Biology Concepts and Hormonal Functions

Year 12 Biology E-Note

• Biology is the most powerful technology; DNA is software, proteins are hardware, and cells are factories.
• The world has many trillion-dollar problems, and biology is the only way to solve them.
• Biology is a software process; trillions of cells make up our bodies, each governed by this process. Current biological software is outdated, having evolved in a different era.
• "Impossible" is not a scientific term.

Award Page

• Students were recognized for academic excellence and practical skills.
• Awards were given for individual academic performance and practical distinction in Biology.

2023/2024 Biology Scheme of Work (Term 1)

• Week 1: Revision from Year 11, Beginning of Term Test, Reproductive System in Plants.
• Week 2: Regulation of Internal Environment of Organisms (I).
• Week 3: Regulation of Internal Environment of Organisms (II).
• Week 4: Plant Hormones.
• Week 5: Nervous Coordination (I).
• Week 6: Nervous Coordination (II).
• Week 7: Peripheral Nervous System.
• Week 8: Sense Organs / Structure and Functions of Neuron.
• Week 9: Sense Organs / Reflex and Voluntary Actions.
• Week 10: Sense Organs / Experiments on Dog, Food, and Bell.
• Week 11: Revision
• Week 12: Examination

Regulation of the Internal Environment (Unit 1)

• Organs usually find themselves in a constantly changing environment requiring self-regulation (homeostasis).
• Homeostasis is maintaining internal stability despite external changes.
• Conditions necessary for proper bodily function: proper chemical concentrations, temperature, pH (acidity), osmotic pressure, etc.

Kidney as a Structure of Homeostasis

• The human kidney is bean-shaped, located in the abdomen, with an outer cortex and inner medulla.
• Tubules called nephrons are present.
• The kidney maintains homeostasis by controlling water, ion, and other substance levels in the blood through osmoregulation and excretion.

Diseases of the Kidney

• Kidney Stone: Small solids (e.g., calcium phosphate) block the nephrons.
• Diuresis: Kidney tubules fail to reabsorb water.
• Nephritis (or Oedema): Inflammatory diseases of the glomeruli; causes kidney swelling.

The Liver as an Organ of Homeostasis

• The liver is the largest gland weighing about 1.25 kg and is located below the diaphragm. It is responsible for filtering the blood, converting glucose to glycogen, detoxification, and producing bile among other functions.

Function of the Liver

• Blood sugar regulation by converting excess glucose to glycogen for storage (insulin).
• Regulation of blood proteins like fibrinogen, prothrombin, and globulin.
• Detoxification (processing harmful substances).
• Biliary function (producing and storing bile for fat digestion).
• Production of heat.

Diseases of the liver

• Diabetes Mellitus: Inability of the liver to convert glucose to glycogen due to lack of insulin.
• Infective Hepatitis (Viral Hepatitis): Inflammation of liver cells due to viruses.
• Gall Stones: Stones formed in the gall bladder; disrupt bile flow.
• Cancer of the Liver: Outgrowth of unregulated cells preventing normal liver function.
• Cirrhosis: Damaged liver cells replaced by useless fibrous tissue.
• Jaundice: Breakdown of red blood cells causing excess bilirubin.

Hormonal Coordination (Unit 2)

• Endocrine system includes glands that produce and release hormones to regulate bodily functions.
• Hormones are chemical messengers carried by the blood stream that affect target organs.

Types of Plant Hormones

• Auxins: Stimulate or inhibit growth, responsible for phototropism (responding to light), geotropism (responding to gravity), and apical dominance.
• -Common examples are; indoleacetic acid (IAA), 2,4-D, and NAA.
• **Gibberellins:**Promote growth, influence fruit development, and break seed dormancy.
• Cytokinins: Stimulate cell division, promote lateral bud growth, delay aging.
• Abscisic Acid: Inhibits growth, promotes dormancy, regulates stomatal opening.
• Ethylene: Stimulates fruit ripening, promotes abscission (leaf/flower fall).

Coordination and Response (Unit 3)

• Coordination is harmonious functioning of all parts.
• Two communication systems are:
• Nervous system - fast, electrical impulses
• Endocrine system - slow, chemical hormones.

The Nervous System

• Central Nervous System (CNS): Brain and spinal cord
• Peripheral Nervous System (PNS): Nerves outside CNS
• Somatic Nervous System (SNS): Voluntary actions
• Autonomic Nervous System (ANS): Involuntary actions;
• Sympathetic: Fight-or-flight response
• Parasympathetic: Rest-and-digest response

The Brain

• Forebrain: Cerebrum, olfactory lobes, thalamus, hypothalamus
• Midbrain: Optic lobes, pineal body, pituitary gland.
• Hindbrain: Cerebellum, pons, medulla oblongata

The Spinal Cord

• Conducts impulses between brain and body.
• Centre for reflex actions.

Reflex Actions

• Involuntary, rapid responses to stimuli.
• Do not involve the brain in the decision-making process

Sense Organs

• Special organs that detect stimuli from the environment:
• Eyes
• Ears
• Nose
• Tongue
• Skin

The Ear

• External ear (pinna, auditory canal)
• Middle ear (eardrum, ossicles)
• Inner ear (cochlea, semicircular canals)

The Eye

• Sclera (outer layer)
• Cornea (transparent front)
• Choroid (middle vascular layer)
• Lens (focuses light)
• Retina (light-sensitive inner layer)
• Optic nerve (carries visual information)
• Accommodation (adjusting focus)

The Tongue

• Taste buds detect taste sensations.