lamarck’s evidence and inference comparisons between current species and fossils: lines of...

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Page 1: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired
Page 2: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired
Page 3: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

Lamarck’s evidence and inference Comparisons between

current species and fossils: lines of descendents

Use and disuse Inheritance of

acquired characteristics

Page 4: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

1. All species produce far more offspring than required just to replace parents. This would result in exponential growth if populations were not limited. ("Essays on Population" by Thomas Malthus)

2. Populations do not, however, increase exponentially. They generally remain stable in size.(Field observations at home and on the voyage of the Beagle)

3. The resources in the environment are limited. (Field observations)

1. Because of the limited resources in the environment, there is competition among individuals. Only a small fraction of the individuals born can survive.

Darwin’s evidence and Darwin’s evidence and inferencesinferences

Page 5: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

Darwin’s evidence and inferences

4. There is variation within species and populations. Some individuals possess characteristics that are better suited to the environment than others. (Field observations)

5. Most physical, and some behavioral characteristics are inherited.(Breeding experiments with pigeons. "Artificial selection")

2. Those individuals with the best characteristics for the particular environment will do a better job of producing and providing for offspring than will others with less "fit" characteristics.

Page 6: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

Darwin’s evidence and inferences

6. Geologic processes are very, very slow. (Principles of Geology by Charles Lyell, work by Hutton, as well as Darwin's own studies of geology)

3. The earth must be very, very old. Over very great periods of time, "good" characteristics have time to accumulate and less fit ones have diminished.

Homologous vs. analogous structures vs.Vestigial structures

Page 7: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

Evolution

Macroevolution:Changes ABOVE the species level

Can change

Gene pool

Can remain constant (equilibrium)

Microevolution:Change in the genetic makeup of a population

Variation

Within populationsPolymorphisms

Between populationsGeographic variation (clines)

Page 8: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

Evolutionary fitness Darwinian vs. relative fitness Altering frequency of

phenotypes

Page 9: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

Preservation of Genetic Variation Diploidy Balanced polymorphism

Heterozygous advantage (sickle cell trait) Frequency dependent selection (fitness

declines if a characteristic becomes too common)

Common moths at a disadvantage since the jays recognized it quickly

Neutral variation Mutations arising in noncoding regions,

pseudogenes, or parts of a coding region may not be selected for or against

Page 10: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

Sexual selection Sexual dimorphism arises since they

influence mating success (not REPRODUCTIVE success)

Intrasexual vs. intersexual selection (mate choice)

Advantage/disadvantages of sex?

Page 11: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

Preservation of allele frequencies

Page 12: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

Hardy-Weinburg Theorem Allele frequencies remain constant from

generation to generation if only Mendelian inheritance is at work (segregation and recombination)

H.W. equilibrium – Population state in which allele frequencies are not changing, so genotype frequencies can be predicted

Page 13: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired
Page 14: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

Conditions for PRESERVING Hardy-Weinberg equilibrium Large population size No gene flow No new mutations Random mating No natural selection

Page 15: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

The goal of natural selection? Evolution is limited by its

ancestry Adaptations are often

compromises Chance and natural selection

interact (natural selection is not random)

Selection can only edit existing alleles (new alleles do not arise ON DEMAND)

Small genetic changes can result in large morphological changes

Page 16: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

Anagenesis vs. Cladogenesis Evolutionary theories

must explain how new species form (macroevolution) in addition to evolution of adaptations in a population (microevolution)

Adaptations ABOVE the species level can help define higher taxa

Page 17: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

What is a species?

More importantly what evidence do we use to distinguish species

Reproductive isolation

Page 18: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

Read through the following definitions of a species: biological, morphological, paleontological, ecological, phylogenetic

Discuss as a group which one you think should be used when classifying species and why

Page 19: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

Allopatric speciation

Page 20: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

Sympatric speciation

Page 21: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

Adaptive radiation

Page 22: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

Punctuated equilibrium

Page 23: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

Small genetic changes can result in large morphological changes

Page 24: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

Small genetic changes can result in large morphological changes

Page 25: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

Species selection

Page 26: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

Phylogeny and Systematics Problem: Organism classification and

evolutionary history Phylogeny: “tribe” “origin”: Evolutionary

history of a species or group of species Evidence:

Fossil record systematics (analytical approach using

morphological or biochemical similarities) Molecular biology represents best method for

VERY closely related species

Page 27: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

Sorting homology from analogy Example: Bat and birds have wings. Is this the

result of divergent evolution (homologous structure) or convergent evolution (analogous structure)?

We need to example the actual bone structure and complexity of it

Homoplasies: analogous structures that evolved independently

Page 28: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

Molecular homologies and molecular clocks

Sequences must first be aligned (problem with deletion mutations?) Problems with molecular

systematics? Molecular homoplasy

Page 29: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

Molecular clocks Calibration: Graph number of nucleotide

differences against known evolutionary branch points (fossil record)

Neutral theory DNA coding for rRNA vs. mtDNA

Page 30: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

Classification Binomial: genus + specific

epithet Homo sapiens Taxon (plural taxa): A

taxonomic unit

Page 31: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

Phylogenetic trees Cladograms A branched diagram

that depicts the evolutionary hypothesis

Depicts pattern of shared characteristics but not evolutionary history

If shared characteristics due to homology, then it is the basis of a phylogenetic tree

Page 32: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired
Page 33: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

Origin of Life Evidence supports this sequence of events

that led to life on earth… 1. Abiotic synthesis of small organic

molecules 2. Joining of monomers to form polymers 3. Packaging of polymers to form

“protobionts” 4. Origin of self replicating molecules that

made inheritance possible

Page 34: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

1. Abiotic synthesis of organic molecules First conditions on earth

Lot’s of water vapor (eventually condensed to form oceans)

N2, nitric oxides, CO2, CH4, NH3, H2, H2S

Reducing atmosphere with energy from UV rays and lightning (postulated by Oparin and Haldane in 1920’s

Oceans were a “primitive soup” of organic molecules

Current conditions on earth Mostly N2, CO2, and O2 O2 comes primarily from

biological splitting of water in cyanobacteria

Evidence: Stromatolites (3.5 billion years old)

Oxidizing atmosphere

Page 35: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

1. Abiotic synthesis of organic molecules Miller-Urey

experiments

Page 36: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

2. Abiotic synthesis of polymers Chains of amino acids can

form spontaneously on hot sand, clay, or rock

3. Formation of protobionts Aggregates of abiotically

produced molecules surrounded by a membrane

“Laboratory” evidence: When lipids or other organic molecules are added to water liposomes form, which can do all the functions of a cell membrane (shrink and expand, transport materials, carry a voltage)

Page 37: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

4. Origin of self replicating molecules

Chech and Altman: RNA plays catalytic role in protein synthesis and can carry out enzymatic like reactions (ribozymes)

Diversity and selection of RNA molecules

Dyson:

Page 38: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

Possible scenario Other scenarios?

Page 39: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

Fossil and geology records

Index fossils (order in which fossils were laid down, but not age)

Radiometric dating Based on decay of

radioactive isotopes Half-life: # of years it

takes for 50% of material to decay

Page 40: Lamarck’s evidence and inference  Comparisons between current species and fossils: lines of descendents  Use and disuse  Inheritance of acquired

A brief history of life

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Kingdom classification