(posted in General Biology)

Sorry - but nobody seems to know the answer to this. Assuming you mean the cluster together was the size of a soccer ball then it's certainly possible these are some kind of eggs, although I'm not sure what from (possibly a gastropod?!?).

If you mean each "egg" was the size of a soccer ball (i.e. twigs in the photo are actually large branches and my perspective is all wrong) then I'd question whether they are even biological!

(posted in Mammals)

I think you are perhaps misinterpreting David's post - he said they are functional when subjected to "female like" endocrine states (induced articficially or by disease).

Are they "useful" - well that depends on what you mean by useful! In an evolutionary sense there is little evidence that male nipples increase fitness (i.e. there would be little cost to losing them) but equally it's not apparent that they impose a cost (i.e. no selection against nipple presence in males) which is normally required for traits to become sex-limited in their expression (think e.g. peacocks tail that is a net benefit for males who need to attract a mate, but is also expensive to produce and increases predation risk - so is a net cost to females). The reason for this of course is that males and females have a shared genetic architecture - so there has to be "conflict" between the sexes to drive the evolution of mechanisms that result in only one sex having particular genes (which can happen through Y linkage in males), or mechanisms to repress gene expression in one sex but not the other (e.g. sensitivity of trait expression to ciruclating hormones in the case of some nipple function, but not presence/absence).

This idea is outlined more eloquently that I can do here:
http://www.scientificamerican.com/artic … e-nipples/

Humans have 22 pairs of autosomes - so 44 autosomes altogether (plus the sex chromosomes, giving us 46 chromosomes in total). For each pair of autosomes a human has - one comes from the egg (so is maternally derived) and one from the sperm (paternally derived) that combined to form the person.

How often (and at what stage) does isolation need to occur to see significant differences in phenotype? Is there a case study for such a process? i.e. not analogy or plausibility argument.

This is almost impossible to answer since there is no single "rule" here. Detection of "significant differences in phenotype" between popoulations is something we do routinely but is of course a function of how hard you look (e.g. how many individuals do you compare between each of two populations, how many traits do you look at).

We then use "common garden experiments" - bringing individuals from both populations into a single (usually lab) environment and ideally letting them breed (within-population) for a few generations so ensure the population differences persist. This tells us the phenotypic differences we see are genetically based (i.e. not totally explained by differerent environmental conditions experienced by the two populations). This type of experiment has been done literally thousands of times on hundreds of different organisms (if you want examples just google "common garden experiment" or "transplant experiment").

However, in any given case the answer to your question depends on a) the degree of gene flow between populations (and whether it is bidirectional), b) the stength of selection on the trait in the two populations, c) the (effective) sizes of the two populations (critical in determining the rate of genetic drift) and d) the genetic architecture (how much variation among individuals in a population is caused by genes, how many genes are there underpinning this, and what are their effect sizes) of the trait you are interested in. We have mathematical models that bring all this information together, but since all parameters vary across any context (set of populations of traits) you might focus on there is no single answer. Also worth remembering that evolutionary time is in generations - so all else being equal divergence happens much quicker in real time (e.g. years) for organsism with short generation times.

Hard to know for sure but its possible that western lowland gorillas from e.g. Congo are might do OK in parts of the Amazon if they became established after an initial translocation. However, leaving aside the fact that we wouldn't actually want to put the Amazonian ecosystem at risk by adding a non-native animal like that, sucesful translocation of wild animals is often unsuccesful. Think of e.g. the stress of capture, transport and release, followed by a requirement for a pretty steep learning curve of what plants were edible/nutritious/poisonous, what predators were dangerous etc etc. If you get past those then other problems could arise, e.g. perhaps some pathogens could host jump from new world monkeys into the gorilla population who would lack resistance etc etc.

So  - in principle - yes they migh do well eventually. In practice getting them established would probably be difficult even if it were deemed desirable.

It could be an egg mass of some sort, but while the photo is a little grainy I suspect this is a Ctenophore of some kind (=comb jelly or sea gooseberry)


Mutation is the process whereby DNA becomes altered.

Genetic variation among individuals is ultimately down to mutation but they are not the same thing. Imagine a population of 1000 individuals all with a genotype AA at a gene. A mutant then arises causing a new version (allele) of the gene, lets call it "a" and one individual carries a copy of this new version

We now have 999 xAA and 1 xAa and no aa genotypes. So there is some variation at this gene, but not much since nearly all individuals we might sample from the population are genetically identical.

Now imagine that some (maybe 10's-100's of) generations later, we look at the population again. It is stable in size so still 1000 individuals - but now the two alleles are equal in frequency - so we might find we have 250xAA, 500xAa and 250x aa. Clearly there is now more variation among individuals in their genotypes, and - if this gene actually influences something we can measure (e.g. body size) we might see more variation in that trait now as well.

So mutation is the ultimate source of (genetic) variation, but the amount of variation present will depend on the allele frequencies. Most mutations are lost by chance (a process called genetic drift), but some may be fixed (go to 100% frequency). So if in the above example all individuals at some stage in the future have genotype aa - then the original allele A has been entirely (and been replaced by the mutation). A mutation is more likely to be lost if it is deleterious (selected against) than if it is advantageous (selected for), but important to bear in mind that chance can be much more important than selection in determining the fate of new mutations in anything but the largest populations.

Fixation is not speciation. Fixation refers to the relacement of an existing allele (or alleles) at a genetic locus by a mutant (i,e, new allele) so that individuals in a single population become genetically identical (at that locus). Speciation occurs when these population-specific genetic processes (selection, mutation, drift) result in so much differentiation between populations (e.g. some pops fixed for some alleles, others for different ones, selection favouring some genes in one population, different genes in another) that individuals from the populations can (or will) no longer succesfully reproduce with each other. This is not generally thought to be a consequence of a mutation being fixed at a single gene, but rather an accumulation of genetic differences between populations at lots of loci (although there are likely exceptions to this generalism). Importantly gene flow (movement and breeding of individuals) among populations acts to reduce among-population genetic differentiation (and hence reduce the likelihood of speciation). This is why isolation is so important - isolated populations will tend to diverge genetically, but gene flow among populations is often sufficient to limit (or even completely nullify) this - meaning speciation will not occur.

Hope that's useful. I realise I have not answered all your questions so will try and respond to more later if other's don't beat me to it!

>p.s. is there a way to respond to an expert's answer as a dialogue?

Nope. Many other sites are based on interactive conversation, ours is a deliberately different model (q+a)!

(posted in Plants & Fungi)

One by itself? Probably not much. Not sure we can answer this - in an empirical question ripe for an experiement  you could have a crack at yourself. Try switching the spuds for radishes in this expt and see what happens. You'd need to find a voltmeter too though I guess.

http://www.homemade-circuits.com/2012/0 … -from.html

(posted in Evolution)

Paracamelus is an extinct genus of animals, known only from fossils, that  are in the family Camelidae (camels, llamas, alpacas etc). By all accounts some of them were very large beasts!

As for how camels evolve... well that's a slightly vague question I'm afraid so hard to answer other than in vague terms (i.e. from camel-like ancestors as a consequence of mutation, natural selection and genetic drift). However, there are quite a few recent papers looking at more specific aspects of camel evolution if you look around. Here's one from a couple of years ago that may be of interest

http://www.nature.com/ncomms/2014/14102 … s6188.html

(posted in Research and Careers)

It's hard to give you specifics, but computing skills are very much part and parcel of most fields of biological research. Often in practice biologists in acadaemia find ourselves collaborating with computer scientists and mathematicians to address our interesting questions using their fantastic skills. This is true for conservation biology at much as other sub-fields like evolutionary biology (my area).

For more practical/less academic aspects of conservation (e.g. with NGOs, or charities) then high-end analytical and coding computing skills may be less essential, but general IT skills, website design etc are all very much part of the workplace.

(posted in Genes, Genetics and DNA)

The key here is that we are "estimating" based on a set of assumptions, not measuring somethingt that is directly observable. Different methods of estimating a parameter are likely to yield somewhat different answers, and may in fact be based on making different underlying assumptions. Sometimes the assumptions underpinning two methods will be equally valid on average (i.e. across different possible scanarios), such that we consider both to be equally sensible.  But in any one scenario (e.g. dating genetic "Adam and Eve") it is likely that the assumptions underpinning one estimation will be better than an other. Unfortunately we don't necessarily always have a way of knowing which method will be best. That said, a key part of paramater esimation is that we should try to quantify the uncertainty in our answer as well. So it may be that two estimates are different but the discrepancy is within the range we miht expect given uncertainy. in statistical terms the estimates may be different, but not "significantly so"

The latest estimates I have seen on dates for genetic Adam (dated from Y chromosomes) and Eve (dated from mtDNA) suggest they are more similar than was first claimed. There may be something newer on this but the article below discusses some of the possible reasons for the originally claimed discrepancy in estimates for the two sexes.

http://www.nature.com/news/genetic-adam … me-1.13478

(posted in Evolution)

Great question - the short answer is that we don't know but have some sensible hypotheses relating to, for instance the Baldwin effect described by Dawkins here

https://richarddawkins.net/2015/04/darw … -instinct/

I think two sources of difficulty around this topic are 1) defining exactly what constitutes "instinctual behaviour"  and 2) a general lack of recognition that complex behavioural routines can potentially be generated by a small set of simple decision rules or heuristics. To give you a very simple example, hatchling turtles emerge onto a beach and head for the sea right? How do they know this is the right thing to do since nobody "told" them? Well basically they don't, they seem to just orientate to and move towards light (and -in the absence of light pollution this means the water). So a very simple sensory bias in this case produces an "instinctual behaviour".

Sorry - but we can't answer that. We do biology not metaphysics.

On a personal level I'd suggest worrying less about the meaning of life and spend more time ejoying the things that are meaningful to you in your life. Not an expert answer, just humble suggestion you can take or leave!

There is debate about this although I am not sure if it is always useful. Humans are quite destructive and there is no doubt we are causing a lot of problems for ourselves, and for other organisms on the planet. So simplistically, if we want less cumulative damage - the two positions we could argue for are reducing the number of people in total or reducing the impact of each person. People who think the first is the solution argue overpopulation is the problem, people who think the second argue it is overconsumption!  I think the split tends to reflect political/philosophical/ethical ideology rather than actual biology.

This may be of interest

[size= 12px]http://www.theguardian.com/sustainable- … ainability[/size]

(posted in Evolution)

It depends on what the tree is depicting a bit.  Nodes by definition represent the ancestors of taxa at the tips, so represent an earlier point in the evolution of the lineage.

However, remembering that species designations are a bit arbitrary anyway (search this site for questions on species concept for more), just because a lineage "splits" it isn't necessarily the case that both descendent lineages have accumulated sufficient change from their shared ancestor to be designated as new species.

The answer is indeed different for different animals so hard to answer this in any quantitative way. However, in basic terms inbreeding (mating among relatives) is more likely to occur as populations become smaller and more fragmented (with reduced dispersal among sub-populations).

Often, but not always, inbreeding results in "inbreeding depression" which is a loss of evolutionary fitness (i.e. higher mortality risk and/or lower reproductive output). This happens because recessive deleterious alleles are more likely to come together in the homozygous state (so that the deleterious effecs are felt) in the offspring of related parents. The amount of inbreedfing depression in a population is therefore dependent on 1) the amount of inbreeding and 2) the load of deleterious mutations in the population. Both of these factors vary a lot among different animal populations.

(posted in Genes, Genetics and DNA)

There is no gene "for nipples" or "for breasts". There are known to be many genes that influence mammalian morphology, growth and development in general, and aspects of breast form/function and disease more specifically. However a specific answer to your questions would require a more specific trait definition. For instance - a number of genes (largely autosomal) have been implicated in studies of susceptibility to breast cancer, while livestock studies have extensively scrutinised genes contributing to variation in milk production (which of course occurs in the breast). However, we don't at this stage have a particularly good understanding of what all these genes are, or the pathways by which they influence breast traits.

I have seen at least some studies indicating X-linkage of some genetic loci thought to be linked to cancer development in breast tissue, although I am not certain if follow up studies have confirmed this. Regardless the current picture is that breat traist of various kinds are influenced by many genes, most of which appear to have fairly small effects on phenotype. We know a large number of these are not on the sex chromosomes, but that we have evidence suggesting some may well be.

This article may be of interest


I suspect others (David?) are better qualified to answer this but broadly speaking, yes there is transfer of maternal antibodies from mother to offspring (via egg yolk in birds, via placenta and milk in mammals like us).  These provide considerable proptection against diseases in very early life but do decay with time - so the protection is not complete and unlimited! Fortunately the offspring immune system, which is often not very competent at birth.hatching becomes fully developed and active. However, it does not "inherit a memory" of pathogens the mother may have been exposed to.

Interesting question! there was a study a few years ago that suggested body size in terrestrial carnivores (or at least mammals) should be limited by energetic constraints imposed by hunting. In simple terms (as I remember it) the costs of hunting when you have a very large body size are unlikely to be met by the pay offs of a succesful hunt. The paper is freely available here so youcan have a look and see if you buy the argument!

http://journals.plos.org/plosbiology/ar … io.0050022

If this is the case then the first thing that springs to mind is that the energetic constraints will be very different in water (and this may permit larger carnivores), while the second thing to note is that the largest animals are planktivores. Although zooplankton at least are animals, in functional terms, planktivory is far more akin to a terrestrial herbivore grazing strategy (hit a food patch, deplete it move on) than to a terrestrial carnivore hunting strategy. So, in otehr words  - perhaps its not about herbivory vs carnivory, but rather about grazing versus hunting.

Hi Bruno,
Quite alot of questions - I'll try and tackle at least some!

>evolution can be described as 'descent with modification'; a change that builds up in a population over time. The changes involved are random mutations to the DNA that is not directed. I also imagine that that change is 'established' in the population before the next change occurs,

Not so. Populations harbour a lot of genetic variance arising ultimately from mutations. Mutations are arising all the time and ultimately proceed to fixation (the mutant allele becomes the only variant in the population) or loss (it disappears from the population). Selection plays a big role here but so does random chance. At any one time there will be lots of mutations at lots of genes at all sorts of different frequencies in a population. So it's definitely not a sequential process at all!

>Are small changes (that have no effect on phenotype) able to be part of this process?

Absolutely, much genetic evolution has no detectable effect on phenotype and may be considered neutral. However, also bear in mind that a mutation may impact some aspect of phenotype that we haven't measured (e.g. change the rate of activity of some enzyme in an obscure metabolic pathway). Also bear in mind that small effects on measured phenotypes may not always be detectable in practice.

Macroevolution is what you "see" when you look for differences at high level taxa (e.g. between species). So almost by definition you do not see "macroevolutionary" change in a population in the way you imply. Rather - lots of small changes accumulate over time so that when you compare lineages that diverged quite a while ago they are now so different as to be viewed as different species/genera/families etc. In fact, the terms micro- and macroevolution are not really used by biologists (but are focussed on a lot by ID/Creationists) but to the extent they are useful (debatable) then the key point (for me) is that microevolution is a process (testable, predictable, observable, measurable over human-relevant time frames) and "macroevolution" is the outcome of that process running for longer times frames (e.g. thousands of generations or more) which are not typically observable for humans (unless you have v short lived organisms to observe).

So don't look for a mutation causing macroevolution. With a few arguable exceptions (which I won't get into here) macroevolution is just the accumulation of microevolutionary change.

>then every small mutation MUST have some positive advantage for that animal to survive -

This does not follow logically to me. Many mutations will have no effect on survival but in general (exceptions being in very small populations) deleterious mutations are unlikely to be fixed in a population due to being selected against. Note that selection acts differently according to local conditions, so a mutation that is advantageous in one population (and ultimately fixed as a result) of a given organisms could be disadvantageous in another (where it is selected out). So whther a mutation is beneficial, deleterious, or neutral may depend on local context a lot.

Hmm, no idea to be honest. The discrete nature of them, and what might be burrows makes me assuem it is something coming out of the sand and popping back in. The tracks are well defined so I'd hazard a guess whatever makes them has a hard shell of some kind (a mollusc or arthropod) but basically... no clue!

Take a spade if you go back there and see if you can dig one up!

Impossible to say without a picture (or perhaps even analysis of the material). If it was an empty shell then perhaps some species of marine algae (i.e. seaweed) although this is unlikely on a live animal since cockles burrow in the sand (and algae needs light!)

It's an interesting concept but to be honest I think hard for us to give you a sensible answer. The great thing about fantasy is of course that anything is possible. However, animal behaviour is very much shaped by evolutionary forces including selection through differential mortality. So if you make death an impossibility then it's hard to say how anything would behave  - perhaps as in this world in the short term would be a sensible starting point!

Hi Chatan,

Sorry but this info is hard to provide given we don't know where in the world you are,
or where you wish to study (where is abroad to you?). Most experts on this site are UK based and (to my knowledge) there are no universities offering degrees in herpetology here - although Bango offers zoology with a specialism in herps.

For function, weight and flexibility are important. It's not just a case of increasing muscle to make falpping heavier wings possible though,  as bigger muscles add more weight. More weight (total, not just wings) means bigger wingspans would be needed to provide sufficient lift. This is turn could limit manouvreability or access to habitats (you need small wingspans to operate in a forest). External "armour" might also interfere with other functions of feathers (insulation, waterproofing etc) if it were applied to extant birds.

You don't say where you are and the picture is a bit grainy but I'd say it is a true bug (ie order Hemiptera) and  - if you are in N america - I'd hazard a guess at teh box elder bug. If so the one in the photo is a nymph rather than an adult (which is also red and black but rather different patterning). IF I am right, they are not harmful to you and while they may do some damage to your plants they are not considered serious pests.


Many fish can also breathe air  - at least to some degree. This is seen in lungfishes, anabantoids (gouramis, bettas etc), and gas exchange can also occur through skin to some extent. See here for eaxmples:


The functional important of these abilities varies among species but being able to breathe air can mean individuals can survive in stagnant pools with low oxygen (some gouramis), travel overland when needed to facilitate migration (eels) or exploit patches of habitat other fishes cannot  (mudskippers).

No need to specialise on a single taxon. Many do of course (e.g. some people are fascinated by primates, or fish, or some particular species of bird), but probably more common among professional researchers is to focus on particular types of behaviour e.g., mate choice, parental care, aggression and the general principles that explain them across taxa.

Regardless, while a masters or PhD project in ethology is  - by its very nature - often quite focussed on a single animal species, we all need to try and see the big picture by reading around what is happening with other species.

Female preference is generally thought to be the driver of most "flashy" male signals like the peacock's tail. In simple terms females prefer a signal (e.g. big tails) and then this preference actually imposes sexual selection on teh male trait causing it to evolve. There are a number of competing hypotheses and models that differ primarily in why the female prefernece should occur in the first instance, but certainly there is no doubt that it does.

More here if you want it

In terms of "conscious thought" this is not really a prerequisite for exhibiting a behavioural preference, animals (including ourselves) do have inbuilt sensory biases and these could be involved. However, it is also very much the case that animals possess cognitive abilities comparable in form (if not always in performance) to ourselves and are able to, for instance, discriminate between males of different "quality". I think the concept of "conscious though" is perhaps problematic to apply as it is not very well defined, but certainly animals can be "intelligent" in the lay sense of the word.

It depends a bit on what sort of biology you are interested in. Some options would be to volunteer for conservation organisation, zoos, aquariums etc. Approach such organisations and be prepared to help out with anything that is needed - even if its adminisatrtive rather than hand on science. Getting a "foot in the door" can be key.

If you are more interested in biomedical science or lab-based biology then it may be harder since as a distance learner you won't regularly come into contact with lab-facing academics. That said I would ask your OU tutor for advice. You might also consider contacting another (local) university's biology department (and/or specific researchers whose work you find particularly interesting) to enquire about possible volunteering opportunities.   Do be prepared for knock-backs - it is actually quite hard for many lab-based biologists to accomodate volunteers from outside their own university as there are quite a lot of insurance/security/safety issues that apply to anyone "working" in potentially dangerous lab environments.

(posted in General Biology)

Class is a "rank" of the taxonomic classification system - just like species, genus, family, order etc. IN terms of this hierarchical classification scheme it comes after order and before phylum (e.g.,  multiple orders belong to the class known as insects, while insects are one of several classes that make up the phylum known as arthropods).

A clade is (I hope ... but our taxonomic experts will correct me if I get it wrong!) a group of organisms (extinct and/or extant) comprising all descendents of a single common ancestor. The idea of grouping organisms into clades (i.e. strictly by evolutionary ancestry) came about after the original classification scheme of which class was part.

So a genus, or an order, or a class is also a clade if it comprises a complete monophyletic group. However, since high level groupings such as "class" were originally assigned based on shared morphology alone, they often do not quite represent the evolutionary relationships we think exist. For instance some classes are "paraphyletic" which means they include a common ancestor and some - but not all - of the descendents. The class "reptilia" provides such an example. At least as traditionally defined it excluded the class aves (birds). However, we now know that birds evolved from reptiles, so if reptilia is to be a monophyletic grouping it must include the birds.

Not sure if that is clear but bottom line is that these days we prefer to organise taxonomy by evolutionary relationship and, to a large extent, this means that the old higher levels taxonomic units like class are falling out of favour. they can be convenient in some circumstances but do not always represent monophyletic clades.

Ah. So the same conditions apply - in that it depends on the strength of selection and amount of genetic variance. However, temporal trends in traits in nature are also determined by changes in the environment which cannot be controlled in the field. So the first challenge for scientists is to try and determine the relative contributions of genetic change (=evolution) and environmental change to what is happening.

For some simple Mendelian traits this is trivial because of an (almost) 1:1 mapping between a genotype we can determine and a trait. In such cases we can literally measures gene frequency changes from 1 generation to the next and see the corresponding trait change. To robustly infer that these changes are adaptive evolution we strictly need to a) understand selection on the trait to make sure changes are in the expected direction and b) rule out genetic "drift" in the absence of selection as an alternative explanation for the change. Note change through drift IS most certainly evolution, but it is not "adaptive evolution" (i.e. response to natural selection) which is I think what Taylor is referring to specifically. Our ability to meet this criteria increases with the number of generations so while we may be able to see change over a single (or few) generations, we may not be able to rule out drift on statistical grounds until we have followed the genotype/trait frequency for longer (e.g. tens of generations).

For "complex" or polygenic traits - those like body weight or parental care behaviour which are likely to depend on many genes of small effect AND many environmental influences, "proving" adaptive evolution is real time is harder within a single population. This is because we can't simply track changing gene frequencies, and thus can never 100% exclude the possibility that some environmental variable we have not measured (and so can't control for) is driving the trait change. We can - and do - use statistical predictions of something called "genetic merit" which is essentially the expected trait value of an individual given everything we know about its genes, and see average merit is changing across generations. Studies to date have mostly done this is 10-20 generations and found statistical evidence for genetic change underpinning trait changes that we can see (and detect easily).

The amount of change per generation is actually a function of how strong the selection is, and how much genetic variation there is in the population. in basic terms the equation is

evolutionary change = strength of selection x genetic variation

When we apply strong selection to populations in experiements we commonly get detectable change over a single generation. Typically however, selection experiments in biology aim for 5-10 generations.

Nice analogy! I would say Mendel though, for me the foundations are the most important part of the tower.

Interestingly for me as a statistical geneticist it turns out that Mendel's results were actually a bit TOO good for some folk to accept as genuine. There's no doubt he was correct in his conclusions, but even the cleanest data in biology has some noise around it and some think Mendel's was suspiciously clean. I don't know the truth of course but there's a nice defense of him here!

http://anth.la.psu.edu/research/weiss-l … Garden.pdf

Just goes to show though that for scientists, it is the process of finding things out, not the person that matters. We all build on the work of our predecessors and doing things properly is (or should be) more important than your actual results.

Nearly all fish have red blood (as in mammals) due to the haemoglobin. Some invertebrates use hameocyanin instead to transport oxygen in teh blood and this gives it a blue colour.

That said, blue/green blood is reported from a some marine fish species. From your photo it is difficult to hazard an idnetification here since key features (heads, tails, overall body shape) are not visible. It would also be helpful to know where in the world you are and what common name (if any) the fish were being sold under.

Some members of the wrasse group (Labridae) have blue/green blood but this is not a wrasse! I have seen an old description of the Japanese eel (Anguilla japonica) having blue blood (but someone may have a better source of info on this). This is a widely farmed species so is readily available in fish marked in much of Asia and has a similar body shape to the picture above but I cannot be sure.

(posted in Evolution)

I don't think many scientists are really trying to do this, but the few that are certainly get a lot of media attention. In one case I know of there was an attempt to "de-extinct" the Pyrrenean ibex using cloning technology. In this case it was an attempt to de-extinct a recently extirpated sub-species for reintroduction. So aside from technical challenge of seeing if it can be done (something many scientists enjoy, just as in any other field) the motivation was to try and repair human damage to the ecosystem (i.e. humans wiped out the ibex, can they fix it).

For mammoths I think the excitement of the technical challenge is the same, but the proposal to reintroduce them to a "pleistocene park" in Siberia was certainly controversial among scientists. The idea of being able to study previously extinct animals is very exciting to zoologists and ecologists, but - even if it could be done - many are worried about disruption to existing ecosystems as you say. So some scientists are in favour and some opposed. Do bear in mind that the rationale for these sort of projects is not just scientific. For instance if someone managed to create a real-life "Jurassic Park" I think they would make a LOT of money!

(posted in Genes, Genetics and DNA)

I am not sure that we know for certain. In principle having more gene copies to produce a cancer-beating protein like p53 seems like a good idea, but in practice there may well be downsides. For instance I have read of a suggested link between p53 and age-related disease (simplistically, having too much p53 may cause early aging).

You are not correct. All else being equal, selection will favour early reproduction as  - with later reproduction there is a greater chance of death before passing on genes (i.e. you get eaten by a predator). However, all else is not normally equal and the evolution of life histories (basically the expected schedules of maturation, reproduction etc) depends on many trade-offs. For instance delaying reproduction till you are larger can be advantageous if small size means you produce less viable offspring or have a reduced chance of surviving to have future reproductive episodes.

For humans the evolutionary puzzle is not that female reproduction does not happen later in life instead of early. Rather it is why females have such a long post-reproductive lifespan (males can continue to father offspring untill death, but the female menopause ends fertility long before current expectations of lifespan).

You don't say what your background is or what sort of job you'd be looking for, and this isn't a career advice site! that said there are lots of molecular biology jobs in SE England generally, witha high concentration of universities, hospitals and biotech companies. You can of course expect competition to be fierce for most good jobs. If you are looking for a technician position then experience and skills with particular techniques is going to make you stand out. You will need to be an EU citizen/have appropriate visas to work unless your have exceptionally specialised skills in which case it is posisble that an employer can argue there are no suitable qualified UK/EU candidates.

(posted in Plants & Fungi)

Your question is a bit unclear to me. Trees  - like all other plants and also animals are composed of cells. plant cells are a bt different to animal ones but you can read about them here


If you mean what is the chemical composition of a tree, then its a mix of water, carbon based organic compounds and various other elements and their compounds.

Whether you go straight for a PhD will depend where you are. in some countries it is more or less required to have an MSc first (US) in others it is not (UK). However, financial constraints aside I would opt for a masters first if you are undecided about what PhD is best, it will also make you more competitive for landing th PhD position you really want.

I would also note that, in terms of studying for a PhD, the key thing to look at is not the program title or even the school/university, but rather the advisor you will be working with and for. I'm not saying the university has no importance, but it is secondary to finding a supervisor with resaerch that excites you and a good track record of fledging independent scientists!

I think what you are saying is that hunting and scavenging have different risks and rewards, and carnivore strategies will haev evolved in response to response to selection imposed by these. If so - I totally agree - behaviours coevolve with physical characteristics too, so there are many solutions to the problem of how to obtain meat (if you are a canivore) or food more generally.

I cannot comment on the importance of scavenging of either dinosaur you mention as this is outside my expertise, but would note that very few hunters around today are averse to a "free meal" if they find one. Of course the relative dependence on scavenging variaes a lot among species, but can also vary among individuals of a species.

For grad school I would say the name of your degree doesn't matter too much and your training is primarily carried out by your supervisor (and often their group). So rather than thinking should you get a PhD in paleontology, versus evolutionary biology or anything else I would think of who you want to work with and train under. The best way to do this is to read lots of papers, and then find out what you can about the authors of the ones that exceit you most!

Others I'm sure will add their comments to this, but while I'm not sure this is exactly what you are referring to, mutualism  - a form of interactions between two species where both benefit - could be seen as a form of "trade" (usually of services rather than property). It is one however, that has evolved such that species interact in this way generally, rather than being an outcome of some cognitive "decision" making process by two individuals involved in any given case.

Lots of examples of multualism provided here:

Hi Mack,

We are mostly UK based and there is a lot of variation in how grad studies work globally. I'm guessing from your message you are probably in US/Canada. Assuming so I would strongly suggest contacting profs whose work you are interested in. Almsot by definition if you pursue a resaearch based degree in science you have to specialise to some degree so there is little point in trying to avoid that. The trick is to work out what you find most exciting and see if you can get into that field.

In terms of future careers - yes there are careers in the fields you mention. Most (but not all) would be in acadaemia (so you'll need an MSc, PhD and postdoc experience ultimately) and it is competitive (so "readily" is not the word I would use... be prepared to fight).

Ultimately my advice for grad school is to do what you love, if you don't know what that is then another option might be to tray and get some work experience for a year of two and then apply when you are more sure of the direction you want to go in.

In general parental care has evolved with a tension between balancing costs for the parents and benefits to the offpsring. Since those costs and benefots differ a lot among species we see a wide range of care strategies. In some animals, parents provide care while in others they don't. In those that do, care can be provided in different ways - some of it before hatching/birth, but a lot of it before.

In fact, sea turtles do provide a lot of care, they just provide it at a stage before the babies hatch. So, for instance, females provision the eggs with nutrient rich yolk to nourish the developing offspring. they also bury the eggs and hide their tracks to avoid drawing the attention of predators. Consider what could happen if the mum stayed around on the beach until the eggs hatched. She'd be unable to feed, and would herself be at risk from terrestrial predators (both big costs to her that might prevent future reproduction). Her presence could also alert predators to the presence of a nest full of tasty eggs - not good news for the offspring.

(posted in General Biology)

great question!

Pure water (H2O with nothing else in it) is usually considered to be odourless (at least to humans!). Often there are other things in the water though (e.g. chlorine if it has been treated), and we can certainly smell other things associated with "wet" areas (e.g. plants), especially if we've been somewhere very dry.

Grit is eaten a lot by seed eating birds. Basically it accumulates in the gizzard and helps to break down the tough seeds by abrasive action (remember birds have no teeth) which makes them more easily digested.

All birds have a gizzard, some other animals do too (see https://en.wikipedia.org/wiki/Gizzard) but not all birds feed on things as tough as seeds so many don't need to ingest large amounts of grit.

(posted in Mammals)

The longer hair around the cheeks is certainly more common in adult male tigers. I don't think there are any studies really testing if this has a function, but I would hypothesise that it related to testosterone expression. It could also have some signalling purpose (i.e. being attractive to females, or making the animal look more physically impressive to put off rival males) but I don't think this has ever been shown. Sadly, it would be quite hard to test this idea properly as there aren't enough tigers to make getting a decent sample size very easy.

I am not sure that there is a single reason in every case, but two factors are:

1) The captive environment may not allow provision of the preferred food which the species has evolved to eat. For instance, while sharks can be generalist predators of course,  it would not be legal or ethical to put live seals into an aquarium containing white sharks.

2) Stress. Chronic stress suppresses appetite. If we can't provide suitable environments for captive animals they will suffer physiological stress responses that suppress appetite, and immune function , and basically cause lots of other problems.