Bell Ringer 92513 NATURAL SELECTION IN ACTION Natural

Bell Ringer 9/25/13

NATURAL SELECTION IN ACTION

Natural Selection in Action Ex. 1: Antibiotic-resistant bacteria Antibiotics meant to kill bacteria A few are naturally resistant and don’t die The survivors live on, reproduce & pass on their adaptation Nearly entire bacteria population will have adaptation after several generations

Natural Selection in Action Ex. 2: Elephants in Uganda Ivory is valuable, so elephants hunted for tusks More tusk-less elephants survive to reproduce and pass on the tusk-less trait Result is an increase in the percentage of tuskless elephants from 1% in 1930 to 15% today

Natural Selection in Action Ex. 3: Insecticide resistant pests Chemical insecticides used to control insect pests A few in a population may be resistant These survive, reproduce & pass on their resistance Many insects have short generation times because they produce many offspring Generation time is the average time between one generation and the next

Competition for Mates Survival of individuals doesn’t guarantee survival of a species Must reproduce to survive Natural selection works based on reproduction Ex: Birds Females often prefer colorful males Result - colorful males have more offspring

Speciation Formation of a new species as a result of change over time is called speciation May occur when a group becomes separated from the original population Over time, new population adapts to new environment Eventually becomes different enough that it can no longer mate with original population New species has formed

Artificial Selection http: //learn. genetics. utah. edu/content/variation/a rtificial/

Things You May Not Know http: //learn. genetics. utah. edu/content/variation/ misconceptions/