Descent with Modification

Complete 15-1 in Guided Reading Workbook

Quest tomorrow (13-14)

Descent with Modification: A Darwinian View of Life

• A new era of biology began in 1859 when Charles Darwin published The Origin of Species

• The Origin of Species focused biologists’ attention on the great diversity of organisms

• To understand why Darwin’s ideas were revolutionary, we must examine them in relation to other Western ideas about Earth and its life

The Darwinian revolution challenged traditional views of a young Earth inhabited by unchanging species

natural theology

• 1700’s

• studying the adaptations of organisms– “ the Creator has

designed each species for a purpose”

Taxonomy

• Carolus Linnaeus– Swedish botanist

• Carolus Linnaeus interpreted organismal adaptations as evidence that the Creator had designed each species for a specific purpose

• Linnaeus was the founder of taxonomy, the branch of biology concerned with classifying organisms

Fig. 22-3

Younger stratumwith more recentfossils

Layers of depositedsediment

Older stratumwith older fossils

• Fossils – relics or impressions of organisms from the past– mineralized in

sedimentary rocks

Hutton and Lyell

• Hutton – gradualism– profound change

results from slow, continuous processes

• Lyell – uniformitarianism– geological

processes have not changed throughout Earth’s history

Population Limits

• Thomas Malthus

• "...in all societies, even those that are most vicious, the tendency to a virtuous attachment is so strong that there is a constant effort towards an increase of population. This constant effort as constantly tends to subject the lower classes of the society to distress and to prevent any great permanent amelioration of their condition."[13]

Jean Baptiste Lamarck

• Use and disuse of parts

• Inheritance of acquired characteristics

Fig. 22-2

American Revolution French Revolution U.S. Civil War1900185018001750

1795

1809

1798

18301831–1836

1837

1859

18371844

1858The Origin of Species is published.Wallace sends his hypothesis to Darwin.

Darwin begins his notebooks.Darwin writes essay on descent with modification.

Darwin travels around the world on HMS Beagle.

Malthus publishes “Essay on the Principle of Population.”

Lyell publishes Principles of Geology.

Lamarck publishes his hypothesis of evolution.

Hutton proposes his theory of gradualism.

Linnaeus (classification)

Cuvier (fossils, extinction)Malthus (population limits)

Lamarck (species can change)

Hutton (gradual geologic change)

Lyell (modern geology)

Darwin (evolution, natural selection)

Wallace (evolution, natural selection)

Voyage of the Beagle (1839 - 1844)

• Darwin’s Voyage - During his travels, Darwin made numerous observations and collected evidence that led him to propose a revolutionary hypothesis about the way life changes over time.

Galapagos Islands• During his travels Darwin was amazed how different organisms were

so well adapted to many different environments. • He saw patterns of diversity • Not just in living organisms, but also in fossil records.• The Galapagos Islands were a microcosm of Evolution

• In 1844, Darwin wrote an essay on the origin of species and natural selection

• In June 1858, Darwin received a manuscript from Alfred Russell Wallace

• 1859 - The Origin of Species

The Origin of Species

• Darwin developed two main ideas:– Descent with

modification explains life’s unity and diversity

– Natural selection is a cause of adaptive evolution

Fig. 22-7

Fig. 22-8

Hyracoidea(Hyraxes)

Sirenia(Manateesand relatives)

Moeritherium

Barytherium

Deinotherium

Mammut

Elephas maximus(Asia)

Stegodon

Mammuthus

Loxodontaafricana(Africa)

Loxodonta cyclotis(Africa)

010425.52434

Millions of years ago Years ago

Platybelodon

Fig. 22-8a

Elephas maximus(Asia)

Stegodon

Mammuthus

Loxodontaafricana(Africa)

Loxodonta cyclotis(Africa)

010425.52434

Millions of years ago Years ago

Platybelodon

Artificial Selection, Natural Selection, and Adaptation

• artificial selection– Super Cow

• Darwin then described four observations of nature and from these drew two inferences

Fig. 22-9

Kale

Kohlrabi

Brussels sprouts

Leaves

Stem

Wild mustard

Flowersand stems

Broccoli

Cauliflower

Flowerclusters

Cabbage

Terminalbud

Lateralbuds

• Observation #1: Members of a population often vary greatly in their traits

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

• Observation #2: Traits are inherited from parents to offspring

• Observation #3: All species are capable of producing more offspring than the environment can support

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Fig. 22-11

Sporecloud

• Observation #4: Owing to lack of food or other resources, many of these offspring do not survive

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

• Inference #1: Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

• Inference #2: This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Natural Selection: A Summary

• Individuals with certain heritable characteristics survive and reproduce at a higher rate than other individuals

• Natural selection increases the adaptation of organisms to their environment over time

• If an environment changes over time, natural selection may result in adaptation to these new conditions and may give rise to new species

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Fig. 22-12

(b) A stick mantid in Africa

(a) A flower mantid in Malaysia

Examples of Natural Selection

Predator: Killifish; preysmainly on juvenileguppies (which do notexpress the color genes)

Guppies: Adult males havebrighter colors than thosein “pike-cichlid pools”

Experimentaltransplant ofguppies

Pools withkillifish,but noguppies priorto transplant

Predator: Pike-cichlid; preys mainly on adult guppies

Guppies: Adult males are more drab in colorthan those in “killifish pools”

EXPERIMENT

• Patients treated with the drug 3TC– interferes with genome replication in

HIV

• 3TC-resistant strains become 100% of the population of HIV in just a few weeks

Evidence of Evolution

• The Fossil Record

• Homologous Structures

• Vestigial Organs

• Similarities in Embryonic Development

• Genetic Code

Evidence of EvolutionEvidence of

Evolution

Fossil RecordHomologous

Body Structures

Early Development

Biogeography

PhysicalRemains

Common Ancestors

SimilarGenes

SimilarGenes

Composed of Which

IndicatesWhichImplies

WhichImplies

BiochemistryProtein,

RNA, DNABiochemical Pathways

Which Indicates

Common Ancestors

The Fossil Record

BiogeographyGeographical Dist. of Species

Common Descent

Homologous Body Structures

• vestigial organ - organ that serves no useful function in an organism

Vestigial Organs

• organ that serves no useful function in an organism

Similarities in early development

Theoretical?• The conclusion that life has evolved is well

supported by an abundance of historical evidence

• Natural selection is widely accepted in science– its predictions have withstood thorough,

continual testing by experiments and observations

• arguments exist among evolutionary biologists whether natural selection alone accounts for the history of life as observed in the fossil record