1. Brief introduction of T rex and other outstanding dinosaurs
2. Evolutionary biologists have researched the gigantism factors for a long time. In recent years, increasing carbon dioxide level is taken as main reason of above situation. In the last Oct meeting, SS presented a more nuanced model.
3. Piggybacking research uncovers some reasons behind. The beasts probably had to have been cold-blooded to maintain constant body temperature.
4. Next, carnivores need large living space and low population density. The landscape they needed was large enough to prevent from extinction. Last, existing competition between them and other gigantic creatures.
5. But scientists hard to accept all the conclusions. They think these dinosaurs are more resemble to warm-blooded mammals. But according to the fossil records, the five known gigantic dinosaurs did have large landmass to live without other competitors.
The continent changes made isolation of some species, scientists need more researching to testify.
1.Before T.rex, T petite
- T.rex broke T mold, tripling body mass over predecessor
2. factors lead to giganitism:
-recent years: increase level of co2->plant->herbivorous dinosaur preyed
-meeting:SS team
3.team identified prerequisites:
-cold-blooded
-extensive geographic ranges+ low population densities+bigger areas continent- size landmassed
-competint large species
4. critics: conclusion hard to swallow
-K.P.:
-dinosaurs warm-blooded mamels in bone histology
-impossible to determine population size of extinct animals
-But so far: fossil record uphold team models
-5 known heavyweights only on vast landmassess
5. strongest support: rise of T.rex
-wastern interior seaway: both sides 3 T. roamed
-water retreated, doubling available habitat: 1lineage remained
petite 娇小的
nuanced 细致入微的
以霸王龙为开始,讨论恐龙进化体积变大的原因。还研究了爬行类大恐龙,提出了个模型,讨论拥有大体积的条件、理由。模型被反驳,大恐龙跟热血动物更像。但是现在的证据无法推翻模型,其他证据还可以支持模型。
P1
- T-rex - features: terrifying
- [while] TLK- modest roots
- Tyrannosaurs - petite/small >> triple>>T-rex
P2 research on theropods for factors of gigantism
- 2 other groups(C&S) also bigger
- Hypo: CO2++>>herb bigger>>herbivorous bigger>>theropods bigger
- More nuanced model - by researching thigh bone
P3
○ [contrary] cold-blooded
□ High cost for heating
□ No need hunting to much
□ Avoid over heating
○ Geo range
□ Meat-eating: wider, density-
□ Big theropods-continent-size
○ Eco pressure for competition for food
□ Compete with bigger rivals
P4
- critics:
○ More like warm-blooded
○ Cannot determine population size
- However
○ Fossils support the model
○ Example: 5 dinosaurs
□ Vast
□ No rivals
□ Of the two, no compete
P5 reinforce model
- 1-2tons>>water retreated>>area doubled>>5.5ton