Diversity and Variation
Chapter 18 Outline: Diversity and Variation
18.1 The Species Concept
TAXONOMY- classifying organisms in ways that reflect relationships and help distinguish one type of organism from another.
SPECIES- group of organisms that is capable of breeding offspring, or mating, with another in nature to produce fertile offspring.
Individual members of a species may look very different from eachother.
Such differences among members of a species are known as variations
Natural selection acts on variation, resulting in changes in species or the evolution of new species
Figure 18.1- five breeds of dogs
Figure 18.2 geographic variation in the human species
Variations in a population- polymorphism, geographic variation, and individual variation
Figure 18.3- individual variation in a human population and in a sheep population
Members of related species may interbreed occasionally
Species is a population of individuals that breed and produce fertile offspring under natural conditions
Figure 18.4- two species of canines
Figure 18.5- two species of bears
18.2 Classification and homologies
Classification is important for both practical and scientific reasons.
Taxonomy plays a role in public health, ecology, key for understanding the unity of life
Figure 18.6- species that come in contact but do not interbreed
Figure 18.7- the male Krause with her two colts
Taxonomists use structure, biochemistry, behavior and genes to classify organisms
Classification focuses on structures that indicate a related evolutionary ancestry
These structural resemblances = homologies
Structures that are similar in appearance and function but are not the result of shared ancestry = analogies
Chemical homologies are also evidence of close evolutionary relationships
Figure 18.8- one way of classifying organisms
Table 18.1 nucleotide sequence of part of a gene in all apes and monkeys
Table 18.2 percent differences among
18.1 The Species Concept
TAXONOMY- classifying organisms in ways that reflect relationships and help distinguish one type of organism from another.
SPECIES- group of organisms that is capable of breeding offspring, or mating, with another in nature to produce fertile offspring.
Individual members of a species may look very different from eachother.
Such differences among members of a species are known as variations
Natural selection acts on variation, resulting in changes in species or the evolution of new species
Figure 18.1- five breeds of dogs
Figure 18.2 geographic variation in the human species
Variations in a population- polymorphism, geographic variation, and individual variation
Figure 18.3- individual variation in a human population and in a sheep population
Members of related species may interbreed occasionally
Species is a population of individuals that breed and produce fertile offspring under natural conditions
Figure 18.4- two species of canines
Figure 18.5- two species of bears
18.2 Classification and homologies
Classification is important for both practical and scientific reasons.
Taxonomy plays a role in public health, ecology, key for understanding the unity of life
Figure 18.6- species that come in contact but do not interbreed
Figure 18.7- the male Krause with her two colts
Taxonomists use structure, biochemistry, behavior and genes to classify organisms
Classification focuses on structures that indicate a related evolutionary ancestry
These structural resemblances = homologies
Structures that are similar in appearance and function but are not the result of shared ancestry = analogies
Chemical homologies are also evidence of close evolutionary relationships
Figure 18.8- one way of classifying organisms
Table 18.1 nucleotide sequence of part of a gene in all apes and monkeys
Table 18.2 percent differences among