Evolution

Charles Darwin Came up with the explanation for natural selection Came up with the explanation for natural selection Traveled on the HMS Beagle as an unofficial naturalist; made many observations and collected much data Traveled on the HMS Beagle as an unofficial naturalist; made many observations and collected much data Most commonly known for his research on the Galapagos Islands; found that many finches existed with various beaks according to their food sources Most commonly known for his research on the Galapagos Islands; found that many finches existed with various beaks according to their food sources

Galapagos Finches

Definitions Adaptation : Characteristics of a population that result in being better suited to their environment (ex- coat color of arctic fox)

Practice ( ) These feet belong to different birds. Three of the birds spend most of their time on the ground, while one bird rarely walks on the ground. Which foot belongs to the bird that is best adapted for grasping branches? A B C D

Speciation Reproductive isolation : the condition in which two populations of the same species cannot breed with one another as a result of different mating seasons or behaviors. Geographic isolation: populations become geographically isolated and can no longer interact/reproduce with one another Leads to speciation : emergence of new species

Evidences of Evolution Homologous structures Homologous structures Analogous structures Analogous structures Vestigial structures Vestigial structures Embryonic development Embryonic development DNA sequences DNA sequences

Homologous Structures Homologous structures: structures that share a common ancestry. Similar structures in two organisms can be found in common ancestors. (Don’t confuse with ANALAGOUS structures!) (ex- forelimbs in vertebrates share a basic group of bones)

Homologous Structures

Practice Practice ( ) All the organisms shown above belong to the Phylum Chordata. The structural similarity in the organisms suggests that — the humerus is the same size in all chordates only animals that walk on 4 legs need the humerus the humerus is attached to the skeleton by immovable joints chordates have common ancestors

Analogous Structures Analogous structures are structures that are similar between species that are NOT closely related due to similar environments Analogous structures are structures that are similar between species that are NOT closely related due to similar environments (ex- streamline body plan of a dolphin and trout) (ex- streamline body plan of a dolphin and trout)

Analogous Structures

Vestigial Structures Vestigial structures: “footprint;” structures in organisms that are used to be evidence of an organism’s evolutionary past. (ex- our appendix; whale pelvis) (ex- our appendix; whale pelvis)

Vestigial Structures

Embryonic Development Embryonic development : similar structures in early stages of development indicate an evolutionary history of organisms.

Embryonic Development

Practice Practice ( ) The above chart shows vertebrate embryo development. Which of these would be least related to the others?

According to the table, as vertebrate embryos develop — reptiles and amphibians grow external ears reptiles and amphibians grow external ears only mammals develop both limbs and external ears only mammals develop both limbs and external ears limbs and external ears grow on mammals and birds limbs and external ears grow on mammals and birds amphibians and humans develop the same structures amphibians and humans develop the same structures

DNA Sequences Comparing DNA sequences is the most accurate way to look how related two species are The more related two species are, the more genes they will have in common, & the larger percentage of their DNA will match The more related two species are, the more genes they will have in common, & the larger percentage of their DNA will match