C3.1
Which sequence correctly shows the biological hierarchy from simplest to most complex?
A. Organ → Tissue → Cell → System
B. System → Organ → Tissue → Cell
C. Cell → Tissue → Organ → System
D. Tissue → Organ → Cell → System
C. Cell → Tissue → Organ → System
Which statement accurately compares the nervous and endocrine systems?
A. Both use electrical signals for long-term control
B. The endocrine system uses hormones transported in blood, whereas the nervous system uses electrical impulses along neurons
C. The nervous system causes slow, widespread changes
D. Hormones are only used in reflex arcs
B. The endocrine system uses hormones transported in blood, whereas the nervous system uses electrical impulses along neurons
Which of the following levels of biological organization represents an emergent property?
A. Cells forming tissues
B. Organ systems forming cells
C. Atoms forming molecules
D. Tissues forming molecules
A. Cells forming tissues
Which observation provides the strongest evidence that an emergent property has resulted from integration of body systems rather than from one organ acting independently?
A. A cheetah increases ventilation, cardiac output and limb muscle contraction simultaneously while pursuing prey.
B. A bird increases heart rate during flight because cardiac muscle cells contain numerous mitochondria.
C. A mammal maintains blood glucose because hepatocytes release glucose from glycogen when stimulated.
D. A neuron propagates action potentials because voltage-gated sodium channels open after threshold is reached.
A. A cheetah increases ventilation, cardiac output and limb muscle contraction simultaneously while pursuing prey.
Which function is most associated with the brain, rather than the spinal cord?
A. Coordinating peristalsis in the gut
B. Rapid reflex withdrawal
C. Integrating auditory and visual information
D. Triggering the knee-jerk reflex
C. Integrating auditory and visual information
Explain why a concentration of auxin that promotes elongation in a shoot may inhibit elongation in a root.
auxin promotes elongation only up to an optimum concentration; above the optimum it becomes inhibitory
root tissue is more sensitive to auxin than shoot tissue, so its optimum concentration is much lower
a concentration near the shoot optimum is therefore above the root optimum, so it inhibits root cells while still promoting shoot cells
A person touches a hot stove and withdraws their hand before feeling pain. This response occurs without conscious awareness.
Which structure mediates this rapid reflex response, and how?
A. Brainstem, by controlling autonomic reflexes
B. Cerebellum, by triggering muscle memory
C. Spinal cord, via a reflex arc using interneurons
D. Cerebral cortex, by integrating sensory input
C. Spinal cord, via a reflex arc using interneurons
Identify the functional difference between the nerve fibre entering the spinal cord and the nerve fibre leaving it.
the fibre entering the spinal cord belongs to a sensory neuron and carries impulses from a receptor / free sensory nerve ending towards the CNS
the fibre leaving the spinal cord belongs to a motor neuron and carries impulses from the CNS to the skeletal muscle / effector
A small number of ripe fruits are placed in a sealed container with many mature but unripe fruits. After some time, ethylene released by the ripe fruits initiates ripening of neighbouring fruits. These fruits subsequently release additional ethylene, causing the rate of ripening throughout the container to accelerate.
What biological consequence results from this feedback mechanism?
A. It slows the ripening right down, so that only one single fruit on the whole plant ripens at any time.
B. It keeps the fruit unripe for far longer, which gives the seeds inside much more time to develop first.
C. It makes the ripening fast and synchronized, so that a whole crop of the fruit ripens close together.
D. It reverses the ripening process again whenever too much ethylene builds up around the ripening fruit.
C. It makes the ripening fast and synchronized, so that a whole crop of the fruit ripens close together.
Compare and contrast the roles of the spinal cord and the brain as integrating centres of the nervous system.
both are parts of the central nervous system that integrate sensory input and produce coordinated motor output
both receive impulses from sensory neurons and send impulses out along motor neurons
the spinal cord integrates unconscious processes such as reflexes, whereas the brain carries out conscious processing
the brain is capable of learning and memory / higher-level processing, whereas the spinal cord is not
Although the _____ is a very important part of the brain associated with body movements, it does not initiate those movements.
Cerebellum
Auxin molecules can enter cells in a stem, but their passive movement across the membrane cannot by itself explain the strongly directional transport of auxin through the tissue. Microscopy shows that one type of auxin transport protein is concentrated at only one end of each cell.
Which mechanism best explains how this asymmetric distribution produces directional auxin transport?
A. Influx carriers on one side of each cell pump auxin inward directionally.
B. Auxin leaks out equally through all sides of every cell by free diffusion.
C. Auxin is carried around the plant dissolved in the transpiration stream now.
D. Efflux carriers on one side of each cell pump auxin outward directionally.
D. Efflux carriers on one side of each cell pump auxin outward directionally.
Explain the feedback pathway by which a sudden increase in arterial blood pressure can cause a change in heart rate.
increased arterial pressure increases stretching / stimulation of baroreceptors located in the walls of the carotid arteries / carotid sinus and aorta / aortic arch
baroreceptors send an increased frequency of nerve impulses to the cardiovascular centre in the medulla
the medulla coordinates the response and alters autonomic nerve signalling to the heart
heart rate decreases (and stroke volume may decrease), reducing cardiac output and opposing the original rise in blood pressure / returning pressure towards its set range
During vigorous exercise, increased cellular respiration alters the concentrations of respiratory gases in the blood.
Explain how these changes can produce coordinated increases in both heart rate and ventilation rate.
increased respiration produces more CO₂, which enters the blood and causes blood pH to decrease / increases H⁺ concentration
chemoreceptors detect changes in CO₂ concentration / pH and oxygen concentration; relevant chemoreceptors are located in the brainstem and peripheral chemoreceptors are associated with the carotid and aortic regions
sensory information is transmitted to / processed by centres in the medulla
the medulla increases nerve impulses to the heart, increasing heart rate and/or stroke volume and therefore increasing transport of respiratory gases
the medulla also increases signalling to the diaphragm and intercostal muscles, increasing ventilation and thereby increasing CO₂ removal / O₂ uptake and tending to restore blood-gas concentrations and pH OWTTE
Outline the role of the spinal cord in coordinating unconscious processes.