Because a circulation is required early - as soon as diffusion no longer can carry materials throughout the body of the fetus.
embryo
When the cell mass is fully implanted in the uterus, it is called a blastocyst. This is an early stage of development in mammalian embryos, just before the embryo begins to form distinct structures.
Embryos grow through a process called embryogenesis, where cells divide, differentiate, and organize into various tissues and organs. This process is guided by genetic information and signaling molecules that direct cell fate and development. As the embryo grows, specialized structures form, ultimately leading to the development of a fully formed organism.
All developing embryos go through a series of stages, from fertilization to differentiation and organ formation. They also possess a similar genetic code, containing the instructions necessary for development. Additionally, all embryos start as a single cell and undergo cell division to form a multicellular organism.
No, sperm and egg unite to form a zygote, a single fertilized cell. That cell divides again and again, forming a blastocyst. The blastocyst implants in the uterine wall (in placental mammals), where the embryo at last develops. Eventually the embryo grows into a fetus, and the fetus undergoes parturition (it is born).
embryo
Gastrulation is a phase early in the development of most animal embryos, during which the morphology of the embryo is reorganized to form the three germ layers: ectoderm, mesoderm, and endoderm.
Identical twins develop from a single zygote that splits into two embryos during early development. Therefore, only one zygote is needed to form identical twins.
When the cell mass is fully implanted in the uterus, it is called a blastocyst. This is an early stage of development in mammalian embryos, just before the embryo begins to form distinct structures.
Embryos are created through the process of fertilization, which involves the fusion of a sperm cell with an egg cell. Following fertilization, the resulting zygote undergoes cell division to form an embryo. This early developmental stage eventually grows into a fetus and then a fully formed organism.
Embryos grow through a process called embryogenesis, where cells divide, differentiate, and organize into various tissues and organs. This process is guided by genetic information and signaling molecules that direct cell fate and development. As the embryo grows, specialized structures form, ultimately leading to the development of a fully formed organism.
All developing embryos go through a series of stages, from fertilization to differentiation and organ formation. They also possess a similar genetic code, containing the instructions necessary for development. Additionally, all embryos start as a single cell and undergo cell division to form a multicellular organism.
Polyphony
polyphony
No, sperm and egg unite to form a zygote, a single fertilized cell. That cell divides again and again, forming a blastocyst. The blastocyst implants in the uterine wall (in placental mammals), where the embryo at last develops. Eventually the embryo grows into a fetus, and the fetus undergoes parturition (it is born).
No, an embryo is not a gamete. A gamete is a specialized reproductive cell (sperm or egg) that fuses with another gamete during fertilization to form a zygote, which then develops into an embryo. An embryo is the early stage of development after fertilization.
During fetal development, the heart begins to form early, around the third week of gestation. By the end of the first trimester, it is roughly the size of a grape, and by week 20, it grows to about the size of a lemon. As the fetus continues to develop, the heart increases in size proportionally, eventually reaching its full size relative to the body by the time of birth.