Difference Between Zygote and Embryo (With Table)

Fertilization is a process that occurs as a result of the fusion of the sperm with the egg. This fertilization leads to the creation of a new organism through sexual reproduction. The new organism goes through various stages before being fully formed. Zygote and Embryo are two such stages that occur in the development of the human organism.

Zygote vs Embryo

The difference between Zygote and Embryo is that Zygote is unicellular, whereas Embryo is multi-cellular. Both of them are distinct stages that are a part of human development. The zygotic stage is followed by the embryonic stage. The two also differ in various other aspects, such as their medical terminology, the method of formation, the results that they produce, etc.

The zygote is the first stage that takes place during the growth process of an organism. It is the original cell that is formed as a result of the union of the female’s ovum with the male’s sperm. The word ‘Zygote’ has been derived from the Greek word ‘zygotos’, which translates to ‘join’ or ‘to join’.

On the other hand, the embryo is the phase that comes after the zygotic stage. This begins as soon as the first cell division occurs in the organism and continues up till birth. The term ‘Embryo’ has its roots in the Latin word, ‘embryum’, which means ‘that which grows.’

Comparison Table Between Zygote and Embryo

Parameters of ComparisonZygoteEmbryo
DefinitionThe zygote is formed due to the union of male and female gametes.The Embryo is one of the stages in the development of an organism. In humans, it occurs eight weeks after fertilization.
CellsIt is unicellular.It is multicellular.
Derived fromThe term zygote has been derived from the Greek word,’zygotos’ which means, ‘to join’.The word embryo has been derived from the Latin word, ‘embryum’ which means, ‘that which grows’.
Medical terminologyThe medical term for zygote is zygocyte.The medical term for the embryo is a diploid eukaryote.
Process of formationThe Zygote is formed through the process of fertilization.The Embryo is formed through the process of embryogenesis.
Results intoThe Zygote undergoes mitosis, as a result of which turns into an embryo.The Embryo continues to grow until the organism takes a fully formed shape, known as a fetus.

What is Zygote?

When the male gamete, sperm fuses with the female gamete, egg, it results in the creation of a new organism. This organism, at the initial stage, is known as Zygote. It is the first stage in the process of development of the new organism. In medical terms, a zygote is referred to as a zygocyte.

When fertilization between haploid ovum cells from the female and haploid sperm cells from the male happens, it is termed sexual reproduction. These two cells then join to create a single diploid cell, known as a zygote. This zygote has only one cell, and hence it is called unicellular.

The zygote carries along with it the DNA of the parents as well as their genetic traits. It contains half the DNA of both mother and father. It is, therefore, the work of the zygote to dispense all the information regarding the genes that is essential for the growth of the newly formed organism.

The zygote undergoes mitosis. Mitosis is known as the process wherein a cell duplicates itself, thereby dividing itself into two identical daughter cells that have the same genetic makeup. This mitosis turns the zygote into an embryo. Hence, it enters the next stage in the development process.

What is Embryo?

The embryo is medically termed a diploid eukaryote. It is formed as a result of the division of the zygote. This process is known as embryogenesis. The unicellular zygote undergoes mitosis to transform itself into a multi-cellular organism called an embryo.

This is the second phase that occurs during the development process of an organism after sexual reproduction begins. Usually, the embryonic stage begins after five days of fertilization. The word embryo has its root in the Latin word, ‘embryum’, which means ‘that which grows.’

The embryonic stage is the phase that begins right after the first cell division is initiated. This period continues up until the organism is born. Even though the term embryo is replaced with the term fetus, when the organism converts into a fully formed baby with legs, arms, etc., the cell division continues.

The stage prior to the embryo is the zygote. This zygote contains half the DNA of both parents. It is from this zygote that the embryo derives its entire genetic makeup. The process of the formation of an embryo is known as embryogenesis. It takes approximately five days for a zygote to convert into an embryo after fertilization.

Main Differences Between Embryo and Zygote

  1. The zygote is the very first stage in the process of the growth of an organism, whereas the embryonic stage is the one that is succeeded by the zygote.
  2. Zygote has its roots in a Greek word which means ‘to join’ or ‘to be yoked’. On the other hand, embryo arises from the Latin word, ‘embryum’, which translates into ‘that which grows’.
  3. The zygote is formed due to the fusion of the male and female gametes, and on the contrary, the embryo is a result of the process of mitosis under which the zygote divides into multiple cells.
  4. The zygote is a unicellular organism that eventually turns into a multi-cellular one, and when it does, it is called an embryo.
  5. The zygotic stage occurs immediately after fertilization, whereas the embryonic stage happens approximately after five days.
  6. The zygote converts into an embryo after undergoing the process of mitosis, and on the other hand, the embryonic stage continues up until birth happens.

Conclusion

When the female gamete called the ovum is fertilized by the male gamete called the sperm, it becomes a zygote. It is a unicellular organism that carries all the forty-six chromosomes that are required for the growth of the newly formed organism. The zygotic stage is the first stage in the life of the organism.

After approximately five days after fertilization, the zygote so formed divides itself into two identical daughter cells. This organism is from here on called an embryo. It goes on its journey and divides again and again, continuing up till the birth. The embryonic stage is the second phase in the development of the organism.

References

  1. https://www.sciencedirect.com/science/article/pii/S1534580711000372
  2. https://academic.oup.com/biolreprod/article-abstract/71/4/1046/2666924
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