History of Developmental Biology

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Questions and Answers

What did Caspar Friedrich Wolff contribute to embryology?

He proposed the Germ Layer Theory. (correct)

He formulated Baer’s law.

He introduced the theory of homunculus.

He developed the Biogenetic law.

Which of the following is an example of Baer’s law?

Hair appears before the notochord.

Brain and spinal cord develop earlier than limbs. (correct)

The heart forms before the digestive organs.

Feathers develop before the skeletal system.

What is the Biogenetic law associated with?

The assertion that embryos pass through adult stages of lower animals.

The inheritance of ancient features from common ancestors. (correct)

The sequence of developmental stages of unrelated organisms.

The development of unique adaptations in embryo to surroundings.

What is one potential application of human stem cell biology?

Creating human cells for organ transplantation Signup and view all the answers

Which concept did August Weismann introduce?

The germ plasm theory. Signup and view all the answers

Which of the following is a potential future impact of advancements in growth factors?

Creation of pharmaceuticals in unusual sources Signup and view all the answers

What does the recapitulation theory suggest?

Ontogeny exactly mirrors phylogeny. Signup and view all the answers

What term refers to the transformation of an organism within its own lifetime?

Ontogenetic development Signup and view all the answers

How does differentiation primarily occur in development?

It results from interactions within gradient patterns Signup and view all the answers

What is indicated by the 'mosaic model of development' proposed by Weismann?

Certain cells possess unique genetic information at their origin. Signup and view all the answers

Which phase is NOT part of ontogenetic development?

Evolution Signup and view all the answers

What ethical issue is associated with human genetic manipulation?

It raises significant social responsibilities Signup and view all the answers

In the context of early embryonic development, 'ids' refers to:

Individual units of heredity. Signup and view all the answers

Which of the following statements best captures a characteristic of developmental biology?

It integrates social discourse with cultural concerns Signup and view all the answers

What concept did Aristotle support regarding the nature of development?

Epigenesis Signup and view all the answers

What did Fritz Muller and Ernst Haeckel's theories primarily emphasize?

The ancient origins of features seen in embryonic forms. Signup and view all the answers

Which of the following disciplines does NOT unify into developmental biology?

Bee Biology Signup and view all the answers

The gradual evolutionary history of a species is referred to as?

Phylogenetic development Signup and view all the answers

What does the study of genetics in developmental biology primarily focus on?

The function of individual genes Signup and view all the answers

What does developmental biology require to explain the process of development?

Information at the cellular and molecular levels Signup and view all the answers

Which of the following is NOT a phase of ontogenetic development?

Preformation Signup and view all the answers

What was the conclusion of Wilhelm Roux's experiment with frog embryos?

The result supported the mosaic development model. Signup and view all the answers

What does the regulative model of development suggest regarding separated cleavage cells in sea urchins?

Each can develop into a whole embryo. Signup and view all the answers

Which statement accurately reflects the impact of embryonic induction found through experimental embryology?

Chemical signals control the developmental pathways of cells. Signup and view all the answers

What major advancement in science began with the discovery of the 3-D structure of DNA in 1953?

Molecular biology and gene manipulation Signup and view all the answers

How has molecular biology been applied in medicine according to recent advancements?

To screen for genetic mutations in embryos or chorionic villi. Signup and view all the answers

What is one application of understanding the genetic basis of human birth defects?

Identifying developmental regulatory genes for treatment. Signup and view all the answers

Which growth regulatory substance has been utilized in clinical practice for treating blood cell depletion due to chemotherapy?

Erythropoietin Signup and view all the answers

Which of the following best describes massive cell rearrangements in embryonic development?

They precede or accompany specifications of development. Signup and view all the answers

Study Notes

Definitions

Embryology: A descriptive study of development.
Developmental Biology: The study of processes and mechanisms behind development primarily through experimentation.
Phylogenetic development: The gradual evolutionary history of a species.
Ontogenetic development: The transformation of an organism within its own lifetime.

Phases of Ontogenetic Development

Gametogenesis: The process of gamete (egg and sperm) formation.
Fertilization: The fusion of an egg and sperm cell.
Cleavage: The rapid cell division of a zygote (fertilized egg).
Gastrulation: The formation of the germ layers (ectoderm, mesoderm, and endoderm).
Organogenesis: The development of organs from the germ layers.
Growth and Histological Differentiation: The increase in size and specialization of tissues and organs.
Metamorphosis/Regeneration: The process of transforming into a different form or regenerating lost body parts.

Historical Background

Aristotle (340 BC): Observed that new structures arose progressively in embryos. He believed that the embryo was formed from menstrual blood interacting with a male vital factor present in the semen. This supported epigenesis (17th century), the idea that the organism develops in a stepwise fashion from an unorganized state.

Preformation Theory

Bonnet and Swammerdam (17th century): Proposed that the embryo was already present in the sperm or egg (animalculists or ovists) which simply grows in size in development.

Germ Layer Theory

Caspar Friedrich Wolff (1759): Postulated that a development force inherent in the matter of the embryo directs the laying down of body parts in sequence. He laid the foundation for the Germ Layer Theory by showing that the material out of which the embryo is constructed is, in an early stage of development, arranged in the form of leaf-like layers.

Baer's Law

Karl Ernst von Baer (1828): More general features common to all members of groups of animals are developed in the embryo earlier than the more special features which distinguish the members of the group.

Biogenetic Law

Fritz Muller (1864), Ernst Haeckel (1868): Features that are inherited from the common ancestor of the group have an ancient origin, and develop earliest during ontogeny.
- This is also known as Recapitulation Theory, the development of individual organisms (ontogeny) follows (recapitulates) the same phases of the evolution of larger, ancestral groups of related organisms (phylogeny).

Germ Plasm Theory

August Weismann (1883): Every germ cell during early development receives a complete set of units of heredity (“ids” or Mendel’s “genes”). Development involves orderly unpacking of an embryo as dictated by ids; interactions between parts make epigenetic development possible.
- This theory led to the mosaic model of development, which suggests that cells cannot change their fate if a blastomere is lost.

Experimental Embryology

Wilhelm Roux (1905): Heat-killed one of the 2 blastomeres of a frog’s egg. The surviving cell developed half of a complete embryo.
- This suggests that development is mosaic.

Regulative Model of Development

H.Driesch (1891), Endres (1895), Spemann (1901), Schmidt (1903): If cleavage cells of a sea urchin were completely separated, each developed into a whole embryo.
- This suggests that development is regulative.

Analytical Developmental Biology

T.H.Morgan (1919), Watson & Crick (1953): Units of heredity are composed of sequences of DNA base triplets that are transformed into proteins, which, in turn, transform the system that is an adult organism.

Applications and Future Impact

Understanding of the genetic or chromosomal basis of many human birth defects.
Identification of several new growth regulatory substances, some of which have entered clinical practice.
Discovered stem cell biology.
Pharmaceutical industry can design potential new therapeutic drugs.
Prenatal screening towards elimination of human congenital defects.
Production of human cells, tissues, or organs for transplantation.
Methods fused with tissue engineering can generate more complex tissues and organs.
Produce pharmaceuticals in the milk of sheep, or vaccines in eggs.

Summary Points

Development is epigenetic, meaning it is regulated by the nucleus but takes place primarily in the cytoplasm.
It involves interactions between parts.
Differentiation is the development of the macromolecular pattern within the cell.

Lingering Thoughts

Developmental Biology is not only a scientific discipline but also a social discourse deeply embedded in cultural concerns.
Reproductive cloning, assisted reproductive technology, abortion, stem cell differentiation, genetic enhancement, gene therapy, environmental estrogens, sex selection, and teratogenesis all converge on developmental biology.
It is crucial that we should be educated toward having more social responsibility.

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Description

Test your knowledge on the key concepts of developmental biology, including phases of ontogenetic development such as gametogenesis, fertilization, and organogenesis. Dive into the processes that shape life from a single cell to a fully formed organism. Challenge yourself and learn about the intricacies of life's development.