Foetus vs. Zygote — What's the Difference?
Edited by Tayyaba Rehman — By Maham Liaqat — Updated on May 19, 2024
Foetus is the developmental stage of an unborn baby from the end of the embryonic stage until birth, whereas a zygote is the initial cell formed after the fertilization of an egg by a sperm.
Difference Between Foetus and Zygote
Table of Contents
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Key Differences
A foetus represents the stage of development in mammals, including humans, from approximately the 8th week after fertilization until birth. During this period, major organs and structures continue to develop and mature. The term zygote, however, refers to the earliest stage of human development, immediately following fertilization, when the sperm and egg merge to form a single cell.
The zygote undergoes rapid cell division, known as cleavage, eventually forming a blastocyst which implants into the uterine wall. This stage is very brief, lasting only a few days post-fertilization. The foetal stage follows the embryonic stage (which lasts up to 8 weeks post-fertilization) and is characterized by significant growth and organ development.
In the zygote stage, the genetic material from the mother and father combines to form a unique DNA blueprint. As the embryo transitions to a foetus, it becomes more complex, developing distinct physical features and functioning organ systems. The foetal stage focuses on growth, refinement, and preparation for life outside the womb.
The zygote is a single-celled entity, marking the beginning of a new organism. The foetus, on the other hand, is a multicellular, more developed entity with recognizable human features, undergoing continuous growth and maturation.
Comparison Chart
Definition
Developmental stage from 8 weeks to birth
Initial cell formed post-fertilization
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Duration
From 8 weeks post-fertilization to birth
Few days post-fertilization
Development
Major organ and structure development
Rapid cell division, forming blastocyst
Complexity
Multicellular with recognizable features
Single-cell with combined genetic material
Focus
Growth and maturation
Beginning of a new organism
Compare with Definitions
Foetus
Development stage after embryonic phase.
The foetus begins to move at around 16 weeks.
Zygote
Rapid cell division.
The zygote divides to become a blastocyst which implants in the uterus.
Foetus
From 8 weeks to birth.
Ultrasound can show detailed images of the foetus at 20 weeks.
Zygote
Combination of genetic material.
The zygote has a complete set of chromosomes from both parents.
Foetus
Human-like appearance.
The foetus starts to resemble a newborn baby in the later stages.
Zygote
Single cell formed after fertilization.
The zygote contains all the genetic information for the new organism.
Foetus
Characterized by organ development.
By the third trimester, the foetus has developed functioning lungs.
Zygote
Beginning of embryonic development.
The zygote undergoes its first cell division within hours of fertilization.
Foetus
Undergoes significant growth.
The foetus gains most of its weight during the last few weeks of pregnancy.
Zygote
Very early developmental stage.
The zygote stage lasts only a few days before becoming an embryo.
Foetus
Variant of fetus.
Zygote
A zygote (from Greek ζυγωτός zygōtos "joined" or "yoked", from ζυγοῦν zygoun "to join" or "to yoke") is a eukaryotic cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information necessary to form a new individual.
Foetus
Alternative spelling of fetus
Zygote
The cell formed by the union of two gametes, especially a fertilized ovum before cleavage.
Foetus
Same as Fetus.
Zygote
The organism that develops from a zygote.
Foetus
An unborn or unhatched vertebrate in the later stages of development showing the main recognizable features of the mature animal
Zygote
A fertilized egg cell.
Zygote
The cell resulting from the union of an ovum and a spermatozoon (including the organism that develops from that cell)
Common Curiosities
What is a foetus?
A developmental stage in mammals from about 8 weeks post-fertilization until birth.
How long does the zygote stage last?
Only a few days, as it rapidly divides and forms a blastocyst.
When does the foetus stage begin?
Around the 8th week after fertilization.
What is the main focus of the foetal stage?
Growth, organ development, and preparation for birth.
What is a zygote?
The initial single cell formed after the fertilization of an egg by a sperm.
Is the zygote visible to the naked eye?
No, it is microscopic.
Does the foetus have a heartbeat?
Yes, a foetal heartbeat can typically be detected by 6-7 weeks of pregnancy.
What happens during the foetal stage?
Major organ systems develop and the foetus grows significantly in size.
Does the zygote have organs?
No, it is a single cell and has not yet formed any organs.
What happens during the zygote stage?
The zygote undergoes rapid cell division and begins the process of becoming an embryo.
Is the foetus fully formed at the beginning of the foetal stage?
No, it continues to develop and mature throughout the foetal stage.
Can abnormalities in development occur at the zygote stage?
Yes, abnormalities can occur at any stage, including the zygote stage.
How is a zygote formed?
By the fusion of a sperm cell with an egg cell.
What does the term "pitted" imply in the context of the foetal stage?
The term "pitted" does not apply to the foetal stage; it is unrelated.
What is the main focus of the zygote stage?
Initial cell division and genetic material combination.
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Written by
Maham Liaqat
Edited by
Tayyaba RehmanTayyaba Rehman is a distinguished writer, currently serving as a primary contributor to askdifference.com. As a researcher in semantics and etymology, Tayyaba's passion for the complexity of languages and their distinctions has found a perfect home on the platform. Tayyaba delves into the intricacies of language, distinguishing between commonly confused words and phrases, thereby providing clarity for readers worldwide.
