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Originally mole-rats were likely the offspring of unrelated, monogamous parents (Hughes et al. 2008) and stayed in their natal nests because of ecological pressures. The benefit was a greater overall fitness because they did not have to face the dangers outside the nest, and the original cost was marginal, as reproductive rights had not yet been lost ( [link] ). Staying in the natal colony, however, reduced access to unrelated mates, which led to inbreeding. Reeve et al. (1990) found that today in naked mole-rat colonies more than 80% of matings that occur are either between siblings or between parents and offspring. Overall, these mole-rats have an average relatedness of 81% to their other colony members (Reeve et al. 1990) while average relatedness between full siblings is 50%.

As relatedness increased due to inbreeding and more individuals remained in the nest, a dominance hierarchy likely formed. The more dominant individuals held more reproductive rights. Gradually, the costs and benefits of staying changed slightly for non-breeders because of the inbreeding. The non-breeders gave up reproductive rights (the cost), thereby diminishing their direct fitness . However, they still had the benefit of avoiding outside dangers. More importantly, they gained greater indirect fitness because they were raising young highly related to them. In this manner they helped pass on their genes indirectly through the offspring of their relative, an act that added to their inclusive fitness. This inclusive fitness was greater on average than if they left to have their own young after the costs for leaving, such as predation and food risks, were taken into account.

Fortress defense and the aridity food distribution hypothesis

Fortress defense and the Aridity Food Distribution Hypothesis are two different hypotheses that use extrinsic factors to explain part of the cause of the rise of eusociality. The fortress defense theory holds that eusociality evolved in order to avoid predation (Queller and Strassmann 1998). Fortress defenders are unique from other social organisms in that they nest and feed within an area protected from predators. In addition, the food they eat is not well distributed. These combined factors favor staying in a safe location with access to food over the risks of leaving and reproducing (Alexander et al. 1991, Queller and Strassmann 1998).

A climate map of Africa.
This is a simplified climate map. Heterocephalus glaber and Cryptomys damarensis are found in the arid regions of the Kalahari Basin, the Horn of Africa, and southwestern Africa.

The Aridity Food Distribution Hypothesis, the second theory based on extrinsic factors, states that eusociality in H. glaber and C. damarensis evolved due to selective pressure from the arid environment that they both inhabit (Faulkes et al. 1997b, [link] ). According to Jarvis et al. (1998), mole-rats find the dry soil of their habitats hard to dig, a constraint that increases their energetic expenses in efforts to obtain resources. These habitats have sporadic rainfall and high evaporation rates ( [link] ), so there is a limited time period in which to work after the rain has stopped before the ground is too hard again (Jarvis et al. 1998). Mole-rat colonies maximize the number of members for cooperative foraging and group living so that after a rainfall they can better exploit the short time they have and reduce the risks of failure in foraging ( [link] ). The two hypotheses examine the ecological factors involved in the evolution of eusociality. Intrinsic factors, such as hormone regulation, however, are also involved.

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Mockingbird tales: readings in animal behavior. OpenStax CNX. Jan 12, 2011 Download for free at http://cnx.org/content/col11211/1.5
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