- IB DP Biology 2025 SL- IB Style Practice Questions with Answer-Topic Wise-Paper 1
- IB DP Biology 2025 HL- IB Style Practice Questions with Answer-Topic Wise-Paper 1
- IB DP Biology 2025 SL- IB Style Practice Questions with Answer-Topic Wise-Paper 2
- IB DP Biology 2025 HL- IB Style Practice Questions with Answer-Topic Wise-Paper 2
What is system integration?
Systems work together to maintain homeostasis.
This is a necessary process in living systems. Coordination is needed for component parts of a system to collectively perform an overall function.
What is the hierarchy of organisation?
Cells, tissues, organs, organ systems and then the organism. This integration is responsible for emergent properties.
What is Emergent properties?
New properties that arise with each step upward in the hierarchy of life, owing to the arrangement and interactions of parts as complexity increases.
Distinguish between the roles of the nervous system and endocrine system in sending messages.
The nervous system uses electrical impulses for fast and targeted communication, while the endocrine system uses hormones for slower and widespread communication.
The nervous system controls immediate responses, while the endocrine system regulates long-term processes and maintains body homeostasis.
What is the Role of blood?
The blood system transports oxygen, nutrients, hormones, waste products, and immune cells between organs.
It delivers oxygen to tissues, carries nutrients from the digestive system, transports hormones, removes waste products, and facilitates immune responses.
What is the role of the brain in processing information?
The brain processes information from multiple inputs and is responsible for learning and memory.
It integrates sensory inputs, forms new neural connections, and stores and retrieves information in specific brain regions.
Difference between conscious and unconscious processes?
The brain integrates information from conscious and unconscious processes. The spinal cord integrates only from unconscious processes. The spinal cord also acts as a relay system transferring information between the brain and the PNS.
Input to the spinal cord and cerebral hemispheres through sensory neurons
Sensory neurons convey messages from receptor cells to the central nervous system.
Output from the cerebral hemispheres to muscles through motor neurons
Muscles are stimulated to contract.
Nerves
Nerves are categorized as either myelinated or unmyelinated fibres based on the presence or absence of myelin sheath.
Myelinated nerve fibres
Individual axons in some nerve fibres are surrounded by a fatty sheath made of myelin. Produced by Schwann cells of PNS and oligodendrocytes of CNS. Spirally wrapped around axon, acts as a insulating layer. Sheath is not continuous along the entire length of the axon. Interrupted at points called nodes of ranvier, hence electrical signals jump from one node to another
Unmyelinated nerve fibers
Myelin sheath is absent – nerve impulses move continuously down the length of the axon but they are slower.
Pain reflex arcs (example of involuntary responses with skeletal muscle as the effector)
Nerve endings in the hand that respond to potentially damaging stimuli act as pain receptors (nociceptors) initiating a nerve impulse in the sensory (afferent) neuron. The impulse travels down the sensory neuron (which enters the spinal cord) to the interneuron (within the spinal cord) to the motor (efferent) neuron (which exits the spinal cord). The impulse transmitted by the motor neuron causes the muscle to contract causing the hand to withdraw.
Pathway for all reflex arcs
Stimulus – sensory neuron – spinal cord – motor neuron – skeletal muscle – response
What is the role of the cerebellum?
The cerebellum coordinates and refines body movements, ensuring accuracy and coordination. It integrates sensory information, compares intended and actual movements, and plays a role in motor learning and memory.
Modulation of sleep patterns by melatonin secretion
The pineal gland secretes melatonin, with higher levels at night signaling sleepiness, while lower levels during the day promote wakefulness. This diurnal pattern helps establish the sleep-wake cycle.
Epinephrine (adrenaline) secretion by the adrenal glands
It increases heart rate and blood flow, promotes glycogen breakdown for energy, enhances calcium release for stronger contractions, and improves muscle fiber sensitivity to acetylcholine. These effects prepare the body for physical activity and optimize muscle performance.
Control of the endocrine system by the hypothalamus and pituitary gland
The hypothalamus controls the endocrine system through the pituitary gland. The hypothalamus produces hormones that regulate the anterior pituitary’s hormone release. The posterior pituitary stores and releases hormones made by the hypothalamus. This coordination ensures proper hormone balance and function in the body.
State about Baroreceptors and chemoreceptors.
Baroreceptors monitor blood pressure.
Chemoreceptors monitor blood pH and concentrations of oxygen and carbon dioxide. Located in the carotid sinus and arch of the aorta.
What is the role of medulla?
The medulla coordinates responses and sends nerve impulses to the heart. It regulates heart rate and stroke volume through the cardioacceleratory and cardioinhibitory centers. This helps adjust cardiac output based on the body’s needs and maintain blood pressure.
What is the role of Chemoreceptors?
pH changes in the blood are monitored by chemoreceptors in the brainstem and lead to the control of ventilation rate using signals to the diaphragm and intercostal muscles.
Control of peristalsis in the digestive system
Initiation of swallowing of food and egestion of faeces being under voluntary control by the central nervous system (CNS) but peristalsis between these points in the digestive system being under involuntary control by the enteric nervous system (ENS). The action of the ENS ensures passage of material through the gut is coordinated.