Monday, January 30, 2006
Friday, January 27, 2006
biological dispersal refers to those processes by which a species maintains or expands the distribution of a population. dispersal implies movement, movement away from an existing population or away from the parent organisms. in the latter case, dispersal may simply involve replacement of the parent generation by the new generation.
dispersal is a universal biological need, and it is to be expected that most higher plants have solved the problem in one way or another through adaptations involving their fruit or seed. examine the fruit of any species and it is likely, with perhaps a bit more knowledge about the ecosystem, to at least intelligently speculate on what these adptations are in that plant.
the co-evolution of plants and animals is a fascinating story in itself. a very significant aspect of this co-evolution involves plant adaptations that take advantage of animal abilities to locomote. these seeds have a tough protective outer-coating so that while the fruit is digested, the seeds will pass through their host's digestive tract intact, and grow wherever(hopefully) they fall.
such fruit attractive to birds is perhaps the most successful of fruit adaptations related to plant dispersal.
Wednesday, January 25, 2006
patterning of the regions ...
Sunday, January 22, 2006
Friday, January 20, 2006
carry on flowers ...
Wednesday, January 18, 2006
crawling star ...
Monday, January 16, 2006
kollegal ground gecko
unlike rats and cockroaches, which are generalists and much the same wherever one find them, lizards are specialists and their evolution unique in the natural world.
lizards are reptiles of the same order, which they share with the snakes. the species range in adult length from a few centimeters (some geckos) to nearly three meters (komodo dragons). geckos are unique among lizards in their vocalizations, making chirping sounds in social interactions. the picture we see is a kollegal ground gecko (geckoella collegalensis) found in the scrub plains of southern peninsular india .
lizards have been on the earth for more than 200 million years, and they make excellent models to study for evolution. during the course of evolution, lizards have undergone limb reduction and loss many times. its easy to think that evolution leads to ever-greater degrees of complexity, but limb reduction shows how animal structure can become less complex even though it becomes more specialised. (-incomplete)
Saturday, January 14, 2006
sloth bear ...
Friday, January 13, 2006
temporary post ...
" what do we know ? " and " how do we know it ? ".
kant approaches the questions by looking at the relationship between knowledge based on reason (what we know purely logically, prior to or independently of experience, or a priori) and knowledge based on experience (what we know based on the input of our senses or a posteriori).
things as they are "in themselves" are unknowable. for something to become an object of knowledge, it must be experienced, and experience is prestructured by the activity of our own minds . we are never passive observers or knowers. in kant's words, "thoughts without content [are] empty, and intuitions without concepts [are] blind".
tomorrow i will finish my earlier post, "what is seeing ?..." by, what i see from that technically poor picture ...
Wednesday, January 11, 2006
what is seeing ?...
Monday, January 09, 2006
at the molecular level, life’s ability to reproduce begins with the replication of DNA, during which two new spirals are created that are exact replicas of the original molecule. sometimes a change in the sequence is called a "mutation".
mutations can occur randomly, from radiation damage (impact with high energy g-rays or cosmic rays), from exposure to chemical agents called mutagens, viruses or simply by error in the DNA replication process.
mutations are considered the driving force of evolution, where less favorable mutations are removed from the gene pool by natural selection, while more favorable ones tend to accumulate.
"adaptations" according to the surroundings can also be referred to as mutation. overwhelming majority of mutations have no significant effect on evolution.
can't say how or when sexual reproduction came to take a hold in nature, but high mutation rates can, under the right conditions, force an asexual organism like bacteria to become sexual and pass on higher mutation rates.
the rate of progressive evolution (the accumulation of beneficial mutations) is faster in populations that reproduce sexually.
Saturday, January 07, 2006
Thursday, January 05, 2006
web of life ...
Tuesday, January 03, 2006
karum kurangu ...
the two great goals of the 21st century are, first, raising people around the world to a decent standard of living, and second, bringing as much of the rest of life through with us. if we can do this, we will obtain the kind of better world that people everywhere believe should be our major human purpose.