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Posts Tagged ‘Asexual reproduction’

Science Sunday #20

Posted by Don McLenaghen on October 30, 2011

– and on the seventh day we learn.
Each week I hope to give a synopsis of the interesting science stories I have heard on my plethora of science podcasts I listen to each week plus anything I pick up scanning the inter-web. This week’s top stories:

Words of the Week:

Theme Asexual reproduction 

Fission – the subdivision of a cell (or body, population, or species) into two or more parts and the regeneration of those parts into separate cells (bodies, populations, or species). Binary fission produces two separate cells, populations, species, etc., whereas multiple fission produces more than two cells, populations, species, etc..

Budding – Some cells split via budding (for example baker’s yeast), resulting in a ‘mother’ and ‘daughter’ cell. The offspring organism is smaller than the parent. Budding is also known on a multicellular level; an animal example is the hydra, which reproduces by budding. The buds grow into fully matured individuals which eventually break away from the parent organism.

Vegetative reproduction  – the formation of miniaturized plants called plantlets on specialized leaves (for example in kalanchoe) and some produce new plants out of rhizomes or stolon (for example in strawberry). Other plants reproduce by forming bulbs or tubers (for example tulip bulbs and dahlia tubers). Some plants produce adventitious shoots and suckers that form along their lateral roots. Plants that reproduce vegetatively may form a clonal colony, where all the individuals are clones, and the clones may cover a large area.

Fragmentation – where a new organism grows from a fragment of the parent. Each fragment develops into a mature, fully grown individual. Fragmentation is seen in many organisms such as animals (some annelid worms, turbellarians and sea stars), fungi, and plants.

Agamogenesis, Parthenogenesis, Spore formation, Apomixis and Nucellar Embryony –  forms of reproduction that do not involve a male gamete, meiosis or syngamy.

This week’s top stories:

The obligatory stories on Zombies <for Halloween> – 

Our appetite for zombies is becoming a growing trend. From computer games and films to organised zombie walks though Britain’s cities, the proliferation of zombies seems to be everywhere. Yet, this high interest in zombies enables researchers to link zombie-like behaviours to current models of public attitudes and actions.

Researcher Dr Nick Pearce will present findings from his new study of Britain’s zombie phenomenon at an event organised as part of the Economic and Social Research Council’s (ESRC) Festival of Social Science 2011. The event will be an interactive talk on the metaphor of the zombie in everyday life, followed by a screening of the first ever zombie film, White Zombie (1932).

“Zombies are very now,” Dr Pearce points out, “but what’s really interesting and potentially worrying is how far today’s zombies – whether on TV, films or computer games have departed from the original concept.”

Early zombies, as first portrayed in the White Zombie film, were the demoralised, undead slaves of voodoo priests. “Crucially, the end of that film and others of its time, spoke of hope and featured the overthrow of the controlling voodoo master by his ‘zombie’ slaves,” Dr Pearce explains. From the late 1960s the nature of zombies changed and they were portrayed as hordes of brain-consuming monsters with no voodoo context and no controlling master.”

“With no voodoo master, today’s zombies have no clear controller to turn against and free themselves from,” Dr Pearce argues. “That means there are no effective plans for resistance and no hope for the future. Zombies may well be popular today because they speak to a similar feeling of powerlessness shared by many members of our society.”

“The key question,” he continues, “is why, like today’s portrayal of zombies, are we unwilling to take a stand against the powers-that-be and are overwhelmed by a lack of political interest. It seems the time is right to reclaim the original zombie concept of a controlling sorcerer but one that can successfully be resisted. Today’s zombie phenomenon is a really good opportunity to get people thinking about who may be wishing to control our brains and what resources we have to resist.”

But what do we feel powerless against? Among the many possibilities, researchers suggest private ownership is a high profile offender. Clearly it’s in the interests of competition to encourage mindless consumerism. “In the past, zombies wandered around consuming brains, but today’s zombies are encouraged to wander around consuming the latest, heavily advertised, branded goods,” Dr Pearce explains. And for those with power, it’s clearly useful to them to have a ‘zombified’ society that does not challenge their decision-making under any circumstances.

Eureka Alert

And some links on zombies…

6 Mind-Blowing Ways Zombies and Vampires Explain America

The American Fascination With Zombies

 

 

Python puts squeeze on heart disease -

The Burmese Python may be best known for its dietary habits: it constricts its prey – which can be as large as the snake itself – then swallows it whole.  And the python can go a full year without food.  Eating habits like this require special demands, among them increased blood flow.  That is why, after ingesting such a large meal, all of the python’s internal organs – including the heart – nearly double in size.

CU-Boulder Professor Leslie Leinwand et all published a study that shows that huge amounts of fatty acids circulating in the bloodstreams of feeding pythons promote healthy heart growth, results that may have implications for treating human heart disease. They found the amount of triglycerides — the main constituent of natural fats and oils — in the blood of Burmese pythons one day after eating increased by more than fifty fold. Despite the massive amount of fatty acids in the python bloodstream there was no evidence of fat deposition in the heart, and the researchers also saw an increase in the activity of a key enzyme known to protect the heart from damage.

“We found that a combination of fatty acids can induce beneficial heart growth in living organisms,” said CU-Boulder postdoctoral researcher Cecilia Riquelme, first author on the Science paper. “Now we are trying to understand the molecular mechanisms behind the process in hopes that the results might lead to new therapies to improve heart disease conditions in humans.”

There are good and bad types of heart growth, said Leinwand, who is an expert in genetic heart diseases including hypertrophic cardiomyopathy, the leading cause of sudden death in young athletes. While cardiac diseases can cause human heart muscle to thicken and decrease the size of heart chambers and heart function because the organ is working harder to pump blood, heart enlargement from exercise is beneficial.

The CU-led team also identified the activation of signaling pathways in the cells of fed python plasma, which serve as traffic lights of sorts, said Leinwand. “We are trying to understand how to make those signals tell individual heart cells whether they are going down a road that has pathological consequences, like disease, or beneficial consequences, like exercise,” she said.

The prey of Burmese pythons can be up to 100 percent of the constricting snake’s body mass, said Leinwand, who holds a Marsico Endowed Chair of Excellence at CU-Boulder. “When a python eats, something extraordinary happens. Its metabolism increases by more than fortyfold and the size of its organs increase significantly in mass by building new tissue, which is broken back down during the digestion process.”

Quirks & Quarks

Science Daily

Eureka Alert

Science

Belief in God destroys your will to accomplish anything! -

Being reminded of the concept of God can decrease people’s motivation to pursue personal goals but can help them resist temptation, according to new research published by the American Psychological Association.

Kristin Laurin, PhD, of the University of Waterloo in Canada. “This is the first empirical evidence that simple reminders of God can diminish some types of self-regulation, such as pursuing one’s goals, yet can improve others, such as resisting temptation.”

A total of 353 college students, with an average age 19 and 186 of whom were women, participated in six experiments to determine how the idea of God can indirectly influence people’s motivations, even among those who said they were not religious.

In one experiment, engineering students completed a “warm-up” word task. They were asked to form grammatically correct sentences using four words from sets of five. Some students were provided either God or God-related words (divine, sacred, spirit and prophet), while the control group used more neutral words (ball, desk, sky, track and box).

Next, each student had to form as many words as they could in five minutes, using any combination of specific letters. The researchers determined the students’ motivation level by the number of words they produced. The more motivated they were, the more words they produced. They were told that a good performance could help predict if they would succeed in an engineering career.

Several weeks before this experiment, the students had been asked if they believed outside factors (other people, beings, forces beyond their control) had an influence on their careers. There was no difference in performance among the participants who did not believe outside factors influenced their career success.

Researchers also measured the importance participants placed on a number of values, including achievement. Participants reminded of God placed the same value on achievement as did participants primed with the more neutral words.

A second set of experiments looked at participants’ ability to resist temptation after being reminded about God. Participants who read a short God-related passage reported greater willingness to resist temptations to achieve a major goal, such as maintaining a healthy weight, finding a long-term relationship or having a successful career. This effect was found only among participants who had previously said they believe an omniscient entity watches over them and notices when they misbehave.

The level of participants’ religious devotion had no impact on the outcomes in any of the experiments, according to the researchers.

Science Daily

Eureka Alert

 

Are bacteria immortal? –

If you think about it, bacteria procreate via fission…that is one mother cell becomes two daughter cells, each of these in turn becomes the mother with daughters of their own. Now, assuming (for the sake of argument) that one daughter is the ‘original’; that a single bacteri  can (baring accident or bleach) live forever…or can it?

A study, conducted by Lin Chao et all, questions that longstanding paradigm. In a paper published in the November 8 issue of the journal Current Biology, they conclude that not only do bacteria age, but that their ability to age allows bacteria to improve the evolutionary fitness of their population by diversifying their reproductive investment between older and more youthful daughters.

“Aging in organisms is often caused by the accumulation of non-genetic damage, So for a single celled organism that has acquired damage that cannot be repaired, which of the two alternatives is better — to split the cellular damage in equal amounts between the two daughters or to give one daughter all of the damage and the other none?”

The answer — bacteria appear to give more of the cellular damage to one daughter, the one that has “aged,” and less to the other, which the biologists term “rejuvenation”.

In a separate study, the UC San Diego biologists filmed populations of E. coli bacteria dividing over hundreds of generations and confirmed that the sausage-shaped bacteria divided each time into daughter cells that grew elongated at different rates — suggesting that one daughter cell was getting all or most of the cellular damage from its mother while the other was getting little or none.

“We ran computer models and found that giving one daughter more the damage and the other less always wins from an evolutionary perspective,” said Chao

Science Daily

Current Biology – Temporal Dynamics of Bacterial Aging and Rejuvenation

 

Insects suffer from fatal stress too -

The mere presence of a predator causes enough stress to kill a dragonfly, even when the predator cannot actually get at its prey to eat it.

“As we learn more about how animals respond to stressful conditions — whether it’s the presence of predators or stresses from other natural or human-caused disruptions — we increasingly find that stress brings a greater risk of death, presumably from things such as infections that normally wouldn’t kill them,” says Rowe Locke.

Rowe et all raised juvenile dragonfly larvae (Leucorrhinia intacta) in aquariums or tanks along with their predators. The two groups were separated so that while the dragonflies could see and smell their predators, the predators could not actually eat them.

“What we found was unexpected — more of the dragonflies died when predators shared their habitat,” says Rowe. Larvae exposed to predatory fish or aquatic insects had survival rates 2.5 to 4.3 times less than those not exposed.

In a second experiment, 11 per cent of larvae exposed to fish died as they attempted to metamorphose into their adult stage, compared to only two per cent of those growing in a fish-free environment. “We allowed the juvenile dragonflies to go through metamorphosis to become adult dragonflies, and found those that had grown up around predators were more likely to fail to complete metamorphosis successfully, more often dying in the process,” says Rowe.

The scientists suggest that their findings could apply to all organisms facing any amount of stress, and that the experiment could be used as a model for future studies on the lethal effects of stress.

Science Daily

Eureka Alert

Ecology – The deadly effects of “nonlethal” predators

 

Imperial Woodpecker returns from the grave -

The imperial woodpecker — the largest woodpecker that ever lived –probably went extinct in the late 20th century in the high mountains of Mexico, without anyone ever capturing photos or film of the 2-foot-tall, flamboyantly crested bird. Or so scientists thought — until a biologist from the Cornell Lab of Ornithology tracked down a 16-mm film shot in 1956 by a dentist from Pennsylvania.

Science Daily

Eureka Alert

Film Documentation Of The Probably Extinct Imperial Woodpecker

Cornell Lab of Ornithology – Return to Durango

 


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