Chapters 46 & 47 - Animal Reproduction & Development

Question 1

Describe different strategies in asexual & sexual reproduction.

Answer 1

• Asexual Reproduction
  
  • Budding: new individual grows from body
  • Fission: splits into new individuals
  • Fragmentation & regeneration: breaks into pieces that regenerate new organisms
• Sexual Reproduction
  
  • Fusion of gametes

Question 2

Describe advantages and disadvantages in asexual & sexual reproduction.

Answer 2

• Asexual Reproduction
  
  • Single organism produces clones via mitosis:
    
    • No mate necessary
    • No energy spent making sperm/eggs
  • Relatively rapid
  • Advantageous in stable environments
• Sexual Reproduction
  
  • Produces genetically unique individual(s)
  • Increases genetic variation
  • Adaptive in changing environments
  • Usually occurs seasonally
    
    • In synch with favorable environmental conditions

Question 3

Describe internal vs. external fertilization.

Answer 3

• Internal Fertilization
  
  • Sperm enters female’s reproductive tract
  • Fewer number of eggs/offspring produceda allows for more care provided from parents
• External Fertilization
  
  • Sperm & egg meet outside of bodies
  • Requires synchronization
  • Large number of eggs/offspring produced.

Question 4

Describe external vs. internal vs. indirect vs. direct development.

Answer 4

• External
  
  • ​Can result from external or internal fertilization
  • Increased risk of predation
• Internal
  
  • _​_Results from internal fertilization
  • Safer, but more energetically expensive
• Indirect
  
  • Juvenile is very different from adult
  • Producing lots of eggs with little amount yolk is energetically cheap
  • Larva undergoes metamorphosis
• Direct
  
  • Juvenile is small, sexually-immature
  • Growth occurs, but little change in form
  • Large and need increased nourishment
  • Very energetically expensive, so decreased numbers of offspring produced

Question 5

Describe the four extraembryonic membranes and their functions of the amniotic egg.

Answer 5

1. Chorion
   
   • Surrroundseverying, functions in gas exchanges
2. Amnion
   
   • encloses embryo in aqueous environment
3. Allantois
   
   • ​​stores waste & forms blood vessels
4. Yolk sac
   
   • _​​_described as yolk in non-mammals, and blood cells in mammals

Question 6

Describe cleavage, gastrulation, organogenesis & major events that happen at each stage.

Answer 6

1. Cleavage
   
   • Mitotic divisions of zygote occurs:
     
     • No increase in size
     • Just dividing multiple times into even-smaller cells
   • Solid morula transforms into hollow blastula with blastocoel (fluid-filled cavity of a blastula

)

2. Gastrulation
   
   • Blastospore indents on on side:
     
     • Blastula cells migrate inward
     • Archenteron forms (cavity)
     • This formation determines if protostome (mouth develops first) vs. deuterostome (anus develops first)
   • Forms a gastrula with 3 embryonic tissue layers
3. Organogenesis
   
   • Germ layers are reorganized into adult-form organs
   • Neural tube & notochord form first (neurulation)
     
     • Neural tube transforms into central nervous system (brain & spinal cord)
   • Somites form from mesoderm along notochord
     
     • Will become verebrae, vertebral discs, axial muscles…

Question 7

Describe the three embryonic germ layers and what they develop to.

Answer 7

1. Endoderm:
   
   • Digestive tract & respiratory system
2. Ectoderm:
   
   • Brain, nervous system, and skin
3. Mesoderm:
   
   • Muscles, skeleton, gonads, excretory system, circulatory system