Download HOMEWORK 06: ANSWER KEY

BIO 295
Islands & Evolution
- from the Galapagos to New York City
HOMEWORK 06: ANSWER KEY
The Beak of the Finch: Chapters 17-20
Answer each question in at least one paragraph (ca. 150-200 words). Refer to the syllabus (section “Written
assignments”) for formatting instructions.
1. Edgar Anderson offered some interesting insights regarding hybridization and habitat
requirements. Which widely used term did Anderson coin? What does this term mean and why is
it an important evolutionary step? How is the second generation of hybrids different from the first
when it comes to habitat requirements and what role does human disturbance play in this
process? What happens when a new habitat opens up? Give some examples mentioned in the
book.
“introgressive hybridization”; backcrossing of hybrids with either line of parents; means of mixing genes;
second generation of hybrids require peculiar (novel and bizarre) habitats, human disturbance creates
“strange” new niches for hybrid recombinations; violent readjustments necessary when new habitats open
up & new ecological niches are created (e.g., first land vertebrates invading terrestrial vegetation, first
appearance of large herbivorous reptiles; colonization of Hawaiian Islands, Galapagos, Lake Baikal;
“whenever species belonging to different faunas and floras were brought together”)
p. 241-244
2. Why did the giant cactus finch go extinct? Why are the Grants so adamant in making sure they
don’t bring fire ants on the island?
Giant cactus finch was specialized in local cactus, when cactus disappeared so did finch, Ecuadoran prison
colony established few years before Darwin’s arrival, made alterations to the landscape (farmland), hunted
local animals (wild pigs, goats, giant tortoises, finches), brought animals (cattle, goats, pigs, cats, rats,
etc.), giant cactus finch was big bird (probably didn’t fly much), not adapted to deal with these changes,
easy prey for cats or rats, when prison colony abandoned island, larger farm animals probably caused
cactus to go extinct, mocking birds went extinct around the same time as giant cactus finch (also nest in
cactus); introduction of new species on Daphne Major would disrupt balance and could cause species to go
extinct quickly
p. 244-248
3. Pesticide use represents a selective pressure for insect species in a similar way the flood/drought
on Daphne Major did for finches. What are the four possible ways that insects can survive
insecticide spraying? Give an example for each one. What mode of selection is occurring when
pesticides are sprayed for cotton pests? (not specifically mentioned in book, extra points for this)
1. Dodge the poison (e.g., mosquitos hang out on hut walls to digest their blood meal, when people started
spraying hut walls in Africa with DDT, some mosquitos would fly through window and fly right back out), 2.
Evolve a way to keep poison from getting under its cuticle (e.g., if diamondback moth lands on poison, will
fly off and leave contaminated legs behind, also called “leg-drop”), 3. Evolve an antidote (e.g., mosquito
Culex pipiens evolved a way to digest poison using specific enzymes), 4. Evolve a way to dodge poison
internally (e.g., insect can shrink/move/lose poison’s target inside body); directional selection
p. 254-255, p. 253
4. What do E. coli strains in the human gut have in common with birds in the Galapagos and what is
“the Levin Archipelago”? What little study did Levin & his wife do and what did they find? (W)hen
we talk about natural selection, we’re not talking about eons (…). It’s not just dead dinosaurs. (p.
259) – what is meant by that statement?
E. coli most common bacteria found in human gut, researchers followed Bruce Levin’s E. coli, watched
strains colonize and go extinct, much like birds in the Galapagos; Levin & his wife took different antibiotics
and watched resistant strains become dominant within days; rapid evolution of resistance to antibiotics in
bacteria that cause diseases like gonorrhea, streptococcus, tuberculosis, salmonella, etc., evolved within
lifetime of doctors now in practice and continue to evolve
p. 258-260
5. How might global warming affect finch evolution in the Galapagos Islands?
could change course of evolution on Galapagos, warming of ocean currents (even just 0.5 °C) can cause
change in global circulation patterns, Galapagos particularly vulnerable, depend on winds and currents for
seasons, if seasons weren’t so variable finches wouldn’t need variable beaks, species could fuse together
and undo all evolutionary work that has forced them apart within 200 years
p. 268-271
6. What are some key innovations in the evolution of humans? Is cultural evolution (the ability to
learn from each other) unique to humans? If not, give examples. What did J.B.S. Haldane mean by
psychological polymorphism in humans and how does this relate to character divergence and the
adaptive radiation of humans?
change from brachiation to walking on the ground which led to rearing up and walking on hind legs, brain
capacity (human brain tripled in size), opposable thumb, modification of hyoid bone which allowed fullthroated speech; no, blue tits & macaque monkeys (among others) can learn tricks from watching each
other; people specialize in different tasks and collectively (in a village) have variety of trades  variation,
each person seeks task for which they are most fit  character divergence, which drives adaptive
radiation
p. 280, p. 282-283, p. 287-288
This concludes the official part of the homework (Happy near-end of the semester!), you will not be
graded on the last question but I will appreciate your answer.
7. How did you like The Beak of the Finch, especially in the context of this class? Anything you would
change about how the book has been used in the class? Would you have preferred a regular
textbook as the main text?