Thermal Relations Hill et al., Ch 8

Updated 10 September 2005

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Introduction

A. Temperature affects most physiological processes (Q10 = 2-3) and thus most organisms

1. Physiological processes (and enzymes) often exhibit optimal response curves; prediction re Tb?

2. Animals live in a relatively narrow range of body temperatures (cf environmental temps); WFig. 8.1

a. predict optimal response within the range

B. Maintenance of Tb range requires heat transfer between body and environment

1. Tb not uniform throughout body; importance of shell/core concept (HFig. 8.4)

a. during activity, metabolic rate increases; more heat must be transferred to the surface to maintain core Tb

2. Responses to temperature variation are variable

a. with thermal strategy

- endotherms (physiological heat source); generally higher Tb, less variable

- ectotherms (environmental heat source); generally lower Tb, more variable

b. with phylogeny within a strategy (Table)

Endotherm taxon	Normal Tb	Lethal Tb
Monotremes	31 ± 2	37
Marsupials