ZOOHCC - 601: Developmental Biology (Theory)
Unit 1: Introduction
Historical perspective and basic concepts
Developmental biology is the study of the processes by which organisms grow
and develop from a single cell to a complex multicellular organism. It is a
field that has been studied for centuries, and its history can be traced
back to ancient Greek philosophers.
The Greek philosopher Aristotle is credited with being one of the first
people to study embryology. He observed the development of chicks inside
eggs and proposed a theory of epigenesis, which suggested that the
development of an organism is the result of a series of progressive changes
in a pre-existing structure.
In the 17th century, the Dutch scientist Antonie van Leeuwenhoek was the
first person to observe the fertilization of an egg by a sperm, using a
primitive microscope. This discovery laid the foundation for the study of
embryonic development.
In the 18th and 19th centuries, many scientists made significant
contributions to the field of developmental biology. The French naturalist
Georges Cuvier was the first to suggest that there were distinct stages in
the development of an embryo. The German scientist Carl Ernst von Baer
observed that embryos of different species share common features during
development, a concept known as von Baer's law.
In the 20th century, the field of developmental biology underwent a
revolution with the discovery of DNA and the development of molecular
biology techniques. In the 1950s, the American scientist James Watson and
the British scientist Francis Crick proposed the double helix structure of
DNA, which provided a mechanism for the transmission of genetic information
from one generation to the next.
Today, developmental biology is a thriving field with many sub-disciplines,
including embryology, genetics, cell biology, and evolutionary biology. It
has led to significant advances in our understanding of how organisms
develop, and has practical applications in fields such as regenerative
medicine and biotechnology.
Basic concepts of development biology
In developmental biology include cell differentiation, morphogenesis,
embryogenesis, gene expression, signaling pathways, homeostasis, and
evolution. Cell differentiation is the process by which cells become
specialized in structure and function, while morphogenesis is the process by
which cells organize into tissues and organs, forming the shape and
structure of an organism. Embryogenesis is the process by which a single
cell, the zygote, divides and differentiates into all the cells and tissues
that make up an embryo. Gene expression is the process by which genetic
information encoded in DNA is converted into proteins or RNA molecules that
perform specific functions in cells. Signaling pathways are the networks of
molecules and biochemical reactions that transmit information between cells,
regulating their behavior and controlling the development and function of
tissues and organs. Homeostasis is the maintenance of a stable internal
environment within an organism, while evolution is the process by which
genetic changes accumulate over time, leading to the emergence of new
species and the diversification of life on Earth.