Lesson 7 Macroevolution Flashcards
Macroevolution
Large scale and long-term evolutionary patterns among many species. Influenced by microevolutionary mechanisms
Deals with more than one species
Adaptive Radiation
Also known as “Divergent Evolution”
The diversification of a common
ancestral species into a variety of
species, all of which are
differently adapted to their
environment.
Considered divergent evolution
because all of the resulting
species originated from (diverged
from) a single common ancestor.
How Adaptive Radiation Works
A species population becomes large
enough for it to spread into
neighbouring environments.
The migrant populations adapt to their
new home (new environment) and
speciation begins
The population of each new species
grows and spreads (radiates) to
neighbouring environments
Speciation occurs again as the new
populations become adapted to their
new habitats and feeding niche
Convergent Evolution
The Evolutionary process in which
similar traits arise in two or more
species because each species has
independently adapted to similar
environmental conditions
NO COMMON ANCESTOR involved
Ex. Octopus Eye and Human Eye
Ex. Birds, Butterflies and Bats
evolved independently and
evolved different types of wings.
BUT, natural selection favoured
variations suitable to the same
environment – the sky.
Co - Evolution
When two organisms that are closely
linked to each other gradually evolve
together
Ex. Predator/Prey
As prey develop better defences (longer
faster legs, harder shells, better
camouflage), predators develop better
killing traits (stronger claws, sharper and
harder teeth, more lethal venom, stronger
jaws)
The Pace of Evolutionary Change
There are two theories on how
fast evolution occurs:
Gradualism
Punctuated Equilibrium
Gradualism
Evolutionary change occurs generation to generation (within a lineage) slowly and steadily before and after a divergence
Large evolutionary changes are
the result of the accumulation of
many small changes.
Proposed and accepted during
Darwin’s time. However, it is difficult to verify in the fossil records
Fossil records showed that species are
often relatively short lived (20000 years) and appear and disappear suddenly
Some longer-lived species have
remained relatively unchanged for
millions of years
Punctuated Equilibrium
Evolutionary change consists of long
periods of stasis (periods of equilibrium with little or no change) interrupted by periods of divergence.
Proposed by Niles Eldredge and
Stephen Jay Gould in the 1980’s
Most species will undergo most of their changes when they first diverge from their parent species. After this there is relatively little change.
Episodes of divergence are triggered by sudden significant changes in the
environment
