Darwin and Evolution 16-1 Darwin’s Voyage 16-2 Ideas that shaped his thinking 16-3 Darwin presents his case 16-4 Evidence of Evolution

Darwin’s Inspiration James Hutton Charles Lyell Jean-Baptiste Lamarck Thomas Malthus

James Hutton-1785 Proposed that: layers of rocks form very slowly or are moved up from the Earth’s surface Earth had to be millions of years old and not a few thousand years old Earth is shaped by geological forces that took place over extremely long periods of time

Charles Lyell-1833 Explained that awesome geological features could be built up or torn down over long periods of time Helped Darwin appreciate the significance of geological phenomena

Jean-Baptiste Lamarck-1809 Proposed that by selective use or disuse of organs, organisms lost or acquired certain traits Proposed that all organisms had a built in tendency toward complexity and perfection Proposed that organisms could alter the size or shape of particular organs by using their bodies in new ways

Lamarck cont. Thought that acquired characteristics could be inherited If you spent much of your life lifting weights to build muscles, your children would inherit big muscles *Didn’t know how traits were inherited* Was one of the first to develop a scientific hypothesis of evolution and realize that organisms are adapted to their environments

Thomas Malthus-1798 Studied population growth Said that if the human pop. Continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone Supported by observation made on the streets of London

Darwin’s Case concluded that animals on the coast of South America that resembled those on the nearby islands evolved differences or descended with modification after separating from a common ancestor 25 years later he published On the Origin of Species after hearing that Alfred Wallace was coming to the same evolutionary conclusions Proposed a mechanism for evolution that he called natural selection Charles Darwin (1809– 1882)

Inherited Variation & Artificial Selection Inherited variation-caused by the variations in genes Artificial selection-nature provides the variation and humans select those variations that are found useful Produced many diverse domestic animals and crop plants

Natural Selection Struggle for existence-members of each species compete regularly to obtain food, living space, and other necessities for life Fitness-ability of an individual to survive an reproduce in its specific environment Adaptation-any inherited characteristic that increases an organism’s chance of survival

Natural Selection cont. Survival of the Fittest-ability to survive and reproduce most successfully – Individuals that are best suited to their environment, with adaptations that enable fitness, survive and reproduce most successfully – Individuals with characteristics that are not well suited to their environment, with low levels of fitness, either die or leave few offspring

Natural Selection cont. Darwin referred to survival of the fittest as NATURAL SELECTION In both artificial and natural selection only certain individuals of a population produce new individuals In natural selection, traits being selected contribute to an organisms fitness (over time) NS cannot be seen directly; it can only be observed as changes in a pop. over many successive generations

Descent with Modification Darwin proposed that each living species has descended, with changes, from other species over time (descent with modification) Common Descent- all species, living or extinct, were derived from common ancestors

Evidence of Evolution Darwin argued that living things have been evolving on Earth for millions of years Evidence could be found in the fossil record, geographical distribution of living species, homologous structures of living organisms, and similarities in early development

Fossil Record Formation of Fossils -evidence of orderly change can be seen when fossils are arranged according to their age. Darwin saw fossils as a record of history of life on Earth Showed that life had been evolving for millions of years

Homologous Structures Homologous structures describes similar body structures that come from common ancestry HS are structures that have different mature forms but develop from the same embryonic tissues *not all homologous structures serve important functions* Vestigial organs-homologous structures that are so reduced in size that they serve no function

Vestigial Organs

Homologous Structures Evolution Homologous structures Vestigial structures Molecules Forelimbs BirdsBatsHumans Hind limbsWhales Human hemoglobin Frog Rhesus monkey Lamprey Mouse Chicken Gorilla Alligators

Similarities in Embryology In early stages of development, chickens, turtles, and rats look similar, providing evidence that they shared a common ancestry. ex. see right picture - The embryos of the tortoise, chick, rabbit, and human resemble one another due to the distinguishing tail, gill slits, and overall shape during early development.

Evolutionary Theory Strengths: – Scientific advances in biology and physics have confirmed and expanded most of Darwin’s hypotheses Weaknesses: – Researches still debate about how new species arise and why they become extinct *There is still uncertainty about how life began*