geogM126 Week 1

mass extinction

One very big, dramatic things ; short period of geological time ( millions of years) where there are major species losses

Background extinctions

natural part of the evolutionary process

deterministic extinctions

can be both mass and background

deterministic extinction definition

* Ongoing force from which there is no escape
* Ie asteroid hitting planet, or humans filling a lake full of endemic  invasive species, mass killing of species
* Humans are a large factor

Stochastic extinction

* Resulting from a normal, yet random change to the environment
* Ie volcano, flood, tornado, etc

functional extinction

Issue is when the population falls below a certain number

* genetic diversity is too small to recover
* species no longer plays an effective role in their ecosystem
* species no longer has a viable population ( due to low population number that affect the production of healthy offspring

lower gene pool ; variability decreases ; genetic diversity _____

decreases

Why is it beneficial to have large populations of a species

less likely to go extinct due to higher genetic diversity being able to withstand different environmental changes

* Is there more reason to save one species over another?

* If one has a greater impact on an ecosystem 
* If one has impacted income pools and appeals to donor
* If one is a keystone species
* Removal=ecosystem crashes
* Attracts more attention to use as an umbrella species 
* Has better function in ecosystem

umbrella species

species which attract attention - when money is spent to save them, the environment around them is also saved, and the entire ecosystem benefits due to this species

Domains

Arcaea, Bacteria, Eukaryotes

Bacteria

*  There are good kind and bad kind 
* Some perform functions necessary to keep animals healthy
* Some in roots of plants doing nitrogen fixing
* Some on forest floor breaking down dead material
* Important bc they are very flexible, have capacity to live in various conditions 
* Bacteria is old
* Fossils found from 3 billion years ago

Arcaea

* Can live in anoxic environments 
* Other extreme environments 
* Thrive in digestive tracts, produce methane
* Originally thought to only live in extreme conditions (e.g. high temperatures, no oxygen)
* Found to be more widespread  

Eukaryotes

protists, fungi, plants, animals,

Taxonomy

Kingdom, phylum, class, order, family , genus, species

**K**ing **P**hillip **C**alls **O**ut **F**or **G**ood **S**oup

Kingdom, phylum, class, order, family , genus, species

species

capable of reproducing a viable offspring together

Order of extinction

Ordovician-silurian, late devonian, permian, triassic-jurassic, cretaceous-tertiary (KT)

__**Ordovician-Silurian**__

* 490 Million years ago 
* Known as “The Ordovician” 
* 3rd largest extinction 
* Happened in __two__ stages, second wave was more devastating
* Ice receded
* Oxygen reduced in water (changing the chemistry of the ocean/freshwater) 
* Animals could not adapt fast enough to Env changes 

Ordovician-Silurian : first wave

* The first freeze
* killed out a bunch of stuff

Ordovician- Silurian : second wave

* Melt of freeze
* wiped out a ton of species that were still recovering

Ordovician-Silurian - time between first and second wave

1 million years

Ordovician-Silurian - climate change

* Scientist think climate change played a big role, but not sure of exact cause
* Appears to have been massive ice age in that time
* Climate change cooling oceans, changing chemistry of the seas
* When glaciers started to recede, oxygen levels in marine waters decline sharply, and majority of life at the time lived in the sea
* 85% of sea life died out in this time
* Climate change happens naturally, but “abrupt” climate change is what fucks everything up 
* Animals have no time to adapt
* The shorter the time frame the less time existing species have to adapt

Late Devonian - general stats

* 354 Million years ago 
* 19% of all families, 50% of all genera, 70% of all species went extinct (this occurred in a span of over 15 million years)
* Basically 25% of all living things went extinct

Late Devonian - sea life

* Sea life badly affected
* Shallow seas particularly bad, reefs hit really badly
* Reefs took 100 million years to recover
* Most of sea bed lost pretty much lost all oxygen
* Change in sea levels, impact events, climate change, new kinds of plants showing up on land and messing with the soil could have caused it
* Only bacteria could survive

Impact events that caused Late Devonian mass extinction 

* Often proposed as reason for dinosaur extinction
* Planet is struck by comet or meteor or asteroid or something large enough to create a global shockwave
* Widespread dust and debris gets into atmosphere and just disrupts the climate
* Impact event extinction things on a much faster timeline than other ones

Pangea

* Laurasia and Gondwana coming together to form pangea
* Gondwana comes first
* Continents a bit separate, then formed pangea, then broke up again
* Pangea super important bc period of time when species could walk all over the land before continental plates began spreading apart 
* Plate tectonic plates not an accepted theory until 1976
* Pangea important bc it gives us fossil evidence of same/similar species on different continents today
* Supporting theory of plate tectonics moving/shifting due to molten activity in the mantle 
* Pangea then split up, so certain plants like ferns, are spread over all these diff continents that are now split up by oceans
* Vicariance
* The geographical separation of a population and results in different, but closely related species(speciation)
* Example: Porcupines found in Africa and South America 
* They are different species now, but they have a common ancestor 
* Causes of separation= large events
* Ex: volcanoes, glacial melts