Chapter 12 The Theory of Evolution Section 1: The Theory of Evolution by Natural Selection Section 2: Evidence of Evolution Section 3: Examples of Evolution Darwin

Section 1 The Theory of Evolution by Natural Selection Objectives: Identify several observations that led Darwin to conclude that species evolve. Summarize the main points of Darwin's theory of evolution by natural selection as it is stated today. Contrast the gradualism and punctuated equilibrium models of evolution.

Section 1 The Theory of Evolution by Natural Selection Darwin Proposed a Mechanism for Evolution Science Before Darwin’s Voyage Lamarck proposed an incorrect mechanism for how organisms evolve, but he correctly pointed out that change in species is linked to an organism’s environment. Lamarck: giraffes stretch their necks and pass this long neck to their offspring. “Acquired Characteristics”

Darwin’s Observations 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.

Section 1 The Theory of Evolution by Natural Selection Darwin Proposed a Mechanism for Evolution continued Growth of Populations : Darwin was influenced by Thomas Malthus, who wrote that populations tend to grow as much as the environment allows. Darwin’s book The Origin of SpeciesThe Origin of Species

Section 1 The Theory of Evolution by Natural Selection Evolution by Natural Selection Natural Selection Natural selection is differential reproductive success and natural selection leads to adaptations in a population. Darwin’s Theory Darwin proposed that natural selection favors individuals that are best able to survive and reproduce and this causes populations to evolve.

Section 1 The Theory of Evolution by Natural Selection Darwin’s Ideas Updated Change Within Populations Natural selection causes the frequency of certain alleles in a population to change over time. Species Formation Under certain conditions, change within a species due to reproductive isolation can lead to new species.

Darwin’s Ideas Updated The Tempo of Evolution Gradualism is a process of evolution in which speciation occurs gradually Punctuated equilibrium is a process in which speciation occurs rapidly between periods of little or no change.

Section 2 Evidence of Evolution Objectives: Describe how the fossil record supports evolution. Summarize how biological molecules such as proteins and DNA are used as evidence of evolution. Infer how comparing the anatomy and development of living species provides evidence of evolution.

Section 2 Evidence of Evolution The Fossil Record Formation of Fossils Evidence of orderly change can be seen when fossils are arranged according to their age.

Evidence: Fossils

Section 2 Evidence of Evolution Anatomy and Development Vestigial Structures Reduced or nonfunctional vestigial structures, such as hind limbs in whales Homologous Structures Homologous structures, structures in different organism that indicate a shared ancestry, include the vertebrate forelimb.

Vestigial Structures

Vestigial Structures: Whale legs

Vestigial Structures: Snake legs

Homologous Structures

Embryological Similarities Vertebrates: animals having a backbone.

Embryological Similarities

Section 2 Evidence of Evolution Biological Molecules Proteins: Differences in amino acid sequences are greater between species that are more distantly related than between species that are more closely related. Nucleic Acids : Differences in DNA sequences are greater between species that are more distantly related than between species that are more closely related.

Section 3 Examples of Evolution Objectives: Identify four elements in the process of natural selection. Describe how natural selection has affected the bacteria that cause tuberculosis. Relate natural selection to the beak size of finches. Summarize the process of species formation.

Section 3 Examples of Evolution Natural Selection at Work Factors in Natural Selection Individuals that have traits that enable them to survive in a given environment can reproduce and pass those traits to their offspring. Evolution of Antibiotic Resistance Experiments show that evolution through natural selection has occurred within populations of antibiotic-resistant bacteria, such as the bacteria that cause tuberculosis.

Section 3 Examples of Evolution Formation of New Species Speciation Speciation begins as a population adapts to its environment. Forming Subspecies Populations of the same species that differ genetically because of adaptations to different living conditions are called subspecies. Maintaining New Species Reproductive isolation through reproductive barriers keeps species from breeding with one another.

Periodical “Evolution by Design” Discover, March, 2009 A revolution in biotechnology which allows scientist to alter genes may bypass natural evolution. Sperm and egg cells have been created from skin cells Pluripotent stem cells have been created from skin cells. These can develop into any type of human cell.

Periodical “Evolution by Design” Discover, March, 2009 Genetic engineering is changing the human genome. Insertion of whole, new chromosomes may soon be possible. “Enhancement Evolution” might replace natural evolution. “Deliberate Selection” might replace natural selection.

Video: Evolution Video LinkLink