Cell Division in Plants and Animals

Topic 2: Cell Division in Plants and Animals

  • Introduction
    • Exploration of the development, characteristics, processes, and interactions of living things.
    • Learning Outcome: Students will be able to investigate different tissues and organs of living things.

Cell Division Overview

  • Cells of living organisms divide and reproduce genetically in a process called cell cycle.
  • The cell cycle is critical in understanding how organisms grow and reproduce.

Key Terminology

  • Mitosis
  • Meiosis
  • Chromosomes
  • Cytokinesis
  • Hormone
  • Anastral
  • Amphiastral
  • Spindle
  • Phragmoplast
  • Gamete
  • Gametophyte

Phases of Cell Division

The Cell Cycle

  • Consists of four major phases:
    1. G1 Phase (Gap 1)
    • The cell evaluates the initiation of cell division.
    1. S Phase (Synthesis)
    • The cell synthesizes DNA and replicates its chromosomes.
    1. G2 Phase (Gap 2)
    • The cell checks the accuracy of DNA replication and initiates repairs if necessary.
    1. M Phase (Mitosis)
    • The actual division of the cell occurs during this stage.

Mitosis

  • Mitosis involves only one cell division composed of four major phases:
    1. Prophase
    2. Metaphase
    3. Anaphase
    4. Telophase
  • The genetic material (DNA) in a cell is duplicated and divided equally between two daughter cells.
  • Mitosis is essential for the replacement of dead or damaged cells and for cells with short life spans.
  • Somatic cells (non-sex cells such as fat cells, blood cells, skin cells) replicate by mitosis.
  • Mitosis takes place in both plant and animal cells, with the key difference occurring in cytokinesis.
    • In animal cells, a furrow or cleavage is formed leading to the formation of daughter cells.
    • In plant cells, due to the rigid cell wall, the formation of furrows does not occur.

Meiosis

  • Meiosis involves two successive divisions that result in a reduction of chromosome number.
  • It comprises two key stages:
    1. Meiosis I
    2. Meiosis II
  • Similar to mitosis, meiosis has the same basic phases but occurs with different events:
    • Meiosis generates gametes (sex cells) in organisms that reproduce sexually, where gametes contain half the number of chromosomes as the original diploid cell.
  • Genetic recombination occurs during meiosis, introducing new gene combinations into a population.
  • The meiotic cell cycle yields four genetically distinct cells, contrasting with the two genetically identical cells produced in mitosis.

Differences in Meiosis Between Plants and Animals

  • In animals, meiosis results in the formation of gametes (sperm and eggs).
  • In plants, meiosis leads to the formation of spores, which develop into gametophytes.

Important Concepts

  • Diploid and Haploid:
    • Diploid cells have two sets of chromosomes (one from each parent).
    • Haploid cells have one set of chromosomes.

Research and Background Information

  • Students should carry out research to understand cell division's importance to organisms, including how human cells divide starting from a fertilized egg.
  • Teachers may provide background information, featuring Anton van Leeuwenhoek’s discoveries with the microscope, enhancing students' understanding of cell structure and division.
  • Suggested resources include models of cell division for mitosis and meiosis, science journals, and online educational platforms to gain further insights into plant and animal cells.