PAETE.ORG FORUMS
Paetenians Home on the Net

HOME | ABOUT PAETE | USAP PAETE MUNISIPYO  | MEMBERS ONLY  | PICTORIAL PAETE | SINING PAETE  | LINKS  |

FORUM GUIDELINES
please read before posting

USAP PAETE Forum Index USAP PAETE
Discussion Forums for the people of Paete, Laguna, Philippines
 
 FAQFAQ   SearchSearch    UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

(Bio) Adaptation:Birds Manipulate Birth Order to Protect Son

 
Post new topic   Reply to topic   printer-friendly view    USAP PAETE Forum Index -> Science Lessons Forum
View previous topic :: View next topic  
Author Message
adedios
SuperPoster


Joined: 06 Jul 2005
Posts: 5060
Location: Angel C. de Dios

PostPosted: Wed Sep 20, 2006 7:02 am    Post subject: (Bio) Adaptation:Birds Manipulate Birth Order to Protect Son Reply with quote






University of Arizona
September 18, 2006

Bird moms manipulate birth order to protect sons

Protecting her kids from peril is the job of every good mom.

When marauding mites turn up in a house finch's nest, she shelters her sons from the blood-suckers by laying male eggs later than those containing their sturdier sisters, according to new research.

Making sure the vulnerable baby boys are exposed to mites for a shorter period allows both the sons and the daughters to survive long enough to leave the nest.

"Sons are more sensitive to the mites than daughters," said Alexander V. Badyaev of The University of Arizona in Tucson. "Mothers minimize sons' exposure to mites by laying male eggs later than female eggs. As a result, the males are in the nest fewer days."

Even so, the male chicks that grow up during mite season end up just as big as ones from the mite-free time of the year.

It's all mom's doing, Badyaev said.

Once breeding female finches are exposed to mites, their bodies make hormonal changes that affect the order of egg laying and accelerates the development of their sons while they're still in the egg.

"We've found a mechanism by which duration of growth can be adjusted to a changing risk of mortality," said Badyaev, a UA assistant professor of ecology and evolutionary biology. He added that this is the first documentation that maternal manipulation of both ovulation and growth influences the duration of development in birds.

Badyaev and his colleagues' article, "Sex-Biased Maternal Effects Reduce Ectoparasite Induced Mortality in a Passerine Bird," is scheduled to be published in the early online edition of the Proceedings of the National Academy of Sciences the week of Sept. 18.

His co-authors are UA graduate students Terri L. Hamstra and Kevin P. Oh and UA research specialist Dana A. Acevedo Seaman. The David and Lucile Packard Foundation, the National Science Foundation and the Silliman Memorial Research Awards funded the research.

One of Badyaev's interests is figuring out how the various developmental periods of birds evolve and how birds can modify those developmental periods to maximize the survival of their young.

There's a trade-off between keeping the kids at home longer so they grow big and strong and getting them out of the nest quickly because nests are targets for predators and parasites, he said.

Since 2002, Badyaev, Oh and their colleagues have been intensively documenting the lives of a population of house finches (Carpodacus mexicanus) on the UA campus.


Throughout the year, the researchers capture birds several times a week to band and measure them and to take DNA and hormone samples. During the breeding season, the researchers locate the nests, keep track of activity in the nest, follow nestling growth and development, and take DNA samples from the chicks.

The researchers have also been counting the numbers of mites on the birds and documented a seasonal pattern. When breeding starts in February, the mites are absent. As winter turns to spring, mites start showing up on the adult females, in their nests and on their nestlings. The exact timing depends on the year.

Mites can kill nestlings.

"When it is safer inside the nest than outside, then there's no need for young to leave the nest until growth is complete, but when mortality risk of staying in the nest is great, chicks need to complete their growth fast and get out as soon as they can," Badyaev said. "What should a mother do in the face of shifting mortality risk?"

"To leave the nests sooner and still survive outside of nests, the kids need to grow faster," Badyaev said. "But the mechanisms which regulate nestling growth in relation to changing mortality were not known."

So the researchers looked to see how finch moms changed their child-rearing strategy so as to always do best by their kids.

The birds lay one egg per day. To successfully raise baby finches in the presence of mites, the mothers altered the order in which male and female eggs were laid.

When mites were absent, the chances of any particular egg being male or female were even. But once mites came into the picture, the mothers laid female eggs first and male eggs last.

Males that grew during mite season did more of their development in the egg before hatching. Their mothers accelerated their sons' growth, both in the egg and after they hatched.

"Mothers essentially hid their sons in the eggs," Badyaev said.

It's remarkable that the fledglings have such similar morphology with or without mites, he said. "Mothers did that by modifying the order of laying of male and female eggs and the pattern of their growth."

*************************************************************

Questions to explore further this topic:

What is evolution?

http://www.blackwellpublishing.com/ridley/toc.asp
http://www.paete.org/forums/viewtopic.php?t=1452
http://www.actionbioscience.or.....enski.html

What is natural selection and adaptation?

http://www.blackwellpublishing.....ation1.asp
http://www.nyu.edu/projects/fi.....ation.html
http://www.mnsu.edu/emuseum/bi.....ction.html

What is adaptation?

http://www.bbc.co.uk/schools/k.....ntro.shtml
http://www.visionlearning.com/.....p;let1=Bio
http://en.wikipedia.org/wiki/Adaptation_(biology)

Animal adaptation (a webquest)

http://www.uen.org/utahlink/ac.....ty_id=4750
http://www.ga.k12.pa.us/Academ...../index.htm

Plant adaptation

http://www.mbgnet.net/bioplants/adapt.html

Adaptation in sexual reproduction

http://www.blackwellpublishing.....ction1.asp

How do animals reproduce?

http://www.saburchill.com/chapters/chap0031.html

How do birds reproduce?

http://www.biology.eku.edu/RIT.....ction.html
http://www.saburchill.com/chapters/chap0034.html
http://www.worldbook.com/featu.....ylife.html

What are Acari?

http://tolweb.org/Acari
http://www.kendall-bioresearch.co.uk/mite.htm
http://www.uky.edu/Ag/CritterF...../mites.htm
http://www.ucmp.berkeley.edu/a.....acari.html
http://www.ento.csiro.au/educa.....carina.htm

Ticks and mites are arachnids

http://hs.onysd.wednet.edu/aca.....index.html
http://pick5.pick.uga.edu/mp/20q?search=Arachnida

What are mites?

http://www.bugwise.net.au/guide/mites-ticks.htm
http://ohioline.osu.edu/hyg-fact/2000/2101.html
http://www.biokids.umich.edu/c.....Acari.html

What are the parasites that affect birds? (An example using purple martins)

http://www.purplemartin.org/update/Parasites.html

What is the role of parasitism in animal evolution?

http://shum.huji.ac.il/~por/ic.....itism.html
http://www.k-state.edu/parasit.....ior53.html

What is evolutionary biology?

http://evonet.sdsc.edu/evoscis.....uction.htm

How is stress related to evolution?

http://www.u.arizona.edu/~abadyaev/res-str.html

What is sexual size dimorphism?

http://www.u.arizona.edu/~abadyaev/res-SSD.html

How are maternal traits related to adaptation?

http://www.u.arizona.edu/~abadyaev/res-mat.html

How is sexual selection related to evolution?

http://www.u.arizona.edu/~abadyaev/res-sex.html

Why do birds evolve with so many different colors?

http://www.u.arizona.edu/~abadyaev/res-col.html

GAMES

http://www.bbc.co.uk/schools/k.....test.shtml
http://www.bbc.co.uk/sn/prehis.....sign.shtml


Last edited by adedios on Sat Jan 27, 2007 3:38 pm; edited 2 times in total
Back to top
View user's profile Send private message Visit poster's website
adedios
SuperPoster


Joined: 06 Jul 2005
Posts: 5060
Location: Angel C. de Dios

PostPosted: Fri Sep 22, 2006 3:09 pm    Post subject: Odd Evolution: Crickets Lose Their Song Reply with quote

Odd Evolution: Crickets Lose Their Song

By Jeanna Bryner
LiveScience Staff Writer
posted: 22 September 2006
04:02 pm ET

In just a few generations, the male crickets on Kauai underwent a drastic genetic change that rendered them incapable of belting out courtship songs, according to a new study.

Typically, male field crickets sport curved wings, and by rubbing a sharp ridge of one wing with a rough part of the other, the cricket produces a mating call.

But this serenade also attracts a parasitic fly. Once the insect spots a singing cricket, it deposits larvae onto the cricket. The larvae burrow into the cricket’s body, where they mature and subsequently kill the cricket as they emerge from its body.

Researchers led by Marlene Zuk, of the University of California, Riverside, have monitored the crickets on Kauai since 1991. With each visit, the team heard fewer and fewer singing crickets. Then, in 2003 they realized the crickets were abundant but 90 percent of the males had flat wings.

The scientists figure that the quiet mutation protects the crickets from the parasitic fly.

For the full article:

http://www.livescience.com/ani.....ating.html
Back to top
View user's profile Send private message Visit poster's website
adedios
SuperPoster


Joined: 06 Jul 2005
Posts: 5060
Location: Angel C. de Dios

PostPosted: Mon Sep 25, 2006 7:55 pm    Post subject: Mother birds give a nutritional leg up to chicks with unattr Reply with quote

Mother birds give a nutritional leg up to chicks with unattractive fathers
25 September 2006
University of Chicago Press Journals


Mother birds deposit variable amounts of antioxidants into egg yolks, and it has long been theorized that females invest more in offspring sired by better quality males. However, a study from the November/December 2006 issue of Physiological and Biochemical Zoology shows that even ugly birds get their day. Providing new insight into the strategic basis behind resource allocation in eggs, the researchers found that female house finches deposit significantly more antioxidants, which protect the embryo during the developmental process, into eggs sired by less attractive fathers.

"For female birds, an important aspect of parental investment is the resources allocated to eggs," writes Dr. Kristen J. Navara (Auburn University and Ohio State University) and her coauthors. "The resources available to any female for reproduction and self-maintenance will be finite and she will inevitably be faced with decisions regarding how much resource to invest in each egg in each clutch she lays."

Male house finches display nutrition-linked plumage ranging in color from bright red to drab yellow. The researchers found that eggs sired by unattractive males (those with less brilliant feathers) had more total antioxidants, including 2.5 times the vitamin E levels, than eggs sired by males with redder, more saturated plumage. Thus, they explain, the deposition of more nutrients could represent compensation for the disadvantages experienced by an offspring from a lower quality male, allowing females to supersede limitations of a suboptimal pairing on her own reproductive success.

"For house finches, a species in which individuals are short-lived [and] present a high risk of death, a focus on the immediate reproductive attempts may be the only viable strategy," write the researchers. "By depositing antioxidants in a compensatory manner, females can maximize the reproductive output from the current nesting effort."


###
Since 1928, Physiological and Biochemical Zoology has presented original, current research in environmental, adaptational, and comparative physiology and biochemistry.

Kristen J. Navara, Alexander V. Badyaev, Mary T. Mendonca, and Geoffrey E. Hill. "Yolk antioxidants vary with male attractiveness and female condition in the house finch (Carpodacus mexicanus)." Physiological and Biochemical Zoology 79:6.
Back to top
View user's profile Send private message Visit poster's website
adedios
SuperPoster


Joined: 06 Jul 2005
Posts: 5060
Location: Angel C. de Dios

PostPosted: Fri Oct 20, 2006 10:17 am    Post subject: Successful Sex Strategy: Be Last in Line Reply with quote

Successful Sex Strategy: Be Last in Line

By Jeanna Bryner
Live Science Staff Writer
posted: 19 October 2006
01:28 pm ET

The early bird might get the worm, but the last in line makes the baby.

From bonobo chimpanzees to fruit flies, many female animals mate with multiple partners that often queue up for the event. Studies have shown that the the last male to mate with a female is the most successful at impregnating her. Nobody has understood why.

The last male can take advantage of a more “sperm-friendly” environment created by males that have copulated before him, according to a new model put forth by David Hosken and David Hodgson of the University of Exeter in the United Kingdom.

For the full article:

http://www.livescience.com/ani.....queue.html
Back to top
View user's profile Send private message Visit poster's website
adedios
SuperPoster


Joined: 06 Jul 2005
Posts: 5060
Location: Angel C. de Dios

PostPosted: Mon Oct 30, 2006 8:01 pm    Post subject: Living in the Desert Reply with quote

Living in the Desert
1 November 2006

Jennifer Cutraro

When you're hot and thirsty, you're likely to drink a glass of cold water or head for a shady spot to cool down. What you surely don't do is shrink your liver to a fraction of its original size.
But that's just what a type of gazelle does to beat the desert heat.

Sand gazelles live in the deserts of Saudi Arabia. These animals allow their livers to shrink by up to 30 percent—all in an effort to conserve water.

It's one of many unusual adaptations that animals make to survive in some of the hottest, driest places on Earth.


For the full article:

http://www.sciencenewsforkids......ature1.asp
Back to top
View user's profile Send private message Visit poster's website
adedios
SuperPoster


Joined: 06 Jul 2005
Posts: 5060
Location: Angel C. de Dios

PostPosted: Sat Apr 07, 2007 7:39 am    Post subject: Latest IPCC report highlights need for integrated climate/hu Reply with quote

International Geosphere-Biosphere Programme
6 April 2007

Latest IPCC report highlights need for integrated climate/human behavior models

Adapting to the global climate change impacts outlined in the IPCC's Working Group 2 Report, "Climate Change 2007: Impacts, Adaptation and Vulnerability", will require new evaluation tools to help choose the best way forward, according to the International Geosphere-Biosphere Programme (IGBP), an international network of environmental scientists.

This quest for adaptation strategies opens a new chapter in global environmental change research that requires not only continued development of sophisticated climate models (and understanding the processes behind them) but also a new integration of those models with predictive descriptions of human behaviour.

"We need to continue discovering how the Earth system works in order to evaluate the numerous ways that humans can adapt to climate change," says Kevin Noone, IGBP's executive director. The additional challenge is to model unpredictable human behaviour and merge this into deterministic Earth system models, explains Noone.

Human adaptation to a changing climate can take many forms, and can have both positive and negative environmental impacts. Small-scale measures could include increased use of air conditioning, architectural changes for more efficient heating and cooling, better forecasting and warning systems for extreme events, and increased water usage. Larger-scale issues could vary from switching to renewable energy sources to attempts at "geoengineering". The large-scale movement of people away from areas adversely affected by climate change and by other environmental and socioeconomic stresses is also a form of adaptation. Each of these options has environmental consequences that must be carefully evaluated before they are implemented. The larger the adaptation scheme, the greater care needs to be taken in considering its application.

"The science needed to support decision making about adaptation requires a sophisticated understanding about how the Earth system works, but goes well beyond just that. We need new tools to help us develop robust "what if" scenarios for different potential adaptation schemes, and their consequences," says Noone. He describes the new tools as new types of models that couple together active, predictive descriptions of human behaviour and choice with the kinds of models used to predict future climate.

Another fundamental issue about adaptation schemes is whether they will contribute to an increase or decrease in equity across the globe. The predictions recently released by the IPCC WG2 show that in many cases the areas facing the largest changes in climate are not only located in countries that have contributed the least to the atmospheric buildup of greenhouse gases, but also those that have the least ability to adapt to them. "One way or another, we will adapt to a changing climate," says Noone. "Adaptation always involves trade-offs. The question is what level of justice and equity we want to build into how we adapt. We still need to build up the kind of basic research linking social and natural science that can be used to provide sound support for decisions about adaptation."

Researchers from IGBP's network of Earth system scientists who authored chapters of the IPCC WG2 report have this to say about adaptation to climate change:

Patricia Romero-Lankao, IPCC WG2 Coordinating Lead Author Chapter 7, "Industry, Settlement and Society" (Deputy Director, Institute for the Study of Society and Environment, National Center for Atmospheric Research): "The underlying conclusion of Chapter 7 is that none of us will escape the impacts of a warming planet. In many cases, global warming will interact with other environmental problems (e.g., deforestation, water scarcity) and make them worse. People in developing countries will be hardest hit by climate change. But as hurricane Katrina and the 2003 heat wave in Europe have showed us, that does not mean that people in the wealthiest countries will be spared."

Tony McMichael, IPCC WG2 Review Editor Chapter 8, "Human Health" (Director, National Centre for Epidemiology and Population Health, Australian National University and Co-Chair, Global Environmental Change and Human Health project of the Earth System Science Partnership): "I welcome the growing emphasis on the modeling of adaptive strategies to lessen the health risks. Recent evidence from extreme heat waves, cyclones and droughts has shown how widely the health impacts vary between old and young, rich and poor, and those with strong versus weak social institutions and supports. Human societies and communities are very varied in resources, culture and behaviour. Stronger linkages between natural and social sciences are now essential if we are to develop realistic integrated models that connect projected climatic change, social change and human vulnerability."

Steve Running, IPCC WG2 Lead Author Chapter 14, "North America" (Professor, Department of Ecosystem Sciences, University of Montana): "For the last twenty years Earth scientists have concentrated on building predictive models of first the physical climate, followed by the integrated biogeochemistry of the planet. Unfortunately, these models operate implicitly as if humans did not exist. The new challenge is to build Earth Systems models that incorporate human policy options, economic preferences, and decision making that can then feed back to influence the biophysical states of the system. The increase in model complexity and interdisciplinary requirements is daunting."

Karen O'Brien, IPCC WG2 Lead Author Chapter 17, "Assessment of Adaptation Practices, Options, Constraints and Capacity" (Associate Professor, Department of Sociology and Human Geography, University of Oslo and Chair, Global Environmental Change and Human Security project of the International Human Dimensions Programme on Global Environmental Change): "Climate change adaptation has both equity and ethical dimensions. It is important to recognize that one person, group or nation's adaptation to climate change may lead to the increased vulnerability of others; this will be especially evident in relation to water access and usage. Modeling these dynamics will be a challenge that requires input from both the biophysical and social sciences."

"Adaptation is a social process that is influenced by differential interests, values, preferences, priorities, resources and power. All of these factors may change in response to ongoing societal transformations, thus the capacity to adapt to climate change can be considered highly dynamic. The way that society adapts to a changing climate has widespread implications for human security."

Gary Yohe, IPCC WG2 Coordinating Lead Author Chapter 20, "Perspectives on Climate Change and Sustainability" (Woodhouse/Sysco Professor of Economics, Wesleyan University): "The WG2 Report calls for adopting a risk management perspective in assessing impacts, adaptation, and sustainable development. Indeed, risk-based portraits of impacts--net of the effects of alternative adaptations--can, when inserted into alternative development pathways at specific locations, offer decision-makers insight into climate risks calibrated in many different metrics (such as millions at risk of hunger or water stress in addition to economic damages)."

"When also cast into the context of alternative mitigation strategies informed by science that describes the full range of possible futures, these portraits can clearly display one of the fundamental conclusions of WG2: adaptation and mitigation will both be required to cope with climate change over the short and long terms."

"Moreover, we now know that these two broad categories of policy options are complementary tools in a policy portfolio designed to reduce climate risk by reducing exposure (through mitigation) and reducing sensitivity to climate impacts (through adaptation)."


###
The International Geosphere-Biosphere Programme (IGBP) is an international, interdisciplinary scientific research program built on networking and integration. It addresses scientific questions where an international approach is the best or the only way to provide an answer. It adds value to a large number of individual, national and regional research projects through integrating activities to achieve enhanced scientific understanding. The Vision of IGBP is to provide scientific knowledge to improve the sustainability of the living Earth.

For more information about IGBP, please visit the website at http://www.igbp.net
Back to top
View user's profile Send private message Visit poster's website
adedios
SuperPoster


Joined: 06 Jul 2005
Posts: 5060
Location: Angel C. de Dios

PostPosted: Tue May 29, 2007 10:35 am    Post subject: How E. coli evolves to adapt to changing acidity Reply with quote

University of Chicago Press Journals
29 May 2007

How E. coli evolves to adapt to changing acidity

One in a series of studies on laboratory studies of selection and evolution
Forthcoming in Physiological and Biochemical Zoology, a fascinating new selection of papers collects leading experimental research in evolution and artificial selection, providing insight into how organisms adapt to changing environmental conditions and fluctuations.

Dr. James Hicks, Editor in Chief of PBZ, explains the momentum behind this collection of papers: "This exciting approach – experimental evolution – allows scientists to investigate the fundamental mechanisms of evolution. Prior to the advent of contemporary laboratory techniques, inferences about evolution were based on observation. Now, we can study evolutionary change as it is happening, by selecting organisms that change rapidly, such as the fruit fly or E. coli. This advantage allows scientists to investigate how changes occur and how they affect an organism's individual physiology and overall community."

In the July/August 2007 issue, the first of three issues that will contain articles from the collection, Bradley S. Hughes, Alistair J. Cullum, and Albert F. Bennett (University of California, Irvine) explore the effect on E. coli of fluctuating acidity, an especially important environmental factor for the bacteria.

E. coli may spend hundreds or thousands of generations in the relatively neutral-acidity colon, with brief exposure to the extreme acidity of the stomach and modest alkalinity in the small intestine during colonization of a new host. With modern sewage handling (or mishandling), the bacteria may also experience exposure to the ocean, with a pH near 8.0, before infecting a new host.

To assess how E. coli might adapt to different environmental conditions, the researchers observed four groups of bacteria. One group was exposed to constant acidity ( pH of 5.3) and another to constant alkalinity ( pH of 7.8 ). A third group was exposed to randomly fluctuating pH levels, and the fourth was exposed to pH levels that cycled daily between acidic and basic conditions.

After at least 1,000 generations, the researchers exposed the groups to either an acidic or basic environment. The groups exposed to acid or base for the entire period had developed into specialists – that is, they displayed significant fitness gains when transitioning into their preferred environment.

In contrast, the groups that evolved in variable pH environments exhibited generalist fitness patterns, with neither group having any significant fitness loss in any of the environments. Interestingly, the researchers also found that there was no significant cost to being a generalist at any tested pH level: "Overall, these comparisons suggest that the jack-of-all-trades may be a master of at least some as well," the researchers write.

"What is interesting here is that the complex patterns of adaptation in the various pH regimes were so different among the groups and revealed the first empirical characterization of the intricacies of evolution in response to variable pH," explain the authors. "Plans for future studies include the extension of this experimental evolution system applied to . . . ways in which E. coli may be evolving fitness to survive within the coastal ecosystem or the human host."

Papers from the focused collection, "Experimental Evolution and Artificial Selection" will also appear in the September/October and November/December 2007 issues.

Focused Issue: Experimental Evolution and Artificial Selection (July/August 2007)

"Do Species Converge during Adaptation" A Case Study in Drosophila"
Carla Rego, Michael R. Rose, and Margarida Matos

"Laboratory Evolution of the Migratory Polymorphism in the Sand Cricket: Combining Physiology with Quantitative Genetics"
Derek A. Roff and Daphne J. Fairbairn

"Evolutionary Adaptation to Freeze-Thaw-Growth Cycles in Escherichia coli"
Sean C. Sleight and Richard E. Lenski

"Using Experimental Evolution to Study the Physiological Mechanisms of Desiccation Resistance in Drosophila melanogaster"
Margaret A. Archer, Timothy J. Bradley, Laurence D. Mueller, and Michael R. Rose

"Experimental Evolution of Olfactory Memory in Drosophila melanogaster"
Frederic Mery, Juliette Pont, Thomas Preat, and Tadeusz J. Kawecki

"An Experimental Evolutionary Study on Adaptation to Temporally Fluctuating pH in Escherichia coli"
Bradley S. Hughes, Alistair J. Cullum, and Albert F. Bennett


###
Since 1928, Physiological and Biochemical Zoology has presented current research in environmental, adaptational, and comparative physiology and biochemistry. Original research results represent a variety of areas, including thermoregulation, respiration, circulation, osmotic and ionic regulation, environmental acclimation, evolutionary physiology, and metabolic physiology and biochemistry.
Back to top
View user's profile Send private message Visit poster's website
adedios
SuperPoster


Joined: 06 Jul 2005
Posts: 5060
Location: Angel C. de Dios

PostPosted: Thu Jul 12, 2007 2:15 pm    Post subject: Evidence that up to 10 percent of human genome may have chan Reply with quote

July 11, 2007
Evidence that up to 10 percent of human genome may have changed very recently revealed by CU researchers

By Krishna Ramanujan

A Cornell study of genome sequences in African-Americans, European-Americans and Chinese suggests that natural selection has caused as much as 10 percent of the human genome to change in some populations in the last 15,000 to 100,000 years, when people began migrating from Africa.

The study, published in the June 1 issue of PLoS (Public Library of Science) Genetics, looked for areas where most members of a population showed the same genetic changes. For example, the researchers found evidence of recent selection on skin pigmentation genes, providing the genetic data to support theories proposed by anthropologists for decades that as anatomically modern humans migrated out of Africa and experienced different climates and sunlight levels, their skin colors adapted to the new environments.

However, the study found no evidence of differences in genes that control brain development among the various geographical groups, as some researchers have proposed in the past.

"We undertook a very careful study of genetic differences within and among major human groups, and aimed to explain why certain parts of the genome differed," said Scott Williamson, the study's lead author and a Cornell assistant professor of biological statistics and computational biology. "We aimed to eliminate as many possible confounding variables as possible, and when all is said and done, we find that as much as 10 percent of the genome may have been affected by one of these bouts of recent selection."

Previous studies at Cornell and elsewhere have searched for signs of selection -- the divergence of genes from a common ancestor millions of years ago -- by comparing an individual human to a chimpanzee or mouse, for example, or by comparing genetic variation in protein coding genes among humans to differences between humans and a chimpanzee. But this study scanned genome sequences that compared many humans to each other throughout the entire genome, with new strict statistical methods that correct for many potential biases that creep into this kind of analysis.

In the latest study, the researchers identified 101 regions of the human genome with strong evidence of very recent selection. These regions include genes that control proteins that help muscle cells attach to surrounding cells (mutations of this gene lead to muscular dystrophy), receptors that relate to hearing, genes involved in nervous system function and development, immune system genes and heat shock genes.

The gene scan method also detected selection in a gene involved in digestion of lactose, an enzyme found in milk. Prior to animal domestication, humans lost the ability to digest milk after infancy. But, as humans migrated and domesticated animals, Europeans and other populations developed a gene for tolerating lactose (and milk) throughout their lives. This finding has been well established in previous research, so arriving at similar results provided an internal validation for the accuracy of the new method.

Overall, close to 10 percent of the Chinese and European-American genomes and only 1 percent of the African-American genome were linked to areas with evidence of recent selection. Since Africans have the greatest genetic diversity and the statistical method searched for areas where the majority of members within a population group have the same genetic changes, signs of evolution were much easier to detect in the less diverse European-American and Chinese genomes.

"It is important to emphasize that the research does not state that one group is more evolved or better adapted than another," said co-author Carlos Bustamante, a Cornell assistant professor of biological statistics and computational biology. "Rather as humans have populated the world, there has been strong selective pressure at the genetic level for fortuitous mutations that allow digestion of a new food source or tolerate infection by a pathogen that the population may not have faced in a previous environment."

Rasmus Nielsen, an adjunct professor of biological statistics and computational biology at Cornell and now a professor at the University of Copenhagen, Denmark, is the paper's senior author.
Back to top
View user's profile Send private message Visit poster's website
adedios
SuperPoster


Joined: 06 Jul 2005
Posts: 5060
Location: Angel C. de Dios

PostPosted: Tue Jul 24, 2007 3:59 pm    Post subject: For Some Male Creatures, Smaller is Better Reply with quote

For Some Male Creatures, Smaller is Better
By Charles Q. Choi, Special to LiveScience

posted: 24 July 2007 07:53 am ET

Sometimes smaller is better for males and sex, new findings suggest.

Often big males have the advantage in the animal kingdom, as their superior size helps them win more contests with competitors in the never-ending effort to mate. Still, University of Kentucky evolutionary biologist Charles Fox and his colleagues wondered if little guys might win against goliaths when it comes to races to females. For instance, "smaller males are presumably better flyers because it's easier for them to fly," Fox explained.

For the full article:

http://www.livescience.com/ani.....etles.html
Back to top
View user's profile Send private message Visit poster's website
adedios
SuperPoster


Joined: 06 Jul 2005
Posts: 5060
Location: Angel C. de Dios

PostPosted: Tue Aug 14, 2007 9:47 am    Post subject: Squirrels Heat Tails to Battle Rattlesnakes Reply with quote

Squirrels Heat Tails to Battle Rattlesnakes
By Charles Q. Choi, Special to LiveScience

posted: 13 August 2007 05:00 pm ET

To protect their young against rattlesnakes, California ground squirrels have evolved a special defense—they heat their tails.

Squirrels in the wild wave their bushy tails at snakes in order to look bigger and more threatening. This upsizing defense is a common tactic in the animal kingdom—cats puff up their fur for the same reason when alarmed.

For the full article:

http://www.livescience.com/ani.....tails.html
Back to top
View user's profile Send private message Visit poster's website
adedios
SuperPoster


Joined: 06 Jul 2005
Posts: 5060
Location: Angel C. de Dios

PostPosted: Wed Aug 15, 2007 10:18 am    Post subject: Adaptation to parasites drive African fishes along different Reply with quote

Public Library of Science
15 August 2007

Adaptation to parasites drive African fishes along different evolutionary paths

Quebec City, Canada - An international team of scientists from Canada (Université Laval), the U.K. (University of Hull, Cardiff University) and Spain (Doòana Biological Station), have discovered that a pair of closely related species of East African cichlid fishes – a group of fish whose diversity comprising hundreds of species has puzzled evolutionary biologists for decades – evolved divergent immune gene adaptations which might explain why they do not interbreed, despite living side by side.

The two species ( Pseudotropheus emmiltos and Pseudotropheus fainzilberi ) are found in the north western part of Lake Malawi. Until now, the only known difference between them was the color of their dorsal fin. Many researchers believe that African cichlids recognize conspecifics from these kinds of colour differences, which are thought to result from sexual selection. However, recent mate choice experiments have shown that female P. emmiltos recognize males of their own species from P. fainzilberi males based on olfactory communication rather than color.

Some of the genes known to influence mating behavior through olfaction in other vertebrate species are genes of the major histocompatibility complex (MHC). These genes code for receptor that bound molecules produced by infectious agents and present them to specialized cells of the immune system which then launch an immune attack on the microbes. They are the most diverse genes found in vertebrate genomes and individuals of some species, including humans, are able to "smell" other individuals’ variability at these genes and adjust their mate choice in order to optimize the effectiveness of their offspring's immune system. Analysis of MHC genes between P. emmiltos and P. fainzilberi revealed that the two species were genetically more different at these sites involved in contacting and presenting molecules to immune cells than at other sites of the gene's DNA sequence that do not play functional roles.

These results show that natural selection has driven the evolution of these genes in different direction between the two species. Furthermore, the researchers showed that infecting parasites found on the two species were significantly different, as predicted based on the known immune function of MHC genes. "The mechanisms having produced the hundreds of species of East African cichlid fishes in a relatively short period of time are unclear", says Jonatan Blais, the senior author of the paper." This is one of the first genetic adaptive differences between closely related East African cichlid species identified. As such, it improves our understanding of the recent evolution of this incredibly diverse group of fish by pointing to a trait that not only diverged for adaptive reasons but may also be involved in mating behavior."

"The precise role that this divergence played in the evolution of reproductive isolation has yet to be studied", comments Louis Bernatchez, co-author of the study." But it offers an exciting new perspective in the study of African cichlids speciation ".


###
Disclaimer

The following press release refers to an upcoming article in PLoS ONE. The release has been provided by the article authors and/or their institutions. Any opinions expressed in this are the personal views of the contributors, and do not necessarily represent the views or policies of PLoS. PLoS expressly disclaims any and all warranties and liability in connection with the information found in the release and article and your use of such information.

The study appears in the August 15 issue of the online, open-access journal PLoS ONE.

Citation: Citation: Blais J, Rico C, van Oosterhout C, Cable J, Turner GF, et al (2007) MHC Adaptive Divergence between Closely Related and Sympatric African Cichlids. PLoS ONE 2(Cool: e734. doi:10.1371/journal.pone.0000734

PLEASE ADD THE LINK TO THE PUBLISHED ARTICLE IN ONLINE VERSIONS OF YOUR REPORT: http://www.plosone.org/doi/pone.0000734
Back to top
View user's profile Send private message Visit poster's website
adedios
SuperPoster


Joined: 06 Jul 2005
Posts: 5060
Location: Angel C. de Dios

PostPosted: Thu Aug 16, 2007 9:36 pm    Post subject: Savanna habitat drives birds, and perhaps others, to coopera Reply with quote

University of California - Berkeley
16 August 2007

Savanna habitat drives birds, and perhaps others, to cooperative breeding

Unpredictable savanna rains may have led to cooperation among birds, study finds
Berkeley -- Delaying having kids to help raise the offspring of others seems like a bad choice if you want to reproduce, but many African starlings have adopted this strategy to deal with the unpredictable climate of their savanna habitats, according to a new study by University of California, Berkeley, and Cornell University biologists. It appears in the Aug. 21 issue of the journal Current Biology.

This behavior, called cooperative breeding, is typical of many animals, from insects and shrimp to birds and even humans, but the reasons underlying its evolution and distribution among such a wide array of species have been unclear.

In the new study, behavioral ecologist and evolutionary biologist Dustin Rubenstein, a Miller Fellow in the Department of Integrative Biology and the Museum of Vertebrate Zoology at UC Berkeley, looked at the complete group of African starlings and found that all of the cooperative breeders among these birds live in savannas - highly seasonal habitats with great variation in rainfall, and thus food, from one year to the next. The species that do not engage in cooperative breeding are found mostly in forests, which have more reliable annual food resources.

"Faced with an uncertain and unpredictable environment, it pays evolutionarily to live and breed in social groups that will help you weather the bad times and make the most of the good times," he said. "Living in cooperative family groups may be like a form of insurance against the unpredictable nature of the environment, because it allows individuals to maximize their reproductive success over the course of their lifetimes."

Cooperative breeding is defined as one member of a group delaying breeding to assist another breeding couple. Because cooperative groups in most birds consist of extended families with grandparents, parents, offspring and other close relatives, helpers are typically related to the group members. Among most birds, females leave the group to try to breed elsewhere, so it is the males who often hang around for a year or two as helpers, primarily bringing food to the nestlings. Although they may occasionally breed with females in the group, the helpers often don't reproduce until later in life.

Helping relatives feed their kids increases the chances of passing on some of your genes, since siblings share a large proportion of their DNA. Yet, despite decades of research, it is still not clear why some animal species, including nearly 10 percent of bird species worldwide, show this apparently altruistic behavior, while other closely related ones do not.

In an attempt to answer this question, Rubenstein looked at the 45 species of starlings endemic to Africa to see if there was any relationship between cooperative breeding and the environment in which the birds live.

"Starlings are a model system in which to test this question because they are one of the most socially diverse groups in the world, exhibiting a wide range of social systems and living in a variety of different habitats across Africa," said Rubenstein.

Of the 117 known starling species worldwide, those in Africa, where savannas are extremely common, are the only ones known to engage in cooperative breeding. Those in the more temperate or jungle environments of Europe, Africa and Asia, including the European starling Sturnus vulgaris introduced to America, do not.

For much of the past decade, Rubenstein has intensively studied the social behavior of a variety of starling species in Kenya, home to 26 species - the most of any country in the world. Noting an apparent correlation between cooperative breeding and habitat in this family, he decided to use this socially diverse group to test several hypotheses about how environmental factors may have influenced the evolution of cooperative breeding.

Rubenstein and colleague Irby J. Lovette, director of the Fuller Evolutionary Biology Program at the Cornell Laboratory of Ornithology in Ithaca, New York, constructed a family tree of the African starlings using DNA from samples they captured on expeditions to Africa, from birds housed in zoos and from museum specimens. They used this evolutionary tree to determine whether specific lineages were associated with savanna or non-savanna habitats.

"What's important here is how many times behavior changed," said Lovette. "If you find the same pattern consistently repeated, you can be confident of cause and effect. In this case, we found cooperative breeding evolved when different starling species moved from forests to savannas."

The researchers found that more than one-third of the African starlings are cooperative breeders, and all live in savanna environments - semi-arid grasslands characterized by unpredictable rainfall patterns. In contrast, they found that most of the non-cooperative species live in forests, which are much more predictable and stable environments.

"If we saw just a single evolutionary origin of the behavior and a single switch in habitat, it would be very weak evidence of a relationship between these factors. But we found that cooperative breeding and habitat changed repeatedly in the same direction at the same points in the tree, so we can make a much more powerful statistical argument that the factors are related," Rubenstein said.

Using long-term rainfall data from the National Oceanic and Atmospheric Administration collected from over 2,000 sites across Africa and going back nearly 150 years at some locations, the researchers showed that African savannas are not only highly seasonal environments, but that rainfall is unpredictable and varies greatly from year-to-year. Statistical analyses and the researchers' evolutionary tree helped them isolate the specific environmental characteristic of savannas that might be responsible for this pattern: temporal, or year-to-year, variability in rainfall.

"Since rain equals food to the birds because it drives patterns of insect availability," said Rubenstein, "we think that by living in family groups with helpers that aid in feeding babies, these birds can cope better in these unpredictable savannas."

Rubenstein noted that this social strategy also helps in good years with lots of rain. Helpers bring enough extra food back to the nest to allow the cooperatively breeding species to breed longer and raise more broods of young than the non-cooperative ones.

"In some cases, the more social species tend to breed longer in benign years and thus produce more offspring," he said. "Often, parents don't have to spend so much time and energy going out and getting food because helpers compensate and do a lot of the parenting."

The origin of cooperative breeding in a savanna habitat may extend beyond starlings, Rubenstein said, noting that the first humans also lived in the savannas of East Africa.

"We think this relationship between sociality and temporal variability in rainfall and, hence, food availability, might help explain the distribution of cooperative breeding in other groups of birds, and even some mammals, living in semi-arid environments around the world," he said.

He added that with global warming, weather patterns are expected to become more variable worldwide and could possibly drive social behavior more toward cooperative breeding among temperate species that don't normally live in family groups.


###
The research was supported by grants from the National Science Foundation, the Chapman Fund of the American Museum of Natural History, a Howard Hughes Medical Institute pre-doctoral fellowship and UC Berkeley's Miller Institute for Basic Research.
Back to top
View user's profile Send private message Visit poster's website
adedios
SuperPoster


Joined: 06 Jul 2005
Posts: 5060
Location: Angel C. de Dios

PostPosted: Thu Sep 27, 2007 4:06 pm    Post subject: Cities Breed the Toughest Birds Reply with quote

Cities Breed the Toughest Birds
By Andrea Thompson, LiveScience Staff Writer

posted: 27 September 2007 11:51 am ET

Urban birds are regular tough guys compared to their country cousins. The avian urbanites adapt to changing environments and noisy, crowded habitats, a new study shows.

Birds that hang out on stoops and city streetlights have to deal with a set of challenges that feathered friends in more natural landscapes never encounter.

For the full article:

http://www.livescience.com/ani.....birds.html
Back to top
View user's profile Send private message Visit poster's website
adedios
SuperPoster


Joined: 06 Jul 2005
Posts: 5060
Location: Angel C. de Dios

PostPosted: Wed Jan 02, 2008 9:24 am    Post subject: Insects' 'giant leap' reconstructed by founder of sociobiolo Reply with quote

American Institute of Biological Sciences
2 January 2008

Insects' 'giant leap' reconstructed by founder of sociobiology

A survey of advanced social organization in insects calls into question the standard explanation for eusociality
The January 2008 issue of BioScience includes an article by biologist Edward O. Wilson that argues for a new perspective on the evolution of advanced social organization in some ants, bees, and wasps (Hymenoptera).

Wilson’s article surveys recent evidence that the high level of social organization called “eusociality,” found in some Hymenoptera (and rarely in other species), is a result of natural selection on nascent colonies of species possessing features that predispose them to colonial life. Wilson concludes that these features, principally progressive provisioning of larvae and behavioral flexibility that leads to division of labor, allow some species to evolve colonies that are maintained and defended because of their proximity to food sources.

Eusociality is a challenge for biologists to understand because worker castes in eusocial species forgo individual reproduction but rear young that are not their own, a behavior that biologists label altruistic. Wilson’s current view about eusociality differs from the assessment in his seminal book Sociobiology: The New Synthesis (1975). According to that widely accepted earlier account, selection acting on individuals that are related (kin selection), rather than on whole colonies, explains eusociality in Hymenoptera. Kin selection is thought to be especially powerful in these animals because of an unusual genetic system, known as haplodiploidy, that they share.

Wilson’s survey in BioScience, which examines the findings of a number of researchers, points out aspects of the occurrence of eusociality that the standard explanation has difficulty accounting for. Eusociality has evolved only a few times, and not all of them were in haplodiploid species. Furthermore, the great majority of haplodiploid species are not eusocial. Wilson holds that selection acting on traits that emerge at a group level provides a more complete explanation for eusociality’s rare instances than kin selection. Kin selection is, he writes, “not wrong” but incomplete.

The view Wilson advocates is controversial because theoretical biologists have thus far been unable to create mathematical models that demonstrate the strong colony-level selection that Wilson postulates. Any theory about eusociality has to explain why selection acting on individuals does not lead some to undermine the colony by reproducing themselves. According to some of Wilson’s critics, the theory he now espouses relies on unacknowledged individual-level selection rather than group selection.


###
BioScience is the monthly journal of the American Institute of Biological Sciences (AIBS). BioScience publishes commentary and peer-reviewed articles covering a wide range of biological fields, with a focus on "Organisms from Molecules to the Environment." The journal has been published since 1964. AIBS is an umbrella organization for professional scientific societies and organizations that are involved with biology. It represents some 200 member societies and organizations with a combined membership of about 250,000.

The January 2008 issue of BioScience includes a Special Section on Managing for Resilience in Coastal Marine Ecosystems, detailed in a separate press release entitled Resilience Concepts Poised to Aid Management of Coastal Marine Ecosystems. In addition to the Special Section, the issue includes the following research articles:

One Giant Leap: How Insects Achieved Altruism and Colonial Life. Edward O. Wilson

Non-native Species and Bioenergy: Are We Cultivating the Next Invader" Jacob N. Barney and Joseph DiTomaso

Transgene Escape Monitoring, Population Genetics, and the Law. Daniel J. Schoen, Jay Reichman, and Norman Ellstrand
Back to top
View user's profile Send private message Visit poster's website
Display posts from previous:   
Post new topic   Reply to topic   printer-friendly view    USAP PAETE Forum Index -> Science Lessons Forum All times are GMT - 5 Hours
Page 1 of 1

 
Jump to:  
You can post new topics in this forum
You can reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group