Developmental Biology

The formation of a multicellular organism from a single cell to a fully grown larva or adult (and the conversion of genotype into phenotype)

The meeting and fusion of a single haploid sperm with a single haploid egg

When embryonic development is initiated by the egg without fertilisation

A period of rapid cell divisions in which the egg is divided into smaller cells

The blastula, surrounding a fluid filled cavity called the blastocoel

A phase of coordinated cell movements which generates the triploblastic structure of the embryo

3;

Ectoderm (outer layer, forms skin and nervous tissue)

Mesoderm (middle layer, forms skeleton, muscle, connective tissue, blood, heart, kidney)

Endoderm (innermost layer, forms digestive tract, and associated organs such as lungs, liver, pancreas)

The formation of an internal nervous system (part of the surface ectoderm following gastrulation)

The differentiation of the organs and tissues so they are fully functional

The transformation of the larva into an adult organism (occurs late in development and may involve remodelling of the body)

• Mouse (mus musculus)
• Chickens (Gallus gallus domesticus)
  
• South African Clawed Frog (Xenopus laevis)
• Zebrafish (Danio rerio)
• Fruit fly (Drosophila melanogaster)
• Nematode worm (Caenorhabditis elegans)
  

Note: there are other ones, research them

When similar genes are inserted into the genomes of very different organisms.

This is used to demonstrate the similarity of Hox genes, Pax6 and BMP/Chordin genes in divergent organisms

Gonads (testes and ovaries respectively)

When the entire egg is cleaved during each division (mouse, frog, worm)

When only part of the egg is cleaved. Restricted to a disc of yolk-free cytoplasm at the animal pole (Zebrafish, chick)

When only part of the egg is cleaved. Restricted to the yolk free cytoplasm covering the egg surface (drosophila).