Evolution Class Notes PDF

Evolution Class Notes Go to the slideshow that should be on Brightspace and take notes on them for later studying that will be on tests in the future. Ask questions in the notes and then provide the answers as a fun twist this time. Evolution Natural Selection Review ⇓ Evolution Summary Note...

Evolution Class Notes Go to the slideshow that should be on Brightspace and take notes on them for later studying that will be on tests in the future. Ask questions in the notes and then provide the answers as a fun twist this time. Evolution Natural Selection Review ⇓ Evolution Summary Notes: So basically natural selection is the evolution of the most adapted species, it's affected by their environment and they make changes so that they can thrive longer. Bottleneck effect is similar but not natural selection, like a wildfire basically the population that survives doesn't represent that entire population but the ones that were more adapted and were killed or less adapted and were killed by the wildfire died by “chance”, being in the wrong place at the wrong time. Smaller populations are affected more because there is more chance of the type of the species to be killed and eliminated for future generations. Founder effect is when a small population of a bigger group, leaves and goes somewhere else and thrives. It again doesn't represent the entire group because only a fraction of it broke off. Bottleneck effect is a form of Genetic drift, natural disaster that cause population B over A let's say to thrive, so it's not natural selection per say, it's a “random” occurrence that alters the future population. Founder affect is the small group that travels from the big group to start their own population. Key Study Notes on Speciation and Reproductive Isolation Reproductive Isolation: ​ Definition: When two populations become reproductively isolated, there is no longer a free exchange of alleles between them. ​ Importance: Leads to the development of distinct species through the lack of gene flow. Prezygotic Mechanisms: ​ Function: Prevent mating or fertilization before a zygote is formed. 1.​ Ecological Isolation: ○​ Populations live in different geographical areas or ecological niches. ○​ Example: Bengal tigers live in forests, while Asiatic lions live on the savannah. 2.​ Temporal Isolation: ○​ Populations mate or are active at different times of the day or year. ○​ Example: Cactus blooms at sunset, while morning glory blooms at sunrise; old finches mate in August, purple finches in June. 3.​ Behavioral Isolation: ○​ Mating rituals differ, preventing successful mating. ○​ Example: Male black crickets and grey crickets rub their legs at different frequencies. 4.​ Mechanical Isolation: ○​ Physical differences prevent successful mating or fertilization. ○​ Example: Insect exoskeletons allow for a "lock & keyfit between male and female. 5.​ Gametic Isolation: ○​ Sperm and eggs can be exchanged, but chemical markers prevent fertilization. ○​ Example: Wind-blown corn pollen won't fertilize milkweed stigma. Postzygotic Mechanisms: ​ Function: Prevent the development of fertile offspring after mating. 1.​ Zygotic Mortality: ○​ A zygote is formed, but it fails to develop to maturity. 2.​ Hybrid Inviability: ○​ Hybrid offspring are born but are unhealthy or die early. 3.​ Hybrid Infertility: ○​ Hybrid offspring are healthy but cannot reproduce. ○​ Example: Donkey x Horse = Mule (sterile). Speciation: ​ Definition: The process by which new species are formed, leading to the reproductive isolation and accumulation of genetic differences. ​ Importance: Speciation involves prezygotic and postzygotic barriers that prevent gene flow and maintain distinct species. Types of Speciation: 1.​ Allopatric Speciation: ○​ Populations are geographically isolated, leading to the formation of separate species. ○​ Example: Fish separated by a dam. 2.​ Sympatric Speciation: ○​ Populations remain in physical contact but stop exchanging alleles, forming separate species. ○​ Example: Sticklebacks in different habitats in the same lake. Summary: ​ Reproductive isolation (both prezygotic and postzygotic) is essential for speciation. ​ Speciation can occur through allopatric or sympatric mechanisms. ​ Aookucatuib is how the new species are formed to cause reproductive isolation. ​ Prezygotic barriers occur before fertilization, while postzygotic barriers prevent the development of viable or fertile offspring.