The Origin and Evolution of Mammals - Moodle

a mammal. The difficulty with all such suggestions
is the difficulty that arises in any kind of keyadaptation
hypothesis (Kemp 1999). As long as
more than one characteristic has appeared in a
descendant organism, it is impossible to test by correlation
which of them is the ‘key character’ and
which are subsidiary ones. And as long as there are
several characters that are functionally interdependent
on one another, it is meaningless to attribute
paramountcy to one and subserviency to others: all
are necessary parts of the single working whole.
Kemp (1982) published a diagrammatic scheme to
illustrate the functional interrelationship between all
Complex
mastication
Increased rate
of food collection
Improved
locomotion
Turbinals
Increased
assimilation
Sustained
muscle action
Diphyodonty Parental care
Improved
sensory
reception
Spatial
control
Eye changes Ear changes
Lactation
High
metabolic rate
Temperature
regulation
Chemical
regulation
Diaphragm
EVOLUTION OF MAMMALIAN BIOLOGY 131
the fundamental mammalian attributes (Fig. 4.14).
He proposed that this was most intelligible when
looked at from the focal point of homeostasis. This
is the maintenance by processes of active regulation
of gradients between the internal environment of
the organism and the external environment. To a
degree it is a sine qua non of life of any kind, of
course. There are inevitable limits to the magnitude
of the gradients that can be so maintained by any
particular organism, and this dictates the physicochemical
boundaries of that organism’s tolerable
habitat. Mammals may be seen as the organisms that
have evolved the highest capacity for regulation of
Mammary glands
Increased
oxygen uptake
Endothermy Hair
HOMEOSTASIS
Complex CNS
Sweat glands
Advanced
endocrine
glands
Secondary
palate
Double
circulation
High blood
pressure
High kidney
filtration rate
Long loops
of henle
Figure 4.14 A schematic
interpretation of the
interrelationships between the
structures and functions of a
mammal (Kemp 1982).