OCR Biology A - 5.1.1 Communication and Homeostasis Part 2
This deck covers key concepts of communication and homeostasis in biology, focusing on adaptations of ectotherms and endotherms, thermoregulation, and various signaling mechanisms.
Why should the carbon dioxide levels be kept constant
Key Terms
Why should the carbon dioxide levels be kept constant
Behavioural adaptations of ectotherms when its too hot
Finding shade Reduce contact/decrease SA exposed to the sun Burrow underground
Behavioural adaptations of ectotherms when its too cold
Basking in the sun Finding a hot surface to lie on Increase SA exposed to sun
Adaptations of endotherms when its too hot
Sweat Vasodilation Hairs and feathers lie down Panting Decrease respiration rate No shivering
How does panting cool down endotherms
Lose heat through water vapour
How does decreased respiration rate cool down endotherm
Respiration is an exothermic reaction
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| Term | Definition |
|---|---|
Why should the carbon dioxide levels be kept constant | CO2 reacts w/ water to form an acid - change in pH can alter protein structure and effect enzymes activity |
Behavioural adaptations of ectotherms when its too hot | Finding shade Reduce contact/decrease SA exposed to the sun Burrow underground |
Behavioural adaptations of ectotherms when its too cold | Basking in the sun Finding a hot surface to lie on Increase SA exposed to sun |
Adaptations of endotherms when its too hot | Sweat Vasodilation Hairs and feathers lie down Panting Decrease respiration rate No shivering |
How does panting cool down endotherms | Lose heat through water vapour |
How does decreased respiration rate cool down endotherm | Respiration is an exothermic reaction |
Vasodilation | Sphincters open Increase in diameter of lumen of arteriole to increase blood flow Heat is lost through radiation |
Vasoconstriction | Sphincters closed Decrease in diameter of lumen of arteriole to decrease blood flow Heat is conserved through radiation |
Thermoregulatory centre | Located in hypothalamus concerned mainly w/ the regulation of heat production, inhibition and conservation to maintain a normal body temp |
Periphery temp receptors | Receptors monitor temp of extremities (early detection for hypothalamus) |
Adaptations of endotherms when its too cold | Vasoconstriction Contraction of erector pilli attached to base hairs Increase respiration Involuntary muscle contraction |
Neuronal signalling | Uses interconnected networks of neurons that signal to each other across synapse junctions Conduct a signal v. quickly and enable rapid response to stimuli that may be changing quickly |
Hormonal signalling | Glands secrete hormones into the bloodstream which bind to receptors on spp cells so the desired response in produced Enables longer term responses |
Endocrine Signalling | Signals are transmitted over longer distances e.g. gland to brain through the blood (insulin) |
Paracrine Signalling | Cytokines diffuse through tissue fluid and act locally on nearby cells No involvement of blood Signal conc. gradient determines how cells act Taken up by cells or degraded by enzymes (short lived) |
Autocrine Signalling | Hormonal/ chemical messenger (autocrine) Binds to autocrine receptors on that same cell, leading to changes to cells Can promote proliferation and therefore cause a tumour |
Contact dependent signalling | Signalling molecule is not secreted but bound to plasma membrane Interacts w/ receptor Particularly important between immune cells (APCs) |
Synaptic Signalling | Electrical signalling | Presynaptic terminal, synaptic terminal, postsynaptic membrane |
Gap Junction Signalling | Communicate directly w/ immediate neighbour through gap junctions Gap junctions connect the cytoplasm via protein channel Allow the passage of ions and small molecules and coordinated contraction of cardiac muscle |
Endotherms | Birds and mammals Control temp within strict limits Variety of mechanisms to control temp Largely independent of external temp |
Ectotherms | Reptiles, fish, amphibians Body temp fluctuate w/ fluctuations in the external temp Relies on behavioural mechanism |
Advantages of endothermy | Largely independent of external temp Activity still possible when external temp is cold Ability to inhabit warmer and colder parts of the world |
Disadvantages of endothermy | Significant part of the energy intake is used in maintaining body temp when cold More food required to be able to respire |
Advantages of ectothermy | Can survive long periods of time w/ out eating | Greater proportion of energy can be used for growth |
Disadvantages of ectothermy | Unable to generate internal heat through respiration Incapable of activity during winter Have to warm up in the day (risk of predators) |