Science in practice and the pastWeek 2

1

The anthropological perspective"A broad perspective that helps us understand the diversity of the human experience within the context of biological and behavioral continuity with other species"

Goals of the anthropological perspective-extend our knowledge to include other cultures-look at the diversity of human experience-avoid ethnocentrism

Ethnocentrism: viewing other cultures from the inherently biased perspective of one's own culture

2

Pre-scientific thinkingYoung Earth: Earth was roughly 6,000 years old

Fixity of species: all forms were created by God and didn't change over time

3

Pre-scientific thinking

Changes in the 18th century

-circumnavigation of the globe

-discovery of the New World

-invention of the microscope

-notion of sun-centered universe

4

Precursors to evolutionary theoryJohn Ray - 18th century Cambridge University minister

Species: distinguish groups of organisms by their ability to mate with each other and produce fertile offspring

I.e., reproductively isolated groups of organisms

Carolus Linnaeus - 18th century Swedish naturalistBinomial nomenclature: system of classification with genus species

E.g., Homo sapiens

5

Precursors to evolutionary theoryJohn Ray - 18th century Cambridge University minister

Species: distinguish groups of organisms by their ability to mate with each other and produce fertile offspring

I.e., reproductively isolated groups of organisms

Carolus Linnaeus - 18th century Swedish naturalistBinomial nomenclature: system of classification with genus species-modern taxonomic system

6

Precursors to evolutionary theoryGeorge-Louis Le Clerc de Buffon - 18th century naturalist

-correlation between changes in the environment and changes in living forms

7

Precursors to evolutionary theoryJean-Baptiste Lamarck - 19th century naturalist

-first to give a mechanism to explain evolution-saw importance of the interaction between organisms and their environment

Inheritance of acquired characteristics -traits altered through use or disuse; and -altered traits are inherited

8

Precursors to evolutionary theoryGeorges Cuvier - 19th century paleontologist

Catastrophism: geologic landscape is the result of cataclysmic eventsExtinction: introduced to explain unknown forms in the fossil record

Charles Lyell - 19th century geologistUniformitarianism: geologic processes operating in the past are still operating today

-deep time vindicated (old Earth)

9

10

11

12

Thomas Malthus - English economist-populations grow exponentially while available resources remain stable

Alfred Wallace (1823-1913)-Independently generated the concept of natural selection-Father of biogeography

Importance of environmental pressures

Discovery of the new world-new observations challenged long-held views-exposure to new plants and animals increased awareness of biodiversity

Views like the fixity of species and a young Earth were disconfirmed

-16-17th Europe became a scientific breeding ground paving the way for evolutionary thought.

*Scientists were now trying to give better explanations to:-replace the disconfirmed ones-explain why biological organisms evolve

13

Historical context

14

1809-1882-Grew up interested in nature and learned about Lamarck and others in college-Observations on a 5-year voyage around the world on the HMS Beagle later inspired his theory of evolution by natural selection

Charles Darwin

15

Artificial selection-All domestic dogs share a common ancestry-There's extreme variation exhibited by dog breeds due to artificial selection

Natural selection in detail - analog with artificial selection

16

Natural selection: process in which individuals with favorable variations survive and reproduce at a higher rate than individuals with unfavorable variations

1. All species are capable of producing offspring at a rate faster than the production of resources (like food)Influenced by Malthus

2. There's biological variation within all speciesInfluenced by Buffon, Lamarck, etc

3. In each generation, more individuals are produced than can survive, because limited resources create competitionInfluenced by Malthus

Natural selection in detail - Eight processes

17

4. Individuals with favorable variations have an advantage over individuals lacking favorable variations.I.e., Individuals have a greater fitness because favorable traits increase their likelihood of survival and reproduction

5. Environmental context determines whether a trait is favored

6. Traits are inherited and passed on to the next generation-individuals with favorable traits contribute more offspring to the next generation, they have greater reproductive successDarwin's addition, independently conceived by Wallace too

Natural selection in detail - Eight processes

18

7. Successful variations accumulate over long periods of time, so later generations may be distinct from ancestral ones.-a new species may appearLyell's uniformitarianism allowed for the plausibility of a slow evolutionary process

8. Geographical isolation contributes to formation of new species as individuals adapt to different environments and respond to different selective pressuresInfluenced by observations and Wallace's biogeography

Natural selection in detail - Eight processes

19

8. Geographical isolation contributes to formation of new species as individuals adapt to different environments and respond to different selective pressuresInfluenced by observations and Wallace's biogeography

Natural selection in detail - Eight processes

20

Reproductive success: number of offspring an individual produces and rears to reproductive age

Fitness: a measure of relative reproductive success of individuals-measured by an individual's genetic contribution to the next generation compared to other individuals

Selective pressure: forces in the environment that influence reproductive success in individuals-what causes distinct species to develop

Important terms for evolution by natural selection

21

Q: How could you turn a pack of wolves into Chihuahuas?

Note: All dogs descended from wolves

If you're given a pack of wolves to breed, how would you start breeding the wolves to eventually make a Chihuahua?

Example 1: Dog breeding