Scientists have come up with a hypothesis known as the "Expensive-Tissue Hypothesis" which is "the idea that there's a trade-off between the demands of the brain and the demands of other organs". In humans, the brain takes up 20% of the overall amount of energy a human has, and less energy is set aside for other organs, such as the organs involved in the digestive system.
Recently, a Swedish team of scientists selected and bred a common species of guppies with the goal of producing fish with bigger brains. What they discovered is that these new fish tended to have smaller guts and produced 19% less offspring than the smaller-brained fish. The results from the experiment support the hypothesis explained above.
The results also seem to show that these big-brained fish have a low fitness level, as they do not produce as many offspring compared to the small-brained fish, but this cannot be concluded because the experiment did not show how well the new fish would do versus the small-brained fish in natural situations (ex. avoiding predators, finding food...). If the new fish survived in higher numbers, it would show that they have a trait with advantages, increasing their overall fitness despite the offspring number setback.
Relevance
This article ties in with the most recent unit, evolution. The scientists who have found a way to breed bigger-brained guppies have used the method referred to as selective breeding; they select animals with desirable traits, and breed them for a higher chance of offspring with that trait. This article also taps into the realm of fitness and evolution. Fitness is "the contribution that an individual makes to the gene pool of the next generation compared to the contributions of other individuals" (Campbell). These big-brained fish seem to have a lower fitness, as they do not produce as many offspring, but their increased brain could help the survive, and therefore they would live to contribute to the gene pool.
Source
http://cosmiclog.nbcnews.com/_news/2013/01/03/16325592-scientists-breed-big-brained-guppies-to-demonstrate-evolutions-trade-offs?lite
by Alan Boyle
1/3/13
When it says "bigger brains", does it mean bigger in terms of size, or in terms of how much energy the brain is using?
ReplyDeleteActually never mind... here is my real question:
DeleteIf the "big brained" guppies bred with other guppies with normal brain size, would the offspring have bigger brains as well, even if it is slightly larger?