In developmental biology, animal embryonic development, also known as embryogenesis, is the developmental stage of an animal embryo. Embryonic development starts with the fertilization of an egg cell (ovum) by a sperm cell, (spermatozoon). Once fertilized, the ovum becomes a single diploid cell known as a zygote.
What is the earliest stage of an animal’s development?
embryo
embryo, the early developmental stage of an animal while it is in the egg or within the uterus of the mother. In humans the term is applied to the unborn child until the end of the seventh week following conception; from the eighth week the unborn child is called a fetus.
How many stages are there in embryonic development?
The process of prenatal development occurs in three main stages. The first two weeks after conception are known as the germinal stage, the third through the eighth week is known as the embryonic period, and the time from the ninth week until birth is known as the fetal period.
What are Erikson’s stages of development?
Erik Erikson’s Stages of Psychosocial Development
| Stage | Psychosocial Crisis | Age |
|---|---|---|
| 1. | Trust vs. Mistrust | 0 – 1½ |
| 2. | Autonomy vs. Shame | 1½ – 3 |
| 3. | Initiative vs. Guilt | 3 – 5 |
| 4. | Industry vs. Inferiority | 5 – 12 |
What are the four essential stages in early animal development?
They occur via four essential stages in early animal development: Fertilization: the process of a single sperm cell combining with single egg cell to form a zygote. Cleavage: rapid, multiple rounds of mitotic cell division where the overall size of the embryo does not increase. The developing embryo is called a blastula following completion
How long does it take for a bovine embryo to develop?
Bovine Development – Bovine, not a typical embryological model, but extensively studied due to commercial value and more recently for breeding using IVF techniques. Development takes about 280 days. The chicken embryo develops and hatches in 20-21 days and historically these were one of the first embryos to be studied.
Why are the early stages of embryonic development important?
The early stages of embryonic development are also crucial for ensuring the fitness of the organism. Fertilization, pictured in Figure 24.23 a is the process in which gametes (an egg and sperm) fuse to form a zygote. The egg and sperm each contain one set of chromosomes.
How long does it take for an animal to develop?
The table below lists the approximate development time for a large number of different animals, ranging from the opossum at 12 days to the elephant at 660 days. Each animal species has different variations +/- the average values shown in the table.
