Reproduction & Development — Practice · Grade 10 Science

Chapter: Cell Division, Reproduction & Development

What this practice covers

By the end of Reproduction & Development you should be able to:

8 questions, numeric, multiple choice and written answer, each with a worked explanation.

Vocabulary used: gamete, zygote, development.

Problem 1

A diploid animal has 18 chromosomes. How many are in a normal gamete?
Answer and explanation

9 chromosomes

Meiosis halves the diploid count.

Problem 2

Which is needed for development beyond increasing cell number?
  1. Differentiation and organization
  2. All genes permanently switching off
  3. Loss of every membrane
  4. Elimination of all signals
Answer and explanation

Differentiation and organization

Cells must acquire coordinated roles and structures.

Problem 3

Can asexual descendants ever differ genetically?
Answer and explanation

Yes. Mutations and other genome changes can introduce differences.

Problem 4

Why does a multicellular embryo need cell signaling as well as cell division? Explain the reasoning in your own words.
Answer and explanation

Signaling organizes specialized tissues rather than only a larger pile of cells.

Division increases cell number.

Signals help coordinate which cells differentiate, move or grow in particular locations.

Response criteria

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

Problem 5

What is one biological advantage of sexual reproduction for variation? Show the reasoning, not just the conclusion.
Hints

Increasing cell number alone does not explain tissue pattern.

Answer and explanation

Combining alleles from parents and meiotic processes generates new genetic combinations.

Problem 6

Does a developmental outcome depend only on DNA sequence?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

No. Gene regulation, cellular interactions and environmental conditions also influence development.

Problem 7

Development coordinates cell state with spatial organizationDevelopment coordinates cell state with spatial organizationPosition, signals and gene regulation influence cell fateStructure formation combines differentiation, movement and selective loss.
Original positional cell-state model; colors denote illustrative states rather than actual germ layers or a measured signal gradient.
Interpret the supplied visual. Does a positional difference in cell fate necessarily imply a mutation occurred at that location?
Answer and explanation

No. Different signals and regulatory states can change development without changing the underlying DNA sequence.

A developmental signal affects cell behavior in a spatial and temporal context. Different positions can expose otherwise related cells to different inputs, changing gene expression and fate. Morphogenesis is formation of biological shape through coordinated growth, movement, interactions and sometimes regulated cell loss. It is not only making more cells, and it does not mean DNA is deliberately rewritten in every location. The resulting structure needs functional relationships among tissues, so interpret cell markers together with position and behavior.

No. Different signals and regulatory states can change development without changing the underlying DNA sequence.

Response criteria

  • Read the structures, axes, directions and units correctly.
  • Connect the evidence with the biological mechanism.
  • Respect stated model assumptions and distinguish an observation from a further inference.

Problem 8

A supplied embryo model divides from 1 to 8 cells while total material is initially comparable. Explain cell number versus size, and how different cell fates could arise without new mutations.
Answer and explanation

Cleavage partitions material among more, smaller cells rather than requiring eightfold growth. Positional signals and gene regulation can change cell fate without new DNA-sequence changes; structure/function evidence must test those outcomes.

Cleavage partitions material among more, smaller cells rather than requiring eightfold growth. Positional signals and gene regulation can change cell fate without new DNA-sequence changes; structure/function evidence must test those outcomes.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the biological mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

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