Table of contents

1. Introduction to Biology2h 42m
2. Chemistry3h 37m
3. Water1h 26m
4. Biomolecules2h 23m
5. Cell Components2h 26m
6. The Membrane2h 31m
7. Energy and Metabolism2h 0m
8. Respiration2h 40m
9. Photosynthesis2h 49m
10. Cell Signaling59m
11. Cell Division2h 47m
12. Meiosis2h 0m
13. Mendelian Genetics4h 44m
14. DNA Synthesis2h 27m
15. Gene Expression3h 6m
16. Regulation of Expression3h 31m
17. Viruses37m
- Viruses
  37m
18. Biotechnology2h 58m
19. Genomics17m
- Genomes
  17m
20. Development1h 5m
21. Evolution3h 1m
22. Evolution of Populations3h 53m
23. Speciation1h 37m
24. History of Life on Earth2h 6m
25. Phylogeny2h 31m
26. Prokaryotes4h 59m
27. Protists1h 12m
28. Plants1h 22m
29. Fungi36m
- Fungi
  19m
- Fungi Reproduction
  17m
30. Overview of Animals34m
- Overview of Animals
  34m
31. Invertebrates1h 2m
32. Vertebrates50m
33. Plant Anatomy1h 3m
34. Vascular Plant Transport1h 2m
- Water Potential
  1h 2m
35. Soil37m
- Soil and Nutrients
  20m
- Nitrogen Fixation
  16m
36. Plant Reproduction47m
- Flowers
  33m
- Seeds
  14m
37. Plant Sensation and Response1h 9m
38. Animal Form and Function1h 19m
39. Digestive System1h 10m
- Digestion
  1h 3m
- Blood Sugar Homeostasis
  7m
40. Circulatory System1h 49m
41. Immune System1h 12m
42. Osmoregulation and Excretion50m
- Osmoregulation and Excretion
  50m
43. Endocrine System1h 4m
- Endocrine System
  1h 4m
44. Animal Reproduction1h 2m
- Animal Reproduction
  1h 2m
45. Nervous System1h 55m
- Neurons and Action Potentials
  1h 8m
- Central and Peripheral Nervous System
  46m
46. Sensory Systems46m
- Sensory System
  46m
47. Muscle Systems23m
- Musculoskeletal System
  23m
48. Ecology3h 11m
49. Animal Behavior28m
- Animal Behavior
  28m
50. Population Ecology3h 41m
51. Community Ecology2h 46m
52. Ecosystems2h 36m
53. Conservation Biology24m
- Conservation Biology
  24m

25. Phylogeny

Phylogeny

General Biology

25. Phylogeny

Phylogeny

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1:29 minutes

Problem 8

Textbook Question

If you were using cladistics to build a phylogenetic tree of cats, which would be the best choice for an outgroup?
a. Kangaroo
b. Leopard
c. Domestic cat
d. Iguana

Verified step by step guidance

Understand the concept of an outgroup: In cladistics, an outgroup is a species or group that is closely related to the group of interest (the ingroup) but not part of it. The outgroup serves as a reference point for determining the evolutionary relationships within the ingroup.

Identify the ingroup: In this problem, the ingroup consists of cats, which includes species like leopards and domestic cats. These are all members of the Felidae family.

Determine the characteristics of the options: Analyze the given options to see which one is least closely related to the ingroup. Kangaroos are marsupials, iguanas are reptiles, and leopards and domestic cats are both felids (members of the cat family).

Select the most distantly related option: The best outgroup is the one that is not part of the ingroup and is evolutionarily distant. Between kangaroo and iguana, consider which one is more distantly related to cats based on their evolutionary lineage.

Conclude the choice: Use the principle of evolutionary distance to finalize the outgroup. The outgroup should help clarify the evolutionary relationships within the ingroup by providing a point of comparison.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Cladistics

Cladistics is a method of classifying organisms based on shared derived characteristics, which are traits that are present in an organism but absent in its ancestors. This approach emphasizes the evolutionary relationships between species, allowing scientists to construct phylogenetic trees that depict these relationships. In cladistics, the goal is to group organisms into clades, which are branches that include a common ancestor and all its descendants.

Outgroup

An outgroup is a species or group of species that is closely related to the group being studied (the ingroup) but is not part of it. In phylogenetic analysis, the outgroup serves as a reference point to help determine the evolutionary relationships and characteristics of the ingroup. By comparing the ingroup to the outgroup, researchers can identify which traits are derived and which are ancestral, aiding in the construction of a more accurate phylogenetic tree.

Phylogenetic Tree

A phylogenetic tree is a diagram that represents the evolutionary relationships among various biological species based on their genetic or physical characteristics. The branches of the tree illustrate how species diverged from common ancestors over time. Understanding the structure of a phylogenetic tree is crucial for interpreting evolutionary history, as it provides insights into how different species are related and the timeline of their divergence.

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Related Practice

Textbook Question

If you were using cladistics to build a phylogenetic tree of cats, which of the following would be the best outgroup?

a. Wolf

b. Domestic cat

c. Lion

d. Leopard

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Textbook Question

You can use a 'one-snip test' to identify monophyletic groups—meaning that if you 'cut' any branch on a tree, everything that 'falls off' is a monophyletic group. Why is this valid?

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Textbook Question

In terms of structure, how do channel proteins differ from carrier proteins?

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Textbook Question

The relative lengths of the frog and mouse branches in the phylogenetic tree in Figure 26.13 indicate that:

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a. Frogs evolved before mice

b. Mice evolved before frogs

c. The homolog has evolved more rapidly in mice

d. The homolog has evolved more slowly in mice

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Textbook Question

Use the fossil evidence shown in Figure 25.6 to determine whether flight evolved earlier in insects or in birds. Is flight an example of homology or convergent evolution? Explain.

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Textbook Question

Which of the following could provide the best data for determining the phylogeny of very closely related species?

a. The fossil record

b. Their morphological differences and similarities

c. A comparison of nucleotide sequences in homologous genes and mitochondrial DNA

d. A comparison of their ribosomal DNA sequences

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Textbook Question

You have discovered an enzyme that appears to function only when a particular sugar accumulates. Which of the following scenarios would you predict to be responsible for activating this enzyme?

a. The sugar cleaves the enzyme to form the active conformation.

b. The sugar is an allosteric regulatory molecule for the enzyme.

c. The sugar is a competitive inhibitor for the enzyme.

d. The sugar phosphorylates the enzyme to form the active conformation.

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Textbook Question

Phylogenies are created based on the principle that all species descending from a recent common ancestor .

a. Should be identical

b. Should share characteristics that evolved in that ancestor

c. Should be found as fossils

d. Should have identical DNA sequences