Theory of Evolution & Microevolution

Chapter 13

Evolution

• Darwin and his theory

• Evolution Evidence

Charles Darwin

Natural Theology

• Based on a literal view of the Genesis Story

• Earth 6,000 yrs old

• No new species

• No physical changes (valleys, mountains)

Putting Darwin in the context of his time

Important people

• Linnaeus

• Lamarck

• Malthus

• Lyell

Linnaeus

• Studying biology to reveal a divine plan

• Developed modern taxonomy

• Made Binomials: Homo sapiens

• Based groupings on morphology

• Did not believe in evolution,

• Taxonomy data would later provide some of best evidence

Lamarck

• Got the genetics wrong

• Stressed acquired traits-(wrong)– Giraffes stretched their necks– Babies had longer necks

• But- said species evolved to be better suited to environment – right!

Malthus

• British economist studied Paris after the revolution

• Limited resources

• Excess population growth

• Struggle to survive,

• competion among individuals

• Survival of the richest

Malthus

• Darwin was influenced by Thomas Malthus’s Essay on the Principle of Population (1798)– Populations

increase geometrically, while food supply increases only arithmetically

Fig. 2.6

Lyell

• British geologist.

• Following Hutton’s work

• Earth is old

• Valleys formed by erosion

• Mountains by uplifting

• Slow processes over LONG periods of time

Fig. 2.13

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North America

Marquesas

SocietyIslands

GalápagosIslands

Valparaiso

Straits of Magellan

Cape Horn

North AtlanticOcean

SouthAmerica

Bahia

Cape VerdeIslands

Tierra del Fuego

FalklandIslands

Port Desire

Buenos AiresMontevideo

Rio de Janeiro

Ascension

St Helena

WesternIsles

CanaryIslands

South AtlanticOcean

Cape ofGood Hope

Africa

Europe

IndianOcean

Madagascar

MauritiusBourbon Island

British Isles

KeelingIslands

King George’sSound

AsiaNorth PacificOcean

PhilippineIslands

Equator

FriendlyIslands

Hobart NewZealand

Sydney

Australia

5 year voyage of the Beagle

Evidence that Made Darwin think..

• The variation among organisms in a population• Biogeography – where species are found around

the globe• Fossil record• Comparative morphology – Linnaeus's

classification• Artificial Selection • Geology and the age of the earth• Malthus and economic theory• Lamarck’s theory and adaptations

Evolution- Just a Theory?

• Theory vs. Law vs. Dogma

Terms:

• Theory – explain a process

• Law- describes a phenomenon, a formula

• Dogma is not testable – beliefs

• Science is limited to things we can measure, test.

• Hypothesis – is an “educated” guess to explain a problem,

Scientific Method

• Problem, observation

• Background information, literature search

• Hypothesis based on previous work

• Experiment to test hypothesis

• Analyze results

• If hypothesis supported – publish a paper.

Darwin’s Theory

• Populations have inherent variation among individuals.

• These traits are heritable• Resources in the environment are limited• Populations have a greater fertility than

their environment can sustain.• Populations would grow exponentially, but

most remain stable in size.

A population of Liguus fascitus

Variation in shell coloration patterns

Darwin’s Theory continued:

• There is a struggle to survive among the offspring called Natural Selection.

• The survivors are better fit

• Fitness is the ability to have more offspring (frequency of genes in the genepool).

Natural Selection

• “struggle “ or competition does not have to be a fight to death

• May just be as simple as a seed germinating earlier and getting established first. It produces 120 seeds. A later germinating plant makes only 50 seeds.

• “Fitness” is the success rate of the offspring in future generations.

Fig. 2.7

Some Evidence for Evolution

• Microevolution- antibiotic, pesticide resistance– Artificial selection

• Fossil record• Biochemical comparisons

– Protein sequences– DNA, gene comparisons

• Morphological comparisons• Embryology• Biogeography• Genetically modified organisms

Fig. 2.9

Fig. 2.5

Fig. CO 2

Fig. 2.10

Evolution in progress around us:

• Antibiotic resistance

• Herbicide, Pesticide resistances

• New disease threats (AIDS, SARS, Ebola, West Nile Virus)

• Climate change

• Introduced species

• Biotechnology ???

Fig. 2.8

Darwin and Human Evolution

• Published “Descent of Man” in 1871

• Wasn’t first to hypothesis our relation to apes

• caused more popular criticism of his general theory

All made by Artificial Selection from wild mustard

Artificial Selection: human designed breeding of plants and animals for desired traits by selecting which individuals get to reproduce.

backbone

pelvic girdle

coccyx (boneswhere manyother mammalshave a tail)

small boneattached topelvic girdle

thighboneattached topelvic girdle

Missing Links

Galapagos Finches

• Specialization to different feeding sources may have diversified the species.

Sexual Selection

Directional Selection modifies Beak depth during

drought periods

Fig. 2.16

Fig. 2.15

Homologous features

• Derived from a common ancestor

• Often do not have similar functions

• Changes in the timing of genes forming body parts can alter their over-all shape.

proportions in infant

proportions in infant

adult

adult

chimpanzee

human

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1

1

1

1

1

2

2

2

2

2

2

2

3

3

3

3

3

3

3

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early reptile

pterosaur

chicken

bat

porpoise

penguin

human

Analogous Features• Have same functions ( by convergence)

• Do not have a common ancestry

• Are not derived from the same ancestral feature

Butterfly and Bird

• No bones in butterfly, not from common ancestor

• Structures not related

Ecotypes

• Populations that adapted to local environmental conditions.

• Still one species – inter-fertile• Can form clines – serial ecotypes along a

gradient– Common garden experiment (e.g. elevation and

yarrow)

• Need to preserve local adaptations in plants– In Botanical garden they always list source of plant– Restoration Ecology – try to propagate local plants to

use in marsh etc. restoration.

Ecotypes forming a cline Fig. 23.8

Convergent Evolution

• Sometimes unrelated species may superficially look alike

• Both species have adapted to similar habitats.

• Evolution comes up with similar adaptations to the conditions

• Does not mean they are closely related

Convergent Evolution

Ocotillo Allauidia

North America Madagascar

Fig. 13.9b