NATURAL SELECTION AND THE EVIDENCE FOR EVOLUTION

NATURAL SELECTION AND THE EVIDENCE FOR EVOLUTION Chapter 15.1

I. CHARLES DARWIN AND NATURAL SELECTION • Evolution: a series of adaptations “over time” • Charles Darwin developed this theory of evolution

I. CHARLES DARWIN AND NATURAL SELECTION • A. Fossils Shape and Ideas About Evolution • Fossils form base of evolutionary thoughts

I. CHARLES DARWIN AND NATURAL SELECTION • B. Darwin on HMS Beagle • Took this ship (HMS Beagle) on a 5 year scientific journey around the world • Collected fossils at every port along route • Compared each to determine evolutionary relationships • Studies provided the foundation for evolution by natural selection: • Organisms with most favorable traits survive and pass those traits on to their offspring.

I. CHARLES DARWIN AND NATURAL SELECTION • C. Darwin in the Galapagos • Galapagos are a group of small islands near the equator • He studied organisms there that are unique to the island, but similar to those elsewhere • Led Darwin to believe that species can “change over time”

I. CHARLES DARWIN AND NATURAL SELECTION • D. Darwin Continues his Studies • Darwin observed that the traits of individuals vary in populations. Variations are then inherited. • Breeding organisms with specific traits in order to produce offspring with identical traits is called artificial selection. • Darwin hypothesized that there was a force in nature that worked like artificial selection.

I. CHARLES DARWIN AND NATURAL SELECTION • D. Darwin Continues his Studies • Natural selection is a mechanism for change in populations. • occurs when organisms with favorable variations survive, reproduce, and pass their variations to the next generation. • Organisms without these traits are less likely to survive

I. CHARLES DARWIN AND NATURAL SELECTION • E. Darwin Explains Natural Selection • In nature, more offspring than can survive are produced • In any population, individuals have variations • Over time, those with favorable variations survive and pass those traits on to their offspring • Over time, individuals with variations look entirely different from their ancestors and make up a large portion of the population

I. CHARLES DARWIN AND NATURAL SELECTION • F. Interpreting Evidence After Darwin • After much investigation, a majority of scientists have accepted Darwin’s theory of Evolution by natural selection

II. ADAPTATIONS: EVIDENCE FOR EVOLUTION • Adaptation: any variation that aids an organisms chance of survival in its environment • Darwin’s theory explains how some of these adaptations may occur

II. ADAPTATIONS: EVIDENCE FOR EVOLUTION • A. Structural Adaptations Occur Over Time • adaptations in species develop over many generations

II. ADAPTATIONS: EVIDENCE FOR EVOLUTION • A. Structural Adaptations Occur Over Time • Mimicry is a structural adaptation that enables one species to resemble another species • a harmless species has adaptations that result in a physical resemblance to a harmful species • Predators that avoid the harmful looking species also avoid the similar-looking harmless species

Syphrid Fly

II. ADAPTATIONS: EVIDENCE FOR EVOLUTION • Camouflage: an adaptation that enables species to blend with their surroundings. • Because well-camouflaged organisms are not easily found by predators, they survive to reproduce.

Camouflage

II. ADAPTATIONS: EVIDENCE FOR EVOLUTION • B. Physiological Adaptations Can Develop Rapidly • Physiological adaptations are changes in an organism’s metabolic processes • Example is penicillin resistant bacteria • Can also be seen in some species of insects and weeds that are pests • Some things develop an “immunity”

III. OTHER EVIDENCE FOR EVOLUTION • A. Fossils • Even though fossil record is incomplete, it still gives scientists a good idea of how organisms evolved • For example, the evolution of the camel

Camel Evolution

III. OTHER EVIDENCE FOR EVOLUTION • B. Anatomy • Homologous structures: structures with common evolutionary origin • same structure, same function, or same in both cases

Homologous Structures Crocodile forelimb Bird wing Whale forelimb

III. OTHER EVIDENCE FOR EVOLUTION • B. Anatomy • Analogous structures: structures that have NO COMMON ORIGIN, but are similar in function • Ex: insect wings and bird wings

III. OTHER EVIDENCE FOR EVOLUTION • B. Anatomy • Vestigial structures: a body structure in a present-day organism that no longer serves its original purpose, but was useful to an ancestor • ex: eyes of blind mole rats, forelimbs of an ostrich, pelvic bone in a baleen whale

III. OTHER EVIDENCE FOR EVOLUTION • C. Embryology • Embryo: the earliest stage of growth and development of both plants and animals • There are several similarities between fish, reptile, bird, and mammal embryos • Both have pharyngeal pouches and a tail • This leads people to believe that all have a distant common ancestor

Embryology Similarities

III. OTHER EVIDENCE FOR EVOLUTION • D. Biochemistry • Nearly all organisms share DNA, ATP, and many enzymes among their biochemical molecules • Scientists compare a specific amino acid sequence, “Cytochrome c” that is present in animals all the way from bacteria to bison (a mammal)

Comparison of Cytochrome c Biochemical Similarities of Organisms Percent Substitutions of Amino Acids in Cytochrome c Residues Comparison of Organisms 5 and 10 Two orders of mammals Birds vs. mammals 8-12 Amphibians vs. birds 14-18 Fish vs. land vertebrates 18-22 Insects vs. vertebrates 27-34 Algae vs. animals 57

III. OTHER EVIDENCE FOR EVOLUTION • D. Biochemistry • If organisms are biochemically similar, then they have fewer differences in amino acid sequences • If organisms are biochemically different, then they have more differences in their amino acid sequences

DON’T FORGET • Today scientists combine all of the following to determine evidence of evolution • Fossils • Anatomy • Homologous, analogous, vestigial structures • Embryology • Biochemical Similarities

Question 1 • ________ is considered to be the fundamental concept of biology. • Genetics • The Modern Theory of Evolution • Artificial selection • Structural adaptation

Question 2 • Breeding organisms with specific traits in order to produce offspring with identical traits is called _________ • Natural selection • Adaptation • Mutation • Artificial selection

Question 3 • Mimicry and camouflage are NOT examples of _________. • Adaptation • Natural selection • Evolution • Artificial selection

NATURAL SELECTION AND THE EVIDENCE FOR EVOLUTION