ENVS 1000U Lecture Notes - Lecture 10: Selective Breeding, Panmixia, Disruptive Selection
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Evolution and Extinction
What is Biological Evolution?
Understanding Biological Evolution is Vital for Understanding Modern Biology!
oinvolves changes in the genetic make-up of populations of species over time
oprovides a mechanism to explain how organisms adapt to their environment
and change over time
ois important to understanding the history of life
oEvolution is critical for understanding antibiotic/pesticide resistance,
agricultural/forestry issues, food production, medicines, etc.
Changes in Species occur due to the Accumulation of Genetic Variation as Species adapt
to new or changing Environmental Conditions
o Mutations = accidental changes in DNA that may be passed on to the next
o Sexual Reproduction = mixes genetic information of two parents - increases
variation in population
o Coevolution = species evolving together by responding to changes in other
oAim to maximize adaptive variations = traits that promote survival and
How are Populations of Species Altered over Time?
1. Genetic Drift
2. Population Bottleneck
3. Founder Effect
Main Mechanism used by Populations to adapt and Evolve is Natural Selection
oIn 1859, Darwin and Wallace proposed Natural Selection as the “mechanism of
What is Natural Selection?
odifferential success in survival and
reproduction of individuals
oresults in certain genetic traits being
passed to the next generation in greater
oover time characteristics of population
Natural Selection acts on Genetic Variation
Evidence of Natural Selection is everywhere!
onatural selection is evident in every adaptation of every organism
oevident in bacteria and fruit flies in laboratories
oevident in selective breeding of animals and plants = artificial selection
Artificial Selection has been used by Humans
othe process of selection for desirable traits conducted under human direction
e.g. artificial selection has led to great variety of dog breeds and foods
Evolution through Natural Selection is not Goal – oriented!
oprocess by which traits that enhance survival and reproduction are passed on
to future generations more frequently than those that do not enhance survival
ois an “editing” mechanism
onot a “creative force”