On the Origin of Species Charles Darwin’s book Charles Darwin’s book Published December, 1859 Published December, 1859 Sold out in one day Sold out in one day “A century and a half later, it still argues the case for evolution better than any other book. “ Edward J. Larson, Evolution

Darwin’s Case for Evolution Artificial Selection

Darwin’s Case for Evolution - Artificial Selection An idea with which people were comfortable An idea with which people were comfortable Farmers select for breeding only the animals or plants that have the traits they like Farmers select for breeding only the animals or plants that have the traits they like Fast horses, plants with the biggest fruit Fast horses, plants with the biggest fruit Named this process “artificial selection” Named this process “artificial selection”

Darwin’s Case for Evolution – Variety also exists in nature – among species (interspecific)

Darwin’s Case for Evolution -and within species (intraspecific)

Darwin’s Case for Evolution In nature, many more individuals are born than can possibly survive. Thomas Malthus connection

Darwin’s Case for Evolution Why can’t they all survive? Limiting Factors ( factors that limit pop. size ) Predation Predation Food supply Competition Food supply Competition Shelter Shelter Mates Mates

Darwin’s Case for Evolution A high rate of reproduction combined with competition for food, shelter, and mates creates a struggle for existence. The fiercest struggle is among individuals of the same species sharing the same niche, habitat, and dangers.

Darwin’s Case for Evolution “Can we doubt that individuals having an advantage, however slight, over others, would have the best chance of surviving and procreating their kind?...This preservation of favorable conditions… I call Natural Selection.” In modern terms: DIFFERENTIAL REPRODUCTION OF SELECTED PHENOTYPES

Natural Selection Measures the ability of a population to survive and reproduce Measures the ability of a population to survive and reproduce Dependent upon environmental factors Dependent upon environmental factors Genotypes (alleles) Genotypes (alleles) phentoypes (traits) phentoypes (traits) survival/repro advantage! survival/repro advantage!

Darwin’s observations High reproductive potential High reproductive potential Overall, population size is stable Overall, population size is stable Limited resources Limited resources Variation Variation

Darwin’s conclusions Competition drives selection Competition drives selection Fitness level determined by adaptations! Fitness level determined by adaptations! The more adaptations… the more evolutionary success! The more adaptations… the more evolutionary success!

Natural Selection Summary Populations of organisms struggle for survival and reproductive success (fitness) Populations of organisms struggle for survival and reproductive success (fitness) Environment determines which genetic variations are most desirable in organisms/populations Environment determines which genetic variations are most desirable in organisms/populations Populations of organisms adapt to their environment to improve fitness Populations of organisms adapt to their environment to improve fitness

WHERE’S THE EVIDENCE? FOSSIL RECORD FOSSIL RECORD BIOGEOGRAPHY BIOGEOGRAPHY COMPARATIVE ANATOMY COMPARATIVE ANATOMY COMPARATIVE EMBRYOLOGY COMPARATIVE EMBRYOLOGY COMPARATIVE BIOCHEMISTRY COMPARATIVE BIOCHEMISTRY

Darwin’s Evidence Fossil Record Over millions of years, deposits compress older sediments below into layers Over millions of years, deposits compress older sediments below into layers Older layers, with older fossils, lie beneath younger layers, with younger fossils Older layers, with older fossils, lie beneath younger layers, with younger fossils

Darwin’s Evidence Fossil Record embryology in extinct organisms similar to that in living organisms embryology in extinct organisms similar to that in living organisms

Variation

Darwin’s Evidence Morphology – Similarities in the form and structure of organisms Similarities in the form and structure of organisms Homologous structures: structures with different mature forms/functions, but which develop from the same embryonic tissues

Darwin’s Evidence Morphology – similarities in the form and structure of organisms Analogous structures: structures with same mature forms/functions, but which develop from the different embryonic tissues structures with same mature forms/functions, but which develop from the different embryonic tissues

Homologous vs. Analagous

Darwin’s Evidence Morphology – Vestigial Organs – Homologousstructures which no longerfunction

VESTIGIAL HUMAN STRUCTURES ? VESTIGIAL HUMAN STRUCTURES ?

Darwin’s Evidence Embryology Similarities in patterns of development among different species today suggest common ancestor: Similarities in patterns of development among different species today suggest common ancestor: Chick Chick Pig Pig Human Human

Darwin’s Evidence Geographic proximity of similar species – species on different Galapagos Islands were similar to one another, but different from those on mainland

Darwin’s Finches

DIVERGENT EVOLUTION DIVERGENT EVOLUTION

Adaptive Radiation

Darwin’s Evidence Convergent Evolution Convergent Evolution Animals living on different continents had different ancestors; however, because some animals on each continent lived under similar ecological conditions, they had similar selection pressures and thus similar features Animals living on different continents had different ancestors; however, because some animals on each continent lived under similar ecological conditions, they had similar selection pressures and thus similar features Placental MammalsAustralian Marsupials

Lamarck vs. Darwin

Remaining 19 th Century Questions Natural Selection Special Creation The complexity and perfection of structures such as the human eye indicates the work of a supernatural Designer. William Paley William Paley Natural selection results in better-adapted organs and organisms, not perfect ones. Charles Darwin Charles Darwin

Remaining 19 th Century Questions What about gaps in the fossil record? What about gaps in the fossil record? What about these “great leaps” forward? What about these “great leaps” forward? Is the Earth old enough for the slow process of natural selection? Is the Earth old enough for the slow process of natural selection? How did human mental and moral attributes evolve? How did human mental and moral attributes evolve? How does inheritance work? How does inheritance work? Where do varieties come from? Where do varieties come from?