Types of Natural Selection Section 21 4 A

Types of Natural Selection Section 21. 4

A. Natural Selection review 1) NS only gets rid of things that are BAD. Neutral or useless traits will not be removed a. (see vestigial structures) b. NOT like use / disuse from Lamark 2) For Natural selection to take place… a. Trait must be genetic (not acquired) b. Must have more than 1 allele c. More individuals born than can live d. One allele must result in greater fitness

3) Natural Selection = the ONLY mechanism of evolution that leads to adaptation a. Evolutionary Adaptation = Δ gene ƒ to better match environment

B. Types of Adaptations 1) morphological = physical form dimorphism & polymorphism 2) physiological = how body functions internally 3) behavioral = behaviors that are not learned but are instinctual are inherited and can undergo evolution

C. Types of Natural Selection 1) Balancing Selection – balanced polymorphism due to heterozygote advantage maintains 2 phenotypes. 2) Stabilizing Selection – selective advantage of Median variation 3) Directional Selection – selective advantage of one extreme 4) Disruptive Selection – selective advantage of Both extremes 5) Sexual Selection – any type of selection that is based on ability to mate

1. Balancing Selelection: Sickle Cell Anemia a)point mutation(a 1 base substitution) b) result = abnormal hemoglobin that makes RBC sickle in low O 2 conditions c) sickled cells block capillaries d) co-dominant Hbn and Hbs e) Malaria caused by protist Plasmodium an endoparasite of RBC f)Heterozygous condition reduces effects of malaria

g)heterozygote advantage creates… h) a balanced polymorphism i) balance between the 2 alleles j) explains prevalence of sickle cell anemia in high malaria areas sickle cell malaria

Frequency Dependent selection May also create balanced polymorphism (balancing selection) Scale eating fish side-blotched lizard

2. Stabilizing Selection : Human babies Low birth weight = more complications High birth weight =more complications Medium weight = Best chance for survival

Stabilizing Selection Wasp lays eggs only at base of spines Peccary likes to eat leaves with few spines

3. Directional Selection: Grant’s finches

4. Disruptive selection: Peppered Moths in polluted area selected for dark color Moths in clean area selected for light color All same inbreeding population

Rock Pocket Mouse http: //media. hhmi. org /biointeractive/films/n atural_selection. html

6. Sexual Selection Lecking behavior http: //www. youtube. com/watch? v=i 8 kj. SEykvns Greater prairie chicken http: //www. arkive. org/greater-prairie-chicken/tympanuchus-cupido/video-09 a. html Wild Turkey http: //www. youtube. com/watch? v=u. GOMJqv 8 BOY Timberdoodle http: //www. youtube. com/watch? v=UEISi. Cmjw. H 8 White tail deer http: //www. wideopenspaces. com/3 -minute-ufc-style-whitetail-buck-fight-video / Bat behavior http: //www. youtube. com/watch? v=n 5 WTVNMZrv. E big horn sheep 1: 18 http: //www. youtube. com/watch? v=Ez 7 RUSCUhzk

D. Adaptations are NOT perfect http: //www. youtube. com/watch? v=c. O 1 a 1 Ek. HD 0&feature=youtu. be