lec 13 Flashcards Preview

Bio 121 > lec 13 > Flashcards

Flashcards in lec 13 Deck (25):

Two extinction types

Actual Extinction
Functional Extinction


Actual Extinction

end of an organism/species
- when the last existing member of a species dies


Functional Extinction

Only a few individuals left
- population not viable
- odds of survival slim
- can be years or decades prior to actual extinction


Mass extinction event

Loss of a large number of species on earth in a short period of time
- does not include minor extinction events(pre-Cambrian, now maybe)


percent of animal species that are extinct



natural extinction rate

1-10 species/five years, 9% of species per million years


Most species survive

1-10 million years(according to the fossil record)


human activity on birds

since 1800, 106 species have been lost, trend has reversed in past two decades, naturally 1-2 birds per hundred years


extinctions correlated with

major environnmental changes
* climate change
* atmostphere(O2)
* Land masses
* continental drift
* floods
* glaciation
* volcanic eruptions
* meteorite impacts


How many major extinction events have there been?



End-Ordovician mass extinction resulted of

Massive glaciers formed over the land, sea levels dropped, ocean temps. dropped, 60% to 70% of all species went extinct.

-Ranked as the second largest of the five major extinctions


Late Devonian Mass Extinction resulted of

Uncertain, though two large meteorites collided with Earth at this time, Impact created massive fires, tsunami, major amounts of dust shoot up into atmosphere, 70% of all species west extinct

This extinction event lasted as long as 20 million years


End-Permian Mass Extinction result of

Enormous meteorite hits Australia, outpouring of lava into the oceans that reduces O2 content of oceans, oceans release toxic CO2 and H2S into atmosphere. These gases poison those that survived the meteorite impact resulting in a 96% decline in species on Earth

-enormous evolutionary significance: on land, it ended the rise of mammal-like reptiles


End-Triassic Mass Extinction result of

Uncertain as to exact cause; however, a large meteorite hit what is now Quebec at this time. About 70% to 75% of all species went extinct

-Most non-dinosaurs and large amphibians eliminated, leaving dinosaurs with little competition


End-Cretaceous Mass Extinction result of

Likely a meteor collision. In addition to a meteor the Indian continent saw significant volcanism that occurred continuously for ~500,000 years. Iridium layer could have resulted from this volcanism. There is no doubt about the significance of the meteor impact, what is in question is how much did the volcano add to the impact


In 1980 Alvarez proposed that an impact could be identified by unusual accumulations of

‘rare earth’ elements (Iridium), called the K-T boundary
Layer of Iridium-enriched rock is found world-wide, and is thicker closer to the Yucatan peninsula


Most famously the dinosaurs disappear after the

cretaceous period (except birds), when about 75% of all species became extinct


Mammals and birds, the latter descended from theropod dinosaurs, emerged as

dominant “large” land animals


Ecology is

the study of the interaction among organisms and their environment including: biotic and abiotic factors.


Biotic factors are

interactions among living things


Abiotic factors are

interactions between organisms and their non-living environment (physical and chemical)


Organismal ecology studies

how an organism’s structure, physiology, and behavior meet the challenges posed by the environment


Population ecology studies

the numbers and distribution of groups of organisms


Community ecology studies

how populations of species interact and form functional communities

-Also studies succession – how species composition and community structure change over time, particularly after disturbance


Ecosystem ecology studies

energy flow and chemical cycling among the various biotic and abiotic components of an ecosystem