Learning from fish -- and other species

Not counting a broken heart, no human -- as far as we know -- can physically regrow a heart. But apparently a zebra fish can.

Recently, Science magazine reported an amazing fish story. After researchers cut out 20 percent of a zebra fish's heart, the fish's blood immediately started to clot. And amazingly, within a short time, heart muscle cells began to proliferate around the wound, eventually replacing the excised portion.

Since all life is of course governed by the DNA every living creature has within it, researchers are hopeful that someday they'll be able to understand the genetic underpinnings of the zebra fish's remarkable ability to regrow its own heart -- and apply that knowledge to damaged human hearts.

Which is one reason to take good care of all the living things on the planet. You never know when one might contain instructions for fixing something wrong with us.

Speaking of living things on the planet, ever wonder how many different kinds there are? Edward O. Wilson, Pulitzer-winning author, entomologist -- he studies ants -- and a guy a lot of people consider to be the father of conservation biology, wanted to know much the same thing.

Wilson estimates, based on a lifetime of research and gathering data from around the world, that the number of plant and animal species currently in existence is between 10 million and 13 million.

Here's a breakdown on some of that data:

Scientists believe that about 98 percent of the living bird species are known. In contrast, less than 1.5 percent of algae species are known. About one-third of all species are parasites.

Although the exact number is unknown, bacteria -- which have DNA -- probably outnumber all living things. An exact count is impossible given our present state of knowledge. But consider that a pinch of soil between your fingers contains as many as a million different kinds of bacteria, most of which are unknown.

Wilson estimates that roughly 13,000 new species pop into existence, or are newly discovered, every year. By means of contrast, he cites numerous scientific studies to come up with a rate of extinction. He concludes that between 1 percent and 10 percent of all species disappear each year. Wilson settles on a 6 percent rate of extinction.

In whole numbers, that would be between 100,000 to 1.3 million species disappearing every year.

So why should we care about any of this? Don't species go extinct all the time? Scientists estimate that during the last great die-off some 65 million years, up to 98 percent of all species kicked the bucket. Many scientists believe it took about 10 million years for species to recover and repopulate the planet after that die-off.

Most scientists agree that the three biggest reasons for species extinctions are loss of habitat, pollution and invasive species. The problem is, if humans reduce species habitat over the course of decades, as opposed to millions of years, then the birth of new species will have no place to occur.

Scientists refer to this as the "death of birth" among species. Which brings us back to the zebra fish.

As we unlock the genetic code connecting all life together, we see that nature has many strategies for survival scattered among millions of species. If, through our neglect, we lose big pieces of that code, it will be like losing some of the great works of literature or some of the best songs of musicians.

The ability of the zebra fish to repair its heart should perhaps give us pause. To look inside our hearts. And see what we can do to protect the mind-boggling diversity that shares the planet with us.

Phil Helfrich is a community outreach specialist with the Missouri Department of Conservation.