Descent with Modification Chapter 19 http palaeo gly

Descent with Modification Chapter 19 http: //palaeo. gly. bris. ac. uk/Palaeofiles/whales/pictures/clad. jpg

Evolution • Change over time in the genetic composition of a population – Individuals do not evolve • Natural Selection – the mechanism by which evolution occurs • Evolutionary adaptation – result of natural selection – increase in frequency of traits in a population

Darwin • Published Origin of the Species in 1859 • Common ancestor – All modern species descend from ancestral species that were different • Natural selection – Population will change from generation to generation, those who are best fit for their environment will go on to live and reproduce

Precursors to Darwin • Aristotle – species were fixed and unchanging • Linnaeus – classified diversity – taxonomy – Binomial nomenclature – genus and species • Hutton – gradualism – slow and continuous change • Cuvier – catastrophism – each boundary in layer represents change – Opposed gradualism • Lyell – uniformatarianism – changes in the present occur at the same rate as the past – Modern geology. . AP Bio 15 -16Evolution19_03 Grand. Canyon_SV. mpg – Lamarck – Acquired characteristics – Characteristics gained during an organisms lifetime are passed to offspring: Incorrect, your scars don’t show up in your children – Ex: giraffe • Wallace – developed a similar theory of natural selection as Darwin

Darwin’s Studies • HMS Beagle • South American coastline – Noticed organisms resembled European species in similar climates • Galapagos Islands – Studied finches and noticed many similarities with key differences in many species of animals – Common ancestor

Origin of the species • 1. Descent with modification – All organisms are related from an ancestor in the remote past – Similar to a tree – more similar species have a common ancestor in the nearer past. – 99% of species that have ever lived are now extinct not all common ancestors are still alive. • . . AP Bio 1516Evolution19_05 Galapagos. Islands_ SV. mpg Trypanosoma: Protist that causes sleeping sickness (fatal w/out treatment)

Origin of the Species • 2. Natural Selection – All species would increase exponentially in size if all organisms that were born reproduced and all offspring survived to reproduce. – Populations tend to remain stable in size. – Resources are limited. • Competition for resources occurs – Organisms within a population demonstrate variation. – Most variation is heritable. • Individuals who inherit favorable traits for their environment are more likely to survive and reproduce. • Unequal reproduction leads to a gradual change in a population toward favorable traits.

Natural Selection • Differential success and reproduction among individuals that vary in their heritable traits based on environment • Creates adaptations of organisms to their environment • If the environment changes new adaptations may arise through mutations or previous characteristics become advantageous in the new enironment: possibility of speciation • Acts on populations NOT individuals • Only affects heritable traits • Environmental factors vary from place to place not all adaptations are favorable in all environments.

(a) A flower mantid in Malaysia (b) A stick mantid in Africa Figure 22. 11

Evolution in Action • Introduced Plant species • Soapberry bugs beak length changing in response to a chance in the food supply • (pg 373)

Evolution in Action • Bacterial Antibiotic Resistance • Natural variation in the bacteria allowed them to survive in the presence of the antibiotic = reproduction of resistant popluations

Fig. 28 -03 l Ameoba: single celled protist Endocytosis 100 µm

Evidences for Evolution • 1. Paleontology • Fossils – remains or traces of organisms from the past. – Found in sedimentary rock • Igneous and metamorphic involve heat so living organisms don’t remain long enough to preserve – Older fossils found in lower layers (strata) – Biogeography – geographic distribution of species • Closely related organism are found in the same geographic regions

Evidences for Evolution • 2. Homologous Structures – comparison of similar structures that have different functions between species. – Ex: human arm and bat wing • Same bone structure with different functions Human Cat Whale Bat

Evidences for Evolution • 3. Embryology – comparison of the early stages of development – Ex: all vertebrate embryos have a tail and pharyngeal pouches during embryonic development Pharyngeal pouches Post-anal tail Chick embryo Human embryo

Evidences for Evolution • 4. Vestigial Organs - structures with little significance in a modern species, yet present and functional in ancestors. – Ex: snakes have small leg bones – Ex: humans have an appendix

Evidences for Evolution • 5. Molecular – comparison of organisms at the molecular level – Ex: DNA, RNA or protein sequences – The more similar the molecular sequences the more similar the organisms – The closer the common ancestor Species Percent of Amino Acids That Are Identical to the Amino Acids in a Human Hemoglobin Polypeptide Human 100% Rhesus monkey 95% Mouse 87% Chicken 69% Frog Lamprey 54% 14%

Question: • Copy Figure 15. 2 (pg. 294) and explain the relationship between the feedback inhibition of enzymes and populations.