TOEFL integrated writing: Endotherms

The reading passage and the professor's lecture both talks about whether modern dinosaurs are endotherms.Although the reading passage believes that dinosaurs are endotherms by citing three evidences,the professor in the lecture casts serious doubts on these opinions.

To begin with;despite the view in the reading passage that fossils found in the polar regions can prove that dinosaurs are endotherms,the professor says this view in unconvincing.She says that the climate of the polar region in the past was warmer that of today,so animals that are not endotherms could live in the polar regions.Even though the polar region was in the cold season,the dinosaurs could migrate to the warm places or hibernate.So the professor objects the first view in the reading passage.

Secondly,even though the reading passage holds the view that the legs underneath the body could prove that dinosaurs are endotherms,the professor gives another explanation.She contends that the legs under the body are not necessarily to indicate that dinosaurs are high-energy runners and that the legs are used to support more weight.Because the dinosaurs' size is big,the legs under the body could give the dinosaurs more advantages.

Finanlly,the professor refutes the point that the Haversian canals imply that dinosaurs are endotherms.She argues that there are growth rings,which could disprove this view,in the dinosaurs' body.These irregular growth rings indicate that dinosaurs cannot grow rapidly or even stopped growing in the cold season.In fact,the endotherms could still grow rapidly even in the cold season.So these growth rings contradict to the opinion that dinosaurs are endotherms