Things Change Over Time

I.Why study Evolution? A. Evolution explains the Diversity and Unity of life 1. Diversity – the abundance of different forms of living things on Earth 2. Unity – the biochemical, cellular, genetic, and physiological characteristics/processes common to all living things

B. What is Evolution?  The change in a species over time (i.e. the gene pool changes due to adaptations) 1. The Process: Descent thru Modification  new life comes into existence over time  all species come from common ancestry  all species comes from existing species via modification

2. The Mechanism: Natural Selection  those best suited for env’t will survive and pass traits to offspring 3. The Result: Diversity and Unity

II. Theories of Evolution A. Lamarck 1. Evolution occurs thru the use and disuse of physical features Ex. Birds  used their front limbs to fly so turned into wings  if didn’t use, they would disappear 2. He was wrong, but first to propose the idea that things “change over time”

B. Carolus Linnaeus 1. Father of binomial nomenclature (taxonomy) 2. Believed that each species had an “ideal” structure & fxn and had a specific place in the scala naturae (ladder of life)

C. Malthus (English economist) 1.Stated that human population would increase faster than food supply  carrying capacity – only a limited number of resources w/in an env’t 2.This idea would be applied to all species 3.This would influence one major aspect of Natural Selection

D. Charles Darwin 1. Made observations on his voyage around the world (H.M.S. Beagle  Galapagos Islands)

Galapagos Islands Darwin’s route

3. In 1859, he published a book of his findings: “The Origin of Species” 4. Four key components to his theory: 2. He proposed: Theory of Natural Selection a. Those organisms who are better suited for their env’t (due to adaptations), are more likely to survive, reproduce, and pass on favorable traits to offspring b. “Survival of the Fittest”

a. Genetic Variation 1. Within a species, there are heritable differences which continue to be passed on (ex. Some plants bear larger fruit, some cows produce more milk) 2. Balanced polymorphism - When nat. selec. favors heterozygotes over homozygotes  example: sickle-cell anemia 3. Sources of variation: mutations, crossing-over, sexual reproduction

b. Adaptation 1. Organisms respond to their env’t…change… and increase their chance of survival 2. Increasing percentage of succeeding generations having beneficial traits.

c. Competition 1. Env’t resources are fixed; however, indiv. produced exceed resources 2. So, reproduction rate exceeds survival rate 3. Indiv. must “compete” for limited resources d. Fitness/Reproduction 1. Some indiv. have better traits, thus better suited for env’t  will likely reproduce 2. Fitness related to particular env’t 3. Relative fitness – fitness of one pheno. v. another Ex. Snowshoe hare: better in snowy env’ts Ex. Darwin’s Finches…

Darwin’s Finches

5. Types of natural selection: a.Directional – a shift in the freq. of a trait in a particular direction  common in changing env’ts Ex. Horseracing: pick horses that can run fastest

b. Stabilizing – selects for avg. pheno. and against extreme pheno.  common in stable, unchanging env’t

c. Disruptive – selects for extreme pheno. and against avg. pheno. b/c subject to predation

III. Evidence of Evolution  What is the evidence for a common ancestry and descent thru modification? A. Five aspects:

1.Fossil Record  radioactive dating: isotopes (Carbon 14)

 Keep in Mind:  the fossil record is not complete  many species live in env’ts that didn’t allow for fossil formation (e.g. grasslands, deserts). You need envt’s with rock, mud, calcium deposits  though incomplete, the record still provides us with evidence of similarities

2. Biogeography a. organisms evolve to adapt to their env’t, then spread to other locations b. there is a distribution of similar species around the world

3. Comparative Anatomy  Related organisms share a unity of body plan and/or function  Example: backbone, rib cage, and arrangement of internal organs are similar in fish, amphibians, reptiles, birds, and humans

a. Homologous Structures  organisms with similar structures, but different functions

b.Analogous Structures – Diff. organisms have body parts with a similar fxn, but not structure. Insect wing Bat wing Bird wing

c.Vestigial Structures  Structures/organs that no longer serve a purpose and have become reduced in size  Examples: 1.Cave fish – no eyes b/c don’t need to see in dark 2. Humans – wisdom teeth, appendix, tail bone

4. Comparative Embriology  Related organisms develop similarly  Example:  All vertebrate embryos develop gill-like structures, even though only fish have gills as adult lamprey turtle chicken cat human

5. Comparative Biochemistry a. all living things use the same basic biological molecules for similar functions; 1. DNA/RNA stores genetic info 2. proteins serve as enzymes 3. ATP, carbs, fats store NRG 4. Lipids build membranes

b. Metabolic systems are similar: 1. photosynthesis/respiration 2. gene expression, protein synthesis c. Basic cell structure is almost universal