Lecture 29 DARWIN NATURAL SELECTION Part 1 Ms

Lecture #29 DARWIN & NATURAL SELECTION Part 1 Ms. Day Honors Biology http: //www. wiley. com/college/test/0471787159/biology_basics/a nimations/evolution. swf

Darwin made two major points in his book called Origins of Species: 1. Many current species are descendants of ancestral species 2. Natural selection is HOW EVOLUTION occurs (current “Theory of Evolution”)

Resistance to the Idea of Evolution • The Origin of Species = Darwin’s book –Shook the deepest roots of Western culture –Challenged a worldview that had been prevalent for centuries • Earth ONLY ~6000 yrs old • It was unchanging!!!!

Lamarck’s Theory of Evolution (1809) • Lamarck hypothesized species change (evolve) over time because of: 1. use and disuse and 2. inheritance of acquired traits • The mechanisms he proposed are unsupported by evidence

• Lamarck’s Theory of Evolution Idea called Use and Disuse • If a body part were used, it got stronger • If body part NOT used, it deteriorated/disa ppeared

inheritance of acquired traits • Will his kids be born with big muscles because he has them?

WILL THE OFFSPRING BE NICELY PRUNED?

Charles Darwin • LOVED nature • Sails on HMS Beagle at 22 and voyaged around world • Noted flora and fauna on islands off of South America • Contributions of Lyell, Hutton and Malthus lead him to his mechanism for evolution • species change through natural selection • http: //www. pbs. org/wgbh/evolution/educators/teachstuds/svideos. html

The Voyage of the Beagle • Collected specimens of South American plants and animals • Observed adaptations of plants and animals that lived many different environments • Main focus = Galápagos Islands near the equator west of South America

The Galapagos Islands • Small group of islands west of South America • Very different climates • Animals on islands unique

England EUROPE NORTH AMERICA PACIFIC OCEAN ATLANTIC OCEAN AFRICA Galápagos Islands HMS Beagle in port Equator SOUTH AMERICA Darwin in 1840, after his return AUSTRALIA Andes Cape of Good Hope Cape Horn Tierra del Fuego Darwin returned 5 years later in 1836 Tasmania New Zealand

Darwin’s Focus on Adaptation • Adaptation= a change in structure or habits, often inheritable to improve survival & reproduction in particular environment – A trait that allows you to live/reproduce better in a certain environment – Acts on variation in population • EXAMPLE – Finches (birds) on Galapagos islands resembled the mainland finch • BUT…Finches had different types of beaks adapted to their type of food

LE 22 -6 Cactus eater. The long, sharp beak of the cactus ground finch (Geospiza scandens) helps it tear and eat cactus flowers and pulp. Seed eater. The large ground finch (Geospiza magnirostris) has a large beak adapted for cracking seeds that fall from plants to the ground. Insect eater. The green warbler finch (Certhidea olivacea) used its narrow, pointed beak to grasp insects.

Darwin’s Overall Observations 1. The # of organisms of each species will increase 2. In nature, populations tend to remain stable in size 3. Environmental resources are limited

More of Darwin’s Observations 5. Populations have variation – no 2 individuals being exactly alike • Much of this genetic variation between individuals is inheritable and can be caused by MUTATION Variation is RANDOM!!!

Darwin’s Overall Conclusions 1. More individuals are made than can be supported by the environment leads to a struggle for existence among individuals • Only a fraction of offspring survive each generation • Survival of the Fittest

Darwin’s Conclusion 2. individuals who inherit characteristics (adaptations) that are most fit (suitable/favorable) for their environment leave more offspring than less fit individuals • Called FITNESS (survival and reproduction) • High survival = more offspring = more fit

Darwin’s Conclusion • Natural Selection – SLOW, not random process causing some traits to become more or less common in a population – Acts on PHENOTYPES (adaptations) influences GENOTYPES – Organisms best adapted to environment survive give genetic traits to future generations while those less adapted tend to be eliminated – Key mechanism to evolution

3 Modes of Natural selection • Directional selection favors individuals that are one type of true bred (Ex: favors RR or rr) • Disruptive selection favors both type of trued breds (Ex: Favors RR and rr) • Stabilizing selection favors heterozygotes and acts against true breed phenotypes (Ex: Favors Rr)

DARK ROCK HABITAT LIGHT/DARK ROCK HABITAT MEDIUM COLOR ROCK HABITAT

3 Types of Natural Selection

https: //www. youtube. com/watch? v=xkw. RTIKXaxg&list=PLZkw Dikqx 4 JKFX 2 k 011 i. J 6 ipt 6 cj 80 Ak 5 Video: How Does Evolution Really Work?

Darwin’s Descent with Modification • descent with modification • refers to idea that all organisms are related and came from a common ancestor • the history of life is like a tree

Darwin’s st 1 Idea: Evolution • What is evolution? – A change over time in the genetic combination of a population give rise to biodiversity • Darwins definition of evolution = Descent with modification Darwin’s 2 nd Idea: Natural Selection • If an environment changes over time, natural selection may result in adaptation to these new conditions new species can also evolve

Evidence for Evolution by Natural Selection HOW DO WE KNOW EVOLUTION WORKS? PPT Lecture #29: Part 2 https: //www. youtube. com/watch? v=l. IEo. O 5 Kd. Pvg https: //www. youtube. com/watch? v=ewtw_n. ZUIDQ&list=PLv. FQy. Vl 48 bpzzmy. VQLp. Ds. Wydy. Bqi_Zc-J

Evidence for Evolution http: //www. sumanasinc. com/webcontent/animations/cont ent/evolution. html 1. Homology • a similarities in characteristic traits resulting from common ancestry 2. Anatomical Homologies • anatomical resemblances that represent variations on a structural theme present in a common ancestor • Called HOMOLOGOUS STRUCTURES • Same development, different function

LE 22 -14 Human Cat Whale Bat

3. Vestigial organs • remains of structures once important in organism’s ancestors – Example: tailbones in humans, appendix, wings on ostrich, wisdom teeth in humans

4. Comparative Embryology

5. Molecular Homologies • Similar genes (DNA), RNA or amino acid sequences –Example • genes shared among organisms inherited from a common ancestor • Ex #1: Homeobox is a DNA sequence in genes that regular development in plants, animals and fungi • http: //www. pbs. org/wgbh/evolution/library/03/4/l_034_04. html

LE 22 -16 Species % of Amino Acids That Are Identical to the Amino Acids in a Human Hemoglobin Polypeptide Human 100% 95% Rhesus monkey 87% Mouse 69% Chicken Frog Lamprey 54% 14% Ex #2: Amino Acid/ Protein sequence

6. Biogeography • the geographic distribution of species Sugar Glider Marsupial • Some similar mammals that have adapted to similar environments have evolved independently from different ancestors Flying Squirrel Eutherian (placental)

7. Fossil Records • Paleontologists have discovered fossils of many transitional forms • Shows variety on organism across time 8. Field Studies

Key Concepts What is the raw material necessary for the mechanism of Natural Selection? • Heritable variations What is the smallest unit of evolution? • Populations (NOT individuals) • Darwin incorporated Lyell’s gradualism into biological evolution combined with Malthus’ observations regarding populations

What is a “theory” is science? • summarizes a hypothesis(es) that have been supported with repeated testing • If enough evidence accumulates to support a hypothesis, it moves to the next step—known as a theory—in the scientific method and becomes accepted as a valid explanation of a phenomenon • a theory is an explanation or model based on observation – theories can be proven or rejected, just like hypotheses.

What is a “theory” is science? • Scientific definition of theory is different from everyday meaning – non-scientific context of “theory” implies that something is unproven or speculative • Scientific definition refers to a comprehensive explanation of some aspect of nature that is supported by a vast (A LOT) body of evidence (data).

Is Evolution JUST a THEORY? ? ? Is it SCIENCE based? • http: //www. pbs. org/wgbh/evolution/educ ators/teachstuds/svideos. html • Video #1: Isn’t Evolution Just a Theory? • https: //highered. mheducation. com/sites/9834 092339/student_view 0/chapter 20/animation__mechanisms_of_evolution. html

Some Cool Evolution Videos… • Poison Newts – http: //www. pbs. org/wgbh/evolution/library/01/3/l_013_07. ht ml • Camouflage “Leaves” – http: //www. pbs. org/wgbh/evolution/library/01/1/l_011_03. ht ml • Evolution of the Eye – http: //www. pbs. org/wgbh/evolution/library/01/1/l_011_01. ht ml • Why Does Evolution Matter Now? (Video #6) – http: //www. pbs. org/wgbh/evolution/educators/teachstuds/svi deos. html