Transcript evolution
Evolution Notes • Darwin explained the theory of evolution by Natural Selection. • “Survival of the Fittest” means organisms that adapt to their environment survive, while organisms that do not adapt disappear. • Natural selection leads to adaptations within a population. Types of Evolution • Microevolution- the change of allele frequencies within a population • Macroevolution- large-scale evolutionary changes : 5 patterns l. Mass extinctions 2. Adaptive Radiation 3. Convergent Evolution 4. Coevolution 5. Punctuated Equilibrium Mass extinctions • More than 99% of all species that ever lived are now extinct • Mass extinctions wiped out food webs & ecosystems • Example: Dinosaurs- asteroid but could have been many factors (volcanoes & continents drifting) Adaptive Radiation • A species or group of species evolves into many new species Convergent Evolution • Unrelated organisms come to resemble one another bird fish mammal Coevolution • 2 species evolve in response to changes in each other over time Central American Swollen-Thorn Acacias Acacia ants and acacia trees Acacias are small, Central American trees in the Leguminosae. They have large, hollow thorns. The acacia ants live in the thorns. On the tips of its leaflets, the plant makes a substance used by the ants as food. The ants defend the tree from herbivores by attacking/stinging any animal that even accidentally brushes up against the plant. The ants also prune off seedlings of any other plants that sprout under “their” tree Punctuated Equilibrium • Rapid evolution after long periods of equilibrium (balance) • Why? Migration, mass extinctions, isolation Evidence for Evolution The fossil record gave us: 1. Descent with modification 2. Homologous Structures 3. Transitional Fossils Descent with Modification • All living organisms are related to one anothercommon descent • Speciation-new species can arise Homologous Structures • structures in different species that may perform different functions but are similar in structure because of their common ancestry • Examples: bat wing, whale flipper, cat claw, Human hand Vestigial Organs – structures of no apparent function to an organism; leftover from ancestry – Examples: snakes have leg & pelvis bones; whale rear limbs Examples of Evolution • Antibiotic Resistance: natural selection has occurred within populations of bacteria • Mutations cause bacteria to change their structure…antibiotics cannot bind to cell surface • Acquiring new genes…bacteria have new enzymes that can deactivate or destroy antibiotic • Ex:Tuberculosis bacteria Examples of Evolution • Darwin’s Finches: Natural selection has occurred in beak size Examples of Evolution • Speciation: begins as a population adapts to its environment.