Evolution: A Revolutionary Idea

Evolution: A Revolutionary Idea

A. What is Evolution?

1. Several definitions

a. descent with modification (Darwin)b. change in gene frequencies within a population

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c. All the changes that have transformed life on earth from its earliest beginnings to the immense diversity existing today

Evolution: A Revolutionary Idea

We can allow satellites, planets, suns, universe, nay whole systems of universe, to be governed by laws, but the smallest insect, we wish to be created at once by special act.

The Evidence of Change?

Fossil Record

“We must, however, acknowledge, as it seems to me, that man with all his

noble qualities... still bears in his bodily frame the indelible stamp of his lowly

origin.”

The Evolution of Evolutionary ThinkingJean Baptiste Lamarck: Inheritance of Acquired Characteristics

Main PointsOrganisms adapted to environmenta. Use and disuse i. organisms lost parts because they did not use them — like

the missing eyes & digestive system of the tapeworm ii. Constant use leads to a larger organ: blacksmit musclesb. Transmission or passing on of acquired characteristics

The Evolution of Evolutionary Thinking

A. Historical Development1. Jean Baptiste Lamarck

2. August Weismann

History

a. Disproved Lamarck ideas by chopping of the tails of mice

b. What?

History

A. Historical Development1. Charles Darwin

a. Study theology at Cambridge

b. 1831 appointed naturalist aboard the ship HMS Beagle

i. mission was to create maps for the British Navy

c. Darwin took surveys and collected samples of plants, animals, rocks, and fossils

History

A. Historical Development1. Charles Darwin

d. Most famous observations: Galapagos Islands where he spent 2 months

e. Eventually sailed around the world 1831-1835

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Evolution

History

A. Historical Development1. Charles Darwin

f. Wrote a 200+ page thesis in 1844 outlining his theory but he did not publish WHY?g. Alfred Wallace: came to similar conclusions as Darwin in 1858 from observations collected in another area of the world

h. Darwin agreed to a joint presentation with Wallace to the same scientific body.

History

A. Historical Development1. Charles Darwin

a. Publishes Origin of Species in 1859

b. How does the public respond to the book?

c. The first printing of the book sold out the first day

A. 5 ideas of Darwin’s Theory1. Overpopulation

a. Organisms produce more young than will surviveb. example:

Fly eggs: 250 eggs by one female in one laying

Praying Mantis young from one cocoon

Baby sea turtles

A. 5 ideas of Darwin’s Theory1. Overpopulation2. Variation

a. There exists in a population a large amount of variation

A. 5 ideas of Darwin’s Theory1. Overpopulation2. Variation

3. Struggle for existencea. What do organisms struggle for?

i. Lion attack

4. Survival of the strongest fittesta. Those that survive are the best adapted

b. Carrying Capacity: how many individuals can the environment support

i. example: deer in CVNP

ii. gazelle attack

5. Natural Selectiona. Environmental pressures select for the best adapted

A. 5 ideas of Darwin’s Theory

b. Animated example: DDT and flies

b. Individuals that survive reproduce and pass on favorable traitsc. “Fittest”: those that reproduce most successful

i. Differential reproductive success

B. People who helped Darwin1. Thomas Malthus

a. minister, economist

b. Wrote: Essay on Populationsc. Predicted that population would grow faster than food supply

d. Lead to Darwin’s idea of struggle for existence

B. People who helped Darwin1. Charles Lyell

a. geologistb. Wrote: Principles of Geologyc. Proposed the idea of Uniformitarianism

i. Geological processes are constant through timeii. Challenged the prevailing thought that the earth was young

iii. Darwin needed large periods of time for natural selection to workiv. Uniformitarinism provided Darwin the time element needed for his theory

B. People who helped Darwin1. Charles Lyell/ Uniformitarianism

Natural Selection: How Evolution Works

OverpopulationGenetic VariationStruggle for ExistenceDifferential Reproductive Success

Selection occurs based on:• the interaction of the environment and the existing population variations• the more severe the environmental pressure, the more severe the selection process

Natural Selection:• the environment shapes or refines organisms adaptations

Environmental Pressures• resources: food, water, shelter• climate: cold, hot, wet, dry• predation: how does one survive?

EvidencesA. Anatomical

1. Fossils a. Remains or traces left in rock strata (layers) by previous organisms (video: becoming a fossil)

b. Preserved in: rocks, bogs, tar amber, ice

c. Types of preserved samples: imprints, castings, and amber

A. Anatomical1. Fossils

d. Transitional recordsi. Classic example: the horse

e. Famous fossilsi. archeopteryx;

• bird or reptile?

Evidences

A. Anatomical1. Fossils

e. Famous fossilsi. Coelocanth: living fossil

Evidences

A. Anatomical1. Fossils

e. Famous fossils

Evidences

A. AnatomicalEvidences

2. Comparative Anatomya. Homologous structures

i. Structures in different species that are similar in structure but serve different functions

A. AnatomicalEvidences

2. Comparative Anatomya. Homologous structures

i. Divergent evolution Divergent evolution

when isolated populations of a species evolve independently adaptive radiation: evolution of many diversely adapted species from a common ancestor

Phylogenetic tree: graphic representation of divergent evolution

adaptive radiation: evolution of many diversely adapted species from a common ancestor

A. AnatomicalEvidences

2. Comparative Anatomyb. Analogous structures

i. Structures shared by different species that serve the same function but look different example: wings of birds and insects example: streamline body of fish and aquatic mammals example: cactus/euphobia

A. AnatomicalEvidences

2. Comparative Anatomyb. Analogous structures

ii. Convergent evolution different species being “shaped” by similar environmental pressures Species bSpecies a

Time

A. AnatomicalEvidences

1. Vestigial structuresa. Inherited organs or parts of organs that are reduced in size or non-functional Examples?

i. appendixii. coccyxiii. wisdom teethiv. ear muscles

A. AnatomicalEvidences

1. Vestigial structures

iv. Whales and pythons: vestigial hind limbsv. Flightless birds: vestigial wings

vi. Blind, cave dwelling animals-vestigial eyes

B. Embyrological evidenceEvidences

1. def: related species exhibit similar embryological development

a. segmented musclesb. gill pouchesc. tubular heart: no chambersd. Aortic arches in gill region

•Found in all vertebrate embryos

•All of these structures are found in fish

Ernst Haeckel

C. Molecular EvidenceEvidences

question: what on the molecular level would suggest relationships between species?

1. DNAa. the more similar the DNA:

i. common proteinsii. common biochemical pathways

WHY?

C. Molecular EvidenceEvidences

1. DNA

How similar?a. 96 – 99% similarity in sequences

C. Molecular EvidenceEvidences

1. DNAb. Found in every organism: from bacteria to “man”c. cytochrome C: found in every aerobic organism / involved with making energy

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C. Co-evolutionEvidences

1. def: species that co-evolve a. bacteria and humansb. ants, fungus, and bacteria

D. Biogeography

1. def: study of the distribution of life around the world

a. example: emus, ostriches, rhea and extinct elephant bird all found in the southern hemisphere

WHY?

C. Co-evolution ExamplesEvidences

EvidencesE. Microevolution

1. def: small changes in variations or gene frequencies occurring in a population of organisms

2. Classic example: Industrial Melanism

a. def: The darkening of several species of moths during the period of industrialization in many countries by the spread of a gene controlling elevated melanin synthesis

a. The selective pressure came from predators (insect eating birds). The moth’s color provides camouflage.b. Moths rest during the daytime on trees.c. In rural areas where the air is clean the trees are covered in lichen. d. The peppered variety is better camouflaged when it rests on these trees. The melanic form is easily seen.e. In industrial areas air is polluted and the lichens die. f. The tree trunks may also be covered in soot giving a black background. g. This favors the melanic form giving them a selective advantage.

2. Classic example: Industrial Melanism

Evidences

Evidences3.Other examples

a. evolution of antibiotic resistant forms of bacteria

b. evolution of insecticide resistant insects (DDT and flies)

EvidencesF. Artificial Selection

1. Def: Selection of desirable traits by man to create organisms with “improved” genetics or desirable traits

EvidencesF. Artificial Selection: plant selection

Two Modes of Evolution1. Microevolution: Small changes within a population or gene

pool or shift in gene frequencies

2. Macroevolution: The formation of new species from other species

The question is: What defines a species?