Transcript Convergent v. Divergent Evolution

Evolution in Action
What is a Species?
• Morphological definition – a species is defined by its
structure and appearance
• Biological definition – a species
is defined by whether or not a population of organisms
that can interbreed, or not with other groups(& produce
fertile offspring). This was proposed by Biologist
Ernst Mayr in 1942.
Modern definition of species
includes components of both
morphological and biological
definitions.
Is the Red Wolf a Separate Species
(from
Glenco: Biology, The Dynamics of Life)
• The red wolf (Canis rufus) can breed with the coyote (Canis
lantrans) and the gray wolf (Canis lupus). Despite this fact,
the three animal types have been classified as separate
species.
• The red wolf skull is midway between gray wolves and
coyotes. Based on these data biologists classified them
as different species.
• Geneticists found shared DNA sequences in all three.
• Geneticists concluded that the red wolf is a hybrid of the
gray wolf and the coyote.
Coevolution – The change in two or more
species in close association with each other
Examples may include: parasite & host
relationships, prey-predator relationships, or
flower-pollinator)
The flower & the
beak of the
hummingbird
is an example of
coevolution.
The long-nosed
fruit bat, and the
flower it feeds
from, have both
coevolved.
• Some microbes have evolved to live within
certain animals, while these animals have
adapted to either benefit from or avoid the
microbes. (example – the protozoan
Trichonympha and the termite)
Convergent Evolution
“Sometimes organisms that appear to be
very similar, are not closely related at all.”
Convergent evolution is the process by which
different species evolve similar traits.
It may occur when unrelated species become
more and more similar as they adapt to
similar environments.
Example of Convergent Evolution:
Sharks and whales have very different
origins. Sharks are fish and whales are
mammals, yet they have adapted
similar traits to their environments.
They both have fins, and streamlined shapes.
Anole Lizards & Convergent
Evolution (Modern Biology pg 308-309)
Anole lizards (Genus Anolis) are found on the
Caribbean Islands of Cuba, Hispaniola,
Jamaica, and Puerto Rico. Body types
correspond to the habitat of each species.
These Anolis lizards
live on the Island of
Hispaniola in the
Caribbean
It seems that there are distinct species of twigdwelling lizards on each Island.
Biologists analyzed the DNA of various species
and found that twig-dwelling species evolved
independently on each island. In other words,
they had different ancestors but evolved similar
adaptations.
The is an
example of
convergent
evolution.
Divergent Evolution – the descendents of a
single ancestor diversify into species that each
fit different parts of the environment.
Caribbean Anole
lizards evolution
must also explain
how the lizards
became adapted
to their particular
habitats.
Adaptive radiation is one important type of
divergent evolution. (Many related species
evolve from a single ancestral species)
If Adaptive Radiation occurs:
A new population in a new environment will
undergo divergent evolution until the
populations fills many parts of the
environment.
Example of Adaptive Radiation:
Galapagos Island Finches & Anole lizards
Example of divergent radiation:
Galapagos Island Tortoises
Artificial Selection: This can speed the
process of divergent evolution.
Example: Humans have bred domestic dogs
for years. Dogs are bred for certain
phenotypic characteristics.
Due to the actions of dog breeders, the process of
divergence among domestic dogs has occurred
many times faster that would have been possible
in nature.
• In the 2000s, geneticists analyzed DNA from 654 dog
breeds, including ancient dog remains and found that all
breeds of dogs share DNA similarities with wolves in
East Asia.
• These findings support the hypothesis that humans first
selected domestic dogs from a wolf population about
15,000 years ago.