Question

Question one: Explain the relationship between metabolic rate and size of mammals.

Question two: Compare and contrast organisms that are homeotherms and terotherms. Identify an ectotherm and an endotherm for each of the two groups (homeotherms and heterotherms).

Question Three: How is temperature regulated in a homeothermic mammal?

Answer 1

1. Metabolic rate is a fundamental property that indicates daily requirements for individuals and therefore has influence on biomass and nutrient flow through communities and the structure and functioning of ecosystems. Metabolic rate has long been recognized to vary with body mass(M). It is given by expression

Metabolic rate =aM^b

The metabolic rate versus body mass relationship has used fr the calculation of basal or resting metabolic rates (BMR or RMR) and has used as an average estimation of species of metabolic rate and body mass instead of individual measurements. However, field metabolic rates (FMR), individual mass and rate phenotypes are more directly ecologically relevant and are probably more directly subjected to selection rather than resting rates and species-average phenotypes, respectively.

2.

Homeotherms are the organism that maintain their body temperature within a narrow range. Heterotherms are animals that can switch between ectothermic and endothermic conditions over short (daily basis) or long periods (continue for an year).

Endotherms are the organisms capable of regulating their body temperature irrespective of external temperatures. They are also known as warm blooded organisms. For example, mouse is an endothermic organism depends on daily feed to carryout its metabolism and tomaintain its body temperature.

Ectotherms are organsims capableof regulating their body temperature according to environmental temperatures. They are also known as cold blooded organisms. For example, Frog is an ectotherm maintains its body temperature according to external temperature.

3. The thermoregulation in homeotherms is carriedout by maintanence of internal metabolic activitites.Endotherms maintain their body temperatures through internal means such as muscle shivering or increasing their metabolism body temperatures. Body heat is generated by metabolism means breakdown of energy reserves (glucose) through biochemical activities in a cell to produce energy in the form of ATP. The endotherms maintain the body heat by having good insulation over te body. Several endotherms are covered by hair or fur externally. In cold temperatures insulation provides necessary heat. If the heat is still not sufficient, the shivering muscles generate ATP and produce the heat. In hot temperatures the excess heat is sent out through body by sweating and cooling the body.

Answer 2

Q. 1:

The metabolic rate decreases as the size of animal increases (inverse realtionship). For example, rats have higher metabolic rate than humans and humans have higher metabolic rate than elephant.

Q. 2:

Homeotherms are the animlas that maintain a constant internal body temperature all the time, eg: humans. Heterotherms also maintain constant internal temperature but they change their body temperature in certain conditions lie hybernation, eg: ground squirrles. Most of the homeotherms and heterotherms are endotherms i.e. they generate their own heat.

Q . 3:

In a homeothermic mammal for example in humans, temperature is regulated by heigher centers in brain namely hypothalamus. A set point is made in the hypothalamus, which causes changes in body activities to maintian that temperature.