New answers tagged

15

This is from Darwin's Notebook B: Transmutation of species from 1837–1838. From what I understand, the tree is a hypothetical depiction of descent used to discuss differences and relatedness between forms/species. This is the text that accompanies and follows the sketch (notebook pages 36-44): I think (sketch) Case must be that one generation ...


1

Adaptation is a change in a trait as a response to selection. As you ask for local adaptation I assume you want examples where sub-populations have either come under different selection and adapted differently, or cases where sub-populations have come under similar selection but not all have had the necessary genetic variation to evolve, i.e. selection has ...


1

Largely an informed guess based on properties of distributions rather than specific knowledge of statistical genetics: a beta distribution is useful for modeling the frequencies of two alleles at one locus. A Dirichelet distribution, which is a multivariate generalization of a beta distribution, would thus be useful for modeling a set of loci. The flip side ...


0

The fact that birds are able to digest seeds doesn't mean all seeds get digested. That may depend on activity as in the article cited by @Christiaan. There will probably be other factors like size and shape of the seed and protective coats around the seed. Humans, whose digestive system is longer than that of birds can digest seeds as well. However, seeds of ...


3

Is there evidence of selection against long proteins and long genes? I am not aware of any such evidence and cursory googling did not reveal studies that researched a correlation between gene selection and gene size. However, the larger a gene, the larger the probability of a deleterious mutation within said gene so I expect that there is some limit to ...


0

In addition to what Ham Radio suggested, checking out Galaxy might not be a bad idea for doing any sort of computation/analysis that would otherwise have to be done on the command line. In particular, check out tools for sequence alignment (BWA and Bowtie), genome assembly (Velvet, Spades, IDBA-UD), and variant analysis (Freebayes, Mpileup, GATK). Good luck! ...


1

You can use BLAST or NCBI resources to do an analysis of something like the duplication of a gene in the HIV virus, for example. If you're looking for a place to start, I would recommend just learning the NCBI database resources.


27

Birds may indeed digest seeds under conditions of rest. It has been postulated that almost all current knowledge on mechanisms of internal seed dispersal has been obtained from experiments with resting animals. A study with the mallard Anas platyrhynchos (common wild duck), claimed to be quantitatively one of the most important seed dispersing animals in ...


0

First, to be clear, the very act of cannibalism does not cause the development of prions, but the consumption of an animal infected with a compatible form of them, particularly when eating nervous or digestive tissue (i.e. the brain, spine, stomach, or intestines). To directly answer your question, yes, there are other animals that are susceptible to prions ...


0

The question is quite unclear but I'll try to say a few words that may help you. You seem to be considering evolution as an individual that decides what is good and what is not. You seem to be considering the evolution as determing at any time point what will be good for a given species. That sounds very wrong. Evolution is much more than Natural Selection ...


3

Mutations are not performed targeting a specific new phenotype. There is no way an organism can "know" the impact of a specific future mutation anyway. A mutation is just a mistake in the replication process. As a consequence the majority of mutations are deleterious and only a handful of mutations are beneficial. It is true though that the mutation rate ...


1

Kostikova et al. 2016. Syst. Biol. developed an algorithm to model trait evolution with inter- and intraspecific variation. The authors use it to show whether a life-history trait (i.e. annual versus perennial) influences the evolution of intraspecific variation in the climatic niches of species While they do not directly incorporate the space ...


0

Mature, viable seeds have to form in most fruits, which involves the maturation of embryonic tissue. That can take a little time, from just a few days in some weed species to months and perhaps longer in some fruits like pineapple.


1

Metrics of interest The two metrics you are interested in are $\pi$ - the mean number of differences between two randomly sampled (with replacement) alleles in a population $d$ - the mean number of differences between two randomly sampled (with replacement) alleles coming from two different species Consider two sequences ATCGTCAAT ATAGTTAAT There ...


0

Unless I am not getting the example you give, it seems to me that there is a classic experiment that does just what you said: the fluctuation test or the luria-delbruck experiment Also, this recent paper from R. Lenski's lab is a good example too. but I am sure there must be others.


0

I am assuming that by longer life, you mean slower aging, because evolution can do little if a mountain falls on a person! So, why don’t organisms have slower, or better, zero rate of aging? The theory I am describing is based upon life history theory. Life history theory assumes that: Resources available to any organism are limited, Life processes like ...


-1

They occur because there is no reason for them to be selected against. Except for a 25% chance of offspring not surviving, in the rare event that the other parent also has the mutation. That recessive, lethal genes can persist in the population is surprisingly one of the reasons that diploid organisms that sexually reproduce are so successful and diverse. ...


-1

It would be beneficial to a population for a lethal gene to evolve in incestuous situations because genetic diversity is then promoted through natural selection. Genetic diversity is necessary for a species to evolve which would improve the chance of survival.


16

Lethal genes evolve simply because of random deleterious mutations and absence of strong selection. Recessive lethal genes Random mutations can make a gene product non-functional or reduce its activity. However, in diploid organisms the other fully-functional copy of the gene can compensate for the non-functional allele. Sometimes both the alleles can ...


4

This is just loose terminology. By ‘lethal gene’ Dawkins means an essential gene with a mutation that renders it inactive. With a recessive gene, the one ‘good’ copy in the heterozygote provides enough gene-product to allow survival, in contrast to the situation in the homozygote where the total absence of gene-product is lethal. With a rare mutation, the ...



Top 50 recent answers are included