Notes, summaries, assignments, exams, and problems for Biology

The Internal Environment

• Refers to the fluids that surround the cells.
• Temperature and composition must be stable for the correct working of cells.
• This internal environment is maintained by the organ systems of the body.
• Interstitial fluid (plasma): Surrounds and bathes the cells.
• Blood and lymph: Collect and distribute substances for the cells (O2, nutrients) and remove waste.

The Circulatory System

• Carries nutrients and oxygen throughout the body and collects waste (blood): Blood Circulatory System.
• Returns excess interstitial fluid to the blood.
• Transports fat to the blood.
• Defends the immune system (lymph): Lymphatic System.

The Lymphatic System

• Lymph capillaries:
  • Thin vessels closed at one end.
  • Collect excess interstitial fluid.
• Lymphatic vessels:

Human Body Systems

1. Respiratory System: The purpose of this system is to take in air, filter it, and take it to the tissues responsible for gas exchange. Oxygen is then transported by blood to all the tissues in the body. Carbon dioxide, a waste product, is reabsorbed and excreted from the body.
2. Skeletal System: This system forms the basic framework of the body. It supports and protects all internal organs. Bones serve as levers (with the attached muscles) for movement, produce blood cells, and store calcium salts, which can be absorbed into the blood when there is not enough calcium in the diet.
3. Endocrine System: The secretion of hormones, which regulate the body's functions chemically, is the function of this system.
4. Urinary System: This system

Keystone Species

Predators that maintain the balance of other species within the ecosystem.

Trophic Cascade

Ecological phenomenon triggered by the removal or addition of top predators, causing changes in the ecosystem through the food chain.

Green World Hypothesis

Hypothesis stating that predators control the number of herbivores.

Food Chains

Illustrate a single pathway of feeding relationships.

Food Web

Represents the complex relationships between multiple species and their various feeding interactions.

10% Law

As energy transfers through trophic levels, 90% is lost, with only 10% retained. This loss occurs due to metabolic reactions, growth and repair, movement, and heat.

Energy Flow

The movement of energy through the food chain.

Energy Pyramid

Measured

The Cori Cycle: Recycling Lactic Acid

After lactate (often referred to as lactic acid) is produced, it is transported by the blood to the liver. In the liver, most of the lactate is converted back to glucose. During periods of rest, this newly formed glucose is efficiently stored as glycogen through a process known as glycogenesis. Approximately one-sixth of the lactate is oxidized to carbon dioxide.

Essentially, during the Cori Cycle, lactic acid is recycled. It is converted to pyruvate, which can then be used for the future conversion to glucose and subsequently stored as glycogen.

Energy Sources Beyond Carbohydrates

While the primary source of energy during physical activity typically comes from carbohydrates and other glucose sources (like... Continue reading "Cori Cycle, Lactate Metabolism, and Fat Energy Pathways" »

Healthy Habits for Sense Organs

Provide multidirectional protection. Eat a healthy diet, avoid harmful substances, have routine examinations, maintain good hygiene, and avoid injuries.

Specific Preventive Measures

Eyes

• Use sunglasses to prevent overexposure to intense light.
• Read or do precision work in bright light.
• Do not rub your eyes when they itch.
• Rest your eyes periodically; look into the distance regularly when working at the computer.

Ears

• Remove excessive earwax by washing the outer ear; do not insert anything into the auditory canal.
• Avoid loud noise; use headphones at a moderate volume to prevent hearing loss.

Skin

• Shower or wash daily.
• Avoid UV radiation, which causes severe sunburn and skin cancer.
• Cover your body or use sunscreen during the

Introduction to Human Reproduction

Human reproduction is sexual, where new individuals are formed from a single cell called a zygote. A zygote originates from the fertilization of two sex cells: an egg cell from the female and a sperm cell from the male.

Humans, as mammals, exhibit internal fertilization and are viviparous, meaning the development of the embryo occurs inside the mother's body.

Stages of Human Reproductive Life

The reproductive life cycle typically has three main stages:

• Puberty: This marks the beginning of the reproductive period, typically occurring between 10-14 years of age.
• Reproductive Period: The active phase of fertility.
• End of Reproductive Life: This phase, often around 50 years of age, is characterized by menopause in females

The Cardiac Cycle

The heartbeat is the movement that pumps blood through the body. It consists of two primary states:

• Systole: Coordinated rhythmic contraction.
• Diastole: Relaxation involving all four chambers of the heart.

Phases of the Cardiac Cycle

1. Atrial Systole: Both atria contract, mitral and tricuspid valves open, and both ventricles fill.
2. Ventricular Systole: Both ventricles contract, semilunar valves open, and blood is pushed through the aorta and pulmonary artery while mitral and tricuspid valves close.
3. Diastole: Atria and ventricles relax, semilunar valves close, and ventricles fill with blood.

The Double Circulatory System

This system keeps oxygenated and deoxygenated blood separate:

• Pulmonary Circuit: Pumps blood between the heart and lungs

The Central Nervous System (CNS)

The Spinal Cord

The spinal cord conducts signals to and from the brain and controls reflex activities.

Meninges: Protective Membranes

There are three membranes containing cerebrospinal fluid, collectively called the meninges, located between the protecting bones and the organs. They are the Dura Mater, the Arachnoid, and the Pia Mater.

CNS Tissues

The CNS is composed of two primary tissue types:

• Grey Matter: Contains neuronal bodies and dendrites. These are control centers that perform specific functions.
• White Matter: Contains neuronal axons covered in myelin.

The Peripheral Nervous System (PNS)

The Peripheral Nervous System connects all the receptors and effectors in the body to the nerve center. It is made up of nerves,... Continue reading "Human Nervous System: Structure, Divisions, and Actions" »

The Excretory System

Organs Involved

• Kidneys: Eliminate toxic substances from metabolism through urine.
• Lungs: Expel CO2 derived from cellular respiration.
• Liver: Bile helps to eliminate waste through feces.
• Sweat Glands: Responsible for sweat excretion.

The Urinary System

Kidneys

• Two organs located at the back of the abdomen.
• Involved structures: Renal artery and vein.
• Primary function: Produces urine.

Urinary Tract

• Ureters
• Bladder
• Urethra

Kidney Structures

• Renal Artery: Carries blood with waste to each kidney.
• Renal Vein: Carries filtered blood away from the kidneys.

The purpose of sexual reproduction is to produce offspring through the fusion of female and male gametes from two individuals (fertilisation).

Asexual reproduction, where a plant can reproduce without involving another plant, is possible in hermaphrodites, which have both male and female organs.

Pollination: Pollen grains travel from the flower to the other plant by wind or by animals.

Fertilisation: When a pollen grain reaches the stigma, the male gamete joins with the female gamete.

Seed Formation: The zygote develops and then grows into a new plant.

Fruit Formation: