Dory's Biology Questions Thread

[GenesForLife]

is your name Tomas Sorensen on Yahoo answers?

http://answers.yahoo.com/question/index ... 316AACZnJi

Why should there be sexual dimorphism in pine cones?

I'll come back to the question as and when time permits, I have some phone calls to make.

[Dory]

is your name Tomas Sorensen on Yahoo answers?

http://answers.yahoo.com/question/index ... 316AACZnJi

Why should there be sexual dimorphism in pine cones?

I'll come back to the question as and when time permits, I have some phone calls to make.

No, Thomas is a dude name, I am not a dude! But, I do browse this section awful lot...and whatever perplexes me I post here hoping you'd help me figure it out. This is my YA profile btw... http://answers.yahoo.com/my/my;_ylt=Aif ... Qt.;_ylv=3 ...

Anyway, I tried to google for the answer, as I always do, before looking to you. About 20% of my questions come from YA, the other 80% are self-occuring.

When it comes to sexual dimorphism among plants genotypes, it rather perplexed me. Does it help to generate more diversity of possible pollinators somehow?

By the way...look at this!

http://rationalia.com/forum/viewtopic.php?f=76&t=16199

[Dory]

Can herbivores digest meat?

[Dory]

Why can't insects grow huge?

[GenesForLife]

Why can't insects grow huge?

Abstract

Background

The correlations between Phanerozoic atmospheric oxygen fluctuations and insect body size suggest that higher oxygen levels facilitate the evolution of larger size in insects.
Methods and Principal Findings

Testing this hypothesis we selected Drosophila melanogaster for large size in three oxygen atmospheric partial pressures (aPO2). Fly body sizes increased by 15% during 11 generations of size selection in 21 and 40 kPa aPO2. However, in 10 kPa aPO2, sizes were strongly reduced. Beginning at the 12th generation, flies were returned to normoxia. All flies had similar, enlarged sizes relative to the starting populations, demonstrating that selection for large size had functionally equivalent genetic effects on size that were independent of aPO2.

Significance

Hypoxia provided a physical constraint on body size even in a tiny insect strongly selected for larger mass, supporting the hypothesis that Triassic hypoxia may have contributed to a reduction in insect size.

http://www.plosone.org/article/info%3Ad ... ne.0003876

ScienceDaily (Aug. 12, 2007) — Researchers at the U.S. Department of Energy's Argonne National Laboratory have cast new light on why the giant insects that lived millions of years ago disappeared.

In the late Paleozoic Era, with atmospheric oxygen levels reaching record highs, some insects evolved into giants. When oxygen levels returned to lower levels, the insect giants went extinct.

The basis of this gigantism is thought to lie in the insect respiratory system. In contrast to vertebrates, where blood transports oxygen from the lung to the cell, insects deliver oxygen directly through a network of blind-ending tracheal tubes. As insects get bigger, this type of oxygen transport becomes far less effective. But if the atmospheric oxygen levels increase, as they did in the late Paleozoic, then longer tracheal tubes can work. This would allow larger-sized insects—even giants—to evolve.

Recent research published in the journal Proceedings of the National Academy of Science helps confirm the hypothesis that the tracheal system actually limits how big insects can be. The research provides a specific explanation for what limits size in beetles: the constriction leading to the legs.

A collaborative team of researchers from Argonne's Advanced Photon Source (APS), Midwestern University and Arizona State University wanted to study how beetles' tracheal systems change as their body sizes increase. The team took advantage of richly detailed X-ray images they produced at the APS to examine the dimensions of tracheal tubes in four beetle species, ranging in body mass by a factor of 1,000.

Overall, they found that larger beetle species devote a disproportionately greater fraction of their body to tracheal tubes than do smaller species.

The team focused in particular on the passageways that lead from the body core to the head and to the legs. They reasoned that these orifices may be bottlenecks for tracheal tubes, limiting how much oxygen can be delivered to the extremities.

“We were surprised to find that the effect is most pronounced in the orifices leading to the legs, where more and more of the space is taken up by tracheal tubes in larger species,” said Alex Kaiser, biologist at Midwestern University.

They then examined the tracheal measurements of the four species to see if they could predict the largest size of currently living beetles. The head data predicted an unrealistically large, foot-long beetle. In contrast, the leg data predicted a beetle that nicely matches the size of the largest living beetle, Titaneus giganteus .

“This study is a first step toward understanding what controls body size in insects. It's the legs that count in the beetles studied here, but what matters for the other hundreds of thousands of beetle species and millions of insect species overall is still an open question,” said Jake Socha, Argonne biologist.

Funding for this work was supported by the National Science Foundation. Use of the APS was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.

http://www.sciencedaily.com/releases/20 ... 194908.htm

[GenesForLife]

Re: The pinecones...

One must note that microspores (or male gametes) do not need to contain extra sources of nutrition for instance whereas megaspores do, as these, after fertilization, contain the zygote and thus need to nourish the zygote, in the range of possible pinecone configurations, the most evolutionarily selectable one would be minimizing the resources needed to produce male gametes while maximizing nutrient availability to the zygote. This would also explain the dimorphism between ovaries and antheridia in gymnosperms, and eggs and sperm cells in metazoans.



PS One must also note that the female cones contain ovules which receive microspores.

[Dory]

Re: The pinecones...

One must note that microspores (or male gametes) do not need to contain extra sources of nutrition for instance whereas megaspores do, as these, after fertilization, contain the zygote and thus need to nourish the zygote, in the range of possible pinecone configurations, the most evolutionarily selectable one would be minimizing the resources needed to produce male gametes while maximizing nutrient availability to the zygote. This would also explain the dimorphism between ovaries and antheridia in gymnosperms, and eggs and sperm cells in metazoans.

First sentence is all you needed to say, the rest after this becomes self-explanatory (in my mind ) thanks!!!

[Dory]

By the way...do you have the names of those giant Paleozoic insects? I'd like to see some artist renditions

Oh and this should be a simple one

Can herbivores digest meat?

[GenesForLife]

Can herbivores digest meat?

Digestion shouldn't be a problem, given that the basic biomolecular constituents of meat aren't very different from plant material, except for relative concentrations.

[GenesForLife]

try Meganeura, a giant dragonfly.

[Dory]

try Meganeura, a giant dragonfly

.

Fucking A I wouldn't say "giants" though....well, RELATIVE to insects, sure...but I was thinking more along the lines of Starship Troopers

Can herbivores digest meat?

Digestion shouldn't be a problem, given that the basic biomolecular constituents of meat aren't very different from plant material, except for relative concentrations.

Interesting.

[Berthold]

...but I was thinking more along the lines of Starship Troopers.

As for that, no luck with arthropods in general. Biggest that ever lived were these. Not really an order of magnitude compared to extant crustaceans.

[GenesForLife]

haha Dory, nice avatar

[Dory]

haha Dory, nice avatar

Hehe....thanks.

I am teh Dory, I got ze molecules powa!!! VSEPR is ma middle name!

I was inspired by this, which is by the wall my wallpaper: