Fossil sites often contain the jumbled bones of several animals, and paleontologists must determine which bone belongs to which animal. The 10 sets of jumbled letters that follow offer a less taxing challenge: Each pair of words contains the names of two animals that commonly occur in a given habitat or region (in parentheses). Can you unscramble the animals? For instance, the two creatures in A are clam and oyster.
A. stormy lace (coral reef) B. return hotel (pond) C. stomach law (rain forest) D. ok diagonal (Australia) E. supine angel (Antarctica) F. fragile info (African grassland) G. a robotic byte (coastal scrub) H. comical person (desert) I. redeem erosion (tundra) J. croaker county (deciduous forest)
Paleontologists study fossils to reconstruct not just individual creatures but the history of life on Earth. To help figure out how species are related, scientists use a method called cladistics, invented by Willi Hennig in 1950. For example, suppose you want to draw an evolutionary tree that includes fish, T. rex, dogs, monkeys, and humans. You might classify those animals based on a few characteristics: Do they walk? have hair? read? The results are tabulated below. Note: Using just these criteria, dogs aren't distinguished from monkeys.
Cladistics assumes that organisms that share a particular characteristic most likely evolved from a common ancestor. Organisms that do not have that characteristic belong on a different evolutionary branch, as shown in the simplified cladogram at right. The red dots show where the tree splits, based on the presence (or absence) of a given characteristic. For instance T. rex, dogs, monkeys, and humans all walk, while fish do not. All five animals could have shared a common ancestor before fish branched off.
Can you match each set of characteristics below with the corresponding cladogram?
1. Has four limbs. Has opposable thumbs.
2. Common household pet. Can be found in dinosaur museums.
3. Still alive today. Common household pet.
4. Hairy. Has a tail.
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