La meiosis reduce a la mitad; la fecundación lo restaura
| English | Español |
|---|---|
| meiosis/meɪˈəʊsɪs/ | meiosis |
| fertilisation/ˌfɜːtɪlaɪˈzeɪʃn/ | fecundación |
What would explain this observation?
- If gametes kept the ordinary body-cell chromosome number, fusion would double it each generation. Meiosis 减数分裂 solves that problem before fertilisation 受精.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- Cells in reproductive organs divide by meiosis to form gametes. Genetic information is copied and the cell divides twice, forming four gametes. Each has one set of chromosomes and the gametes are genetically different. GCSE Biology requires this overall account, not recall of named meiotic stages or detailed chromosome-exchange mechanisms.
- meiosis: Division producing gametes with one chromosome set; fertilisation: Fusion of gametes restoring the normal chromosome number.
Una especie modelo tiene 24 cromosomas en células ordinarias. ¿Qué número debería contener un gameto?
La fusión de dos gametos restaura el número normal de cromosomas en la nueva célula. La nueva célula se divide por mitosis, aumentando el número de células. A medida que se desarrolla el embrión, las células se diferencian y se especializan. Copiar el ADN antes de la división no significa que los gametos finales conserven dos juegos de cromosomas.
Asociar cada término técnico con su significado preciso.
Usar las definiciones para distinguir cantidades y procesos relacionados.
Choose evidence that can test it
- Fusion of two gametes restores the normal number of chromosomes in the new cell. The new cell divides by mitosis, increasing the number of cells. As the embryo develops, cells differentiate and become specialised. Copying DNA before division does not mean the final gametes keep two chromosome sets.
- Use coloured chromosome cards to represent sets, label a body cell and gamete clearly, and trace two gametes into one fertilised cell. Keep chromosome number separate from the number of cells. State that a simple card model demonstrates number conservation rather than all mechanisms producing variation.
¿Qué dos hábitos hacen que la investigación o modelo en este caso sean más defendibles?
Utilice tarjetas de cromosomas de colores para representar juegos, etiquete claramente una célula corporal y un gameto, y rastree dos gametos hacia una sola célula fecundada. Mantenga el número de cromosomas separado del número de células. Indique que un modelo simple de tarjetas demuestra la conservación numérica más que todos los mecanismos que producen variación.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: in a fictional species, an ordinary cell has 18 chromosomes. Each gamete has 9. Fertilisation combines 9+9 to restore 18; later mitosis maintains 18 in each ordinary daughter cell. Four gametes each having 9 means 36 chromosomes across four separate cells, not 36 within each gamete.
A fictional species has 32 chromosomes in ordinary cells. Find the number in a gamete. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
Una especie ficticia tiene 32 cromosomas en células ordinarias. Encuentra el número en un gameto.
El resultado es 16 cromosomas. Conocido: en una especie ficticia, una célula ordinaria tiene 18 cromosomas. Cada gameto tiene 9. La fecundación combina 9+9 para restaurar 18; posteriormente la mitosis mantiene 18 en cada célula hija ordinaria. Cuatro gametos que tienen cada uno 9 significan 36 cromosomas en cuatro células separadas, no 36 dentro de cada gameto.
Check the conclusion and its limits
- Meiosis does not make four identical ordinary body cells. Fertilisation is fusion rather than a division. The four-cell outcome is the specification’s overall model; detailed gamete development and stage names are outside this objective.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Fertilisation halves the chromosome number. This claim is false: Meiosis does not make four identical ordinary body cells. Fertilisation is fusion rather than a division. The four-cell outcome is the specification’s overall model; detailed gamete development and stage names are outside this objective.
Meiosis halves; fertilisation restores: Fusion of two gametes restores the normal number of chromosomes in the new cell. The new cell divides by mitosis, increasing the number of cells. As the embryo develops, cells differentiate and become specialised. Copying DNA before division does not mean the final gametes keep two chromosome sets.
La fecundación reduce a la mitad el número de cromosomas.
La meiosis no produce cuatro células corporales idénticas. La fecundación es una fusión, no una división. El resultado de cuatro células es el modelo general de la especificación; el desarrollo detallado de los gametos y los nombres de las etapas están fuera de este objetivo.
División que produce gametos con un solo juego de cromosomas: escribe el término técnico.
meiosis significa División que produce gametos con un solo juego de cromosomas.