Unit 7: Chapter 19

• Chapter 19 focuses on Descent with Modification, particularly Darwin and natural selection

Descent with Modification

• Evolutionary change is based on interactions between populations and their environment leading to adaptations, ultimately increasing fitness
• Evolution defined as descent with modification (Darwin) and change in a population's genetic composition from generation to generation

Aristotle

• Believed species were fixed and unchanging, arranged on a ladder of increasing complexity known as Scala naturae from 384-322 BCE
• Creationism as described in the Old Testament posits the Earth at approximately ~6000 years old, with perfect species individually designed by God for a specific purpose

Carolus Linnaeus

• Carolus Linnaeus (1707-1778) is the founder of taxonomy
• He developed binomial nomenclature (Genus, species)
• Classified organisms into Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species
• Linnaeus's classification system was based on anatomy and morphology

George Cuvier

• Cuvier (1769-1832) was a paleontologist who studied fossils
• He noticed deeper strata (rock layers) contained fossils that differ from current life
• Cuvier opposed the idea of evolution
• Boundaries between strata represent catastrophic events leading to species destruction and repopulation by immigrant species

James Hutton and Charles Lyell

• Hutton (1726-1797) proposed that geologic change is gradual and continuous
• Lyell (1797-1875) argued that Earth's processes occur at the same rate in the past and present, suggesting that Earth is very old
• Slow and subtle changes in organisms can lead to big changes over time

Jean-Baptiste de Lamarck

• Lamarck (1744-1829) published theory of evolution in 1809
• He proposed "use and disuse," suggesting body parts used more become bigger, stronger (e.g., giraffe's neck)
• Lamarck also suggested the Inheritance of Acquired Characteristics where modifications can be passed on
• Lamarck is noted as recognizing that species evolve, but his explanation of acquired characteristics was flawed

Thomas Malthus

• Malthus (1766-1834) proposed that more babies are born than deaths
• The consequences of overproducing within an environment include war, famine, and disease, which limit human population

Charles Darwin

• Charles Darwin (1809-1882) was an English naturalist
• In 1831, Darwin joined the HMS Beagle for a 5-year research voyage around the world
• He collected and studied plant and animal specimens, bones, and fossils
• A notable stop on the voyage was the Galapagos Islands
• Darwin waited 30 years before publishing his ideas on evolution
• Alfred Russell Wallace published a paper on natural selection first in 1858
• Charles Darwin published "On the Origin of Species by Means of Natural Selection" in 1859
• Darwin did not use "evolution" but "descent with modification"

Natural Selection

• Adapations enhance an organism's ability and survival in specific environments like desert foxes with large ears and artic foxes with small ears
• In natural selection, nature decides, and it works on individual organisms
• In artificial selection, humans decide and selective breeding occurs
• Natural selection can create substantial changes over long periods of time, just like humans create substantial changed in less time with selective breeding

Key Ideas of Natural Selection

• Competition for limited resources results in differential survival
• Individuals with favorable adaptations are likely to survive, produce offspring, and pass traits to offspring
• If an environment changes or individuals move to a new environment, new adaptations and species may arise
• Populations evolve, not individuals

Evidence for Evolution

• Direct observation
• Homology
• Fossil record
• Biogeography

Direct Observations of Evolution

• Examples include insect populations becoming resistant to pesticides like DDT, antibiotic-resistant bacteria like MRSA, and peppered moths in polluted vs non-polluted environments

Homology

• Homology is a characteristic in related species with a similarity that differs in functions
• Example: Homologous structures: similar anatomy from common ancestors
• Example: Embryonic homologies: similar early development

Convergent Evolution

• Convergent evolution means related species can resemble each other and have similar environments
• Analogous structures: similar structures, function in similar environments
• Example: Torpedo shape of shark, penguin, & dolphin

Fossil Record

• Fossils are remains or traces of organisms from the past
• Fossils are found in sedimentary rock
• Paleontology refers to the study of fossils
• Paleontology shows evolutionary changes that occur over time and the origin of major new organism groups
• Prokaryotes were the oldest fossils which evolved into Eukaryotes (fish, amphibians, reptiles, birds and mammals)

Biogeography

• The geographic distribution of species
• Species in nearby geographic areas resemble each other
• Continental drift and Pangaea explains similarities on different continents
• Endemic species are found at a specific geographic location and nowhere else
• Marine Iguanas in the Galapagos is an example of an endemic species

Recap of Natural Selection

• Evolution = change in population over time as organisms adapt to environment.
• Overproduction of offspring leads to competition for resources, and heritable difference between individuals in environment
• Individuals with adaptations have differential reproductive successes which can change the genetic compostion of the population over generations
• Individuals do NOT evolve, populations evolve!