Evolution 15

The Big Idea The theory of natural selection explains evolution and the diversity of life.

Main Idea #1 Charles Darwin developed a theory of evolution based on natural selection.

The 1st Scientific Hypothesis of Evolution French biologist Jean Baptiste de Lamarck offered the first complete explanation of evolution in 1809. He was the first to argue that fossils were the remains of extinct animals. His concept was transformational, meaning individuals transform their own traits in order to evolve.

Uniformitarianism Geologist Sir Charles Lyell - the principle of uniformitarianism. Two parts: laws of physics and chemistry remain the same throughout earth’s history past geological events occurred by natural processes similar to those that observed today He said Earth’s age must be measured in millions of years.

Charles Robert Darwin 1809-1882 In 1831, Darwin sailed aboard the very small ship the HMS Beagle. During his 5-year voyage, he collected a wide variety of flora and fauna from South America and surrounding islands. He found long extinct fossils, including seashells in the Andes Mountains at an altitude of 13,000 feet. He also witnessed earthquakes and severe erosion that helped to confirm his ideas about geology.

Darwin & The Galapagos Islands These volcanic islands are on the equator, 600 miles west of Ecuador. Each island varied in tortoises, iguanas, mockingbirds, and ground finches. The islands had similar climate, but varied greatly in vegetation. Darwin inferred that island species originated in South America, and were modified over many years under the varying conditions of different islands.

Darwin (continued...) Darwin conducted the remainder of his work at home in England, where all of his notebooks had been sent home ahead of him in October 1836. His travel journal, The Voyage of the Beagle, was published three years later, but he continued his research on the evolution of species by natural selection. Darwin first presented his ideas in a paper in 1844, but did not began writing the larger volume until 1856. By 1858, he had received a manuscript from Alfred Russel Wallace summarizing his ideas on natural selection. Geologist Lyell was instrumental in convincing Darwin to publish a joint paper with Wallace. Darwin’s book On the Origin of Species by Means of Natural Selection was published in 1859. All printed copies sold out in one day.

Darwin’s Theory of Evolution Darwin’s work actually included 5 separate theories Perpetual Change is the basic theory of evolution on which the others are based stating that the world is constantly changing. Common Descent (controversial theory) states that all forms of life descended from a common ancestor. Multiplication of Species - species divide and split into different species, which can no longer interbreed Gradualism - large differences actually originate from an accumulation of many smaller differences Natural Selection - explains the selective processes of the environment, through a phenomenon called adaptation.

Natural Selection & Speciation

Natural Selection The Ideas Behind Natural Selection Individuals in a population show variations. Variations can be inherited. Organisms have more offspring than can survive on available resources. Variations that increase reproductive success will have a greater chance of being passed on.

Types of Evidence of Evolution Fossil Record Comparative Anatomy Homologous Structures - similar structures inherited from a common ancestor Vestigial Structures - structures that are reduced forms of functional structures in other organisms; get smaller over generations Analogous Structures - structures that have similar function, but not similar shapes; not inherited from a common ancestor

Evidence (continued...) Comparative Embryology - many embryos share characteristics that are not alike in the adult form Comparative Biochemistry - the more closely related two species are, the more amino acid sequences they will share Geographic Distribution - evolution may be closely linked to climate and geographical characteristics

Speciation Speciation is the evolutionary process by which new biological species arise. Allopatric speciation - a physical barrier divides one population into one or more populations mountain ranges, lava flows, channels between islands, wide rivers believed to be the most common type of speciation Sympatric speciation - no physical barrier separates the populations the ancestor species and new species live side by side

Types of Evolution Chemical Evolution - formation of organic molecules from inorganic substances primordial soup; chemicals in the early ocean giving rise to organic, and eventually, living matter Organic Evolution - changing of a species into something different by the accumulation of small changes over time