ASSIGNMENT 1: LEARNING AND TEACHING SCIENCE
The process of using internal and environmental mechanisms to regulate the body
temperature within the optimum range is termed thermoregulation (Campbell, Reece, &
Mitchell, 1999). Thermoregulation is one component of homeostasis, which means
‘steady state’, and is a term used to describe the constant internal environment of an
animal’s body (Campbell et al., 1999). This paper will investigate and analyse commonly
held alternate conceptions regarding thermoregulation as a component of homeostasis.
Heat exchange can occur with the environment which can affect an animal’s body
temperature. This may occur via radiation, evaporation, conduction or convection
(Campbell et al., 1999).
Endotherms, e.g. mammals, can also gain heat from internal cell metabolism. Ectotherms,
e.g. fish and reptiles, only gain significant heat from environmental heat exchange
(Hickman, Roberts, & Larson, 1998). This does not mean ectotherms are ‘cold-blooded’.
When basking in the sun, some lizards achieve much higher body temperature than our
own. This also does not suggest that ectotherms have a highly variable body temperature,
although some do, for example some fish live in environments that are at constant
temperature.
Campbell et al. (1999) and Hickman et al. (1998) explain that temperature regulation to
achieve homeostasis involves a number physiological and behavioural adaptations
including:
 Changing the amount of blood flow to the skin to either conserve heat by
constriction of outer blood vessels, which results in less blood being exposed to
the environment or to lose heat by relaxing the outer blood vessels to increase
amount of blood exposed to the environment. This explains the observation of
having blue lips when cold and why we are red-faced when hot;
 Cooling by increasing evaporative heat loss, for example by sweating or panting;
 Behavioural, for example moving in and out of the shade; and,
 Changing the amount of metabolic heat produced by muscle movement or
shivering.
Common student (and teacher) alternate conceptions
The conception that all ectotherms have a highly variable body temperature does not
acknowledge that some environments are constant in temperature and that the
ectothermic animals can thermoregulate using behavioural mechanisms (Hickman et al.,
1998). It is common for students to believe that only endotherms can achieve homeostasis
due to their constant body temperature (Barrass, 1984). They confuse having a constant
body temperature with homeostasis. This is commonly accompanied by the alternate
concept that ectotherms are cold-blooded because they cannot control changes body
temperature (Soyibo, 1995).
Students in a study by Westbrook and Marek (1992) commonly did not consider the
appropriate factors influencing body temperature or attributed causes to other factors.
This is evidenced by such conceptions as; body temperature does not change because ‘it’s
not supposed to’, the body temperature only changes when you get sick, and that body
temperature did not change because the atmosphere did not change. There was also
confusion over how endothermic animals produce body heat, with some students
attributing the ‘friction from the blood’, presumably as it travels through the blood
vessels, as causing body heat (Westbrook & Marek, 1992).
Students frequently do not attribute perspiration as a regulatory process to cool the body
and incorrectly link it to exercise (Kjærnsli, Angell, & Lie, 2002, Westbrook & Marek,
1992). For example, exercise increases heart rate and ‘sets off sweat glands’, ‘Sweat
removes body fat from body’, and perspiration ‘means your cells are working harder and
they lose water’ (Westbrook & Marek, 1992).
Studies by Arnaudin and Mintzes (1985), and Yip (1998) of alternate conceptions
regarding the circulatory system have shown students attribute the red or flushed
appearance of the skin when the environmental temperature increases to increased blood
pressure. This conception is linked to persistent alternate ideas about the circulatory
system, specifically regarding relationships between flow rate, blood pressure and vessel
diameter (Yip, 1998).
Discussion
The notion that ectotherms are ‘cold blooded’ and do not regulate their temperature,
Soyibo (1995) believes, stems from a figure commonly found in biology texts that is
intended to illustrate that endotherms can manifest their own body heat whereas
ectotherms cannot, see Figure 1. This powerful visual tool is deceiving when used to
discuss thermoregulation, as this one was, because it compares body temperature at a
given environmental temperature. In reality the snake could influence its environmental
temperature by moving location.
Figure 1. Animal body temperature for given
environmental temperatures. Extracted from
Campbell et al. (1999).
Barrass (1984) believes that students confuse homeostasis as having a constant body
because humans are used as example and we achieve homeostasis, and have a constant
body temperature. Hickman et al. (1998), suggests that the terminology ‘hot and cold
blooded’ are so entrenched in our language that ‘biologists may find it easier to accept
usage than change people’, even if the terminology is subjective and non-specific.
Alternate conceptions that student have in biology can relate between topics, for example
concepts that a student holds regarding the circulatory system will influence what
understandings they develop of homeostasis (Alkhawaldeh, 2007). Studies by Sungur,
Tekkaya, & Geban (2001), Alkhawaldeh (2007), and Yip (1998) suggest that not only is
the mastery of topics within biology necessary, but also interdiscipline concept
knowledge from physics and chemistry is required to understand circulatory system and
homeostasis concepts. These may account for the alternate conceptions regarding the
circulatory system and cell metabolism as knowledge from other concepts and subjects is
required.
Concept understanding is also linked to cognitive development level. ‘Concreteoperational’ students will understand concrete concepts, those that are developed by
direct experience, while ‘formal-operational’ students will understand formal concepts by
postulatory-deductive reasoning, that is, the ability to imagine the entire system by
comprehending and logically piecing together the component concepts (Lawson &
Renner, 1975).
Simpson and Marek (1988) demonstrate that formal thought is required to understand
homeostasis. Thus, students who are ‘concrete-operational’ may not be able to
understand the homeostasis concept fully. This is evidenced by the specific alternate
conceptions regarding perspiration. Students attribute meaning based on observed or
direct experience, for example, when exercising students have both an elevated heart rate
and perspire, they conclude that heart rate ‘sets off sweat glands’. Also, students associate
sweaty exercise with fat burning and hence the common ‘Sweat removes body fat from
body’ conception. Whereas the process of the elevated heart rate supplying more blood
to deliver oxygen to the cells, which are using energy and producing heat due to activity
while perspiration is cooling the body by evaporative heat transfer, is not observable and
requires theoretical systems understand.
References
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