - it removes some ...


1

The honest answer to this and many other similar evolutionary questions is that we don't know the answer. We can sample information from many different points along an organism's developmental timeline using the fossil record, genetics, etc. and reconstruct various states of said organism's development. The overwhelming evidence is that evolution is the ...


1

What do you mean by gene-centric view of evolution I am not totally sure you know what really means the gene centric view of evolution. Everybody agrees that selection (also) acts on genes and that selfish genetic elements exist. I think that what one calls the gene centric view of evolution is nothing but the modern synthesis of evolution (following the ...


1

Could not fit in a comment... This post (and the excellent answer from Richard Smith-Unna) lists the species that have the smallest genome that we are aware of in different clades. Yes we can/could sequence these tiny genomes and try to understand what each sequence does. I think that to understand the minimum requirements for life you will mostly be ...


1

Evolution is about descent with modification. Spontaneous generation doesn't have that. It's about modern organisms emerging from raw molecules. If flies spontaneously appeared from rotting cow meat, why would they have DNA that made them look like they were evolutionarily related to other insects?


1

You can see the wikipedia article on meristem. The apical meristem differentiates into floral meristem that gives rise to flowers. From this the cells specifically expressing APETALA3 (AP3), PISTILLATA (PI), AGAMOUS (AG) and SEPALLATA (SEP) would give rise to the stamen [ref]. CRC gene is essential for female development and plants lacking this will not ...


1

"I imagine that turtle looking up at that food, and sub-consciously wishing to get to it, constantly straining, for it's entire life time. It seems plausible to me that we (advanced life) could have a biological mechanism to "write" needed alterations into either our own DNA or our reproductive DNA over time, triggering the very specific ...


1

If rates of meiotic recombination DIDN'T vary across species - THIS would require an explanation! After all, evolution creates diversity, not homogeneity. I can only wonder that more recombination would allow for a faster diversification. The more DNA you shuffle, the more distinct each individual offspring may be (though I'm not 100% sure). The ...


1

The problem with Intelligent Design is that it doesn't appreciate that the forces that shape species (and individual organism) have to be constant and ongoing or the species disappears. The past matters little, it's what happens right here, right now that keeps species in any particular form. Biological system are not static structures like a building. You ...


1

As I have already mentioned in my other post, the most important role of urea synthesis by humans is blood pH regulation and urine concentration, so it is not just about excreting a waste product. I don't think human body is very special in this case, so I think most of the urea excreting mammals use urea for the same purposes. The urea is created from NH4+ ...


1

There are many different ways to do this, depending on what assumptions you make on e.g. stable age structure, distribution of offspring, haploidy/diploidy, population growth etc. As you probably know, there are also two main approaches to effective population sizes, namely ones based on; 1) the rate of inbreeding ($N_{e,i}$) and 2) the increase in variance ...


1

This article claims to be a new level of evidence for group selection. Its a little early to tell at this point whether the critics will be moved. They have not been in the past! sorry if this is a bit short - its late, but i'll try to come back and do more later..



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