Developmental Biology

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Developmental Biology

• Maria Schiuma
• Ana Sollitto
• Marilyn Ralph
• Michael Buckwald
• Dan Atzmon

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Introduction

• It has been said that what separates modern
  man from all of our predecessors is our
  imagination and curiosity our ability to look
  into the swirling abyss and ponder what lies
  beyond. It is this very same innate curiosity and
  imagination that virtually compels us as a
  species to question our own origins and those of
  the creatures around us. In this search for an
  answer to the question of from where we came,
  many theories have been suggested and almost as
  many have been readily disproved. Yet Charles
  Darwins Theory of Evolution has survived and
  flourished supported by an ever broadening
  array of scientific evidence, including that
  garnered through studies of developmental
  biology.
• By carefully examining and comparing the
  way organisms grow and develop, developmental
  biology provides unique opportunities for
  scientists to view the conditions under which
  certain ancestral relationships and biological
  processes evolve and thus pushes us closer to the
  end of our ongoing quest for an answer to the
  ever-present questions of our most fundamental
  origins.

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Important Terms

• Developmental Biology a field of biology that
  studies the way organisms grow and develop and
  then compares these methods to those applied by
  similar organisms in order to understand how
  certain processes and relationships have evolved.
  
• Developmental Biologist One who actively
  studies and pursues studies pertaining to
  developmental biology.
• Embryology the study of organisms during their
  early stages of development. Careful study of
  Embryology can shed significant light on the
  various relationships between fully developed
  organisms.
• Morphogenesis a category encompassing all of
  the processes that give rise to tissues, organs
  and structural anatomy.
• Evolution the Darwinian process of change
  arising in certain populations through successive
  generations as a result of natural selection
  acting via mutations to bring about gradual
  changes.
• Homologies Similarities in biological structure
  arising from ancestral evolutionary ties.

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Comparative Embryology

• Key tool used by evolutionary biologists to prove
  evolution
• Compares developing embryos in all stages of
  development of different species
• Stages of development are analogous to evolution
• If embryos of two species are similar in just
  early stages, then their evolution diverged at an
  earlier stage
• Animals with similar embryonic development have
  very similar characteristics
• i.e. same kingdoms, phylum, etc.

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Descriptive Embryology

• Study of the normal sequence of events in the
  formation of organs during the embryonic period
  in different organisms
• Can relate the developing processes of each
  species to see if any similarities occur,
  therefore showing a connection in evolution
• The normal sequence of events for most mammals
  is
• Progress through cleavage, blastula, and then the
  gastrula stages
• Neuralation
• Brain starts to develop
• Spinal Chord
• Heart
• External body structures eyes, ears, limbs
• Internal Organs
• Produces own blood
• Becomes motile
• When studying developing embryos, scientists
  discovered several causes for birth defects such
  as spina bifida and anencephaly both occur when
  abnormalities arise in the neuralation sequence
  of development

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Evidence for Evolution

• Does human embryonic development mirror
  evolution?
• Embryonic recapitulation human embryo develops
  in steps that retrace evolution by showing the
  stages ancestors went through
• Ontogeny recapitulates phylogeny - Haeckel
• Vestigial organs structures that were functional
  in the past but have now lost their function
• (yolk sac, gill slits, tail)
• Moral issue abortion

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Human Embryonic Development
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Chemical Homologies

• Uses DNA
• Pseudogenes Junk DNA
• The more the sequences of two animals differ, the
  more remote (both in relatedness and in time) is
  their common ancestor
• The more related two animals are in Linnean
  Classification System, the greater chemical
  homologies

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DNA and Evolution

• Vertebrates have DNA homologies, ex. portions of
  Hemoglobin gene
• Human and Chimp DNA differs less than 1.7,
  coding regions less than 0.4
• DNA hybridization used to test
• Believed that humans branched off of chimp
  evolution

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Division of Labor

• Maria PPT, Evidence for Evolution
• Ana Chemical Homologies
• Marilyn Descriptive Embryology
• Michael Introduction, Important Terms
• Dan Comparative Embryology