NRES 101 February 12, 2019 admin Possible reasons why more species occur near the equator ? More time without geological disruptions (e.g. , glaciers) ? Competition among species is more intense ? Climatic stability How does speciation normally occur? Allopatric speciation (one population becomes separated into two or more) What factors lead to speciation? ? Natural Selection ? Variation within a trait ? The trait provides a reproductive advantage ? Trait is heritable ? Sexual Selection ? Genetic Drift Death of dinosaurs cataclysmic event such as asteroid struck off Yucatan peninsula and caused drastic climate change wiping out 70% of life on earth Pleistocene Changes o Environmental changes (e.g. glaciers) lead to allopatric speciation Death of the megafauna ? Overkill hypothesis ? Climate change hypothesis ? Disease hypothesis ? Meteor hypothesis Recent Extinctions o Current extinction rate is higher than the baseline rate o Both rare and common species can go extinct o Island Effect Top 3 reasons for extinction ? Invasive species ? Hunting ? Habitat loss How many species have gone extinct in Illinois over the last century few There are more ____ species than amphibians, reptiles, birds, and mammals combined fish Why are there so many freshwater species of fish given the relatively low amount of freshwater habitat? Freshwater is easier to live in than saltwater and is generally warmer What is the skeleton of sharks made of? Cartilage Related posts: Omega-3 fatty acids, fish oil, alpha-linolenic acid ENVS4000 Conservation Biology NRS 223 Test 2 ENSC 320 Exam
