Summary: Biology Ii Quiz 8

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• 1 Biology II Quiz 8

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• Explain the importance of embryo polarity during cleavage. Compare the characteristics of the animal hemisphere, vegetal hemisphere, and gray crescent in amphibian embryos.

  Embryo polarity is crucial for developmental patterning. Key characteristics include:
  

  • Animal hemisphere: More cells, active development; contains future nervous system.
  • Vegetal hemisphere: Yolk-rich, supports nutrition, dependent on embryo growth.
  • Gray crescent: Crucial for gastrulation, establishes body axes.

• Describe the process of gastrulation and explain its importance. Explain how this process rearranges the embryo. List adult structures derived from each of the primary germ layers.

  Gastrulation - rearranges the cells of a blastula into a three-layered embryo, called a gastrula, which has a primitive gut 
  

  • Three layers produced by gastrulation are called embryonic germ layers 
  • Ectoderm - forms the outer layer
  • Endoderm - lines the digestive tract
  • Mesoderm - partly fills the space between the endoderm and ectoderm 

  
  Importance:
  

  • Establishes body plan.
  • Ensures proper organ formation.

• Describe the formation of the notochord, neural tube, and somites in a frog.

  • Early in vertebrate organogenesis, notochord forms the mesoderm, and the neural plate forms from ectoderm . 
    
  • Neural plate soon curves inward, forming the neural tube 
  • Mesoderm lateral to the notochord forms blocks called somites 

• List examples of organs or systems for each embryonic germ layer

  Ectoderm - Cornea and lens of eye, Nervous system, Tooth enamel
  Mesoderm - Skeletal system, muscular system, and excretory system 
  Endoderm - Liver, pancreas, and thymus 

• Describe the two general principles that integrate our knowledge of the genetic and cellular mechanisms underlying differentiation

  • During early cleavage divisions, embryonic cells must become different from one another 
    
  • After cell asymmetries are set up, interactions among embryonic cells influence their fate, usually causing changes in gene expression 

• Describe the process of fate mapping and the significance of fate maps.

  Fate mapping - general territorial diagrams of embryonic development. Significance includes:
  

  • Understanding tissue formation
  • Studying cell differentiation
  • Identifying stem cell potentials

• Explain the significance of Spemann's organizer in amphibian development.

  • Based on their famous experiment, Spemann and Mangold concluded that the blastopore's dorsal lip is an organizer of the embryo
    
  • The organizer initiates inductions that result in formation of the notochord, neural tube, and other organs 

• Distinguish between asexual and sexual reproduction.

  • Asexual reproduction - creation of offspring whose genes all come from one parent 
    
  • Sexual reproduction - creation of offspring by fusion of male gametes (sperm) and female gametes (eggs) to form zygotes 
    

• List and describe four mechanisms of asexual reproduction.

  Fission - Separation of a parent into two or more individuals of about the same size
  Budding - Two new individuals arise from outgrowths of existing ones
  Fragmentation - breaking of the body into pieces, some or all of which develop into adults
  Parthenogenesis - Process in which an egg develops without being fertilized 

• Define parthenogenesis. Note examples of invertebrate and vertebrate species that use this

  Process in which an egg develops without being fertilized. 
  

  • Several genera of fishes, amphibians, and lizards reproduce onlu by a complex form of parthenogensis