Chapter 4 Flashcards
the fossil record
based on the sequence of fosiils found within rock strata and the ages of rocks and fossil scientists have established a geological record
the history of earth is divided into three eons
- archean
- proterozoic
- phanerozoic (most recent)
the phanerozoic is the most recent eon and it is divided into three eras
- palezoic
- mesozoic
- cenozoic
- eras are further subdivded into periods
- the boundaries of eras are marked by mass extinctions
- lesser extinctions often mark the boundaries of periods
paleozoic era
virtually all life was aquatic
mezozoic era
-an abundance of reptile fossil were found here as a well as being the era of the dinosaur
the beginning of mammals and flowering plants also occurred in this era
-at the end of this era all but the form of dinosaurs were extinct
cenozoic era
was an explosive evolution of mammals, birds, and angiosperm plants
-because this era is the most recent occurring approximately 65 million years ago, more is known about it and the periods are further sun-divided into epochs
the continental drift
german meterologist Wegner proposed that the earth began as one great mass which broke up into continents that then drifted into their current positions
- continental drift is the slow, continuous movement of earths crustal on the hot mantle
- important geological processes occur at plate boundaries
sliding plates
are earthquakes zones
colliding plates
forming mountains
pangea
means all the land and is the term assigned to the superconinent
- 250 million years ago plate movements brought all of the previously separated land masses together to form pangea
- this brought species that has been evolving in isolation back together to compete with one another
- it also lowered the sea level, draining shallow coastal seas probably killing marine organisms that inhibited these environments
- terrestrial environments were also cold and dry
- the formation of pangea reshaped biological diversity and caused a number of extinctions, but provided lots of opportunity for those organisms that survived the changes
the break up of pangea
the breakup of pangea led to the modern arrangement of continents
- this breakup occurred 180 million years ago
- the gradual collision of India and Eurasia resulted in the formation of the Himalaya mountains
- Australia marsupials became isolated when the continents separated and placental mammals arose on other continents
the breakup of pangea- lung fishes
ancient vertebrates called lung fishes have unique pattern of distribution that can be explained by the breakup of pangea
-fossilized lung fishes have been found on all continents except Antarctica therefore the lungfishes must have evolved when pangea was intact
mass extinctions
reasons that extinctions may occur include
-destruction of habitat
-unfavourable climatic changes
-changes in the biological community
intro of predators
intro of compeitiors
-there have been 5 mass extinctions over the past 500 million years
each of these mass extinctions led to 50% or more of the earths species becoming extinct
-whatever the reason for them mass extinctions profoundly affect biological diversity
-removes species which are thriving due to highly advantageous features
anthropogenic activity
activities mediated by humans
adaptive radiation and mass extinction
dramatic adaptive radiation occurs following mass extinctions
various ecological niches that have been vacated by extinction are filled by surviving organisms