Beginning of Life People

-Since the beginning of life people have been curious about living things, how many different species there are, what they look like and how do they live. Scientists are seeking to answer these questions and many more about the organisms that are inhabiting the earth. In recent years developmental biology has acquired the powerful tools of molecular biology and genetics and by examining the DNA and RNA proteins in the genetic material of cells, scientists have been able to study the regulators of development at the cellular level. This has led to a better understanding of a "body plan": how a fertilized cell can organize its cleavage and development into a more complex organism.

The earth's present life forms are appearing to have evolved from many common ancestors going back to the simplest one-cell organisms almost three billion years ago. Animals and plants have a great variety of body plans, with different overall structures and arrangements of internal parts to perform the basic operations of making or finding food, deriving energy and materials from it, synthesizing new materials, and reproducing. When scientists classify organisms, they consider details of anatomy to be more relevant than behavior or general appearance. For example, because of such features as milk-producing glands and brain structure, whales and bats are classified as being more nearly alike than are whales and fish or bats and birds. At different degrees of relatedness, dogs are classified with fish as having backbones, with cows as having hair, and with cats as being meat eaters.