Environmental Science
Name: ______________________________
Chapter 2: The Organization of Life
Goal: The student will explain the process of evolution by natural selection, explain the concept of adaptation
and describe the steps by which a population of insects becomes resistant to a pesticide.
Vocabulary:
1. Natural selection2. Evolution3. Adaptation4. Artificial selection5. Resistance-
Chapter 2.3: Evolution
 Organisms tend to be well suited for their natural environment
 Ex: Kangaroo rats are suited for areas with very little water (desert): never need to drink water, eliminate
very little water, active at night
Evolution by Natural Selection
 Scientists want to how the close match between organisms and their environment came about. Charles
Darwin, 1859, proposed an answer. He observed that members of a population differ from each other in
form, physiology and behavior; some differences are due to heredity (passed from generation to
generation)
 Environment influences which individuals have offspring; certain traits allow some individuals to
survive and have offspring
Nature Selects
 Natural selection describes the unequal survival and reproduction from the presence or absence of
particular traits; over the years, characteristics change over time
 Evolution is a change in the genetic characteristics of a population from one generation to the next
 Ex: a herd of deer live in lowland areas with warm climate; some become separated in the high
mountains where the temperatures are cold most of the year; many die in the cold; the survivors might
have thicker fur; they go on to reproduce with offspring having the desirable trait; this is an adaptation
(an inherited trait that increases and organisms chance of survival and ability to reproduce)
Coevolution
 Organisms evolve adaptations to other organisms as well as their physical environment.
 When two or more species evolve in response to each other, it is called coevolution
 Ex: Honeycreeper’s (a bird) has a long curved beak. The flower of the lobelia flower has its structures
deep in the flower. The honeycreeper gets pollen on its head when it drinks the nectar of the flower.
When it goes to another flower, it pollinates the flower.
Evolution by Artificial Selection
 Many populations of plants and animals do not live in the wild but instead are cared for by humans.
People control how these plants and animals reproduce and therefore, how they evolve. Ex: wolf and


Chihuahua are closely related but humans have bred the ancestors of today’s wolves to produce the
variety of dog breeds we have today.
The selective breeding of organisms by humans for specific characteristics is called artificial selection.
We use artificial selection for many of the fruits, grains and vegetables we eat today. We save the seeds
that produce the best and use those seeds for the next generation crops.
Evolution of Resistance
 Sometimes humans cause populations of organisms to evolve unwanted adaptations. Ex: Insects
become resistant to pesticides; bacteria become resistant to antibiotics.
 Resistance is the ability of one or more organisms to tolerate a particular chemical designed to kill it.
The organism contains a gene that allows it to break the chemical down into harmless substances.
 When humans try to control pests and bacteria, they promote the evolution of resistant populations.
Pesticide Resistance
 Ex: Evolution of pesticide resistance among corn pests:
 Pesticide is sprayed on corn to kill grasshoppers; most die but a few survive. They have the gene that
protects them from the pesticide. The surviving grasshoppers pass that gene on to their offspring.
 Every time the corn is sprayed, the insect population changes to include more and more resistant
grasshoppers making the pesticide useless
 The faster the organism breeds, the faster its population can evolve
Extinction
 The irreversible disappearance of a population or a species is called extinction
 When the last individual of an organism dies, the species is considered extinct
 This is a natural process but humans are causing species to disappear at an alarming rate
Lesson Reflection:
1. Complete The Evolution of Thicker Fur in a Deer Population handout. Use page 45 in your book.
Number 4 on your paper is a combination of 4 &5 in the book, or you can go to my webpage for the
completed handout.
2. Complete The Evolution of Pesticide Resistance handout. See my webpage for the completed handout.
Assessment:
1. Explain what an adaptation is and provide three examples.
2. Describe one way in which artificial selection can benefit humans.
3. Explain how a population of insects could become resistant to a pesticide.
Active Reading: Evolution
Lesson Extension (Technology/Application/Connection to Real World):
 Peppered Moth Simulation