Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
The Mystery of the Red Panda Essential Question: What KINDS OF EVIDENCE do scientists use to understand evolution? If you visited the bamboo forests of central China, you might be lucky enough to glimpse a black and white Giant Panda (Ailuropoda melanoleuca) lumbering through the trees. If you were even luckier, and looked closer, you might see a small, red brown, bushy-tailed Red Panda (Ailurus fulgens) sharing the same habitat and food source. With its thick, beautiful coat, its fluffy ringed tail, its dark, spectacled eyes and its playful nature, the Red Panda is a favorite of zoo-goers everywhere. However, this cute little creature has caused some major arguments among biologists. Is it truly a cousin of the Giant Panda? Is it evolutionarily more closely related to the American raccoon? Did it evolve from a red fox, or maybe a bobcat? When scientists try to answer evolutionary questions like this one, evidence. they examine FOUR major types of PAUSE - Tell your table partner, what you think this creature is most closely related to, and give ONE reason why! Homologous Structures: How many of your partners used evidence that had to do with the Red Panda’s traits (what it looks like)? When Darwin first published his theory of evolution, much of his evidence came from similarities in the body structures of different species. Animals with similar body plans probably shared a common ancestor. Similar structures that related species inherited from a common ancestor are called Homologous Structures. The pictures below show the bones of the forelimbs of four animals, a human, a cat, a whale, and a bat. The presence of the same bones in all forelimbs show that these species share at least one homologous structure, so we know they evolved from a common ancestor. But what can homologous structures tell us about our red panda mystery? The Red Panda has evolved a ‘thumb’ perfect for eating bamboo, just like a giant panda. But their overall body structure, adapted for climbing, seems more similar to a raccoon. We need more evidence! The Fossil Record: Darwin didn’t only use evidence from similarities between living creatures for his evolutionary theory. He also observed similarities between living species and their fossilized ancestors. A fossil is the preserved remains or traces of an organism that lived in the past. The Fossil Record is all the millions of fossils that scientists have collected so far. It shows us how life on earth has changed over time. The first animal species appeared around 540 million years ago, and according to the fossil record, new species have been emerging, evolving, and disappearing ever since. Similarities between living species and fossils show us what organisms’ ancestors looked like. What does the Fossil Record tell us about our friend the Red Panda? Well fossils of Red Panda ancestors have been found in its current habitat and even as far West as England. The most recent common ancestor shared by Red Pandas and Giant Pandas lived almost 40 million years ago, and it seems to have had a more recent common ancestor with raccoons and perhaps weasels. However, the evidence still wasn’t totally conclusive. \ Embryology: An Embryo is a unborn offspring in the early stages of development. Even though organisms like a turtle, a rat, and a chicken look very different when they are adults, early in their development they look very similar. Embryology is the study of the early development of different species. If embryos of different species look similar early on, it is evidence that these species shared a common ancestor. Embryology is good evidence for evolution in general, but it doesn’t provide specific enough evidence to help us understand the Red Panda’s evolution. One more form of evidence will be necessary! DNA: Similarities in development and in homologous structures are of course a result of similar DNA, which provides the instructions for building traits like the Red Panda’s ‘thumb’. Recently, in the last 50 years or so, scientists have been able to examine the DNA of different species. The more similar the DNA, the more closely species are related evolutionarily. Usually, when scientists look at DNA evidence, it matches with the evidence from homologous structures, fossils, and embryos. For example, Alligators and Crocodiles look very similar, and it turns out their DNA is very similar too! But sometimes looking at DNA brings surprises. For example, an elephant shrew looks like a mouse or gerbil, but its DNA is actually more closely related to elephant DNA! DNA evidence is currently the most reliable form of evidence we have for evolutionary relationships. So when scientists actually looked at Red Panda DNA, what did they find? Well, like most scientific answers, it was more complicated than expected, but it looks like the Red Panda is a living fossil! The debate is still going on, but it looks like the Red Panda evolved as a species before Bears or Racoons, and that the common ancestor they share was something in the mustelid or weasel family. The Red Panda is only distantly related to its neighbor the Giant Panda, despite sharing the same habitat and food source, but it took all four major forms of evolutionary evidence to settle the argument! Done? Pick up a notecard and write 3 study questions based on the article, 2 level ones and 1 level 2 (answers on back of card!)