Endotherms 1 Flashcards
What are the shared derived characteristics of chordates?
Notochord, dorsal hollow nerve cord, pharyngeal slits, muscular post-anal tail
What are the milestones in chordate evolution to the vertebrates?
The tunicates and lancets which are the deepest oldest branches of chordate phylogeny which is a basic form of a chordate
This was followed by the craniates which are chordates with a head where we see the beginning of hunting with presence of a skull, brain, mouth and sense organs
After this stage vertebrates were formed
What are the defining features of vertebrates?
Increased genetic diversity particularly in the Hox and Dlx gene family
The presence of a vertebral column which may be complex and enclose the spinal cord, cartilaginous or bony and replace the notochord after embryonic development
What terms other than warm/cold blooded can more accurately be used describe an animal’s physiological temperature?
These terms a misleading as some cold blooded animals can still generate heat internally
More accurate terms inclduce endo/ectotherm and home/hetero therm
How are bats different to how a warm blooded animal would traditionally be viewed?
When they rest during the day their body temperature drops to be similar to that of the environment, when they hibernate this can become the same as ambient temperature
What is regional heterothermy in fish?
Some fish maintain parts of the body at higher temperatures particularly the eyes, brain and swimming muscles
Where is endothermy seen in insects?
This can occur in bumblebees, honeybees and some moths
This can be essential for the maintenance of heat around flight muscles which is achieved via a heat exchange mechanism this can reduce heat loss in cold weather allows heat loss in hot weather
Where does endothermy occur in reptiles?
This can occur in leatherback turtles which maintain an external body temperature that can be 18 degrees above external temperature through a counter current system and a subepidermal adipose layer and brown adipose tissue which is thermogenic
Marine iguanas can use vasoconstriction to minimize heat loss from core when swimming in cold ocean
Female pythons shiver to keep eggs warm
What are the advantages of endothermy?
It allows the animal to be able to perform vigorous activity for longer such as long distance running and flying
The animals are buffered from environmental extremes typical of terrestrial habitats
However these advantages come at a cost of a greater basal metabolic rate so endotherms must consume more food than equivalent ectotherms
What are the modes of heat exchange?
Convection, radiation, evaporation and conduction
What adaptations do endotherms have for heat exchange?
Hair, feathers, or fat layers these are adaptations for insulation which minimize and assist heat loss
Vasodilation and vasoconstriction can be used to warm or cool the skin and counter-current heat exchangers
There is evaporative heat loss but panting, sweating, bathing and secretions
There is also behavioural adaptation mainly in ectotherms but some things like huddling and seeking shade might occur
Metabolic adaptations such as non-shivering thermogenesis and muscle activity like shivering, flight muscles in insects
