Chapter 22

Chapter 22 Darwin’s origin of species

challenged long-standing Western ideas, especially those of the Christian church

Earth only a few thousand years old

unchanging forms of life made individually during single week by Creator

Chapter 22Plato (427 – 347 BC) 2 worlds:

(1) ideal & eternal real world(2) world of imperfection that we

perceive through our senses thought evolution would be counter-

productive in world already populated by perfect species

Aristotle (384 - 322 BC)

all living things arranged on scale of increasing complexity

each form had rung on ladder, with every rung filled

species are permanent and perfect

natural theology

dedicated to discovering Creator’s plan by studying nature

adaptations seen as evidence that the Creator designed each and every species for a particular purpose

Linnaeussought to discover order in the diversity of life “for the greater glory of God”

specialized in taxonomy(developed binomial nomenclature)

clustering of species implied no evolutionary kinship

fossils (sedimentary rocks)

layers show that a succession of organisms has populated Earth throughout time

paleontology

developed by Cuvierdocumented succession of

fossils in Paris Basinadvocated catastrophism:

each boundary corresponded with a catastrophe of some kind(flood, drought, etc.)

Hutton

explain current landforms by looking at mechanisms currently operating in the world(Ex. canyons formed by river)

gradualism: profound change is cumulative product of slow, but continuous change

Lyell

incorporated Hutton’s ideas into uniformitarianism

geologic processes have not changed throughout the history of the Earth

Lamarck

oversaw invertebrate collection at Natural History Museum of Paris

could see lines of descent when comparing current species with fossils

Lamarck’s ideas

use & disuse Ex. blacksmith hammering, giraffe stretching

inheritance of acquired characteristicschanges during lifetime could be acquired by offspring

Darwin—HMS Beagle

goal was to chart unknown S. American coastline

Darwin observed adaptations of plants and animals

many characteristics were distinct from those of Europe

Darwin—Galapagos species found nowhere else in the

world read Lyell’s “Principles of Geology” began to believe that the Earth

was very old and constantly changing

considered link between origin of new species and adaptation to environment (Ex. finches)

Darwin—theories

saw evolution as an explanation for life’s unity and diversity

developed concept of natural selection to explain adaptive radiation

Galapagos finches

Darwin—Natural Selection and Adaptation 1. natural selection is differential

success in reproduction 2. natural selection occurs through

an interaction between the environment and the variability inherent among the individual organisms making up a population

3. the product of natural selection is the adaptation of populations of organisms to their environment

Natural Selection—related ideas Malthus essay on human population connection between natural

selection (struggle for existence) and capacity of organisms to “overproduce”--many eggs laid, young born, and seeds spread, but few leave offspring

(potential offspring are eaten, freeze, starve, diseased, etc.)

Natural Selection—related ideas

in each generation, environmental factors filter heritable variations favoring some over others--differential reproduction results in favored traits being disproportionately represented in the next generation

Natural Selection—related ideas

power of selection seen in artificial selection (breeding)--Darwin thought the same process could be just as powerful over 100s and 1000s of generations--slight advantages accumulate over generations (gradualism)

Natural Selection—SUMMARY

1. diverse forms of life have arisen by descent with modification from ancestral species

2. mechanism of modification has been natural selection (working over tremendous time periods)

population

group of interbreeding individuals belonging to a particular species and sharing a common geographic area--individuals do not evolve--evolution can only be measured in populations

population--examples insecticide-resistant insects

--initial use kills 99% of insects--subsequent sprayings are less effective--natural selection is cause

HIV strains resistant to medication(these cases are rapid enough to be

observed in short period of time…)

evidence of evolution HOMOLOGY

--similar characteristic resulting from common ancestry* anatomical

(a) mammal forelimb(b) remodeling / retrofitting(c) vestigial organs

* embryological: Ex. pharyngeal pouch* molecular: Ex. DNA & RNA codes

evidence of evolution HOMOLOGY

--form a layered pattern, with all life sharing the deepest layer and each smaller group adding fresh homologies to those they share with larger groups--tools of molecular biology have corroborated evolutionary trees

(Ex. Amino acid sequences of hemoglobin)

evidence of evolution BIOGEOGRAPHY

--geographic distribution of species--species tend to be more closely related to other species from the same area than to other species with the same way of life, but living in different areas--islands provide models for this idea

evidence of evolution FOSSIL RECORD

--oldest known species are prokaryotes (supports chemistry, molecular, and cell biology evidence)--chronology: Ex. Fossil fish predate all other vertebrates--transitions: signs of change should be seen in fossil record (Ex. changes in shape of human skull)