Fertilization — Science definition

Defined in 2 courses:

Where it is taught

In use

When a haploid sperm (23) later fertilizes a haploid egg (23) at fertilization, the full diploid number of 46 is restored — half from each parent — and the cycle can begin again in the next generation.

Meiosis & Sexual Reproduction

Questions using fertilization

Problem 1

Is fertilization the same event as every later cell division?
Answer and explanation

No. Fertilization combines gametes; later divisions and development produce and organize cells.

Problem 2

Explain why meiosis (followed by fertilization) keeps a species' chromosome number constant from one generation to the next.
Answer and explanation

Meiosis halves the chromosome number when it makes gametes, so each gamete carries only one set. When two gametes join at fertilization, the two halves add back up to the full number, keeping it constant instead of doubling each generation.

Problem 3

A species has diploid number 16. What is the normal gamete number and zygote number after fertilization? Explain the reasoning in your own words.
Answer and explanation

Gametes have 8 chromosomes; the zygote has 16.

The gamete has one set, half of 16: 8.

Two normal gametes combine: 8+8=16.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

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