Thermoregulatory System

Question 1

what is homeostasis?

Answer 1

maintaining of internal environment as response to external stimulus

Question 2

what’s temperature homeostasis?

Answer 2

body detects changes and then responds to correct them to a set point by mechanism called negative feedback

Question 3

what’s an endothermic animal?

Answer 3

maintain constant body temp independently of their environment

Question 4

what are the temps for a human, dog, pig and chicken?

Answer 4

human - 36.1-37.2
dog - 37.9 - 39.9
pig - 38.7 - 39.8
chicken - 40.6 - 43.0

Question 5

where is the thermoregulatory system?

Answer 5

hypothalamus

Question 6

what detects the changes in temperature?

Answer 6

thermoreceptors in the brain and the skin

Question 7

what are the two centres involved with temperatures?

Answer 7

heat gain centre - when animals get too cold
heat loss centre - when animals get too hot

Question 8

what happens when temperatures change?

Answer 8

1. change in temp stimulates thermoreceptors which trigger action potentials to relay information via sensory neurone to hypothalamus
2. hypothalamus sends information via motor neurons to the effectors (skin)
3. a response occurs such as sweating and vasodilation of arterioles to allow heat to escape from skin if body too hot

Question 9

responses to high temperature

Answer 9

vasodilation - arterioles dilate which allows more blood to enter the capillaries
pilorelaxation - pilli erector muscles relax which lowers the hairs and feathers on the skin so that air can circulate, allows for convection and evaporation.
sweating - glands secrete heat onto skin where it evaporates and takes heat from the body. adrenal and thyroid glands secrete adrenaline and thyroxine which reduces metabolic rate and heat generation
gular fluttering - increases heat loss through the mouth it occurs in birds when they rapidly flap membranes in throat for evaporation
panting - process of evaporation of water through nasal passages, mouth, lungs, and birds air sacs.
behavioural changes - stretching out body gives larger s.a for heat loss or seeking of shade.

Question 10

responses to a low temperature

Answer 10

vasoconstriction - arterioles constrict so less blood flow to the skin
piloerection - pils erector muscles contract causing hairs or feathers on skin to raise to trap an insulated layer reducing heat transfer from the skin. moulting can also help
shivering - muscles contract and relax rapidly and cause heat to be produced by friction and respiration
brown adipose tissue - cells take lipids and run them through the mitochondria to generate heat. it is present in almost all mammals.
behavioural changes - curling up causes a smaller surface area for the heat to escape. animals may move to warmer areas and show increased movement

Question 11

metabolic rate in animals

Answer 11

endothermic - can adjust their metabolic rate to regulate their internal body temperature. metabolic reactions give off heat so animals can alter their internal temperature by changing their metabolic rate
ectothermic - cannot use this mechanism on their environment

Question 12

countercurrent mechanism

Answer 12

heat is exchanged between two sources flowing in opposite directions. in heat regulation the flowing sources are the blood stream, when body temp drops the arteries carry warm blood away from the heart while veins take deoxygenated into the heart. as these two pass the warm arteriole blood transfers most of its heat to the cool venous blood and body temp is balanced

Question 13

extremes of temperature

Answer 13

hypothermia - body cannot maintain normal body temperature changes, there are three phases (symptoms dependent)
- mild, weaknesses, shivering, lack of alertness
- moderate, muscle stiffness, low BP, slow breathing
- severe, fixed or dilated pupils, inaudible heartbeat, difficulty breathing, coma

hyperthermia - the elevation of the body temp above the normal. fever hyperthermia results from inflammation within the body. non fever results from all other causes of increased body temperature. symptoms are panting, dehydration, reddening of the gums, decrease in urination, uncoordinated movements and unconsciousness can also cause organ dysfunction and death.

Question 14

physiological adaptations

Answer 14

adaptations in an animals body processes e.g., snakes are physiologically adapted to produce venom which they use in defence against predators

Question 15

anatomical adaptations

Answer 15

adaptations in an animals shape and structure e.g., bat forelimb has become adapted to form wings, improving their access to suitable food sources

Question 16

behavioural adaptations

Answer 16

adaptations in an animals language, tool use and survival strategies, e.g., migration, in some bird species to avoid harsh environments

Question 17

evolution definition

Answer 17

a change in characteristics over several generations

Question 18

specification definition

Answer 18

the formation of a new species as part of the evolutionary process

Question 19

variation

Answer 19

differences between organisms, it can include variations in diet, behaviour and aesthetics. variation between animals is linked to differences or changes in the DNA because of this variations are passed down to offspring

Question 20

natural selection

Answer 20

some variations give an animal an advantage over other animals, e.g., being able to run for longer, reach higher branches or have better camouflage. animals with advantageous variation are more likely to survive and are more likely to reproduce as variation is heritable.

Question 21

speciation

Answer 21

over time it can lead to evolution of a species. if animals in a species develop different variations which both give them advantages it could lead to the species separating into 2 species

Question 22

adaptions of a polar bear

Answer 22

large feet with fur on the soles improves the grip on the ice

small s.a to vol ratio and small ears to reduce heat loss

strong legs help catching their prey when swimming and running

thick layer of adipose under the skin for insulation and energy

sharp teeth and claws for feeding and defending

pregnant females hibernate

highly developed sense of smell and hearing

Question 23

different types of selection pressures that affect variation

Answer 23

stabilising - reduces variation. between animals Dna. extreme phenotypes are reduced and proportion of animals with average phenotype is increased

directional - encourages a particular new phenotype usually in response to environmental changes

diversifying - increases variation between animals DNA, extreme phenotypes become more common and average phenotypes are reduced