Evolution - Extinction questions?

Question

1. On average, how long does a species exist before going extinct?
2. What do rocks of the early Triassic show? Why?
3. When and where did the first human-like primates appear? (I know they first appeared in Africa but I don't know about how many millions years ago?)

I have hard time finding answers to these questions. Can someone help me?
Thank you.

Answer 1

1.) The amount of time a species is alive on the planet is completely random. for example archaeopteryx was on the planet for less than a million years, while pteranodon lived for 45 million years, sabertooth tiger lived for 24 million years and t-rex lived for 20 million years
2.) Scientists study the layers in the rock to see how old it is. according to the principle of original horizontality. god thats a big word... NEway it states that the layers closer to the surface are younger than the rocks that are down deeper in the ground. so when a paleontologist finds a fossil he looks at the sediments and matches them up with layers of rock in the ground thus determining the age of the fossil or rock. So the rocks of the early triassic would show what life existed in the time period. It also shows how much volcanic activity was around.
3.) The first human like primates appeared 1.8 million years ago

Well... does that help?
I g2g im missing the begining of the hills have eyes

Answer 2

The average lifetime of a species, even if we knew
it, would be relatively meaningless because there
appears to be so much variability in duration depending on the particular circumstances. A
species limited to a single island or small group of
islands, the dodo on Mauritius, for example, might
have a very short lifespan because any major
natural disaster could eliminate it entirely. In the
case of the dodo, of course, the disaster was the
killing of the birds by humans and the even worse
introduction of other animals that killed them - rats,
pigs, monkeys, etc. On the other hand, an animal
in a stable habitat of large extent might persist for
many millions of years without significant change
or danger of extinction, the horseshoe crab of the
Atlantic Coast, for example. Actually fossils of
the horseshoe crab are few, so we don't know how old it is, but there have been other kinds of
horseshoe crabs for a very long time.

The rocks of the Triassic show the early development of the reptiles. I don't know just when the first mammals appeared, but they came
not too long after, geologically. They have been
around about as long as the dinosaurs, though they
didn't become common and dominant on land
until the dinosaurs died out at the end of the
Cretaceous. As to why, the only answer is, because that's what was there.

The age of the early human-like primates keeps
changing with new discoveries and new interpretations of the data, but it's roughly 4-6
million years ago, probably closer to 4 than 6. Of
course this depends on how human-like you
require them to be. The ancestral apes of much
earlier were still fairly human-like, as the living ape
species are.

Answer 3

1) It is hard to say, as some species exist longer than others.
http://www2b.abc.net.au/beasts/newposts/0/topic517.shtm
says about a million years.
http://www.guardian.co.uk/life/interview/
says 2-3 millions years.
http://www.case.edu/artsci/math/alexander/reviews/br5.html
says about 5 million years
Biologst Ernst Mayr estimated the life of a species at around 100,000 years. So there is no firm answer for this question.

2) Triassic rocks and the fossils show that life was very different then. The Triassic is the first of the three epocs in which the dinosaur were the dominant life on Earth. The rocks and fossils show how different life was then.

3) http://anthro.palomar.edu/earlyprimates/first_primates.htm
The earliest primates came into existance about 60 million years ago. The earliest human-like was about 6-8 million years ago.