<< Chapter < Page Chapter >> Page >

What does this mean?

When all the members of a species die out the species has become extinct. A species is deduced to be extinct if it stops appearing in apparently later (more recent) rock. There seem to have been times in the earth’s history when many species have become extinct at about the same time. Such an event is called a mass extinction.

Five major mass extinctions

Evolutionists think that there were five large mass extinctions, with the two largest being:

  • The first major mass extinction is said to have occurred at the end of the Permian period. This is thought to have been about 225 million years ago. At that time 90% of marine life seems to have become extinct.
  • The second is thought to have occurred about 65 million years ago, at the end of the Cretaceous Period. This led to the disappearance of the dinosaurs.

Each time a mass extinction seems to have happened, many new kinds of fossils appear in later (more recent) rocks. These are considered new because their fossils were absent from older-dated rocks. Transitional evolutionary ancestors of these new organisms are also not found in older rock. This sudden appearance of new species is explained as follows. After a mass extinction a large part of the environment is cleared of the life forms which had previously dominated (controlled) the earth. This makes way for new forms to evolve and fill the many new vacant ecological niches (open spaces in the ecosystem).

Possible causes of mass extinctions

Mass extinctions can be caused by various factors. These may be extra-terrestrial, due to climate change, caused by humans, genetic, or due to continental drift:

  • Extra-terrestrial events are caused by something outside of the earth, e.g. by a meteorite. At least two mass extinctions are thought to have been caused by huge meteorites striking the earth. A meteorite is s chunk of rock from outer space, which enters the earth’s atmosphere. These meteorites are thought to have been about 10 km in diameter. Some scientists believe that such impacts happened many millions of years ago. Other data suggests that a meteor of diameter 200km hit the earth only a few thousand years ago. This does not fit in with the geological time scale and is usually ignored. (This is based on observations of the changing tilt of the earth’s axis, made over a period covering most of recorded history.
  • Climate change can cause extinction.
  • Link to simulation - glaciers (External Link)
  • Human activity can cause extinction. Humans are destroying the habitat of many types of plants and animals. This is done by chopping down forests and draining swamps to grow crops and to build houses.
  • Continental drift might have caused extinction. According to the theory of continental drift, all land used to be joined in a supercontinent called Pangaea. This later split into Laurasia in the north and Gondwanaland in the south. There is much evidence for this. As the continents moved apart, some populations were split and moved apart. This could have caused extinction as habitats and climates changed as a result of the continental drift.

See (External Link)

What killed the dinosaurs: (External Link)

Biodiversity: the 6th great wave: (External Link)

Vertebrate extinction crisis (videos): (External Link)&id=db50e9fd5d&e=&utm_source=ARKive&utm_campaign=db50e9fd5d-IUCN_Press_Release10_27_2010&utm_medium=email

Activity: mass extinctions

1. How do extinction events seem to help the process of evolution?
2. Name any four possible causes of mass extinctions.
3. Complete this table:

Geological time period when extinction is thought to have occurred. Years before present when evolutionists think this happened Main feature of extinction event
End of the Permian period.
Dinosaurs became extinct.

Activity: Answers

1. How do extinction events seem to help the process of evolution? They possibly cleared the earth of previously dominant species, allowing new species to evolve into the ecological niches this opened up.
2. Name any four possible causes of mass extinctions. Meteorites, volcanoes, climactic changes (e.g. ice age / global warming), man-caused (e.g. over-hunting), due to genetic deterioration
3. Complete this table:

Geological time period when extinction is thought to have occurred. Years before present when evolutionists think this happened Main feature of extinction event
End of the Permian period. 225 million years ago 90% of marine life became extinct
End of Cretaceous era 65 million years ago Dinosaurs became extinct.

Questions & Answers

what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
why and for what was five kingdom of classification of organisms introduced
give the ans as fast as possible
Comment on the ozone depletion over the period of 1982 to 1996
Mpho Reply

Get the best Algebra and trigonometry course in your pocket!

Source:  OpenStax, Siyavula: life sciences grade 10. OpenStax CNX. Apr 11, 2012 Download for free at http://cnx.org/content/col11410/1.3
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Siyavula: life sciences grade 10' conversation and receive update notifications?