Exam 23: Evolutionary Patterns: Phylogeny and Fossils

You have found fossils of a new species of ape that walks upright. After 11 additional years in the field you discover a fossil of what you think is the common ancestor of the new species of ape and all other gorillas. What types of data would give you the BEST information on the environment of this ancestral organism?

The phylogeny below shows: (left to right) Zoonar/K. Jorgensen/age fotostock; S Sailer/A Sailer/age fotostock; J & C Sohns/age fotostock; Michael Dick/ Animals Animals-Earth Scenes; FLPA/Jurgen & Christi/age fotostock; Yellow Dog Productions/Getty Images.

Examine the following table of characters in four different species of flower. Based on the matrix, which character defines a synapomorphy shared by species A and B? Species A Species B Species C Species D Presence of sepals yes yes yes no Number of petals five five ten ten Arrangement of petals whorled whorled whorled whorled Number of carpels ten ten ten five

The specific types of homologies used to develop phylogenies are shared derived characters or:

The half-life of ¹⁴C is 5730 years. If a sample contained 100% ¹⁴C and 0% ¹⁴N at a point in time 17,190 years ago, then what percentage of ¹⁴C would it contain today?

In 2027, an unmanned rover lands on Mars, scoops pieces of ancient sedimentary rock into its interior, and then makes careful chemical analyses. Back on Earth, scientists are astonished to find that the rocks contain traces of RNA, much like that in ribosomes. Some of the scientists conclude that the rover has found evidence of Martian life, while others interpret the presence of RNA as evidence that the rover was contaminated by microorganisms on Earth before launch. Statements 1-4 below list four possible outcomes of a molecular phylogenetic test of the two hypotheses. Rank the outcomes in order of INCREASING support for the hypothesis that life originated independently on Earth and Mars. 1) The RNA found by the rover has no close resemblance to that found in terrestrial organisms. 2) Molecular phylogenetic analyses place the Martian RNA close to that of the bacterium E. coli. 3) Molecular phylogenetic analyses place the Martian RNA as a sister group to all known RNAs of bacteria, archaea and eukaryotes. 4) Molecular phylogenetic analyses place the RNA near the bottom of the bacterial branch of the tree of life.

The remarkable fossil of the "fishapod," Tiktaalik, which lived about 375 million years ago, is a beautiful example of an intermediate form, having the attributes of both fish (scales, fins) and tetrapods (a flat head, mobile neck). The presence of Tiktaalik and other fossils of other organisms that lived around the same time shows clear evidence that tetrapods were derived from fish, implying that the grouping "fish" is paraphyletic. Imagine now that there was no fossil record. Would it still be possible to determine whether or not "fish" is paraphyletic?

According to the fossil record, when did the earliest animals appear on Earth?

The phylogeny below was generated using molecular data. C is the node representing the common ancestor of humans and chimpanzees; B is the node representing the common ancestor of the cow and human/chimpanzee lineages; A is the node representing the common ancestor of the salmon and cow/human/chimpanzee lineages. Imagine that a researcher is interested in finding the approximate dates of A, B, and C. Give two approaches that would help resolve the timing of the nodes in the phylogeny.

You are given a character matrix for four different taxa showing character states for eight different morphologic characters. How many alternative phylogenetic hypotheses can be generated with the four taxa?

Based on the phylogenetic tree in Fig. 23.22, what character did the last common ancestor of both reptiles and mammals NOT possess?

Examine Figure 23.2 below. According to the figure, the closest relatives of turtles are:

The same intron was sequenced from five different taxa (taxa A-E) whose evolutionary relationships are disputed. The data matrix given shows six variable sites (1-6 in left column) in the DNA sequences obtained from each of the five species. Taxon A serves as the outgroup for this analysis. taxon tax n tax n taxon taxon 1 2 3 4 5 6 Which of the phylogenies below explains the relatedness between these taxa with the FEWEST evolutionary steps?

When comparing trees with various hypotheses of evolutionary relationships among a group of animals, the tree with _____ changes would be the preferred candidate.

Examine Figure 23.2 below. If we defined a taxon to include only the coelacanths and lungfish but not their most recent common ancestor, it would be a _____ group.

According to Figure 23.2 below, the most recent common ancestor of a bird and a turtle is also the most recent common ancestor of a bird and which other group?

You find a fossil that you think is about 350 million years old. You decide to use ²³⁵U to date a volcanic ash bed just below the key specimen. If you are correct, what approximate percentage of the original ²³⁵U would you expect to remain in your sample?

Phylogenetic reconstruction based on shared derived characters is called:

Which of the following character states would be MOST helpful in identifying sister groups?

Which of the following statements is TRUE regarding a phylogenetic tree?