Exploring and Classifying Life
Section 4 How are living things classified?
A. Classification systems
1. _____________ classified organisms more than 2,000 years ago.
2. Carolus Linnaeus introduced a system based on ____________________ of organisms.
3. Modern systems based on phylogeny—the __________________________ of an organism
4. Today’s classification system separates organisms into 6 _______________.
a. Kingdoms are the first and ____________ category.
b. The smallest classification category is a ____________.
c. Organisms that belong to the same species can mate and
produce __________________________.
B. _________________________—two-word system used by Linnaeus to name species
1. First word identifies the __________, or group of similar species.
2. Second word tells something about the species—what it looks like, where it is found, or ____________________.
3. Why use scientific names?
a. To ______________________________
b. To show that organisms in the same genus are ______________
c. To give ______________________________
d. To allow information to be ________________ easily
C. Tools for identifying organisms
1. ________________—descriptions and illustrations of organisms
2. Dichotomous keys—detailed ___________ of identifying characteristics that include scientific names
Adaptations Over Time 31
Section 1 Ideas About Evolution
A. __________________—changes in inherited characteristics of a species over time
1. A species is a group of organisms that share similar ________________________ and can __________________ among
themselves.
2. Lamarck’s theory of _________________ characteristics was not supported by evidence.
B. Darwin’s model of __________________
1. Darwin _____________________ that plants and animals on islands off the coast of South America originally came from
Central and South America.
2. Darwin _________________ that species of finches on the islands looked similar to a mainland finch species.
3. Darwin reasoned that members of a population best able to survive and reproduce will pass their traits to the next generation;
over time, differences can result in separate ________________.
C. Darwin’s hypothesis became known as the theory of evolution by _______________________ — organisms with traits best suited to
their environment will more likely survive and reproduce.
D. __________________—an inherited trait that makes an individual different from other members of its species; an adaptation is a
variation that makes an organism better suited to its environment.
1. Many ______________________ factors can cause changes in the sources of genes.
2. Geographic __________________ can make two populations so different they become different species.
E. Two models explain the ______________ of evolution.
1. ___________________—describes evolution as a slow, ongoing process
2. The _______________________________ model says gene mutation can result in a new species in a relatively short time.