Embryonic Development

Embryonic stem cells derived from the inner cell mass of a blastocyst are pluripotent, not multipotent. Pluripotent cells can give rise to almost any cell type in the body, whereas multipotent stem cells are more restricted and can only develop into a limited range of cell types.

From a biological standpoint, the germ (or germinal disc) is the most important part of the egg because it contains the genetic material and is where embryonic development begins if the egg is fertilized. However, the phrasing 'most important part' is somewhat subjective.

Hatching is the specific term used when young animals, such as birds, reptiles, or insects, break through their eggshells to emerge. Germination refers to plants sprouting from seeds, while being born typically refers to live birth in mammals.

The life cycle of a frog typically progresses from egg (first stage) to tadpole (second stage), then to froglet (third stage, where it has legs and a shrinking tail), and finally to adult frog.

The primary function of the endosperm in angiosperms is to provide nutrition to the developing embryo.

The two polar nuclei are located in the large central cell, situated just below the egg apparatus at the micropylar end.

The ovule attaches to the placenta via the funicle (stalk). The hilum is the junction point where ovule and funicle connect, analogous to a seed's attachment point.

Hox genes are a group of related genes that control the body plan of an embryo along the head-tail axis, including the development of limbs.

The ectoderm is the outermost germ layer and gives rise to the epidermis (skin), the nervous system, and sensory organs like the eyes and ears. Mesoderm forms muscles and bones, while endoderm forms internal organs like the lungs and intestines.

The inner cell mass (embryoblast) of the blastocyst is responsible for forming the embryo itself and associated structures like the yolk sac and amnion, while the outer trophoblast forms the placenta.

Embryology is the branch of biology that studies the development of embryos and fetuses. Comparing these developmental stages across species provides evidence for common ancestry.

Endosperm is the nutritive tissue formed during double fertilization in angiosperms. It provides the necessary energy and nutrients to support the growth of the embryo until it can photosynthesize.