Binary fission may be as old as the very first forms of life – over 3.5 billion years old. However, the process has remained unchanged ever since then. Read on to explore binary fission in bacteria and amoeba reproduction in detail.
Binary Fission Definition
“Binary fission is a form of asexual reproduction in which an organism divides into two, each part carrying one copy of genetic material.”
What is Binary Fission?
Binary fission is a type of asexual reproduction typically observed in prokaryotes and a few single-celled eukaryotes. In this method of asexual reproduction, there is a separation of the parent cell into two new daughter cells. This process happens with the division and duplication of the parent’s genetic matter into two parts. Here, each daughter cell receives one copy of its parent DNA.
It is a primary method of reproduction in prokaryotic organisms. Binary Fission occurs without any spindle apparatus formation in the cell. In this process, the single DNA molecule begins replication and then attaches each copy to various parts of the cell membrane. When the cell starts to get drawn apart, the original (actual) and replicated chromosomes get apart.
However, asexual mode of reproduction has a significant drawback. All resultant cells are genetically identical, mirror copies of each other and the parent cell. Most antibiotics work on this principle. If a parent cell is vulnerable to an antibiotic, then all resultant daughter cells are vulnerable too. If a mutation occurs in their genes, then it can render a particular strain resistant to antibiotics.
Prokaryotes such as E. coli, Archaea as well as eukaryotes such as euglena reproduce through binary fission.
Binary fission is a form of cell division in eukaryotes. In prokaryotes, it is a form of asexual reproduction
Binary Fission in Bacteria
The process of binary fission is usually rapid, and its speed varies among species. The time required by bacteria to double the number of cells it has is called doubling time. Furthermore, each species requires specific conditions for its growth. These conditions include pH levels, temperature, oxygen, light, moisture, osmotic pressure.
For instance, mesophiles thrive at moderate temperatures ranging from 20 °C to 45 °C. The ambient temperature of the human body is 37 °C, which means many of the disease-causing bacteria are mesophiles. Mycobacterium tuberculosis is the bacterium that causes tuberculosis in humans. It divides every 15 to 20 hours, which is very slow when compared to other pathogenic bacteria such as Escherichia coli, which can divide every 20 minutes.
On the other end of the spectrum are the extremophiles. These bacteria can survive extremely harsh conditions such as high temperatures, high salinity, highly acidic environments and more. For instance, the Deinococcus radiodurans is an extremophilic bacteria that can survive a thousand times more radiation than a person can. Under normal circumstances, it can divide every 48 hours. However, when exposed to harsh conditions like drought, it can slow down its growth rate until more favourable conditions arise.
Read more: Bacteria
The steps involved in the binary fission in bacteria are:
Step 1- Replication of DNA
The bacterium uncoils and replicates its chromosome, essentially doubling its content.
Step 2- Growth of a Cell
After copying the chromosome, the bacterium starts to grow larger in preparation for binary fissions. It is followed by an increase in cytoplasmic content. Another prominent trait of this stage is that the two strands migrate to opposite poles of the cell.
Step 3-Segregation of DNA
The cell elongates with a septum forming at the middle. The two chromosomes are also separated in this phase.
Step 4- Splitting of Cells
A new cell wall is formed at this phase, and the cell splits at the centre, dividing the parent cell into two new daughter cells. Each of the daughter cells contains a copy of the nuclear materials as necessary organelles.
Amoeba Reproduction-Binary Fission in Amoeba
Amoeba is a unicellular organism, and just like bacteria, it reproduces through binary fission. After replicating its genetic material through mitotic division, the cell divides into two equal-sized daughter cells. In this method, two similar individuals are produced from a single parent cell. An amoeba that is about to undergo division grows larger, and eventually, its nucleus extends and divides into two. The division of cytoplasm follows the division of the nucleus. So, two amoebae are produced from a single parent, and the parent’s identity is technically “lost.”
Read More: Nutrition in Amoeba
To know more, watch the video given below:
Amoeba reproduces asexually through binary fission. In this process, an individual divides itself into two daughter cells. These are genetically identical to each other.
Similarities:
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- During binary fission as well as mitosis, chromosomes are copied before a cell divides and forms two new daughter cells.
Differences:
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- Mitosis is a process of cell division, observed in all eukaryotes -organisms with a true nucleus.
Binary fission is a process of asexual reproduction carried out by all prokaryotes- organisms without a true nucleus as well as in some eukaryotes.
- Mitosis is a process of cell division, observed in all eukaryotes -organisms with a true nucleus.
Listed below are different types of Binary fission:
- Simple Binary fission
- Longitudinal Binary fission
- Oblique Binary fission
- Transverse Binary fission
Explore more about binary fission in bacteria and amoeba, or other related topics by registering at BYJU’S. Alternatively, discover more interesting topics in biology on BYJU’S Biology.
Further Reading:
- Gram Positive Bacteria
- Gram Negative Bacteria
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Sexual reproduction is the combination of (usually haploid) reproductive cells from two individuals to form a third (usually diploid) unique offspring. Sexual reproduction produces offspring with novel combinations of genes. This can be an adaptive advantage in unstable or unpredictable environments. As humans, we are used to thinking of animals as having two separate sexes—male and female—determined at conception. However, in the animal kingdom, there are many variations on this theme.
Hermaphroditism occurs in animals where one individual has both male and female reproductive parts. Invertebrates such as earthworms, slugs, tapeworms and snails, shown in Figure 24.5, are often hermaphroditic. Hermaphrodites may self-fertilize or may mate with another of their species, fertilizing each other and both producing offspring. Self fertilization is common in animals that have limited mobility or are not motile, such as barnacles and clams.
Mammalian sex determination is determined genetically by the presence of X and Y chromosomes. Individuals homozygous for X (XX) are female and heterozygous individuals (XY) are male. The presence of a Y chromosome causes the development of male characteristics and its absence results in female characteristics. The XY system is also found in some insects and plants.
Avian sex determination is dependent on the presence of Z and W chromosomes. Homozygous for Z (ZZ) results in a male and heterozygous (ZW) results in a female. The W appears to be essential in determining the sex of the individual, similar to the Y chromosome in mammals. Some fish, crustaceans, insects (such as butterflies and moths), and reptiles use this system.
The sex of some species is not determined by genetics but by some aspect of the environment. Sex determination in some crocodiles and turtles, for example, is often dependent on the temperature during critical periods of egg development. This is referred to as environmental sex determination, or more specifically as temperature-dependent sex determination. In many turtles, cooler temperatures during egg incubation produce males and warm temperatures produce females. In some crocodiles, moderate temperatures produce males and both warm and cool temperatures produce females. In some species, sex is both genetic- and temperature-dependent.
Individuals of some species change their sex during their lives, alternating between male and female. If the individual is female first, it is termed protogyny or “first female,” if it is male first, its termed protandry or “first male.” Oysters, for example, are born male, grow, and become female and lay eggs; some oyster species change sex multiple times.
Summary
Reproduction may be asexual when one individual produces genetically identical offspring, or sexual when the genetic material from two individuals is combined to produce genetically diverse offspring. Asexual reproduction occurs through fission, budding, and fragmentation. Sexual reproduction may mean the joining of sperm and eggs within animals’ bodies or it may mean the release of sperm and eggs into the environment. An individual may be one sex, or both; it may start out as one sex and switch during its life, or it may stay male or female.
- Which form of reproduction is thought to be best in a stable environment?
- asexual
- sexual
- budding
- parthenogenesis
- Which form of reproduction can result from damage to the original animal?
- asexual
- fragmentation
- budding
- parthenogenesis
- Which form of reproduction is useful to an animal with little mobility that reproduces sexually?
- fission
- budding
- parthenogenesis
- hermaphroditism
- Genetically unique individuals are produced through ________.
- sexual reproduction
- parthenogenesis
- budding
- fragmentation
- Why is sexual reproduction useful if only half the animals can produce offspring and two separate cells must be combined to form a third?
- What determines which sex will result in offspring of birds and mammals?
Answers
- A
- B
- D
- A
- Sexual reproduction produces a new combination of genes in the offspring that may better enable them to survive changes in the environment and assist in the survival of the species.
- The presence of the W chromosome in birds determines femaleness and the presence of the Y chromosome in mammals determines maleness. The absence of those chromosomes and the homogeneity of the offspring (ZZ or XX) leads to the development of the other sex.