Lecture 1: Introduction Flashcards
Who said, “The greatest progressive minds of embryology have not looked for hypotheses; they have looked at embryos.” (1955)?
Jane Oppenheimer
Developmental Biology is the merging of which two (2) sciences?
Embryology and Genetics
How a single fertilized egg can give rise to a complex organism
Concept
The Central Paradox of Life
Why is developmental biology unique among all other biological sciences?
It explains how a single cell develops into a multicellular organism with different cell types.
What phrase is used to describe developmental biology’s role in biological disciplines?
Based on Scott F Gilbert
“The stem cell of biological disciplines”
Name three biological disciplines that have their ancestry in developmental biology.
If you can, name another 5; | Based on Scott F Gilbert
- Genetics
- Cell Biology
- Oncology
(other acceptable answers: immunology, evolutionary mechanisms, neurobiology, systems biology)
What happens to developmental biology as it continues to evolve?
Based on Scott F Gilbert
It buds off more disciplines while retaining its own identity.
Which fields are reasserting the importance of the developmental perspective? (2)
Based on Scott F Gilbert
Evolutionary biology and oncology
oncology-the study of cancer
Fill in the blank: Developmental biology remains __________, __________, and relatively __________.
Based on Scott F Gilbert
- Vigorous
- pluripotent
- undifferentiated
What is the study of the origin and development of an organism from a fertilized egg to the period resembling an adult form?
Embryology
Embryology begins with the union of what two gametes?
Male and female gametes
An immature organism contained within the coverings of an egg or within the body of the mother
embryo
When does the embryonic period strictly end? (3)
- Metamorphosis
- hatching, or
- birth
Why is the scope of embryology often broadened beyond the embryonic period?
Because developmental processes continue throughout an organism’s life
What are two (2) additional processes studied in embryology beyond early development?
- Asexual reproduction
- regeneration
Name three (3) modern sciences that have foundations in embryology.
Name other 6 if you can.
- Anatomy
- genetics
- physiology
(other acceptable answers: pathology, evolution, histology, immunology, cellular biology, ecology)
What is mainly responsible for the great diversity of animals?
Mechanisms of organism development
What major question does embryology help answer regarding vertebrates and invertebrates?
What makes vertebrates different from invertebrates?
What does developmental biology deal with? (2)
- Organogenesis
- postnatal development
Name two examples of postnatal development processes. (2)
- Metamorphosis
- tissue repair
Abnormal proliferation of cells (tumors)
Developmental Biology
neoplastic growth
The regrowth of body parts from pieces of an organism
Developmental Biology
regeneration
The repair of tissue at various levels of complexity, from molecular to organismal.
Developmental Biology
tissue repair
What does developmental biology study in relation to genetics?
Genetic mechanisms involved in the development of an organism
What is the relationship between genotype and phenotype?
Genotype is translated into phenotype
Give an example of a project that mapped genes to study phenotype expression.
Human Genome Project
A zebra-donkey hybrid that is two times bigger than an ordinary zebra foal
zebroid foal
Give the six (6) fields of embryology
- Descriptive embryology
- Comparative embryology
- Experimental embryology
- Chemical embryology
- Reproductive biology
- Teratology
Field of embryology that accounts for the processes of development transforming a single-cell zygote into a multicellular organism.
descriptive embryology
What question does descriptive embryology aim to answer?
“What” happens during development
What method was developed to describe developmental processes in three dimensions?
descriptive embryology
Three-dimensional wax plate reconstructions
Field of embryology that analyze the similarities and differences in the development of different vertebrate groups.
Comparative embryology
What phrase suggests that embryonic development reflects evolutionary history?
“Ontogeny recapitulates phylogeny”
Explain “Ontogeny recapitulates phylogeny”
The phrase “Ontogeny recapitulates phylogeny” is based on Ernst Haeckel’s now-discredited Recapitulation Theory. It suggests that during embryonic development (ontogeny), an organism passes through stages resembling its evolutionary ancestors (phylogeny).
For example, human embryos briefly exhibit features like gill slits, similar to fish. However, modern biology recognizes that while embryonic development may reflect some evolutionary relationships, it does not strictly repeat ancestral forms.
Why was comparative embryology significant in the 19th century?
It was driven by an interest in evolution, which was a dominant factor in biology
Who conducted the first known study of comparative developmental anatomy?
Aristotle
What are the three ways animals are born, according to Aristotle? (3)
Short description and some examples
- Oviparity – from eggs (e.g., birds, frogs, most invertebrates)
- Viviparity – live birth (e.g., eutherian/placental mammals)
- Ovoviviparity – eggs hatch inside the body (e.g., certain reptiles and sharks)
What are the two major cleavage patterns in embryos, as identified by Aristotle? (2)
Short description and some examples
- Holoblastic cleavage – entire egg divides into smaller cells (e.g., frogs, mammals)
- Meroblastic cleavage – only part of the egg forms the embryo, while the yolk serves as nutrition (e.g., chicks)
What two important structures did Aristotle first understand in embryology? (2)
- placenta
- umbilical cord
At what stage do embryos of different species look nearly identical?
Stage 1
What is the primary focus of experimental embryology?
Testing hypotheses by manipulating embryos through experiments
What types of transplantations are used in experimental embryology? (2)
Include short description
- Homotransplantation – transplanting tissues/organs within the same species
- Xenotransplantation – transplanting tissues/organs between different species
What significant recent xenotransplantation experiment was conducted at NYU Langone?
The successful transplantation of two genetically engineered pig hearts into recently deceased humans
Who pioneered experimental embryology and introduced “developmental mechanics” to determine the causes of individual development?
Wilhelm Roux
What was the goal of Wilhelm Roux’s “developmental mechanics”?
To determine the causes of individual development through controlled experiments
What are the two major theories on embryo development that Roux studied? (2)
- Preformation
- Epigenesis
Germ cells contain miniature preformed adults that unfold during development
Preformation
The embryo develops through gradual changes from an initially formless zygote
Epigenesis
What are the two types of differentiation according to Wilhelm Roux? (2)
- Self-differentiation
- Dependent differentiation
Factors responsible for development are inherent in the specific part of the embryo
Self-differentiation
Development depends on external conditions
Dependent differentiation
Who coined the term epigenetics?
Conrad Waddington
It describes the interaction between genes and the environment in shaping an organism’s development
Epigenetics
What did Waddington emphasize about genetic factors in development?
That genetic factors are among the most important determinants of development
The study of conception, contraception, and early embryonic development
reproductive biology
What are the key research areas in reproductive biology? (5)
Include short description
- Normal gametogenesis – Formation of sperm and egg cells
- Transport of gametes and fertilization – How sperm meets egg
- Endocrinology of reproduction – Hormonal regulation
- Early embryonic development – Initial stages of embryo growth
- Implantation of the mammalian embryo – Attachment to the uterus
Why did reproductive biology grow rapidly as a field?
Due to increasing research on conception and contraception problems
The chemical and physical events that occur during development
chemical embryology
Which factors are analyzed in chemical embryology?
The interaction of chemical and physiological processes that influence embryo development
During which decades did chemical embryology emerge as a field?
Year range
1930s – 1940s
The study of birth defects and developmental abnormalities
teratology
What are the two main causes of birth defects studied in teratology? (2)
Include a short description each.
- Genetic Events – Mutations, aneuploidy, translocations
- Exogenous Factors – External influences like drugs, radiation, alcohol, bacteria, and viruses
Give an example of a well-known teratogen and its effect.
Include a short description.
Thalidomide – Caused limb deformities in babies when taken by pregnant women
When did teratology emerge as a field of study?
During the Middle Ages
A condition where the long bones of the limbs are either absent or severely deficient, leading to flipper-like limbs.
Phocomelia
What is the origin of the term “Phocomelia”?
Phoco- (seal) + Melia- (limb), meaning limbs resembling a seal’s flipper.
What are the main causes of Phocomelia? (3)
- Genetic inheritance (mutations)
- Exposure to radiation
- Thalidomide drug intake during pregnancy
Why was Thalidomide prescribed to pregnant women?
It was marketed as a mild sedative and anti-nausea drug in the late 1950s and early 1960s.
It led to severe congenital disabilities, primarily Phocomelia (limb deformities), and became a major medical scandal.
Thalidomide babies
It examines embryonic development, postnatal growth, metamorphosis, regeneration, and tissue repair at all levels (molecular to organismal).
Developmental Biology
How has modern reproductive technology contributed to Developmental Biology? (2)
Through In-vitro fertilization (IVF) and Embryo Transfer (ET), allowing childless couples to have genetically related children.
A baby conceived through IVF, where fertilization occurs outside the body before embryo transfer to the uterus.
Test Tube Baby
What are the advantages of IVF & Embryo Transfer (ET)? (4)
✅ Overcomes infertility – Enables conception in couples with reproductive issues.
✅ Genetic screening – Can detect genetic diseases before implantation.
✅ Surrogacy option – Helps individuals who cannot carry a pregnancy.
✅ Cryopreservation – Allows storage of embryos for future use.
What are the disadvantages of IVF & Embryo Transfer (ET)? (4)
❌ Fertility drugs – Can cause ovarian hyperstimulation syndrome (OHSS).
❌ Multiple births – Higher risk of twins/triplets, leading to pregnancy complications.
❌ Ethical concerns – Embryo manipulation, cloning, and gene editing raise moral questions.
❌ Surrogacy issues – Surrogate mothers may refuse to give up the child.
What is one major ethical concern surrounding IVF?
The fate of unused frozen embryos and their potential disposal or use in research.
What are some experimental techniques related to embryo manipulation? (3)
Include a short description each.
- Chimeras – Combining cells from different embryos.
- Cloning – Producing a genetically identical organism.
- Gene Transfer – Editing genes to correct mutations.
What are the risks associated with fertility drugs used in IVF?
Overstimulation of ovaries, leading to Ovarian Hyperstimulation Syndrome (OHSS), which can cause severe swelling, fluid buildup, and organ damage.
A process where an egg is fertilized by sperm outside the body and then implanted in the uterus.
In-vitro fertilization (IVF)
The process of placing an embryo into the uterus or fallopian tube for pregnancy.
Embryo Transfer (ET)
The creation of a genetically identical organism from a single parent.
Cloning
Who was the first cloned animal, and where was it cloned?
Dolly the sheep, cloned at the Roslin Institute from an adult somatic cell.
What question did Aristotle pose in embryology?
How different parts of the embryo are formed.
What are the two theories of embryonic development Aristotle defined? (2)
- Preformation – A miniature embryo already exists and only grows larger.
- Epigenesis – New structures form gradually (like knitting a net).
The sperm contained a miniature human (homunculus) that grew inside the womb.
Who believes this concept?
Spermists
The ovum contained a tiny organism that grew when stimulated by sperm.
Who believes this concept?
Ovists
Who supported the Ovists’ theory, and what did he discover?
Charles Bonnet discovered parthenogenesis, where eggs can develop without fertilization.
In which organisms is parthenogenesis common? (5)
✅ Aphids
✅ Ants
✅ Wasps
✅ Bees
✅ Rarely in lizards and snakes
- He studied the structure of advanced fetuses.
- Limit: Their small size, making them hard to study.
Galen (130-200 A.D.)
What solved Galen’s problem in the 17th century?
microscope
They first observed human sperm using a crude microscope.
Anton Van Leeuwenhoek & Hamm (1677)
What else did Van Leeuwenhoek see in a drop of pond water? (3)
- Bacteria 🦠
- Protozoa 🏞️
- Sperm cells
✅ Founder of Modern Reproductive Biology
✅ Described ovarian follicles
✅ First to describe Fallopian tubes
Reiner De Graaf (1672)
Who demonstrated that both male and female sex products are necessary for development?
Lazzaro Spallanzani
Who performed the first artificial insemination in a dog (1785)?
Lazzaro Spallanzani
Who disproved John Needham’s findings on spontaneous generation and proposed that microorganisms came from the air and not spontaneous generation?
Lazzaro Spallanzani
Who is considered the Father of Modern Pathology and Physiopathology?
Marcello Malpighi
Who published the first microscopic account of chick embryo development (1672) and accurately described chick embryo development inside an egg?
Marcello Malpighi
What structures did Malpighi discover in the kidney and spleen?
Malpighian corpuscles
Who discovered red blood cells and capillaries connecting arteries and veins?
Marcello Malpighi
Who developed the science of comparative embryology and discovered the existence of germ layers in embryos?
Karl Ernst von Baer
General features of an animal group appear earlier in development than specialized features.
Von Baer’s Law
Who proposed the Germ Layer Theory (ectoderm, mesoderm, endoderm)?
Karl Ernst von Baer
Who discovered the chick notochord and mammalian egg?
Karl Ernst von Baer
Who described the laws of embryology in Über Entwickelungsgeschichte der Thiere (1828, 1837)?
Karl Ernst von Baer
Who proposed that embryonic development occurs through progressive remodeling and growth and formulated the Theory of Epigenesis to counter preformationism?
Caspar Friedrich Wolff
Who proposed the Cell Theory (cells are the basic unit of life, arise from other cells, and contain genetic information)? (2)
Matthias Schleiden & Theodor Schwann
What fundamental principle about development did Schleiden and Schwann support?
Development occurs via epigenesis.
Who distinguished between somatic cells (body cells) and germ cells (gametes)?
August Weismann
What is the role of germ cells according to Weismann?
They perpetuate the species and pass inherited characteristics.
What is Weismann’s Theory of Nuclear Determination?
The nucleus contains factors that are asymmetrically distributed to daughter cells, determining their fate.
What model did Weismann propose based on the idea that the egg contains discrete localized determinants?
The Mosaic Model
What did August Weismann propose about the distinction between soma and germ cells?
Soma (body) protects and perpetuates germ cells, while germ cells pass on genetic information to offspring.
What are the major phases of the vertebrate reproductive life cycle?
13 phases
Adult → Gametogenesis → Egg + Sperm → Fertilization → Cleavage → Gastrulation → Organogenesis → Fetal Growth → Hatching/Birth → Juvenile → Adult → Gametogenesis
What does the Post-Reproductive Period include? (2)
Senescence → Death
Who proposed the Recapitulation Theory (Biogenetic Law)?
Ernst Haeckel
What is the core idea of Haeckel’s Recapitulation Theory?
Ontogeny (development of an organism) recapitulates phylogeny (evolutionary history).
What experiment did Hans Driesch perform on sea urchin embryos?
He separated blastomeres at the two-cell stage and found that each could develop into a whole embryo.
What key concept did Driesch’s experiment demonstrate?
the ability of an embryo to develop normally even if some cells are removed or rearranged.
Regulative development
What are totipotent and pluripotent cells?
- Totipotent cells: Can generate all cells in an organism.
- Pluripotent cells: Can generate many but not all cell types.
A small embryonic region (dorsal lip of the blastopore) that controls body organization.
Spemann-Mangold Organizer
Grafting the organizer region onto another embryo induced the formation of a secondary body axis, leading to a partial second embryo.
What is this experiment?
Spemann-Mangold Transplantation Experiment (1924)
Who distinguished between genotype and phenotype?
Wilhelm Johannsen (Danish biologist)
Genetic information inherited from parents.
Genotype
Observable traits, internal structures, and biochemical characteristics at any stage of development.
Phenotype
What does the relationship between genotype and phenotype describe?
How genetic information is expressed during development to create a functional organism.
Who conducted the Ablation Experiment (Embryonic Extirpation)?
Wilhelm Roux (1896)
What was the result of Roux’s Mosaic Development Experiment on frog embryos?
Destroying one cell at the two-cell stage resulted in only half an embryo forming, supporting the Mosaic Mechanism of development.
What was the purpose of Roux’s experiment?
To test Weissman’s Mosaic Development Theory by determining whether embryonic cells could compensate for missing parts.
Who worked on mutant genes in mice and Drosophila in the 1930s? (2)
- Salome Gluecksohn Waelsch
- Conrad Hal Waddington
What field did Gluecksohn and Waddington contribute to?
Developmental Genetics – the integration of genetics and embryology.
Development is shaped by causal interactions between different parts of an organism, with genetic factors being crucial but not the only influence.
What is this and who defined this?
Epigenetics according to Waddington
Besides genes, what other factors influence development?
- Environmental factors
- epigenetic modifications
- cellular interactions
- biochemical signaling
