● Wrote first textbooks in zoology and treatises on reproduction and development
Spontaneous generation - scientific theory by Aristotle that states living organisms arise from nonliving matter and that such processes were regular.
Hermaphroditism - condition where a living organism has both male and female reproductive parts
Bisexual reproduction - believed that the semen provides the force towards development and the menstrual blood provided the matter
Modeling principle of any organism is “energia” or “entelecheia”, the principle bearing its goal and end in itself. The ultimate energy is called its psyche or soul
3 types of soul operating in the organism
vegetative
animal: when they start to move
spiritual: when they have consciousness
RENAISSANCE OF DEVBIO
ovaries and testes, eggs and semen then eventually sperm were studies
advent of microscope
RENAISSANCE OF DEVBIO
William Harvey (1578-1657)
proposed that organisms, but not all, come from egg
Omne vivum ex ovum
Exercitationes de Generatione Animalium
RENIASSANCE OF DEVBIO
Spermists - claim that the embryo comes from one sperm only; disputed by physics
RENIASSANCE OF DEVBIO
Ovissts - all generations will come from an egg only; disputed by physics
RENIASSANCE OF DEVBIO
Preformationism - ovists and spermists theory
RENIASSANCE OF DEVBIO
Leeuwenhoek (1632 - 1723) and Hartsoeker - so-inventors of the microscope claimed to have seen little men inside individual spermatozoa
RENIASSANCE OF DEVBIO
Van Leeuwenhoek A. - spermatic animalcules
RENAISSANCE OF DEVBIO
Dalenpatius - Homunculi in the human male semen
RENAISSANCE OF DEVBIO
Needham - Preformation according to the ovist theory
Hartsoeker N. - human spermatozoan with homunculus
RENAISSANCE OF DEVBIO
Emboitement Theory - physics; hindi pwede na one sperm will hold all future gen
The emboîtement theory proposed that all living beings were created at the same time, and each female carried within her all future generations in a miniature form.
Fertilization Discovered
Lazaro Spallanzani (1729-1799) - first to observe that female egg develops only in the presence of male semen but believed that spermatozoa were parasites
Fertilization Discovered
Oscar Hertwig (1875) - both sperm and egg contribute to form an embryo
Preformation vs. Epigenesis
Epigenesist - embryo forms gradually out of formless materials in the yolk (Caspar Friedrich Wolf (1738-1794))
Preformation vs. Epigenesis
Vitalism - vital force to life is the prime mover for such grand unfolding of the organism
COMPARATIVE EMBRYOLOGY
Karl Ernst von Baer (1792-1876)
another vitalist
discovered eggs in many mammalian species
preformed comparative studies
COMPARATIVE EMBRYOLOGY
Ernst Haeckl (1834-1919)
built on Baer's study and proposed the controversial biogenetic law which gave scientific basis for racial discrimination of the Third Reich
bastardized von Baer
COMPARATIVE EMBRYOLOGY
Embryo Resemblances: von Baer
stage where one would look very alike from the other (even if it comes from diff eggs)
all vertebrates pass through same stages and possess similar structures that will later on differentiate into different structures and appendages
pass through similar stages that will later on differentiate them from each other
COMPARATIVE EMBRYOLOGY
>>> vs. Haeckl
every stage of the development of organisms is final
--- Lower forms: every stage is final (single stage)
every organism has a hierarchy: there are higher forms and lower forms
there are lowly forms of human beings and cultures
there are super races and primitive races
ERA OF EXPERIMENTAL EMBRYOLOGY
E.B. Wilson
leading cytologist at the turn of the century
recognized that embryonic development is a manifestation of changes in the cell
ERA OF EXPERIMENTAL EMBRYOLOGY
T.H. Morgan and Wilson
lively debate on whether the determinants of development came from the nucleus or cytoplasm
(Morgan: cytoplasm, Father of Modern Genetics)
its the DNA that is unique in the nucleus
ERA OF EXPERIMENTAL EMBRYOLOGY
Studies fueling the debate
August Weismann (1834-1914)
germ plasm theory
zygote: during division; each cell got different proportions
blind
multicellular organisms consist of germ cells that contain and transmit heritable information, and somatic cells which carry out ordinary bodily functions.
ERA OF EXPERIMENTAL EMBRYOLOGY
Studies fueling the debate
Wilhelm Roux
very first to manipulate zygotes or oocytes
Father of Experimental Dev Bio
exp on frog eggs (1888)
fertilized eggs on 1st cleavage -> 2 cells -> killed on of cells -> to prove what happens to the dead and living cell -> living cell: continued to divide -> alive: half embryo -> died
tama daw ang preformationism: kalahati lang kc ang nabuhay
ERA OF EXPERIMENTAL EMBRYOLOGY
Studies fueling the debate
Hans Driesch
perfected ROux's exp
tinusok tapos pinaghiwalay; ung buhay part nabuhay to develop into a whole embryo
experimented on sea urchin eggs (1876-1941)
ERA OF EXPERIMENTAL EMBRYOLOGY
Studies fueling the debate
Theodore Boveri and Sutton (1902)
chromosome thoery
genes
different labs
Boveri - Europe; Sutton - US
ERA OF EXPERIMENTAL EMBRYOLOGY
Studies fueling the debate
Gregor Mendel
rediscovered paper
hereditary traits come from things from the mother and the father
ERA OF EXPERIMENTAL EMBRYOLOGY
Studies fueling the debate
Wilson's Advocacy
Nucleus is the source of determinants that guide morphogenesis and differentiation of blastomeres in embryo
believed in the studies of Boveri and Sutton
ERA OF EXPERIMENTAL EMBRYOLOGY
Studies fueling the debate
Side of TH Morgan
Morgan: believed that the cytoplasm was the source of determinants causing differentiation of the cells and guiding morphogenesis
exp on ctenophore seemed to prove him correct
Works of Nettie Stevens: proved him wrong; this caused him to champion the nucleus and chromosomes as guides of morphogenesis
Established presence of sex chromosomes on nucleus
ERA OF EXPERIMENATAL EMBRYOLOGY
Studies of Genetics was Born from this Conflict
those who believed in chromosomes as morphogenetic guide separated from those who believed in cytoplasm; they established genetics as a science
they concentrated on chromosomes and genes to explain all aspects of development
but many issues were unresolved
Unresolved Issues
How exactly do genes determine hereditary trait?
How does the nucleus regulate metabolism?
How do the chromosomes which were identical in every cell of the organism direct different and changing types of cytoplasm?
Geneticists must provide evidence that genes control early stages of dev of structures not the terminal stages
What about the phenomenon of sex determination were environment determines sexual phenotype?
BIRTH OF MODERN GENETICS
these unanswered questions caused a deep divide and caused “genes people” to form their own society, journal, lingo
they started an era of modern day genetics
BIRTH OF MODERN GENETICS
The Embryologist's Concerns
the die hard embryologist turned to study cellular and tissue interactions leading to the discovery of...
BIRTH OF MODERN GENETICS
...discovery of:
Hilde Mangold and Hans Spemann
discovered the primary organizer
dorsal lip: organizes 2nd set of cells??
Spemann: got Nobel Prize, Mangold did not because she was only a student