galapagos finch lab

Biology: Principles & Exploration Galapagos Finch Lab Name: __________________________

Activity Series Dr. Witty 1

It may seem curious that of all the animals in the Galapagos, this group of very drab and dull birds is most closely associated with Darwin's name. He was neither the first to see them (they are mentioned in passing by Captain James Colnett in 1798) nor did they figure much in his writings subsequent to the "Voyage of the Beagle". Despite the fact that they intrigued Darwin, they are far too complex a group of animals for Darwin to have understood. Nevertheless, they played an important role in helping him recognize the reality of the evolutionary process. The name was first applied in 1936, and popularized in 1947 by the ornithologist David Lack, who published the first modern ecological and evolutionary study of the finches. Today Darwin's finches are the subject of intense study, and they are revealing much about the evolutionary process.

Darwin's finches share similar size, coloration, and habits. Their salient difference is in the size and shape of their beak. However, beak shapes can be very variable, and the size and shape in one individual can overlap into the range of another species. There are presently 14 species of birds recognized as Darwin's finches - 13 in the Galapagos, and one on Cocos Island.

Some students wonder why we need to worry about naming the finches, asking instead “why can't we just enjoy them for what they are”? There is power in a name; to know the name is to understand the named. This is especially so in that branch of biology known as taxonomy. The taxonomist not only applies a name to an organism, but, by ranking those organisms into hierarchies of names, attempts to portray evolutionary relationships. Since 1758, taxonomists have used the system of Linnaeus to organize the living world. Linnaeus gave each organism a binomial: genus and species, which are ranked in higher and higher groupings:

Kingdom A group of related phyla Phylum A group of related classes

Class A group of related families Order A group of related genera Genus A group of related species Species An individual type of organism. Genus and species names are always

italicized with the species name in lower case lettering

It should be clear from this table that the only "real" entity is the species. The higher groupings are merely an assessment of how species are thought to be related to other species, and different taxonomists may very well disagree. Among the Darwin's finches, there is general agreement as to the existence of 13 Galapagos species, although there may be one or two more or one or two less, depending on how one assesses several unusual populations. There is disagreement, however, about how those 13 species are organized into genera. Traditionally, the finches are divided into four groups, each representing a single genus: the ground finches (Geospiza), the tree finches (Camarhynchus), the warbler finch (Certhidea) and the Cocos finch (Pinaroloxias). As a group, the tree finches are more heterogeneous than the ground finches and it is current practice to subdivide the tree finches into three genera: Camarhynchus (the tree finches), Platyspiza (the vegetarian finch) and Cactospiza (the woodpecker and mangrove finches). On the other hand, finch expert David Steadman feels that splitting the finches into six genera emphasizes their differences and suggests that all of the finches should be united as 14 species in the singe genus Geospiza to emphasize their similarities!! But whether you split them into six genera or lump them into one, everybody pretty much agrees on the same 14 species. The only real entity is the species. The table on the next page gives the genus and species names for all of the finches:

Common Name Genus Species Ground Finches



Identification of finches can be extremely intimidating. Pictured below are eleven of the fourteen “Darwin” Finches.



The table below shows the distribution on the Galapagos Islands.

Modified from "A Field Guide to the Birds of Galapagos"

If we believe that two species share a common ancestor, then as one traces the species back in time, they should become closer and closer in form. The definition of the term "species" includes the presence of a fertility barrier between individuals of different species. Our current understanding of evolution is that new species are born when the population of the ancestor species is split. Once the gene pool is separated, the two populations may be subject to different natural selection pressures, and hence, evolve in separate ways. A glance at the table of Distribution of Darwin Finches on Visitor Islands shows that similar finches, such as the cactus finch and the large cactus finch do not coexist on the same islands. The large cactus finch shows what can happen in the presence and absence of a competitor species.



Give three different reasons as to how does beak shape/size has an impact on the finch getting the necessary amount of food to sustain life. 1.) 2.) 3.) Give two different reasons besides beak shape/size and food size that explains the difficulty in obtaining the necessary amount of food to sustain life in each habitat. (A specific reason may be repeated only twice.) Prairie

Woodland Lake

Farmland

Ground Cover Swamp

Identify strategies that could be used to obtain as much food as possible from each habitat. Prairie

Woodland Lake

Farmland

Ground Cover Swamp



DATA TABLE: Total Number and Type of Food Collected

Prairie Habitat Beak Type/ Food Type Rice Sunflower Seeds Corn Nuts Soft Insects Hard Insects

Tweezer Beak Clothes Pin Beak Spoon Beak Plier Beak Woodland Habitat Beak Type/ Food Type Rice Sunflower Seeds Corn Nuts Soft Insects Hard Insects

Tweezer Beak Clothes Pin Beak Spoon Beak Plier Beak Lake Habitat Beak Type/ Food Type Rice Sunflower Seeds Corn Nuts Soft Insects Hard Insects

Tweezer Beak Clothes Pin Beak Spoon Beak Plier Beak Farmland Habitat Beak Type/ Food Type Rice Sunflower Seeds Corn Nuts Soft Insects Hard Insects

Tweezer Beak Clothes Pin Beak Spoon Beak Plier Beak Ground Cover Habitat Beak Type/ Food Type Rice Sunflower Seeds Corn Nuts Soft Insects Hard Insects

Tweezer Beak Clothes Pin Beak Spoon Beak Plier Beak Swamp Habitat Beak Type/ Food Type Rice Sunflower Seeds Corn Nuts Soft Insects Hard Insects

Tweezer Beak Clothes Pin Beak Spoon Beak Plier Beak



Convert all of the food collected from each beak type into total number of calories obtained by using the following information. Enter those values in the data table. Rice = 5 calories Almonds = 10 calories Corn = 2 calories Insects = 15 calories Seeds = 8 calories

DATA TABLE: Caloric Intake Values for Each Habitat

Tweezer Beak Prairie Woodland Lake Farmland Ground Cover Swamp

Rice Nuts Corn

Insects Seeds Total

Clothes Pin Beak Prairie Woodland Lake Farmland Ground Cover Swamp

Rice Nuts Corn

Insects Seeds Total

Spoon Beak Prairie Woodland Lake Farmland Ground Cover Swamp

Rice Nuts Corn

Insects Seeds Total

Pliers Beak Prairie Woodland Lake Farmland Ground Cover Swamp

Rice Nuts Corn

Insects Seeds Total



Construct a bar graph that demonstrates the total amount of calories each type of “bird” was able to obtain in each habitat. Color-code each habitat as: Green = prairie Brown = woodland Blue = Lake Yellow = farmland Red = ground cover Black = swamp The information below is the total number of calories that each “bird” needed to survive: Tweezer Beak = 50 calories Clothes Pin Beak = 100 calories Spoon Beak = 200 calories Pliers Beak = 100 calories Which of your birds survived in each habitat? How do your findings compare to the data table and graph of the class results? How do your findings compare to the predictions you made in prelab?

galapagos finch lab

Documents