Evolution Evolution What is evolution It is the

Evolution

Evolution • What is evolution? – It is the process of biological change by which descendents come to differ from their ancestors

Scientists • Scientists who began studying evolution: – Linnaeus (1700’s) • Developed classification system of organisms • Proposed that organisms arose from hybridization

Scientists • Buffon (1700’s) – Used evidence of past life – Proposed that species shared ancestors instead of arising separately – Proposed earth was much older than 6000 years

Scientists • Erasmus Darwin (1731) – Proposed all living things were descended from a common ancestor – Later expanded upon by his grandson

Scientists • Lamarck (1809) – Didn’t believe in extinction – Species evolved instead – Proposed that changes in environment caused behavior to change – Organism passes on these traits to offspring – “Inheritance of acquired characteristics”

Charles Darwin • Darwin took a trip to the Galapagos Islands aboard the HMS Beagle • He studied the inhabitants of the island

What did Darwin find?

Charles Darwin • Findings and conclusions: – Variation among species – Led him to believe species adapt to their environment – Adaptation- feature allows an organism to better survive in an environment – Leads to change in populations over time

Examples of Adaptations

horned lizard pistol shrimp aye archer fish

Charles Darwin • Natural Selection – Individuals inherit beneficial adaptations and produce more offspring than others

Charles Darwin • 4 principles of natural selection: 1. Variation - Differences among organisms 2. Overproduction - More offspring increases chance for survival 3. Adaptation - Certain variations allow to survive better 4. Descent with Modification - Over time, more individuals in the population will have the beneficial traits

Natural Selection Variation Adaptation Overproduction Descent with Modification

Fossil Evidence • No fossil evidence that contradicts evolution has been found • Allows us to see transitions of species over time

Anatomical Evidence • Homologous structures – Features that are similar in structure, but different in function in different organisms – Supports common descent

Anatomical Evidence • Analogous structures – Structures that perform similar function

Anatomical Evidence • Vestigial structures – Unused features – Structure had a function in early ancestor – Helps support common ancestry and evolution

Molecular Evidence • All living things have DNA • Organisms carry pseudogenes – Genes that do not function (vestigial) • Cells have very similar proteins – Marine worms have same proteins in the eye as vertebrates Ø Comparison of milk protein in whales and hippos: • Hippo TCC TGGCA GTCCA GTGGT • Humpback Whale CCC TGGCA GTGCT

Match the structure Homologous, analogous, or vestigial B A C

Population Distributions • Normal Distribution – Frequency of a certain phenotype is near the mean

Population Distributions • Directional Selection – Selection favors phenotypes at one extreme – Population shifts toward advantageous trait

Population Distribution • Stabilizing Selection – The intermediate is favored and becomes the most common

Population Distribution • Disruptive Selection – Both extreme phenotypes are favored

Genetic Drift • Bottleneck Effect – Occurs after an event greatly reduces the size of a population – Ex. Overhunting of elephant seals

Genetic Drift • Founder Effect – Occurs after a small # of individuals colonize a new area – Ex. Emerald ash borer

Sexual Selection • Occurs when certain traits increase mating success • Two types: • Examples: – Intrasexual • Physical competition among males – Intersexual • Displays among males Giraffe fight Bird display – Intersexual

Long-tailed Widowbird Male Female

Evolutionary Classification • Cladogram – Evolutionary tree that proposes how species may be related to each other through common ancestors • Clade – Group of organisms that share certain traits

Evolutionary Classification Cladogram for modes of transportation: Bicycle Car Motorcycle Airplane On foot walking bicycle motorcycle car airplane wings motor wheels Passengers enclosed