 |
|
How does one sex grow larger than the other?
January 30, 2007Why are males larger than females in some animal species (such as most mammals), females larger than males in others (such as most insects), and why are the sexes alike in yet other species (such as several birds)? Further, how is such sexual size dimorphism achieved when it exists? If males and females grow at the same rate, then the larger sex has to extend its growth period. Alternatively, the larger sex can grow faster.
A group of 13 researchers from 10 countries investigated the latter questions using comparative data on 155 species of insects and spiders (arthropods) from 7 major groups. The results, published in the February issue of The American Naturalist, suggest that, generally, growth rate differences between the sexes are more important than growth period differences in mediating size dimorphism in arthropods. Nevertheless, depending on the species group, males and females tend to have equal growth periods (beetles and water striders), males have longer growth periods than females (two groups of flies), or males have shorter growth periods than females (so-called protandry), albeit not quite in proportion to the size difference between the sexes (spiders, butterflies, and Hymenoptera, i.e. bees, ants, wasps, and alike).
As in most arthropod groups females are larger, they must therefore generally grow faster, an interesting pattern markedly different from primates and birds, which were also analyzed and in which differences in growth period between the sexes were generally more dominant. Three potential explanations for why female arthropods can grow faster than males are discussed. The most intriguing of these explanations is that, although it is generally cheaper to produce (small) sperm than (large) eggs, it may be costlier to produce male gonads and genitalia than it is to produce female gonads and genitalia. As a result, males might need more time to mature at larger body sizes.
This world-wide collaboration developed because most people work and thus have data on only particular animal groups. Wolf Blanckenhorn of the Zoological Museum at the University of Zurich in Switzerland called together all these researchers to investigate this specific idea about the evolution of sexual size dimorphism that had occupied him for quite some time.
University of Chicago Press Journals
This world-wide collaboration developed because most people work and thus have data on only particular animal groups. Wolf Blanckenhorn of the Zoological Museum at the University of Zurich in Switzerland called together all these researchers to investigate this specific idea about the evolution of sexual size dimorphism that had occupied him for quite some time.
University of Chicago Press Journals
Growth Rate News and Current Growth Rate Events RSSDuck-billed dinosaurs outgrew predators to survive
With long limbs and a soft body, the duck-billed hadrosaur had few defenses against predators such as tyrannosaurs. But new research on the bones of this plant-eating dinosaur suggests that it had at least one advantage: It grew to adulthood much faster than its predators, giving it superiority in size.
Vine invasion? UWM ecologist looks at coexistence of trees and lianas
Among the hundreds of species of woody vines that University of Wisconsin-Milwaukee ecologist Stefan Schnitzer has encountered in the tropical forests of Panama, the largest has a stalk nearly 20 inches in circumference.
Vitamin C injections slow tumor growth in mice
High-dose injections of vitamin C, also known as ascorbate or ascorbic acid, reduced tumor weight and growth rate by about 50 percent in mouse models of brain, ovarian, and pancreatic cancers, researchers from the National Institutes of Health (NIH) report in the August 5, 2008, issue of the Proceedings of the National Academy of Sciences.
Unheard of life history for a vertebrate
There is a newly discovered life history among the 28,300 species of known tetrapods, or four-legged animals with backbones.
When it comes to female red squirrels, it seems any male will do
Researchers have found that female red squirrels showed high levels of multimale mating and would even mate with males that had similar genetic relatedness, basically mating with their relatives.
Reforestation using exotic plants can disturb the fertility of tropical soils
In many regions of the world, the impact of human activity on the environment intensified considerably over the past century. The high world population growth rate and the expansion of areas given over to crop production associated with climatic changes (longer periods of drought, irregular rainfall patterns) induced by global warming, have contributed to the acceleration of desertification.
Does fishing on drifting fish aggregation devices endanger the survival of tropical tuna?
Fishermen hold empirical knowledge that tuna aggregate under floating objects, such as lengths of old rope, pieces of wood, or even large marine mammals.
Does fishing on drifting fish aggregation devices endanger the survival of tropical tuna?
Fishermen hold empirical knowledge that tuna aggregate under floating objects, such as lengths of old rope, pieces of wood, or even large marine mammals.
Global warming will negatively impact tropical species
Global warming is likely to reduce the health of tropical species, scientists from UCLA and the University of Washington report May 6 in Proceedings of the National Academy of Sciences.
Work with power grids leads to cell biology discovery
Gene therapy, in which a working gene is inserted into a cell to replace a faulty or absent gene, is a promising experimental technique for the prevention and treatment of disease.
More Growth Rate News Articles
 | Jump Start Your Business Brain: Scientific Ideas and Advice That Will Immediately Double Your Business Success Rate by Doug Hall Doug Hall shares data-proven methods that can make sales, marketing, and business development measurably more... |
| Are You a Transhuman?: Monitoring and Stimulating Your Personal Rate of Growth in a Rapidly Changing World by Fm-2030. | |
 | A Homeowner\'s Guide to Mortgage Acceleration by Tony G. Jones Save thousands in interest costs. Reduce the term, build equity faster, and own your home "free and clear". Turn your mortgage into an investment... |
 | Stocks for the Long Run: A Guide to Selecting Markets for Long-Term Growth by Jeremy J. Siegel If anyone told you that investing in the stock market was the safest investment you could make, you might raise an eyebrow. However, if Jeremy Siegel tells you this, prepare to be convinced. Siegel's book, Stocks for the Long Run, is a comprehensive and highly readable history of the stock market that dramatically makes the case for long-term investing in stocks. In summing up his approach to... |
 | How to Capture a First-Rate Mate: Attracting Beauty, Brains and Bucks Are you tired of dating the same old losers? Do you justify it by saying: 'There's nobody interesting in this town. I don't meet any exciting people in my job.' Or 'All the good ones are taken.' You know you're too good for the pool of potential partners you've been swimming in. So why do you stay? You've probably become more discriminating than you were in the past. But just as newly slender... |
 | Motivator Teacher Shrink: How to Attract and Develop Highly Successful Salespeople by Bob Teichart This book will give sales leaders the ability to diagnose the root cause of a performance problem, build trusting relationships, eliminate hiring mistakes, develop a planning and accountability system and accelerate learning through an effective coaching review... |
| Why Growth Rates Differ: Postwar Experience in Nine Western Countries by Edward F. Denison | |
 | Wildlife Population Growth Rates The core message of this study is that key insights emerge from understanding what determines population growth rate, and that application of the approach will make ecology a more predictive science. What determines where a species lives? And what determines its abundance? Despite great progress in the twentieth century, much more remains to be done before we can provide full answers to these... |
| The Flat Tax: Freedom, Fairness, Jobs, and Growth by Daniel Mitchell Daniel Mitchell, Senior Fellow at The Heritage Foundation, discusses the many advantages of the flat... | |
| Modern Economic Growth Rate Structure and Spread by Simon Kuznets |
| © 2008 BrightSurf.com |