I. What are species? A. In Latin= “Kind” B



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Species

Kimarr Dempsey

Max Karpyak
I. What are species?

A. In Latin= “Kind”

B. One of the basic units of biological classification

C. A group of organisms capable of interbreeding and producing fertile offspring

D. Most modern definition: “a species is a systematic unit which is considered a species by a competent systematist (a specialist of the group)” (Mayr 1988).
II. Species Concepts

A. Mayr suggests all species concepts and definitions can be grouped under 4 headings

1. .

a. Differs from other species by constant diagnostic characteristics

b. If it looks like a carrion crow, it is, and if it looks like a raven, it’s a raven

c. What about variation among and within populations?

2. .

a. Only individual objects exist in nature, thus, species have no reality in nature

b. In other words, scientists have created the notion of species, and if it wasn’t for this word or way of classifying organisms, they would have each been thought of as just “things” in our environment.

3. .

a. A species is a single lineage of populations or organisms that maintains an identity separate from other such lineages and which has its own evolutionary tendencies and historical fate (Futuyma 354).

b. The application of the biological species concept to multidimensional assemblages of populations (Mayr 1988).

4. .

a. Species are groups of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups (Mayr 1988)

b. Properties for a species to fit in this concept:

i.
ii.
iii.

B. Good quote by Ernst Mayr:

“It seems as if every scientist has come up with their own species concept on the problem of species. It must be emphasized that the species is not an invention of taxonomists or philosophers, but that is has reality in nature” (Mayr 1988)


III. Ernst Mayr



A. The accidental explorer. He was at the right place at the right time.

B. His life in short:

1. Born in 1904 in Germany, Mayr trained as a medical student, but found that he had more interest in studying birds and biology

a. Spotted a pair of rare ducks that launched his career

b. - a species not seen by anyone in 80 years



2. Worked as volunteer between semesters at the ornithological part of the Berlin Museum under the advisor Erwin Stresemann

a. Mayr later described: “It was as if someone had given me the key to heaven”

4. He completed his doctorate in ornithology at the University of Berlin under Dr. Carl Zimmer

5. Published his first book Systematics and the Origin of Species in 1942 which was a combination of Darwin’s evolution ideas and genetics

6. Joined the faculty at Harvard University in 1953, where he also served as director of Museum of Comparative Zoology from 1961 to 1970

7. Retired in 1975 as emeritus professor of Zoology

8. He received awards including the National Medal of Science, the Balzan Prize, the Sarton Medal of the History of Science Society, the International Prize for Biology, and the Lewis Thomas Prize for Writing about Science

9. Died in February 3, 2005 at the age of 101
C. Contributions to Biology:

1. Solomon Islands and Fiji

a. Using the Island’s robins, Mayr was able to show that the sexes are not determined by sex hormones, but by geographic isolation.

b. On one island, both sexes of the robin species were drably colored. The other had them both brightly colored, and on another island the male was bright and the female drab.
2. Redefined Species in Terms of Breeding Populations

a. If two subspecies of geese that look alike are in contact but do not interbreed, they are considered separate species.

b. On the other hand when the snow goose and the blue goose look very different they are also considered different species. That is until the naturalists found that they flock together and interbreed, they were reclassified as a color phase belonging to a single species.



3. How Species Evolve:

    1. Through appearance of geographic barriers

    2. Few “founders” settling in a new area beyond species customary range

      1. Small population can become established

      2. First step toward reproductive isolation

      3. Over time the colony inbreeds

      4. Local conditions exert their selective pressures

      5. Descendants become increasingly different from their ancestors

      6. What do you think happens if the two groups ever reunite?


    1. This kind of evolution is called Peripatric Evolution

      1. Emphasized by Mayr in the 1950s

      2. One of the foundations for the Theory of Punctuated Equilibrium

      3. Does anyone remember what is the Theory of Punctuated Equilibrium?

IV. Terms to Know About Species

A. Semispecies: One of several groups of populations that are partially but not entirely isolated from one another by biological factors—hybridizing entities

B. Sibling Species: Species that are difficult or impossible to distinguish by morphological characters, but may be discerned by differences in ecology, behavior, chromosomes, or other such factors.

C. Sister Species: Two species with an immediate common ancestor

D. Superspecies: A collection of semispecies

E. Race: culturally defined or scientific?

V. Issues With Species

A. Hybrids

1. “Always misused as a mix of anything, but it does have a real scientific meaning” (Richardson)

2. Definition: occurs when offspring are produced by interbreeding between genetically distinct populations (Futuyma 373)

3. Can represent intermediate stages in the process of speciation, and can even be the source of new adaptations or new species.

4. Examples

a. Ligers

i. They are sterile

ii. Is that really a true hybrid then?

iii. Liger Video

b. Mules

c. Wholphins

i. A cross between bottlenose dolphin and a false killer whale.

ii. Have been reported to exist in the wild

      1. Currently kept in captivity and can produce fertile offspring




References
Futuyma, D. (2005). Evolution. Sinauer Associates Inc.
Mayr, Ernst. (1988). Toward a New Philosophy of Biology. Harvard University Press Cambridge, Massachusettes. (1)
Mayr, Ernst. (1963). Systematics and the Origin of Species from the Viewpoint of A Zoologist.
Mayr, Ernst (1990). Populations, Species, and Evolution. Oxford University Press. London, England.
Milner, Richard. (1990). The Encyclopedia of Evolution. Facts on File Inc. New York, NY.

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