How do cells multiply? - Cell division
Here’s the diagrammatic infographic comparing Plant Cell Division and Animal Cell Division — it visually breaks down the stages of mitosis and highlights the key differences in cytokinesis:
Click here to view the diagram
🌿 Plant Cell Division
- Mitosis Stages: Prophase → Metaphase → Anaphase → Telophase
- Cytokinesis: Formation of a cell plate that becomes the new cell wall
- Structure: Rigid cell wall guides division
- Example: Root tip cells dividing for growth
🐾 Animal Cell Division
- Mitosis Stages: Prophase → Metaphase → Anaphase → Telophase
- Cytokinesis: Formation of a cleavage furrow that pinches the cell in two
- Structure: Flexible cell membrane allows furrow formation
- Example: Skin cells dividing for healing
This visual makes it easy to compare how both types of cells go through similar mitotic stages but differ in how they physically split.
Would you like a simplified table or flashcards to help memorize the differences between plant and animal cell division for exams or quick revision?
Assessment statements
• Outline the stages in the cell cycle, including interphase (G1, S and G2), mitosis and cytokinesis.
• State that tumours (cancers) are the result of uncontrolled cell division and that these can occur in any organ or tissue.
• State that interphase is an active period in the life of a cell when many metabolic reactions occur, including proteinnsynthesis, DNA replication and an increase in the number of mitochondria and chloroplasts (in some plant cells).
• Describe the events that occur in the four phases of mitosis (prophase, metaphase, anaphase and telophase).
• Explain how mitosis produces two genetically identical nuclei.
• State that growth, embryonic development, tissue repair and asexual reproduction involve mitosis.
New cells are needed to replace cells which have died or to allow an organism to grow. Cells divide by a process known as mitosis, which is one phase of a series of events known as the cell cycle.
The cell cycle
The cycle of a cell’s life can be divided into three stages, as shown in
1 interphase
2 mitosis (division of the nucleus)
3 cytokinesis (division of the cytoplasm).
Interphase
During most of the life of a cell, it performs the task for which it has been
pre-programmed during diff erentiation. This period is called interphase.
Part of interphase is spent in preparation for cell division (the G2 phase)
and part of it is the period immediately after division (the G1 phase).
The two stages of cell division are the separation and division of the
chromosomes (mitosis), and the division of the cell into two daughter
cells (cytokinesis).
If a cell is examined during interphase using a light microscope, very
little activity is visible. The cell carries out its normal activities, but also
prepares itself for mitosis. The DNA in the chromosomes is replicated
(S phase) so that after cell division there will be exactly the same number
of chromosomes in the two daughter cells. Many proteins necessary
for the division need to be synthesised. The number of mitochondria
increases so that the respiratory rate can be rapid to provide energy for
cell division. In the case of plant cells with chloroplasts, the number of
chloroplasts increases so there are suffi cient for each daughter cell.
Mitosis
There are four distinct stages in mitosis, though the process is continuous,
with each stage running into the next. There are no intervals in between
stages. Figures 2.21 and 2.22 show in detail the stages of mitosis.
Prophase
During prophase, the chromosomes become visible. During interphase
they have been drawn out into long threads, allowing the cellular
machinery access to the genes. Now, the chromosomes coil several times
to produce a supercoil. The chromosomes appear shorter and thicker, and
can now be seen using a microscope. Each chromosome is composed
of two threads of DNA, the two identical copies that were made during
interphase. These two copies are called the sister chromatids and are
attached to each other at a place called the centromere. Also visible at this
time are structures known as centrioles, which move to opposite sides of
the cell as microtubules form between them. This structure is called the
spindle. As prophase draws to a close, the nuclear envelope breaks down.
Metaphase
Metaphase begins when the nuclear envelope has broken down. As it
disappears, more space is created so that the chromosomes can move into
position during their division. The sister chromatids align themselves on
the microtubules in the middle, or equator, of the spindle and are attached
by their centromeres.
Anaphase
During anaphase, the centromeres split and the sister chromatids pull
apart and move towards the centrioles at opposite sides, or poles, of the
cell as the spindle fi bres shorten. Each sister chromatid is now called a
chromosome again.
Telophase
Once the two sets of chromosomes reach their opposite poles, the spindle
fi bres break down and a nuclear envelope forms around each set of
chromosomes. At the same time, the chromosomes uncoil and become
invisible through a light microscope.
Following telophase, in animal cells, the plasma membrane pinches in
and the two new nuclei become separated. Eventually, during cytokinesis,
the two sides of the plasma membrane meet and two completely new
cells are formed. Each has a complete set of chromosomes, cytoplasm,
organelles and a centriole.
It is vital that these two new cells are genetically identical. Mitosis
allows an organism to grow more cells from the original fertilised egg
during development of an embryo. It also means an organism casn repair
injured tissue by replacing damaged cells, and make new cells to replace
old ones.
Many organisms reproduce themselves using mitosis. One example
is binary fi ssion in unicellular Amoeba, and budding in yeast is another.
Reproducing in this way is known as asexual reproduction as no
gametes are involved and the off spring are genetically identical to the
parent. Asexual reproduction is very common in the plant kingdom. For
example, strawberry plants produce runners that develop into genetically
identical new plants, and bulbs like lilies produce miniature bulbils that
grow into mature plants genetically the same as the parent.
Mitosis and tumours
In most cases, mitosis continues until a tissue has grown suffi ciently or
repairs have been made to damaged areas. But sometimes mitosis does not
proceed normally. Cell division may continue unchecked and produce
an excess of cells, which clump together. This growth is called a tumour.
Tumours can be either benign, which means they are restricted to that
tissue or organ, or malignant, where some of the abnormal cells migrate
to other tissues or organs and continue to grow further tumours there. In
animals, these abnormal growths are known as cancers and can take many
diff erent forms in diff erent tissues. If they are allowed to grow without
treatment they can cause obstructions in organs or tissues and interfere
with their functions. Cancer is caused by damage to genes, but it cannot
be thought of as a single disease because the gene damage can be caused
by diff erent factors. Mistakes in copying DNA, environmental factors that
cause damage or genetic predisposition as a result of inheritance can all be
important factors in causing cancer.
18 List the main stages of the cell cycle in order.
19 Name the stage of the cell cycle that:
a precedes mitosis
b follows mitosis
20 State the result of uncontrolled cell divisions.
21 Describe what happens in a cell during interphase.
22 List in order the four stages of mitosis.
23 State three uses of mitosis in plants and animals.
End-of-chapter questions
1 Prokaryotic cells diff er from eukaryotic cells because prokaryotic cells:
A have larger ribosomes
B have smaller ribosomes
C contain mitochondria
D have more than one nucleus (1)
2 The correct order of the stages in the cell cycle is:
A cytokinesis → mitosis → G1 → G2 → S
B mitosis → S → G2 → G1 → cytokinesis
C mitosis → G1 → G2 → S → cytokinesis
D cytokinesis → G1 → S → G2 → mitosis
3 Explain how the properties of phospholipids help to maintain the structure of the plasma membrane. (2)
4 Explain how the surface area to volume ratio infl uences cell size. (3)
5 a Some ions can move across the membrane by passive or active transport. Distinguish between active
transport and facilitated diff usion of ions. (2)
b Digestive enzymes leave the cell by exocytosis. Describe the process of exocytosis.
Cells multiply through several methods depending on whether they are prokaryotic or eukaryotic, and whether the organism reproduces asexually or sexually. Here’s a clear breakdown:
🦠 In Prokaryotic Cells (Bacteria, Archaea)
- Binary Fission
- Most common method.
- DNA replicates, the cell elongates, and then divides into two identical daughter cells.
- Budding (rare in bacteria)
- A small outgrowth develops and separates into a new cell.
🧬 In Eukaryotic Cells
Asexual Methods
- Mitosis
- Somatic (body) cells divide to produce two genetically identical daughter cells.
- Important for growth, repair, and maintenance.
- Budding (in yeast and hydra)
- A small bud grows on the parent cell/organism and eventually detaches.
- Fragmentation (in some fungi, algae, and simple animals)
- A piece of the organism breaks off and develops into a new individual.
- Vegetative Propagation (plants)
- New plants grow from roots, stems, or leaves without seeds.
Sexual Method
- Meiosis
- Produces gametes (sperm and egg cells) with half the chromosome number.
- Fusion of gametes during fertilization restores the full chromosome set.
- Ensures genetic variation in offspring.
📊 Quick Comparison
| Method | Organisms/Cells | Outcome |
|---|---|---|
| Binary Fission | Bacteria, Archaea | Two identical cells |
| Mitosis | Animal & plant somatic cells | Two identical cells |
| Meiosis | Gamete-producing cells | Four genetically unique cells |
| Budding | Yeast, Hydra | New organism from parent |
| Fragmentation | Fungi, algae, planaria | New organism from fragment |
| Vegetative Propagation | Plants | New plant from part of parent |
📌 Takeaway:
- Prokaryotes multiply mainly by binary fission.
- Eukaryotes use mitosis for growth and repair, meiosis for sexual reproduction, and other methods like budding or fragmentation in specific organisms.
Would you like me to create a diagram showing binary fission, mitosis, and meiosis side by side so you can visually compare these multiplication methods?
It looks like you’re asking about binary fission and binary fusion of cells — let’s break them down clearly:
🔬 Binary Fission
- Definition: A type of asexual reproduction where a single parent cell divides into two identical daughter cells.
- Process:
- DNA replication.
- Cell elongation.
- Division of cytoplasm.
- Formation of two identical cells.
- Where it occurs:
- Prokaryotes (bacteria like E. coli).
- Some unicellular eukaryotes (e.g., Amoeba, Paramecium).
- Key point: Produces genetically identical offspring, ensuring rapid population growth.
⚡ Binary Fusion (often confused with fission)
- Definition: Fusion means joining of two cells rather than splitting. It’s not a standard term in cell biology like “binary fission.”
- Examples of fusion processes:
- Gamete fusion (fertilization): Sperm cell fuses with egg cell to form a zygote.
- Cell fusion in tissue culture: Two different cells merge to form a hybrid cell (used in research).
- Viral fusion: Viruses fuse with host cell membranes to enter.
- Key point: Fusion is about combining cells, not dividing them.
📊 Quick Comparison
| Feature | Binary Fission | Binary Fusion |
|---|---|---|
| Process | One cell splits into two | Two cells merge into one |
| Type | Asexual reproduction | Fertilization, hybridization, or viral entry |
| Genetic Outcome | Identical daughter cells | Genetic mixing or hybrid cell |
| Examples | Bacteria (E. coli), Amoeba | Sperm + Egg → Zygote, cell culture fusion |
📌 Takeaway:
- Binary fission = division (splitting into two).
- Binary fusion = union (joining into one).
Would you like me to create a diagram showing binary fission vs binary fusion side by side so you can visualize the difference more easily?
The general term used for cell multiplication is cell division.
🔬 Types of Cell Division
Mitosis
- Occurs in somatic (body) cells.
- Produces two genetically identical daughter cells.
- Used for growth, repair, and maintenance.
Meiosis
- Occurs in reproductive cells (gametes).
- Produces four genetically unique daughter cells with half the chromosome number.
- Ensures genetic variation in sexual reproduction.
Binary Fission
- Common in prokaryotes (bacteria, archaea).
- One cell splits into two identical cells.
- Simple and rapid process.
📌 Summary
- The umbrella term is cell division.
- In prokaryotes, multiplication happens by binary fission.
- In eukaryotes, it happens by mitosis (growth/repair) and meiosis (sexual reproduction).
Would you like me to prepare a diagram showing mitosis, meiosis, and binary fission side by side so you can visually compare the three methods of cell multiplication?
Definition and Mechanism
- 2 Sources
Comparison with Budding
- Division type: Binary fusion produces two equal daughter cells, while budding forms an outgrowth (bud) that grows into a new organism.
- Parent identity: In binary fusion, the parent cell’s identity is lost as it divides; in budding, the parent remains largely intact.
- Symmetry: Binary fusion is symmetric; budding is asymmetric, with the offspring smaller than the parent.
- Speed: Binary fusion is generally faster than budding.
- Occurrence: Binary fusion occurs mainly in unicellular organisms, whereas budding can occur in both unicellular and multicellular organisms.
Biological Significance
In summary, binary fusion is a fundamental asexual reproduction mechanism that ensures genetic continuity and rapid proliferation, distinct from other methods like budding in its symmetry, speed, and cellular outcome.
🌱 Methods of Budding
1. Yeast Budding (Unicellular)
- A small bud forms on the parent yeast cell.
- The nucleus divides by mitosis.
- One nucleus migrates into the bud.
- The bud grows and eventually separates.
- Example: Saccharomyces cerevisiae (baker’s yeast).
2. Hydra Budding (Multicellular Animal)
- A bud develops on the parent Hydra due to repeated cell division at one site.
- The bud grows tentacles and a mouth.
- It detaches to become an independent Hydra.
3. Sponge Budding
- Sponges produce external buds that detach, or internal buds (gemmules) that survive harsh conditions and later develop into new sponges.
4. Plant Budding (Vegetative Propagation)
- A bud forms on the parent plant (e.g., potato tubers, onion bulbs).
- These buds grow into new plants under favorable conditions.
5. Budding in Protozoa
- Some protozoans reproduce by budding, where a small daughter cell forms and separates.
📊 Quick Comparison
| Organism Type | Example | Budding Method |
|---|---|---|
| Unicellular | Yeast | Small bud forms, nucleus divides, bud detaches |
| Multicellular Animal | Hydra | Bud grows into miniature Hydra, detaches |
| Sponges | Freshwater sponges | External buds or internal gemmules |
| Plants | Potato, Onion | Vegetative buds grow into new plants |
📌 Takeaway: Budding is a versatile method of multiplication seen in both unicellular and multicellular organisms. It ensures rapid reproduction and survival, especially in simple organisms.
Would you like me to create a diagram showing budding in yeast vs Hydra side by side so you can visualize both processes clearly?
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