* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Principles of Evolution
Survey
Document related concepts
Evolutionary landscape wikipedia , lookup
Sex-limited genes wikipedia , lookup
The Selfish Gene wikipedia , lookup
Co-operation (evolution) wikipedia , lookup
Population genetics wikipedia , lookup
The Descent of Man, and Selection in Relation to Sex wikipedia , lookup
Kin selection wikipedia , lookup
Hologenome theory of evolution wikipedia , lookup
Genetics and the Origin of Species wikipedia , lookup
Introduction to evolution wikipedia , lookup
Transcript
Natural Selection So which changes stick around and which ones don’t?? Whichever traits provide a benefit are selected • Nature selects those organisms that are adequate enough to grow up (survive), mate and produce offspring. • That’s why this process, Natural Selection is a non-random process of sorting out genotypes and resulting phenotypes that don’t work. Is nature the only thing that selects traits? • In artificial selection, people are the choosers This is why some ridiculous traits (by nature’s standards) may show up in a populations In Natural Selection the environment is the chooser Natural selection is a nonrandom process by which traits are selected for by nature because they provide some survival benefit. Natural selection is a mechanism of evolution. • There are four main principles to the theory of natural selection. – Variation of heritable traits – overproduction and struggle for survival – adaptations arise over many generations – descent with modification Fitness is the measure of survival ability and ability to produce more offspring in the population, directly tied to the unequal # of produced by breeding pairs of the •offspring . same species. Differential reproduction. Natural selection acts on existing variation. • Natural selection can act only on traits that already exist. • Structures take on new functions in addition to their original function. five digits wrist bone How do we get variation? All that selection pressure can alter the normal distribution of traits. The outcomes of this are called “modes of selection.” 3 types of modes of selection: 1) Directional-one of the 2 extreme phenotypes is favored by selection pressure. 3 types of modes of selection: 1) Directional-one of the 2 extreme phenotypes is favored by selection pressure. 2) Stabilizing-the middle phenotype is favored by selection 3 types of modes of selection: 1) Directional-one of the 2 extreme phenotypes is favored by selection pressure. 2) Stabilizing-the middle phenotype is favored by selection 3) Disruptive/Diversifying: Both extreme phenotypes are favored by selection Another outcome of fitness is Sexual selection It occurs when certain traits increase mating success. • Occurs due to higher cost of reproduction for females. – males produce many sperm continuously – females are more limited in potential offspring each cycle There are two types of sexual selection. – Intra-sexual selection: competition among males – Inter-sexual selection: males display certain traits to females Species can shape each other over time. • Two or more species can evolve together through coevolution. – evolutionary paths become connected – species evolve in response to changes in each other – Two types: beneficial & competitive beneficial Competitive https://www.youtube.com/watch?v=vOzI8O-oUgo Why is nature so cruel?? • Limited resources means that organisms compete with themselves and others for survival. Because of this, nature weeds out inadequate individuals from the group so that only the most able produce diverse offspring. • Descent with modification allows each generation to try and produce “better” offspring in terms of survival. • But even those offspring won’t all live and reproduce • Biotic potential versus environmental resistance.