1. Chapter 18 Organizing Information About Species

2. 18.1 Bye Bye Birdie
Huge migratory flock of Asian finches caught up in wind storm
Blown 7,000 miles across the open ocean to the Hawaiian archipelago
Enough individuals survived to found a new population
Adaptive radiations gave rise to Hawaiian honeycreepers

3. Bye Bye Birdie Human habitation of the Hawaiian islands
Polynesians arrived around 1,000 A.D.
Europeans arrived in 1778
Conditions changed to threaten bird survival
Forests cleared to grow imported crops
Predators of the bird population introduced
Malaria, rats, and mongooses

4. Bye Bye Birdie Honeycreepers had lost defensive traits
At least 43 species became extinct by 1778
Another 43 species have become extinct since then, despite conservation efforts begun in the 1960s
Of 18 species that remain, only 2 are not in danger of extinction

5. Figure 18.1 Three honeycreeper species: going, going, gone.
A A Palila (Loxioides bailleui ) feeds on the seeds of the mamane plant, which are toxic to most other birds. The one remaining Palila population is declining because mamane plants are being trampled by cows and gnawed to death by goats and sheep. About 2,176 Palila remained in 2012.
Figure 18.1 Three honeycreeper species: going, going, gone.
B The unusual skewed bill of the Akekee (Loxops caeruleirostris) allows this bird to easily pry open buds that harbor insects. Avian malaria carried by mosquitoes to higher altitudes is decimating the last population of this species. In 2008, about 3,111 remained.
C This male Poouli (Melamprosops phaeosoma)—rare, old, and missing an eye—died in 2004 from avian malaria. There were two other Poouli alive at the time, but neither has been seen since then.
(A) © Eric VanderWerf/Pacific Rim Photos; (B) © JCourtesy of © Lucas Behnke; (C) Bill Sparklin/Ashley Dayer.

6. 18.2 Phylogeny
Phylogeny: the evolutionary history of a species or group of species
Character
A quantifiable, heritable trait
Examples: number of segments in a backbone

7. Phylogeny Traditional classification schemes
Group organisms based on shared characters
Do not necessarily reflect evolutionary history
Evolutionary biologists determine common ancestry by looking for derived traits
Derived traits are characters present in a group but not in its ancestors
EX: 4 limbs…did all organisms have 4 limbs?

8. Phylogeny Clade Cladistics Group sharing one or more derived traits
Each species is a clade
A hypothesis based on the available information
Cladistics
Making hypotheses about evolutionary relationships among clades
Method: when there are several possible ways a group of clades can be connected, the simplest is probably the correct one (Occam’s Razor)

10. Cladistics Parsimony analysis Evolutionary tree
Process of finding the simplest pathway
Identify path in which defining derived traits evolved the fewest number of times
Evolutionary tree
Diagram of evolutionary connections
Called a cladogram
Each line represents a lineage
Node is a point of branching into two lineages called sister groups

11. multicellular with a backbone
earthworm tuna
A Evolutionary connections among clades are represented as lines on a cladogram. Sister groups emerge from a node, which represents a common ancestor.
lizard
mouse human
earthworm
multicellular
tuna
multicellular with a backbone
lizard
multicellular with a backbone and legs
mouse
multicellular with a backbone, legs, and hair
Figure 18.3 An example of a cladogram.
human
B A cladogram can be viewed as “sets within sets” of derived traits. Each set (an ancestor together with all of its descendants) is a clade.

13. 18.3 Comparing Form and Function
Clues used to piece together history
Fossils
Body form and function of organisms alive today
Homologous structures
Body parts that appear in separate lineages
Evolved in a common ancestor
May be used for different purposes
Same genes involved in development

14. 2 1 3
pterosaur 4 1 2
chicken 3 2 3
penguin 1 2 3 1 4
stem reptile 5
porpoise
2 3 4 5 1 2
Figure 18.4 Morphological divergence among vertebrate forelimbs, starting with the bones of an ancient stem reptile. The number and position of many skeletal elements were preserved when these diverse forms evolved; notice the bones of the forearms. Certain bones were lost over time in some of the lineages (compare the digits numbered one through five). Drawings are not to scale.
bat 3 4 1 5 2 3 4 5
human 1 2 3 4 5
elephant

15. Morphological Divergence
Evolutionary pattern that changes the body form from a common ancestor
Example: limb bones of vertebrate animals
Stem reptiles crouched low to ground on five-toed limbs
Five-toed limbs became adapted to different purposes
Flight in birds and bats
Flippers in penguins and porpoises
Support weight in elephants
Disappeared in snakes

16. Morphological Convergence
Body parts that appear similar in different species
Not always homologous
May have evolved independently subject to the same environmental pressures
Called analogous structures
Examples: bird, bat, and insect wings

17. Figure 18. 5 Morphological convergence in animals
Figure 18.5 Morphological convergence in animals. The surfaces of an insect wing, a bat wing, and a bird wing are analogous structures. The diagram shows how the evolution of wings (red dots) occurred independently in three separate lineages.
Insects wings
Bats wings
Humans Birds Crocodiles
wings
limbs with 5 digits
ancient common ancestor
© 2016 Cengage Learning, photo, © iStockphoto.com/DanCardiff, © Taro Taylor, © Alberto J. Espiñeira Francés - Alesfra/Getty Images

18. Morphological Convergence
Example: American cacti and African euphorbias
Similar external structures adapt plants to desert environments
Pleated structure allows plants to swell to store water and contract when water is used
Branching Stems Covered In Longitudinal Ribs
Smaller leaves And Short Spines
Spreading, Shallow, Fibrous Root System
Water Storage System - Succulent Stems
Crassulacean Acid Metabolism (CAM)

19. 18.4 Comparing Biochemistry
Mutations change a genome’s DNA sequence over time
Most mutations are neutral
DNA altered independently of other lineages
Genomes of closely related species
More similar to one another than distantly related species

20. DNA and Protein Sequence Comparisons
Biochemical comparisons
Used together with morphological comparisons to provide data for hypotheses about shared ancestry
Closely related species tend to have more similar proteins
Number of amino acid differences
One measure of relatedness
Another clue: which amino acids differ

21. honeycreepers (10)
song sparrow
Gough Island finch
deer mouse Asiatic black bear
bogue (a fish)
Human
thale cress (a plant)
baboon louse
baker’s yeast
Figure 18.6 Example of a protein comparison. Here, part of the amino acid sequence of mitochondrial cytochrome b from 20 species is aligned. This protein is a crucial component of mitochondrial electron transfer chains. The honeycreeper sequence is identical in ten species of honeycreeper; amino acids that differ in the other species are shown in red. Dashes are gaps in the alignment.

22. DNA and Protein Sequence Comparisons
Proteins for species that diverged relatively recently may have identical amino acid sequences
Examine nucleotide sequence for differences
Nucleotide comparisons
Use DNA from nuclei, mitochondria, or chloroplasts

23. DNA and Protein Sequence Comparisons
Mitochondria
Inherited intact from one parent (usually the mother)
Contain their own DNA
Reproduce by dividing
Differences in mitochondrial DNA sequences of maternally related individuals
Due to mutations

24. DNA and Protein Sequence Comparisons
Some genes highly conserved
Change little or not at all over time
Others are not conserved
DNA barcoding
Technique to identify an individual’s species

25. 18.5 Comparing Patterns of Animal Development
Animals have similar patterns of embryonic development
Same master genes direct the process
Mutation in a master gene typically unravels development completely
Master genes tend to be highly conserved (HOX)
Variations in master gene expression patterns
Affect onset, rate, or completion of early development steps

26. Figure 18. 8 Visual comparison of vertebrate embryos
Figure 18.8 Visual comparison of vertebrate embryos. All vertebrates go through an embryonic stage in which they have four limb buds, a tail, and divisions called somites along their back. From left to right: human, mouse, bat, chicken, alligator.

27. Figure 18.9 How differences in body form can arise from differences in master gene expression. Expression of the Hoxc6 gene is indicated by purple stain in two vertebrate embryos, chicken (left), and garter snake (right). Expression of this gene causes a vertebra to develop ribs. Chickens have 7 vertebrae in their back and 14 to 17 vertebrae in their neck; snakes have upwards of 450 back vertebrae and essentially no neck.

28. 18.6 Applications of Phylogeny Research
Phylogeny helps us understand how to conserve species existing today
Hawaiian honeycreeper species
As more species become extinct, genetic diversity dwindles
Lowered diversity means group is less resistant to change
More likely to suffer catastrophic losses

29. Applications of Phylogeny Research
Phylogeny tells us which honeycreeper species are most different
These are most valuable in task of preserving genetic diversity
Helps focus limited conservation resources

30. Applications of Phylogeny Research
Cladistics analysis
Correlate past evolutionary divergences with behavior and dispersal patterns of existing populations
Yield information useful in conservation efforts

31. Conservation Biology Example: blue wildebeest
Current populations in the African savanna found to be less similar genetically than they should be
Analysis helped conservation biologists discover patchy distribution of preferred food plants
Prevented gene flow between populations
Restoring appropriate grasses in intervening, unoccupied areas of savanna would help populations reconnect

32. Medical Research Study of virus evolution
Viruses grouped into clades based on biochemical characters
Viruses can mutate each time they infect a host
Genetic material changes over time

33. Medical Research Example: H5N1 avian flu virus
Very high mortality rate in humans
Virus replicates in pigs without causing symptoms
Pigs transmit the virus to other pigs and humans
Phylogenetic analysis indicated virus jumped from birds to pigs at least 3 times since 2005
One of the isolates could be transmitted among humans
Increased understanding aids in vaccine research

34. Points to Ponder
What are the different methods that phylogeneticists use to classify evolutionary change? How have these methods changed over time?
For each of the following pairs of structures, determine if they are analogous or homologous, and explain why:
Moth wing and bird wing
Shark fin and dolphin fin
Octopus eye and human eye