• Question: how come trees and turtles out live us?

    Asked by elizabethlee to Andrew, Ash, Gem, Paige, SJ on 28 Jun 2012.
    • Photo: SarahJayne Boulton

      SarahJayne Boulton answered on 28 Jun 2012:

      Hey Elizabeth, another great question!!

      Have you ever heard of the Rate of Living Theory of Ageing? It’s one of the thing’s I’m working on at the moment. The theory is that if an organism lives really fast, consuming lots of energy and making their cell’s batteries (the mitochondria) generate a lots of stress in a short space of time then they will not live very long. The rate at which an organism turns over energy is called it’s metabolism. Compared to humans a mouse has a very high metabolism, and only lives about 2 years, whereas a giant tortoise has a very low metabolism and can live for nearly 200 years!!

      Trees are a bit different to us (duh!) and they have different metabolic demands as they generate a lot of their own food by photosynthesis. Regardless, trees grow very slowly, and lots of them get rid of their stress damaged parts by shedding their leave and bark. This gives trees really good mechanisms for dealing with the stress caused by their metabolism.

      So it’s possible that lifespan is all to do with metabolism!

      There are lots of other factors to consider though like activity and diseases, and at this stage the rate of living theory is literally just a theory at this stage, but it’s pretty much the best explanation we’ve got at the minute!!
      Otherwise, no-one really knows!?

    • Photo: Paige Brown

      Paige Brown answered on 29 Jun 2012:

      Great question! I agree with SJ that it is all about metabolism… The human body has SO many different parts and molecules, complex DNA structure which has to be fixed of mutations every second of the day, beating hearts made of soft tissues, and high metabolism compared with tortoises.

      “Every species has its own “life history,” or schedule according to which it passes on its genes to the next generation. Some animals invest their time and energy in having lots of babies while they’re young; others use their resources to live longer.” http://www.slate.com/articles/news_and_politics/explainer/2006/03/why_do_giant_tortoises_live_so_long.html

      Stress is also a large part of humans lower lifespan that turtles, for example. Humans put stress on their bodies ALL the time, from eating unhealthy things, to getting lots of sunlight that can potentially harm our DNA (that is why you should always wear sunscreen!), to stressing our hearts with hard labor. Turtles, well… they don’t work too hard! Between their slow reptilian metabolisms, lack of predators and lack of stress, they can live a LONG time! Trees are similar in that they have VERY slow metabolism… they don’t even have to move around! But stresses on the trees, like air pollution, can actually limit the lifespan of trees to around 100 years… same as us!

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