Which of the following statements is true a The blastomeres

Which of the following statements is true? a. The blastomeres rearrange themselves to form three germ layers during metamorphosis. b. Gastrulation produces a gastrula with ectoderm, mesoderm, and endoderm. C. The blastocoel forms during morphogenesis. d. The neurula forms a gastrula during fertilization. e. Cell divisions are very slow during cleavage.

Solution

1. Gastrulation is a phase early in the embryonic development of most animals, during which the single-layered blastula is reorganized into a trilaminar (Three-layered) structure known as the gastrula. These three germ layers are known as the ectoderm, mesoderm, and endoderm. So, option b is true.

2. Morphogenesis is the biological process that causes an organism to develop its shape. It is one of three fundamental aspects of developmental biology along with the control of cell growth and cellular differentiation, unified in evolutionary developmental biology. Statement b is true.

3. The ectoderm differentiates to form the nervous system (spine, peripheral nerves and brain), tooth enamel and the epidermis (the outer part of integument). It also forms the lining of mouth, anus, nostrils, sweat glands, hair and nails.In vertebrates, the ectoderm has three parts: external ectoderm (also known as surface ectoderm), the neural crest, and neural tube. The latter two are known as neuroectoderm. Option d is the correct answer.