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Unlock This CourseIonising radiation is a powerful force that can dramatically change living organisms. Unlike the harmless light from your phone screen, ionising radiation carries enough energy to knock electrons out of atoms, creating charged particles called ions. This process can seriously damage the building blocks of life - our DNA.
Understanding how radiation affects living things is crucial in our modern world. From medical X-rays to nuclear power plants, we encounter ionising radiation in many situations. Some organisms have even evolved amazing ways to survive in highly radioactive environments!
Key Definitions:
There are three main types: Alpha particles (stopped by paper), Beta particles (stopped by aluminium) and Gamma rays (need thick lead to stop them). Each type affects living tissue differently, with gamma rays being the most penetrating and dangerous.
When ionising radiation hits a living cell, it's like throwing rocks at a delicate watch mechanism. The radiation can damage cells in two main ways: direct damage and indirect damage.
Direct damage happens when radiation hits DNA molecules directly. Think of DNA as a twisted ladder - radiation can break the rungs or even snap the whole ladder in half. This creates breaks in the DNA strand that the cell must try to repair.
One side of the DNA ladder breaks. Cells can usually fix this quite easily, like repairing a broken shoelace.
Both sides of the DNA ladder break at the same spot. This is much harder to repair and often leads to cell death or mutations.
The chemical letters (bases) in DNA get changed, like changing an 'A' to a 'T' in a sentence. This can alter the genetic message.
Most radiation damage actually happens indirectly. Radiation hits water molecules in cells (remember, we're about 70% water!), creating highly reactive particles called free radicals. These free radicals then attack DNA and other important cell parts.
It's like radiation creating tiny molecular terrorists inside your cells. These free radicals bounce around, causing chaos until they're neutralised by the cell's defence systems or cause permanent damage.
After the 1986 Chernobyl nuclear disaster, scientists expected to find a wasteland. Instead, they discovered thriving populations of wolves, bears and other animals. While many show genetic mutations and shorter lifespans, some species have adapted remarkably well. Certain fungi even feed on radiation, breaking it down for energy - nature's incredible ability to adapt in action!
When cells can't properly repair radiation damage, mutations occur. These genetic changes can be passed on when cells divide, potentially leading to cancer or other health problems.
Cancer develops when normal cells transform into rapidly dividing, uncontrolled cells. Radiation can cause this transformation by damaging genes that normally control cell growth and division.
These genes normally help cells grow and divide in a controlled way. When radiation damages them, they can get stuck in the 'on' position, causing cells to divide uncontrollably - like a car accelerator that won't release.
These act like cellular brakes, stopping damaged cells from dividing. When radiation knocks out these genes, cells lose their ability to stop dividing when they should - like a car with broken brakes.
Different types of radiation exposure can lead to specific cancers. The risk depends on the radiation dose, the type of radiation and which parts of the body are exposed.
Blood cancer that develops when radiation damages bone marrow cells. Often the first cancer to appear after radiation exposure.
Common after exposure to radioactive iodine, especially in children. The thyroid gland concentrates iodine, making it vulnerable.
Can develop from external radiation exposure. UV radiation from the sun is actually a form of ionising radiation that causes skin cancer.
One of the most concerning effects of ionising radiation is its ability to cause genetic mutations that can be passed to future generations. When radiation damages reproductive cells (eggs and sperm), these mutations can affect offspring.
Understanding the difference between these two types of mutations is crucial for grasping radiation's long-term effects.
These occur in body cells and only affect the individual. Like getting a scar - it doesn't affect your children. Most radiation-induced cancers come from somatic mutations.
These occur in reproductive cells and can be passed to offspring. Like changing the blueprint that gets copied - all future generations might be affected.
Scientists have studied the children and grandchildren of atomic bomb survivors for over 70 years. Surprisingly, they found no significant increase in genetic defects in the children of survivors. This suggests that while high radiation doses can cause germline mutations, the human body's repair mechanisms are quite effective at preventing most hereditary damage.
Amazingly, some organisms have evolved ways to survive in highly radioactive environments. These adaptations show us how evolution can work even in the most extreme conditions.
Some organisms are naturally more resistant to radiation than others. Understanding these differences helps us learn about both evolution and potential medical treatments.
These microscopic 'water bears' can survive radiation doses 1000 times higher than what would kill humans. They have amazing DNA repair systems.
Some fungi near Chernobyl actually use radiation as an energy source, like plants use sunlight. They contain melanin that can harvest energy from gamma rays.
Famous for radiation resistance, they can survive doses 10 times higher than humans. Their cells divide more slowly, giving more time for DNA repair.
In areas with high natural radiation or after nuclear accidents, some populations have evolved increased resistance over just a few generations - evolution in fast-forward!
For example, some bird populations near Chernobyl now have higher levels of antioxidants in their blood, helping them cope with radiation damage. This shows how quickly natural selection can work when the pressure is strong enough.
Despite its dangers, ionising radiation has many beneficial uses in medicine and research. Understanding both the risks and benefits helps us use radiation safely and effectively.
Radiotherapy uses high-energy radiation to kill cancer cells. The trick is delivering enough radiation to destroy tumours while minimising damage to healthy tissue. Modern techniques can precisely target cancer cells.
X-rays, CT scans and nuclear medicine use small amounts of radiation to see inside the body. The benefits of early disease detection usually outweigh the small cancer risk from the radiation exposure.
A chest X-ray exposes you to about the same amount of radiation you'd get from natural background sources in 10 days. A CT scan is equivalent to about 2-3 years of background radiation. While these seem like large amounts, the medical benefits usually justify the small increased cancer risk.