miércoles, 20 de mayo de 2009
IdA lEmUr mOnKeY
Scientists have unveiled a 47-million-year-old fossilised skeleton of a monkey hailed as the missing link in human evolution.
The search for a direct connection between humans and the rest of the animal kingdom has taken 200 years - but it was presented to the world today at a special news conference in New York.
The discovery of the 95%-complete 'lemur monkey' - dubbed Ida - is described by experts as the "eighth wonder of the world".
They say its impact on the world of palaeontology will be "somewhat like an asteroid falling down to Earth".
Researchers say proof of this transitional species finally confirms Charles Darwin's theory of evolution, and the then radical, outlandish ideas he came up with during his time aboard the Beagle.
Sir David Attenborough said Darwin "would have been thrilled" to have seen the fossil - and says it tells us who we are and where we came from.
The search for a direct connection between humans and the rest of the animal kingdom has taken 200 years - but it was presented to the world today at a special news conference in New York.
The discovery of the 95%-complete 'lemur monkey' - dubbed Ida - is described by experts as the "eighth wonder of the world".
They say its impact on the world of palaeontology will be "somewhat like an asteroid falling down to Earth".
Researchers say proof of this transitional species finally confirms Charles Darwin's theory of evolution, and the then radical, outlandish ideas he came up with during his time aboard the Beagle.
Sir David Attenborough said Darwin "would have been thrilled" to have seen the fossil - and says it tells us who we are and where we came from.
miércoles, 29 de abril de 2009
domingo, 26 de abril de 2009
jueves, 16 de abril de 2009
jueves, 19 de marzo de 2009
EXOCYTOSIS
EXOCYTOSIS:is the durable process by which a cell directs the contents of secretory vesicles out of the cell membrane. These membrane-bound vesicles contain soluble proteins to be secreted to the extracellular environment, as well as membrane proteins and lipids that are sent to become components of the cell membrane.
pHaGocYtOsIs
phagocytosis
The process by which a phagocyte (a type of white blood cell) surrounds and destroys foreign substances (such as bacteria) and removes dead cells.
DIFFUSION
DIFFUSION:a type of passive transport, therefore, it is a net movement of molecules in and out of the cell across the cell membrane along a concentration gradient.
OsMoSiS
Osmosis is the movement of a liquid through a membrane when the movement is caused by a difference in the concentration of the liquid on either side of the membrane. When osmosis happens liquid will move from the side of the membrane with the higher concentration of the liquid to the side of the membrane with the lower concentration. An important example of osmosis is water moving in to and out of cells.
OSMOSIS
Osmosis is the movement of a liquid through a membrane when the movement is caused by a difference in the concentration of the liquid on either side of the membrane. When osmosis happens liquid will move from the side of the membrane with the higher concentration of the liquid to the side of the membrane with the lower concentration. An important example of osmosis is water moving in to and out of cells.
miércoles, 4 de marzo de 2009
2ND PART
All cells, whether prokaryotic or eukaryotic, have a membrane that envelops the cell, separates its interior from its environment, regulates what moves in and out (selectively permeable), and maintains the electric potential of the cell. Inside the membrane, a salty cytoplasm takes up most of the cell volume. All cells possess DNA, the hereditary material of genes, and RNA, containing the information necessary to build various proteins such as enzymes, the cell's primary machinery. There are also other kinds of biomolecules in cells. This article will list these primary components of the cell, then briefly describe their function.
COMPLETE INFORMATION ABOUT THE CELL
The cell is the structural and functional unit of all known living organisms. It is the smallest unit of an organism that is classified as living, and is often called the building bricks of life.[1] Some organisms, such as most bacteria, are unicellular (consist of a single cell). Other organisms, such as humans, are multicellular. (Humans have an estimated 100 trillion or 1014 cells; a typical cell size is 10 µm; a typical cell mass is 1 nanogram.) The largest known cell is an unfertilized ostrich egg cell.[2]
In 1835 before the final cell theory was developed, a Czech Jan Evangelista Purkyně observed small "granules" while looking at the plant tissue through a microscope. The cell theory, first developed in 1839 by Matthias Jakob Schleiden and Theodor Schwann, states that all organisms are composed of one or more cells. All cells come from preexisting cells. Vital functions of an organism occur within cells, and all cells contain the hereditary information necessary for regulating cell functions and for transmitting information to the next generation of cells.[3]
The word cell comes from the Latin cellula, meaning, a small room. The descriptive name for the smallest living biological structure was chosen by Robert Hooke in a book he published in 1665 when he compared the cork cells he saw through his microscope to the small rooms monks lived in
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