Animal Reproduction Methods Quiz

Embryonic Development in Animals

• Cells from one end of the blastula fold inwards, eventually filling the blastocoel, producing two layers of embryonic tissues: the ectoderm (outer layer) and the endoderm (inner layer).
• Gastrulation is unique to animals; it’s not found in fungi or other multicellular eukaryotes.
• The pouch formed by gastrulation, called the archenteron, opens to the outside via the blastopore.

Hox Genes in Animal Development

• Hox genes are crucial in animal evolution because they play a fundamental role in determining the body plan and segment identity during embryonic development.
• Hox proteins coordinate the development of various structures along the anterior-posterior axis, e.g. legs, antennae, and wings in fruit flies, or the different types of vertebrae in humans.
• The Hox family of genes is highly conserved, with a similar arrangement along chromosomes across animal phyla.
• The number of Hox copies varies among animal phyla, e.g. least in jellyfish, most in vertebrates.

Developmental Events in Animals

• Development occurs at many points in the life cycle of animals.
• Fertilization creates a spherical diploid zygote that undergoes embryonic development.
• Stages in early embryonic development of animals:
  • Cleavage transforms the zygote into an eight-cell embryo.
  • Continued cleavage produces a multicellular, hollow blastula.
  • Gastrulation forms a gastrula with different layers of embryonic tissues.

Characteristics of Animals

• Development is a fundamental characteristic of animals.
• Asexual reproduction is found in nearly half of all animal phyla.
• Mechanisms of asexual reproduction:
  • Fission or fragmentation occurs commonly in invertebrate animals.
  • Budding is found only among invertebrates.
  • Parthenogenesis is the development of an embryo from an unfertilized egg cell.
• Benefits of asexual reproduction:
  • Supports rapid population growth when conditions are favourable.
  • Provides an alternative to sexual reproduction when reproductive opportunities are limited.
  • Some species can alternate between sexual and asexual strategies.