2006-06-28 23:19:17 · 6 answers · asked by ck 1 in Environment
seems like evolution was experimenting with size. it went big then small
2006-06-29 04:13:45 · answer #1 · answered by shiara_blade 6 · 1⤊ 0⤋
Very generally speaking within any contiguous evolutionary period, that is between major extinction events, the largest species tend to become larger. I assume that one of the few open environmental niches is that of organisms larger than any currently alive. That open opportunity is filled by the largest individuals of the largest species. Those individuals out reproduce their smaller brothers and sisters and so that species tends to get even bigger.
The largest dinosaurs evolved near the end of the most recent very long stable period and so were very large.
Mammals were on their way to growing to giant size too. There where many examples of "mega fauna" on earth between about 100,000 and 10,000 years ago. However humans evolved over that time and changed the dynamic by evolving a big brain instead of a big body. Humans appear to have killed off most of the mega fauna shortly after they encountered them. The one exception is Africa where the mega fauna co evolved with humans and therefore evolved defenses that were successful in pre-technology times. However technology has developed much faster than evolutionary change can take place in mega fauna and so now even the African mega fauna is nearing extinction by humans.
2006-07-03 08:58:31 · answer #2 · answered by Engineer 6 · 0⤊ 0⤋
Giant animals can evolve naturally over millions of years, when food sources are plentiful. When the climate is warmer, cold-blooded animals (like lizards), plants, and insects grow larger, while warm-blooded animals (like mammals) shrink. When the climate is colder, such as in the Ice Ages, warm-blooded animals get larger, while cold-blooded animals evolve smaller. Many of the large animals that exist today are leftovers of the hot and cold periods of the earth. Some examples of leftover animals are the crocodile (from the time of dinosaurs) and the polar bear, the world's largest bear today
2006-07-04 12:48:37 · answer #3 · answered by MTSU history student 5 · 0⤊ 0⤋
they lived a long time. A dinosaur is a lizard-they never stop growing. the environment was also different back then (when?).
2006-06-29 00:27:59 · answer #4 · answered by Terrence J 3 · 0⤊ 0⤋
not all dinosaurs are so big. Maybe gravity pull them down and thus their babies become shorter day after day? :)
2006-06-29 04:58:55 · answer #5 · answered by Fraller Dude 1 · 0⤊ 0⤋
becoz its dino saur
2006-06-28 23:22:29 · answer #6 · answered by suppy 2 · 0⤊ 0⤋