Download The Mystery of the Red Panda Essential Question: What KINDS OF

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.
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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!
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