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’t2. This idea would be applied to all species3. 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 IslandsGalapagos 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. Competition1. Env’t resources are fixed; however, indiv. produced exceed resources2. So, reproduction rate exceeds survival rate3. Indiv. must “compete” for limited resources

d. Fitness/Reproduction

1. Some indiv. have better traits, thus better suited for env’t will likely reproduce2. Fitness related to particular env’t3. 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, thenspread 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 seein 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 info2. proteins serve as enzymes3. ATP, carbs, fats store NRG4. Lipids build membranes

b. Metabolic systems are similar:

1. photosynthesis/respiration2. gene expression, protein synthesis

c. Basic cell structure is almost universal