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

Lymph Nodes and Nephrons

Lymph Nodes

Lymph nodes are made of lymphatic tissue located in specific areas of some lymphatic vessels. They make lymphocytes and release lymph plasma.

Nephrons

Nephrons are the structural and functional units of the kidneys. They are tubes with one closed end and are surrounded by blood capillaries. Nephrons are responsible for filtering blood and forming urine, regulating water and mineral content.

• Bowman's Capsule: Initial zone
• Convoluted Tube: Long twisted tube with two main parts, proximal and distal
• Loop of Henle: Section located between the proximal convoluted tube and the distal zone

Urinary System

Ureters

Ureters are thin tubes that start from each kidney and end in the bladder, an elastic bag in which urine accumulates....

Non-specific defenses

act against any type of microorganism or foreign particle. This action is carried out by phagocytes: white blood cells that trap and eliminate pathogenic microorganisms. This process is called phagocytosis.

INFLAMMATORY RESPONSE

is a non-specific defense mechanism. When pathogens get through the external barriers, the blood cells dilate to increase the blood flow. The result is pus.

Specific defenses

act against specific microorganisms or foreign molecules. Other types of leukocytes, called lymphocytes, produce proteins called antibodies. Antibodies are specific for each microorganism and destroy or inactivate the invading agents.

INCUBATION - this is the time between the moment the pathogenic agents invade organisms and the...

Population Genetics

Microevolution

Change in the collective genetic material of a population.

Bell Curve

Shows the frequency of a trait in a population.

Gene Pool

Describes the total genetic information available in a population.

Hardy-Weinberg Genetic Equilibrium

Principle based on a set of assumptions about an ideal hypothetical population that is not evolving.

Immigration

Movement of individuals into a population.

Emigration

Movement of individuals out of a population.

Gene Flow

Process of genes moving from one population to another.

Sexual Selection

Tendency of females to choose the males they mate with based on certain traits.

Stabilizing Selection

Individuals with the average form of a trait have the highest fitness.

Disruptive Selection

Individuals with...

Biology Study Notes

Enzymes and Molecules

• Enzymes are organic molecules that function to start and regulate chemical reactions.
• The largest molecules in our bodies are nucleic acids.
• The human body is primarily composed of oxygen, nitrogen, hydrogen, and carbon.

Genetics and DNA Structure

• A genome is an organism’s complete set of DNA, containing all the information needed to build and maintain that organism.
• DNA molecules exist in the shape of a double helix.
• There are about 3 billion chemical base pairs in human DNA, with approximately 1%–2% coding for a gene.
• A gene is essentially a sequence of many codons in a DNA molecule.
• Portions of DNA molecules that do not contain codes for proteins are called introns.
• The DNA code is shared by all living

Extracellular is inactive DNA or RNA surrounded by proteinIntracellular – active inside a host cell/ viral reproductionprotein capsid - Viral nucleic acid presentcapsomere- protects genetic materialretroviruses: ss RNA hepadnaviruses: dsRNA enveloped”- membrane lipid bilayer (host)& proteins (virus)naked-+ viral DNA complex viruses- icosahedral head/ helical tail/ Tail fibers attach to host cellviral replication: the virion attaches host specific/ proteins interact w/ receptors on surface/ if receptor not present= can’t infect. 2. Phages often complex3.active/intracell/ production of new virions/ viral mRNA is required SS DNA ->DS DNA -> mRNA / DS DNA= mRNA (w/polymerase) RNA polymerase” to make mRNA from viral RNA/ SS RNA

Animal Respiration

Breathing is essential for respiration. Animals breathe by inhaling oxygen and exhaling carbon dioxide. This gas exchange occurs via the respiratory system.

Respiratory Systems

Respiratory systems require thin, moist surfaces covered in blood vessels for efficient gas exchange. This facilitates oxygen uptake and carbon dioxide expulsion.

Cutaneous Respiration

Gas exchange through the skin (thin and moist). Examples include earthworms and adult amphibians.

Branchial Respiration

Gas exchange through gills (surrounded by blood vessels). Examples include fish and some crustaceans.

Tracheal Respiration

Gas exchange via internal tubes (tracheae) carrying air directly to cells. Examples include terrestrial arthropods.

Pulmonary Respiration

Gas...

1. DNA: The Molecule of Inheritance

• In eukaryotic cells, genetic material is condensed into chromosomes, which consist of two chromatin strands made of DNA and proteins.
• The double helix model of the DNA molecule was proposed by Watson and Crick in 1953.

Basic Components of DNA

A molecule of DNA is formed from thousands of nucleotides. Each nucleotide is made up of:

• Deoxyribose
• Nitrogenous base
• Phosphate

There are 4 types of nitrogenous bases: Adenine (A), Thymine (T), Guanine (G), and Cytosine (C). When nucleotides join together, they form a chain where deoxyribose alternates with phosphate. The nitrogenous bases are attached to the deoxyribose.

Structure of DNA

• DNA is made up of two chains (strands) of nucleotides twisted around each other in the shape

Plant Biology and Classification

Plants perform photosynthesis because their cells contain chloroplasts with a green pigment called chlorophyll.

Plant Categories

• Non-flowering plants: Mosses and ferns.
• Flowering plants: Gymnosperms (e.g., pine trees) and angiosperms (e.g., apple trees, which produce fruit).

Plant Structures

• Mosses: Feature a capsule containing spores, a filament, phyllodes (leaf-like structures), and rhizoids for soil fixation.
• Ferns: Possess leaves, spores that grow in a sorus, and underground stems.
• Gymnosperms: Typically evergreens.
• Angiosperms: Typically deciduous.
• Flower Anatomy: Anther, stigma, style, ovary, ovules, calyx, and filament.

Fungi, Bacteria, and Viruses

Fungi

Fungi are composed of hyphae that form a mycelium. Groups include:...

Microorganisms: Bacteria and Viruses

Bacteria: Key Characteristics

Bacteria are single-celled, prokaryotic microorganisms. They possess ribosomes, typically around 1000nm in size.

Viruses: Key Characteristics

Viruses are non-cellular genetic elements that are obligate intracellular parasites, meaning they must use living cells to reproduce. Their size ranges from approximately 20-300nm.

Viral Structure Explained

A typical viral structure includes:

• Nucleic Acid (Genome): This is the genetic material, which can be either DNA or RNA.
• Capsomeres: Protein subunits that assemble to form the capsid.
• Viral Nucleocapsid: The combined structure of the nucleic acid and its surrounding protein capsid.
• Core Wall (Capsid/Envelope): A protective shell, often referred

Understanding Pathogens: Viruses and Bacteria

Infectious diseases are caused by various pathogens, primarily viruses and bacteria, affecting different systems of the human body. Below is a summary of common diseases, their classification, and typical symptoms.

Common Viral Infections

• Influenza (Flu)

  System Affected: Respiratory System

  Classification: Virus

  Symptoms: Fever, body aches, tiredness, and cough.

• Herpes Simplex Virus (HSV)

  Classification: Virus (DNA)

  After the initial infection, the virus remains inactive in the human body and later reactivates under certain circumstances, such as stress, menstruation, or temperature changes. Symptoms are highly variable, and herpes lesions can appear anywhere on the body.

• Human Immunodeficiency Virus (HIV)