Body plans & regulation in multicellular organisms II (4/4)
Apical Dominance
Definition: Apical dominance is the phenomenon where cells in apical buds produce a hormone (auxins) that inhibits the growth of lateral buds.
Mechanism: The concentration of auxins in the apical bud prevents the lateral buds from developing, allowing the plant to focus its growth upwards.
Hormonal Regulation: Auxins are essential as they help plants sense and respond to environmental stimuli, thus adjusting their body plan accordingly.
Cellular Forms in Animals
Unicellular vs Multicellular: Animals can exist in both unicellular and multicellular forms.
Example: Clonoflagellates are unicellular; however, they can form multicellular shapes (e.g., balls) for movement using their flagella.
Multicellularity Requirement: Persistent multicellularity is necessary for organisms termed as 'animals', requiring development and differentiation during embryonic stages.
Nervous System Development
Role of Nervous System: The nervous system facilitates complex behaviors through various structures.
Ganglia: In more advanced species, ganglia allow for organized responses, enabling organisms to process sensory data and exhibit more complex behavior.
Behavioral Response: Example of an organism that can leave its burrow to collect resources which demonstrates coordinated behavior through its nervous system.
Homeostasis and Control Mechanisms
Basic Circuit for Homeostasis: The minimal requirement for maintaining homeostasis includes:
Sensor: Detects a stimulus.
Control Center: Compares received data to a set point.
Effector: Carries out the response as dictated by the control center.
Feedback Mechanisms:
Positive feedback loops can enhance responses in certain situations.
Central vs Peripheral Nervous System:
Central Nervous System (CNS): Includes the brain and spinal cord responsible for processing information.
Peripheral Nervous System (PNS): Comprises all the nerves outside the CNS that can either transmit sensory data or carry motor instructions.
Motor System's Role: It modulates bodily functions, like slowing down digestion during flight response for survival.
Responses and Signals
Signal Processing:
Once information is relayed to the control center, it triggers responses by releasing signals into the bloodstream that travel throughout the body.
Absence of receptors means no response can occur, highlighting the importance of receptor proteins and cell differentiation in this process.
Hypothalamic Role: The hypothalamus acts as a primary control center for various regulatory functions including thermoregulation.