3.5-3.8 Flashcards
(22 cards)
Define environmental resistance and give examples.
Factors that limit population growth. Abiotic: temperature, pH. Biotic: competition, disease.
What is succession?
A sequence of changes in community structure over time, ending in a climax community.
How can farming reduce its carbon footprint?
Grow crops for humans, reduce meat, reduce packaging and food miles.
What is nitrogen fixation and which bacteria perform it?
Conversion of atmospheric nitrogen to ammonia by Rhizobium and Azotobacter.
Define nitrification.
Conversion of ammonium to nitrites by Nitrosomonas, and then to nitrates by Nitrobacter.
What is denitrification?
Reduction of nitrate to nitrogen gas by anaerobic bacteria in waterlogged soils.
What is homeostasis?
The maintenance of a constant internal environment.
What is osmoregulation and which organ is key?
Regulation of water potential; the kidney plays the major role.
Describe ultrafiltration in the nephron.
High-pressure filtration at the glomerulus forces water, ions, and small molecules into Bowman’s capsule.
What is selective reabsorption?
Reabsorption of useful substances (glucose, amino acids) in the proximal convoluted tubule.
How is water reabsorbed in the nephron?
Via osmosis in the loop of Henlé, distal tubule, and collecting duct.
What hormone regulates water reabsorption?
ADH (antidiuretic hormone) increases permeability of the collecting duct.
How does ADH affect urine concentration?
More ADH → more water reabsorbed → concentrated urine. Less ADH → dilute urine.
What are the two divisions of the nervous system?
Central nervous system (CNS) and peripheral nervous system (PNS).
What is the difference between sensory, relay, and motor neurons?
Sensory: from receptor to CNS. Relay: within CNS. Motor: from CNS to effector.
Describe the structure of a myelinated neuron.
Cell body, axon, myelin sheath, nodes of Ranvier.
What is resting potential?
-70mV inside axon; maintained by sodium-potassium pumps.
What is the action potential process?
Depolarisation (Na⁺ in), repolarisation (K⁺ out), hyperpolarisation, return to resting potential.
What is the refractory period?
Time during which a second action potential cannot be generated.
How is a synapse transmitted?
Neurotransmitter (e.g., acetylcholine) is released from presynaptic vesicle, crosses synaptic cleft, binds to receptors.
What is spatial and temporal summation?
Spatial: multiple neurons trigger one. Temporal: rapid impulses from one neuron build up.
What are the effects of drugs at synapses?
May mimic (agonist), block (antagonist), or inhibit breakdown of neurotransmitters.
