In reproductive biology, syngamy which is the fusion of male and female gametes results in the formation of which type of zygote in sexually reproducing organisms?

Introduction / Context:
Syngamy is a key event in sexual reproduction. It refers to the fusion of two haploid gametes, usually a male gamete sperm and a female gamete egg, to form a new cell. Understanding the ploidy of the resulting cell is fundamental in genetics and life cycle biology. This question asks what is formed directly by syngamy.

Given Data / Assumptions:

• Male and female gametes are haploid cells containing one set of chromosomes.
• Syngamy is the process of fusion of these gametes.
• The term zygote refers to the cell formed immediately after fertilization.
• We assume standard sexual life cycles in animals and many plants.

Concept / Approach:
Each gamete contains a single set of chromosomes n. During syngamy, the nuclei of the two gametes fuse, combining their genetic material. The resulting zygote has two sets of chromosomes, one from each parent, and is therefore diploid 2n. This diploid zygote can then undergo mitotic divisions to develop into a new organism. The zygote is not haploid, and syngamy does not produce gametes but consumes them.

Step-by-Step Solution:
Step 1: Recall that gametes are formed by meiosis and contain a haploid set of chromosomes. Step 2: Understand that syngamy is also called fertilization and involves fusion of these two haploid nuclei. Step 3: When two haploid sets combine, the chromosome number becomes diploid. Step 4: The newly formed cell after fusion is called a zygote. Step 5: Therefore, the zygote produced by syngamy is diploid. Step 6: Options mentioning gametes or haploid zygote do not fit this basic ploidy logic.

Verification / Alternative check:
Genetics diagrams of life cycles show that meiosis reduces chromosome number from diploid to haploid while fertilization restores it from haploid to diploid. This alternation ensures stable chromosome number between generations. In humans, each gamete has twenty three chromosomes, and the zygote after syngamy has forty six, which is the diploid number. Similar patterns are seen in many plants and animals, confirming that syngamy produces a diploid zygote.

Why Other Options Are Wrong:
Option A, haploid zygote, is incorrect because the defining feature of a zygote after fertilization is that it is diploid. Options C and D refer to male gametes, which are present before syngamy, not produced by it. Option E, haploid sporophyte, is incorrect in most textbook life cycles where the sporophyte is diploid and arises from the zygote, not haploid.

Common Pitfalls:
Some students confuse syngamy with meiosis and think that ploidy is reduced, when in fact syngamy restores the diploid state. Others may mix up terms like zygote, sporophyte, and gametophyte between plant and animal life cycles. Keeping track of chromosome sets and when fusion or reduction happens helps avoid such mistakes.

Final Answer:
Syngamy results in the formation of a Diploid zygote.