Life Processes and Movement

  • Movement in Living Organisms:
    • Some movements result from growth (e.g., a seed germinating).
    • Others are independent of growth (e.g., animals running, chewing, playing).
    • Movement is often a response to environmental changes and helps organisms adapt to their surroundings.
  • Examples of Responses:
    • Cats run after mice, plants grow toward light, and humans respond to heat or light to protect themselves.

Control and Coordination in Animals

  • Why Control is Necessary:
    • Movements are triggered by environmental changes and need to be controlled for appropriate responses.
    • Specialized tissues like nervous and muscular tissues handle this control.

Nervous System in Animals

  • Function of the Nervous System:
    • Detects environmental changes via receptors (e.g., taste by gustatory receptors, smell by olfactory receptors).
    • Transmits signals as electrical impulses via neurons.
  • How Information Travels in Neurons:
    • Receptors detect signals → Chemical reactions generate electrical impulses → Impulses travel through neurons → Chemical signals pass across synapses to other neurons or muscles.
  • Structure of a Neuron:
    • Parts: Dendrite (receives input), Axon (transmits impulse), Synapse (converts electrical to chemical signals for further transmission).
    • Nervous tissue: Organized network of neurons specialized in conducting impulses.

Reflex Actions

  • What is a Reflex Action?
    • Sudden, automatic response to a stimulus without conscious thought (e.g., pulling hand from a flame).
    • Reflex Arc:
      • Simplified pathway in the spinal cord connects input and output nerves for quick response.

The Brain: Control Center

  • Regions and Functions of the Brain:
    • Fore-brain: Responsible for thinking, voluntary actions, and sensory processing.
    • Mid-brain and Hind-brain: Control involuntary actions (e.g., heartbeat, breathing).
    • Cerebellum (Hind-brain): Maintains posture, balance, and precision in voluntary actions.
  • Brain Protection:
    • Enclosed in a bony skull and cushioned by fluid to absorb shocks.

Muscles and Movement

  • How Muscles Work:
    • Muscles move by shortening their shape due to specialized proteins reacting to nerve signals.
    • Types: Voluntary muscles (controlled by thought) and involuntary muscles (function automatically).

Coordination in Plants

  • Lack of Nervous System:
    • Plants lack nerves or muscles but respond to stimuli (e.g., touch, light, gravity).
  • Types of Plant Movements:
    1. Independent of Growth: Rapid movements like leaves of a sensitive plant folding upon touch.
    2. Dependent on Growth: Directional movements like stems growing upward and roots downward.
  • Mechanism of Movement:
    • Information travels via electrical-chemical signals (no specialized tissues).
    • Cells change shape by adjusting water content (swell/shrink) to produce movement.

Extra Insights and Competitive Exam Tips

  • Reflex Action vs. Voluntary Action:
    • Reflex actions are quick and automatic, bypassing the brain initially. Voluntary actions involve conscious decision-making in the fore-brain.
  • Neurons:
    • Know terms like synapse, dendrite, and axon for understanding impulse transmission.
  • Brain Functions:
    • Match brain parts with their functions (e.g., cerebellum = balance, medulla = involuntary actions).
  • Plant Movements:
    • Remember the role of water content changes in plant cell movements.

Movement Due to Growth in Plants:

  • Some plants, like the pea plant, use tendrils to climb. Tendrils touch objects and grow towards them by wrapping around. This happens because the part of the tendril in contact with the object grows slower than the part away from it.
  • Plants often grow in response to light, gravity, or chemicals, which leads to directional movements called tropism. Examples include phototropism (shoots grow towards light, roots grow away) and geotropism (roots grow downwards, shoots grow upwards due to gravity).
  • Other types of tropism are hydro (response to water) and chemo (response to chemicals), like the growth of pollen tubes towards ovules.

Growth-related Movements:

  • Plant movements can be fast (e.g., sensitive plants) or slow (e.g., sunflowers following the sun). Growth movements in plants happen slowly.
  • In animals, growth is also controlled. For example, human arms grow in specific directions, not randomly. Both plants and animals use chemicals for communication, like hormones.
  • Hormones in plants, such as auxins, help direct growth by diffusing to parts where growth needs to be stimulated. For instance, auxin helps a shoot bend towards light by causing the cells on the shaded side to grow longer.

Hormones in Plants:

  • Plant hormones include auxins (promote growth), gibberellins (help in stem growth), and cytokinins (promote cell division). Abscisic acid inhibits growth and causes wilting.

Hormonal Communication in Animals:

  • In animals, hormones also control responses and growth. For example, adrenaline prepares the body for fight-or-flight situations by increasing heart rate and breathing.
  • Hormones like thyroxine regulate metabolism, while growth hormones control overall body growth. Insulin helps regulate blood sugar levels.
  • Feedback mechanisms ensure hormones are secreted in the right amounts, such as insulin secretion when blood sugar levels rise.

Important Animal Hormones:

  • Iodine helps the thyroid produce thyroxine, which controls metabolism. Lack of iodine leads to goitre.
  • Growth hormone controls physical growth; lack of it in childhood leads to dwarfism.
  • Sex hormones like testosterone and estrogen cause puberty changes.

Key Points:

  • Control and coordination in plants and animals are regulated by hormones and the nervous system.
  • Hormones help with communication within organisms, often using feedback systems to regulate their levels.

THERE ALL ARE THE NOTES OF CHAPTER 6. AND AFTER SOME TIME YOU GET IMPORTANT QUESTIONS HERE. *#THANKS FOR VISITING, VISIT AGAN#* 😊