Notes, summaries, assignments, exams, and exercises for Biology for Secondary education

How Organisms Obtain Nutrients

Unicellular Organisms: Direct Nutrient Exchange

Unicellular living organisms perform nutrition by exchanging substances directly with their surrounding environment. Nutrients and oxygen enter the cell through a plasma membrane, through which waste is also expelled.

Multicellular Organisms: Systemic Nutrition

Multicellular living organisms, such as human beings, have most cells that do not come into direct contact with the outside world and cannot exchange substances with it directly. The nutrition function is performed through the joint action of different systems that act as intermediaries between the outside world and cells.

Essential Body Systems for Human Nutrition

The Digestive System: Nutrient Absorption

The digestive

Muscular Functions

• Pectoralis Major: Horizontal shoulder abduction.
• Biceps: Elbow flexion.
• Triceps: Elbow extension.
• Trapezius: Scapular retraction.
• Latissimus Dorsi: Shoulder adduction.
• Gluteus Medius: Hip extension.
• Gastrocnemius: Ankle extension.
• Rectus Abdominis: Spinal flexion.
• Deltoid: Shoulder adduction.

Bone Classifications

Long Bones

These are among the longest bones in the body, such as the femur, humerus, and tibia. Long bones are characterized by having a body that is longer than it is wide.

Short Bones

Defined as being approximately as wide as they are long, their primary function is providing support and stability with limited movement. Examples include the carpals and tarsals.

Flat Bones

These are strong, flat plates of bone. Their main function...

Translation

• mRNA (Messenger RNA): Conveys genetic information from DNA to the ribosome.
• tRNA (Transfer RNA): Helps decode the mRNA sequence into a protein.
• rRNA (Ribosomal RNA): The RNA component of the ribosome, essential for protein synthesis.
• Ribosome: Protein builders that connect one amino acid at a time to build long chains.
• Codon: A sequence of three DNA or RNA nucleotides in mRNA.
• Anticodon: Binds with the codon in the ribosome.
• Amino Acid: A simple organic compound.
• Start Codon: The first codon of an mRNA transcript translated by a ribosome.
• Stop Codon: A nucleotide triplet within mRNA that signals the termination of translation.
• Peptide Bond: A covalent chemical bond formed between two amino acid molecules.
• Polypeptide: An organic polymer consisting

Understanding Ecosystems

An ecosystem encompasses all plants, animals, and other organisms in a specific location, along with its climate. It also includes the relationships among organisms (e.g., for food) and between organisms and their environment.

Biotope: The Physical Environment

Composition of Blood

Blood is made up of cells suspended in a liquid called blood plasma. Blood plasma is a yellowish substance made up of water containing various dissolved molecules: minerals, nutrients, waste products, proteins and hormones.

Three types of blood cell:

• Red blood cells: These are the most common type of blood cell. They contain hemoglobin and have no nucleus.
• White blood cells: There are different types: neutrophils, eosinophils, basophils, lymphocytes and monocytes; these cells help to protect the body from infections.
• Platelets: These are not true cells; they contain substances that allow the blood to coagulate, which prevents hemorrhages.

Functions of Blood

• It transports nutrients and oxygen to cells.
• It collects waste products.

Most living things obtain their energy either directly or indirectly from the energy of sunlight captured through photosynthesis.

Photosynthesis in 2 Stages

1. Pigments in the leaves' cells (chlorophyll) capture or absorb the sun's energy, which is used to power the second stage. The leaf cells also need water (absorbed through roots) and carbon dioxide (that enters through small openings on the undersides of leaves called stomata).
2. Inside the chloroplasts, water and carbon dioxide are transformed into glucose and oxygen. Plants use glucose for food and store what they don't need as starch (energy for later use) and cellulose (that makes up the cell walls). Oxygen and water exit the leaf through the stomata.

Stomata

Carbon dioxide enters the plant...

Stage B: The Digestion Process

Digestion is the second stage of the digestive process, where food is transformed into nutrients that the body can absorb.

Digestion primarily takes place in the stomach (a large cavity in the digestive tract with muscular walls) and the first portion of the small intestine, the duodenum.

Steps of Digestion

1. The bolus reaches the stomach, entering through the cardiac sphincter (the entrance door of the stomach). This sphincter acts as a double-way door.
2. Once in the stomach, the bolus is mixed with two substances secreted by the stomach walls:
   • Pepsin: An enzyme used to break down proteins.
   • Hydrochloric Acid (HCl): Lowers the pH to activate pepsin and destroy pathogens.

   This mixing process is aided by the movements of the

Homeostasis and Fluid Regulation

What is Homeostasis?

Homeostasis is the property of a system that regulates its internal environment and tends to maintain a stable, constant condition.

Examples of Homeostatic Regulation:

• Body temperature
• Blood glucose levels
• Lactates in muscles

Physiological Response to Fluid Balance Changes

Fluid flows collectively through the nephrons in the kidney into the collecting duct system. Ultimately, waste is excreted as urine.

Consequences of Imbalance:

• Dehydration
• Kidney stones

The Circulatory System: Blood Components

• Red Blood Cells (RBCs): Carry oxygenated blood from the lungs to the body's organs and muscles.
• White Blood Cells (WBCs): Defend the body's immune system against infection by germs.
• Platelets: Help the blood clot

Circulatory System Elements

The circulatory system includes:

• Veins, arteries, and capillaries: These vessels transport blood throughout the body.
• Heart: This organ pumps the blood.

Arteries vs. Veins

Arteries and veins differ in structure and function:

• Arteries: Have thick, elastic walls that stretch and spring back, propelling blood forward. They carry blood away from the heart.
• Veins: Have thinner walls that cannot stretch as much. They often have valves to prevent the backflow of blood, carrying blood to the heart.

Capillary Structure and Function

Capillaries form a network connecting arteries and veins throughout the body. Their walls are only one cell thick, facilitating the diffusion of nutrients and oxygen into tissues. This process occurs via...