Why variation helps

The idea

If a niche is drastically altered, a population suited to it could be wiped out, but individuals carrying variations have some chance to survive; variation is thus useful for the survival of species over time.

Warmer water

A population of bacteria lives in temperate waters. Then the water becomes warmer because of global warming.

What do you think happens to the bacteria?

• Most die, but a few that resist heat survive
• All of them survive
• All of them die

Bacteria in warming water

Press Next step.

A chance to survive

If a niche changes a lot, a population suited only to the old niche could be wiped out. But if a few individuals have variations, they have some chance to survive. Variation cannot protect each individual, but in a population it helps the species continue.

If a niche is drastically altered, a population suited to it could be wiped out, but individuals carrying variations have some chance to survive. Variation is thus useful for the survival of species over time.

Notes

If a niche is drastically altered, variants may survive when the rest are wiped out, so variation is useful for the survival of species over time.

Check yourself

Water for a population of bacteria becomes much warmer. Which bacteria are likely to survive?

Why does variation help a species?

Which of these can change a niche, according to the book?

• All of them, equally. Most of the bacteria would die. Only the few heat-resistant variants survive.
• The few variants that resist heat — correct. Yes!
• The ones that look exactly like the others. Most of these bacteria would die. The few variants that resist heat are the ones that survive.
• It makes every individual safe. Variation does not protect every individual, but in a population it is useful for the survival of the species.
• It keeps the niche from ever changing. Niches can change for reasons beyond the control of the organisms, such as a rise in temperature.
• Some individuals with variations may survive when the niche changes — correct. Yes!
• A rise in temperature or a meteorite hit — correct. Yes!
• The organisms deciding to leave. The book says niches can change because of reasons beyond the control of the organisms.
• Their own DNA copying. The book names changes such as temperature, water levels or meteorite hits, which are beyond the organisms' control.