Transcript 28.4_Homeostasis

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Review How do the immune systems and
endocrine glands help to maintain homeostasis
Apply Concepts Describe how the circulatory and
endocrine systems of migrating wildebeest help
maintain homeostasis
Review Define ectoderm and endotherm
CH 28 ANIMAL SYSTEMS II
28.4 Homeostasis
Homeostasis
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Control of internal conditions
Essential to an organism’s survival.
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Digestive, respiratory, circulatory, excretory,
nervous, muscular, and skeletal systems are all
interconnected and work together to maintain
homeostasis.
Endocrine Glands
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Regulate body activities by releasing hormones
into the blood.
Body Temperature Control
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Requires three components:
 Source
of heat
 Way to conserve heat when necessary
 Method of eliminating excess heat when necessary.
Ectotherms
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Regulate body temperature primarily by absorbing
heat from, or losing heat to, their environment
Most reptiles, invertebrates, fishes, and
amphibians.
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Relatively low metabolic rates when resting- don’t
generate much heat
Lack effective body insulation so body heat is easily
lost
Warm up by basking in the sun and often use
underground burrows.
Endotherms
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Regulate body temperature, at least in part, by
using heat generated by its body
Birds and mammals
High metabolic rates that generate heat, even
when they are resting
Conserve body heat primarily with insulating
feathers, fat, fur, or hair
Reduce body temperature by sweating and
panting.
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Ectotherms need much less food than similar-size
endotherms need
Ectothermy is a more energy-efficient strategy in
consistently warm environments
Large ectotherms have trouble in cold
temperatures trying to warm up.
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Evidence suggests that at least some dinosaurs
were endotherms
Current evidence suggests that endothermy has
evolved at least twice among vertebrates
 Once
in the bird line
 Once for mammals.