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

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 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:

Understanding Key Human Muscles and Their Functions

Temporalis

• Origin: Along temporal lines of the skull.
• Insertion: Coronoid process of the mandible.
• Action: Elevates the mandible.

Masseter

• Origin: Zygomatic arch.
• Insertion: Ramus of the mandible.
• Action: Elevates the mandible and closes the jaw.

Sternocleidomastoid

• Origin: Attaches to the sternal end of the clavicle and manubrium.
• Insertion: Mastoid region and lateral nuchal line of the skull.
• Action: Flexes the neck.

Pectoralis major

• Origin: Cartilage of ribs 2-6, sternal body, and medial clavicle.
• Insertion: Greater tubercle and intertubercular groove of the humerus.
• Action: Flexion, adduction, and medial rotation at the shoulder.

Biceps brachii

• Origin: Coracoid process of the scapula.
• Insertion: Tuberosity

Eukaryotic Cell Organelles: Structure and Function

Cell Membrane

All cells are covered by the cell membrane. It supports and protects the cell, forming a barrier between the cell and its environment. It also controls the movement of materials into and out of the cell, helping to maintain homeostasis.

Cell Wall

The Cell Wall is found only in plant cells and is primarily made of cellulose. Its functions include:

• Providing structural support and protection.
• Allowing the diffusion of gases into and out of the cell.

The strength provided by the cell walls enables plants, such as trees, to stand tall and grow against gravity.

Nucleus

The Nucleus is a spherical, membrane-bound organelle. It directs most of the cell's activities and contains the cell's hereditary