Evolution—The Theory and Its Supporting Evidence - The Changing Earth: Exploring Geology and Evolution - page 478

Deer Camel Whale Sea cow Elephant Hyrax Horse

◗ Figure 18.8 Divergent Evolution Divergent

evolution of several types of placental mammals
from a common ancestor. Divergence accounts for
descendents that differ from their ancestors and
from one another.

Common
ancestor

Microevolution and Macroevolution
Micro and macro are prefixes that mean “small” and “large,”
so microevolution is any change in the genetic makeup of a
species. For example, house sparrows were introduced into
North America in 1852 and have evolved so that members

mammals elsewhere—for example, catlike marsupial
carnivores and true cats. Parallel evolution, in contrast,
involves closely related organisms, such as jerboas and
kangaroo rats, that independently evolved comparable fea-
tures (Figure 18.9b).

◗

North America South America Figure 18.9 Convergent and Parallel Evolution

Saber-toothed cat Marsupial carnivore

Early
camel

Camel-like
litoptern

Early
rhinoceros

Toxodon

Kangaroo rat Jerboa

Similiar features
develop

Convergence

Divergence

Distantly related ancestors

Common ancestor

Parallel evolution involves the
independent origin of similar features
in closely related organisms.

Convergent evolution takes place when distantly related organisms
give rise to species that resemble one another because they adapt in
comparable ways.

a b