LS7B Week 6

A taxon that includes a single common ancestor and all its descendants is a _____ group.

monophyletic

Of the following taxonomic categories, which is the MOST inclusive?

class

Traditional levels of taxonomy are nested in categories from least to most inclusive. This same relationship is also represented on a phylogenetic tree by moving from the terminal (most recent) nodes to the earliest nodes.

True

The nodes on a phylogenetic tree represent:

common ancestors.

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

Phylogenetic trees could be considered physical representations of hypotheses―those that seek to establish the evolutionary relationships between different organisms.

Seals and penguins both have streamlined body forms that allow them to move through water efficiently. This similarity in body shape is MOST likely the result of:

convergent evolution.

Imagine that a scientist discovers a new, flying species of mammal that resembles a winged rabbit. What can the scientist say about this organism?

If molecular sequence data show that bats and this new species share a common ancestor not shared by other mammals, the wings of these two species would be considered homologous.

Traits that are similar in two species as a result of common ancestry are referred to as:

homologous.

Based on Figure 23.7, which of the following are examples of convergent evolution?

wings in birds and bats

The nodes on a phylogenetic tree represent:

common ancestors.

Phylogenetic trees represent hypotheses about the evolutionary relationships among groups of organisms.

True

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?

crocodile

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

synapomorphies.

Characters that are similar because of descent from a common ancestor are:

homologous.

Which of the following is MOST likely to fossilize?

a crayfish that died in its muddy burrow by a creek

Mass extinctions:

All of these choices are correct.

The LARGEST mass extinction occurred at the end of which period?

Permian

Why is the fossil record of marine life more complete than that of organisms living in terrestrial ecosystems?

Marine habitats are places where sedimentation is more likely than erosion.

Fossils’ contributions to phylogenetic trees include:

All of these choices are correct.

What is the FIRST event in the fossilization process?

burial of the organism by sediments

The discovery of Tiktaalik roseae was significant for which of the following reasons?

It provided evidence that terrestrial vertebrates are descended from fish.

We expect the fossil record to be incomplete for all of the following reasons EXCEPT:

All biomolecules, including lipids and pigment molecules, decay immediately after death.

Data from phylogenies based on living organisms and data from the fossil record are in agreement when the tree of life is examined as a whole, but are often contradictory when individual branches are examined.

False

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

mammary glands

Evolution’s patterns manifest as nested similarities nesting occurs between molecular sequences of evolutionarily related organisms, and between the different taxa arranged in a phylogenetic tree.

True

Why is agreement between the fossil record and phylogenies constructed from living organisms considered to be strong evidence of evolution?

It is unlikely that two independent methods of investigation would result in the same pattern by chance alone.

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

580 million years ago

When several possible phylogenetic trees can be produced from a data set, the MOST parsimonious tree is the one that shows the:

smallest number of evolutionary changes.

How do fossils provide evidence of evolutionary history?

Fossils provide a record of extinct species.

Imagine that a researcher has created two possible phylogenetic trees for a group of organisms―one that hypothesizes that five character changes occurred in a given group, and one that predicts only two character changes occurred in the same group. If the researcher wants to choose a phylogenetic tree based on parsimony, she will pick the phylogenetic tree with two character changes as her working hypothesis.

True

The fossil record is often used to infer phylogenetic history. Which of the statements accurately supports this assumption?

Events that occur early in the fossil record are represented by branching events nearer to the root of a phylogenetic tree.