Mechanisms of Macroevolution

Macroevolution

large scale changes in allele frequency over long periods of time that produce drastic changes in physical features

(the accumulated effect of microevolution (evolutions) over a long period of time)

what happens to organisms and the environment overtime

over time, as an environment becomes more stable, organisms wouldn’t change all that much

what drives macroevolution

1. plate tectonics

2. mass extinctions

3. adaptive radiations

plate techtonics

the earth’s crust is broken into pieces/plates

what is the name of the states where tectonic plates are in constant motion

continental drift

plate tectonic regions

thicker regions of crust form land

thinner regions are covered in ocean

results of plate tectonics

with each separation of land masses, species become isolated from each other and are subjected to potentially different environments

how does plate tectonics explain marsupial existence

marsupials are similar to placental mammals, except they care for their young in external pouches while they develop instead of in a uterus. However in all other regions of the world placental mammals dominate

what is the only marsupial found in North America and what does this suggest?

the only marsupia found in North America is the opossum; this suggests that because there are other marsupials outside of australia the evolution of marsupials must have occurred before Australia was separated from other landmasses

mass extinctions

extinctions/losses of 50% of all species in a short time

the vast majority of species that have existed in life’s history are now extinct.

There are many reasons for this including the loss of habitat and climate change

the biggest disasters in history

Ordovician

Devonian

Permian

Triassic

Cretaceous

Ordovician extinction

85% death rate

likely causes:

• rapid global cooling

• falling sea levels

Results:

• destroyed coastal areas

• chemical reactions affected by cold

Devonian extinction

70% death rate

likely causes:

• asteroid impact(s)

• rapid global cooling

Results:

• local destruction from debris

• ocean life affected by temperature

Permian extinction

95% death rate

likely causes:

• volcanic activity

• increase in methane and CO2

• rapid global warming

Results:

• oxygen removed from oceans

• desertification of land

Triassic extinction

76% death rate

Likely causes:

• increase in methane and CO2

• rapid global warming

Results:

• desertification of land

• frequent heat waves

Cretaceous extinction

80% death rate

likely causes:

• asteroid impact

• volcanic activity

• falling sea levels

Results:

• widespread fires

• plants disrupted by global ash cloud

• “nuclear winter”

Adaptive radiations

evolutionary periods in which many species evolve from a common ancestor

when do adaptive radiations occur

after mass extinctions because many ecological roles, or niches, are available to be filled

what is a “bonus” driver of macroevolution

artificial selection

artificial selection

the process by which humans selectively breed organisms for desired traits

what occurs and is the result of artificial selection?

humans select traits they desire in other organisms and cross individuals who have those traits; those selected traits become more common in the next generation

what is the goal of evolution

there is no goal.

Evolution simple describes how life adapts to an ever-changing environment.

what is the complexity of life a byproduct of?

natural selection; we observe that life today is far more complex than th earliest life on earth.