Transcript 09 Patterns in evolution 2016

Evolution occurs in patterns
What are the important patterns
of macroevolution?
Macroevolution is a large-scale evolutionary
change, that usually occurs over long periods of
time, and leads to formation of a new species.
There are four major evolutionary patterns:
1.Divergent evolution
a. Adaptive radiation
b. Allopatric speciation
c. Sympatric speciation
2.Convergent evolution
3.Coevolution
4.Extinction
1. Divergent Evolution
Divergent evolution describes
evolution toward different traits in
closely related species.
a. Adaptive radiation – when an
ancestral species undergoes
rapid genetic changes in
response to environmental
changes, resulting in many
descendent species. Like
Galapagos finches, the
descendent species are still
finches but adapted to a wide
range of environments.
kit fox
red fox
ancestor
Kit foxes coat colours are
adapted to the sandy desert
and they have large ears to
release heat compared to kit
foxes that live in the forest.
1. Divergent Evolution
The other two major types of divergent evolution are:
b. Allopatric speciation – a starting population is
geographically divided and over time the separated
groups can evolve into different species.
c. Sympatric speciation – a new species forms
beside the ancestor species. This usually occurs with
polyploidy changes in plants.
2. Convergent Evolution
Convergent evolution
occurs when similar traits
arise in unrelated species.
Each species has
independently adapted to
similar environmental
conditions.
Evolving wings lets an animal catch prey and
escape predation. This often results in analogous
structures like the wings.
3. Coevolution
Coevolution occurs when adaptations in one species cause
further adaptations in a mutualistically related species. The
evolutionary paths of predators and prey are connected. When
the predator runs faster so do does the prey or both species
become extinct. Many hosts and parasites coevolve. Many plants
can only reproduce if their flowers match a specific pollinator.
4. Extinction
When the Burgess Shale fossils were first examined by Charles
Walcott he mistakenly thought that all the ancient fossils would
have descendent species alive today. Some fossils are for extinct
species. We now know that many of the Burgess Shale fossils
represent extinct species. What known species could Walcott
possibly have connected to this fossil?
Hallucigenia
The Rate of Evolutionary Change
Darwin and many other evolutionary biologists
assumed evolution would always occur at a steady
rate called gradualism. In 1972 Stephen Jay
Gould and Niles Eldredge suggested an alternative
model, punctuated equilibrium. They stated that
evolutionary history has many long periods with
little evolutionary change in species. This
equilibrium can be followed by a shorter time with
many evolutionary changes as species adapt to a
rapidly changing climate, geology or environment.
Evidence now shows that both models of
evolutionary change are occurring together.