evolution chapter 15. evolution: the change over time of the genetic composition of populations...

EVOLUTION

CHAPTER 15

• Evolution: the change over time of the genetic composition of populations

• Natural Selection: populations of organisms can change over the generations if individuals having certain heritable traits leave more offspring than others (differential reproductive success)

• Evolutionary Adapations: a prevalence of inherited characteristics that enhance organisms’ survival and reproduction

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EVOLUTIONARY HISTORY– Linnaeus - taxonomy - Lyell - uniformitarianism

– Hutton - gradualism - Darwin - evolution

– Lamarck - evolution - Mendel - inheritance

– Malthus - populations - Wallace - evolution

– Cuvier - paleontology - Count Buffon - evolution

RESISTANCE TO THE THEORY OF EVOLUTION

RESISTANCE TO THE THEORY OF EVOLUTION

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DARWIN’S INFLUENCES

Taxonomy matured during mid-eighteenth centuryLinnaeus believed in:

He developed the binomial system of nomenclature

System of classification for living things Count Buffon:

Wrote 44-volume catalog of all known plants and animals

Suggested descent with modification

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Lamarck = First biologist to: Propose evolution Link diversity with environmental adaptation

Concluded more complex organisms are descended from less complex organisms: SIMPLE TO COMPLEX

Proposed inheritance of acquired characteristics – Lamarckianism

DARWIN’S INFLUENCES

Passing on Acquired Traits

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DESIRE TO CHANGE

Use and Disuse

HMS BEAGLE VOYAGE• Invited to travel around the

world– 1831-1836 (22 years old!)– makes many observations of

nature• main mission of the Beagle was to

chart South American coastline

• While on the voyage of the HMS Beagle in the 1830s, Charles Darwin observed– similarities between living and fossil

organisms

– the diversity of life on the Galápagos Islands, such as blue-footed boobies and giant tortoises

Figure 13.1A

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FINCHES

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MALTHUSOverpopulation and

species control

LYELLEarth is subject to slow but continuous cycles of erosion

Proposed uniformitarianism, rates and processes of change are constant

DARWIN’S INFLUENCES

• Darwin became convinced that the Earth was old and continually changing– He concluded that living things also

change, or evolve over generations

– He also stated that living species descended from earlier life-forms: descent with modification (originally Buffon and Erasmus Darwin)

• All organisms are related through decent from an ancestor that lived in the remote past.

1. Population has Variation2. Variations may be favorable3. More offspring are produced than survive4. Survivors have favorable traits5. Populations change over time

DARWIN’S 5 MAJOR CONCLUSIONS

ON THE ORIGIN OF SPECIES

• ......ALL THIS LEADS TO HIS THEORY OF NATURAL SELECTION and SURVIVAL OF THE FITTEST

• 1859 Publication

• Wallace influence

Early 19th century

IndustrialRevolution

WITNESSING NATURAL SELECTION

Evolution evidence: Fossils

• The fossil record shows that organisms have appeared in a historical sequence

• Many fossils link early extinct species with species living today

– These fossilized hind leg bones link living whales with their land-dwelling ancestors

Figure 13.2G, H

2006 Fossil Discovery of Early Tetrapod

• Tiktaalik– “missing link” from sea to land

animals

• Similar structure

• Similar development

• Different functions

• Evidence of close evolutionary relationship– recent

common ancestor

Evolution evidence: Homologous Structures

spines

tendrilssucculent leaves

colored leaves

Homologous structures

leaves

needles

Evolution evidence: Analogous Structures

Separate evolution of structures

similar functions similar external

form different internal

structure & development

different origin no evolutionary

relationship

Don’t be fooledby their looks!

Evolution evidence: Comparative

Embryology

• Modern animals may have structures that serve little or no function– remnants of structures that were functional

in ancestral species– deleterious mutations accumulate in genes

for non-critical structures without reducing fitness

• snakes & whales — remains of pelvis & leg bones of walking ancestors

• eyes on blind cave fish

• human tail bone

Evolution evidence: Vestigial Structures

Evolution evidence: Molecular Biology

• Similarities in DNA, proteins, genes, and gene products

• Common genetic code

Closely related species have sequences that are more similar than distantly related species

DNA & proteins are a molecular record of evolutionary relationships

Fig. 22-20

• Darwin’s observations of biogeography, the geographic distribution of species, formed an important part of his theory of evolution

• Islands have many endemic species that are often closely related to species on the mainland

Evolution evidence: Biogeography

• Insecticide & drug resistance

–insecticide didn’t kill all individuals

–resistant survivors reproduce

–resistance is inherited

–insecticide becomes less & less effective

NATURAL SELECTION IN ACTION

• Artificial breeding can use variations in populations to create vastly different “breeds” & “varieties”

““descendantsdescendants”” of the wolf of the wolf

““descendantsdescendants”” of wild mustard of wild mustard

ARTIFICIAL SELECTION