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

Understanding Reflexes

A reflex is an involuntary motor response. The reflex arc follows this path: receptor → afferent nerve → CNS → efferent nerve → effector.

Deep Tendon Reflexes (Monosynaptic)

• Biceps (C5–C6, musculocutaneous): Elbow flexion.
• Triceps (C6–C7, radial): Elbow extension.
• Brachioradial (C5–C6, radial): Elbow flexion.
• Patellar (L3–L4, femoral): Knee extension.
• Achilles (S1–S2, tibial): Plantar flexion.

Superficial Reflexes (Polysynaptic)

• Corneal: CN V–VII.
• Abdominal: T7–T12.
• Cremasteric: L1–L2.
• Anal: S4–S5.

Plantar Reflex and Lesions

The normal plantar reflex results in toe flexion. A Babinski sign (big toe extension + fanning) indicates an Upper Motor Neuron (UMN) lesion.

• UMN Lesions: Hyperreflexia, clonus, Babinski

Evidence of Evolution

Biological evolution refers to all the changes that have occurred in living things since they appeared on Earth, which have produced biodiversity. There is a lot of evidence to support the theory of evolution and no evidence against it.

Anatomical and Morphological Evidence

Fossil Evidence

Evolutionary Series

Fossil records from different time periods show the slow, progressive evolution of species. Horse fossils are one of the best-preserved examples of this.

• Evolutionary Links: These are organisms from two different groups that show intermediate stages of development from a primitive to a more modern form.
• Living Fossils: Organisms that still retain primitive characteristics.
• Faunal Succession: The chronology of strata shows

Genetic Engineering

Genetic engineering is the process of changing the DNA composition in organisms using laboratory techniques.

Obtaining Recombinant DNA Using Vectors

Recombinant DNA is an artificial molecule obtained from organisms. The stages include:

• Locate the required gene and analyze its nucleotide sequence.
• Isolate the gene with enzymes that cut DNA into specific sections.
• Connect the gene to a transportation vector, such as virus DNA or bacteria. The combination of the gene and vector results in recombinant DNA.
• Introduce the recombinant DNA into the cell.

Polymerase Chain Reaction (PCR) Technique

• Heat DNA to separate the strands.
• Add DNA polymerase enzyme and nucleotides to the tube to synthesize complementary strands.
• Separate the formed strands

Excretory System Notes

Excretion

Excretion: Process of eliminating waste substances from metabolic reactions.

Although the kidneys are the main organs of excretion, several other organs also excrete wastes. They include the liver, skin, and lungs. All of these organs of excretion, along with the kidneys, make up the excretory system. This lesson focuses on the role of the kidneys in excretion. The roles of the other excretory organs are summarized below:

• Kidneys: Responsible for filtering the blood and forming urine.
• Lungs: Expel carbon dioxide produced during cell respiration.
• Sweat glands: Excrete sweat, a liquid with a composition similar to urine.
• Liver: Expels waste that comes from toxins, medicines, and digestion of food.

Urinary System

The kidneys...

Circulatory System

Blood is a viscous, red, and saline liquid (approximately 5 liters). It is composed of:

• Plasma (55%): A yellowish liquid made of water and substances such as nutrients and hormones.
• Blood Cells: Produced in the bone marrow, there are three types:
  • Red blood cells (erythrocytes): Transport oxygen from the lungs to the cells using a red protein called hemoglobin.
  • White blood cells (leukocytes): Essential components of the immune system.
  • Platelets: Fragments of cells that function to stop bleeding.

Blood Functions

• Transport nutrients
• Transport oxygen and carbon dioxide
• Transport waste products
• Regulate body temperature
• Participate in the immune system
• Prevent hemorrhages

Blood Vessels

• Arteries: Transport blood from the heart to the organs.

The Urinary System and Excretion

Elimination of Waste Products

The urinary system plays a crucial role in eliminating waste products, including toxic substances produced during cellular metabolism, that are released into the blood.

Organs Involved in Excretion

• Kidneys (Urinary System)

  Eliminate toxic substances resulting from cell metabolism through urine.

• Lungs

  Eliminate carbon dioxide (resulting from cell metabolism: cell respiration).

• Liver

  Eliminates waste from digestion through bile, which is eventually eliminated with feces.

• Sweat Glands

  Eliminate waste* through sweat, a liquid similar to urine but more diluted.
  *Toxic substances resulting from cell metabolism.

Kidneys

Two bean-shaped organs located along the posterior wall of the abdominal cavity....

Osmosis and Passive Transport

Osmosis is the movement of particles from a high concentration to a low concentration. Specifically, it is the movement of a solvent, such as distilled water, through a semipermeable membrane. This process occurs when two solutions with different concentrations of solutes are present in the same recipient.

Mitosis: Somatic Cell Division

Mitosis creates identical cells through cell division. This process is essential for growth and produces body cells, also known as somatic cells.

Phases of Mitosis

• Prophase: Chromosomes become visible and begin condensing.
• Metaphase: The nuclear membrane breaks down, and the chromosomes line up in the middle of the cell.
• Anaphase: The chromatids separate and move toward opposite sides

Oparin’s Theory of the Origin of Life

1. The primitive atmosphere was made up of gases: ammonia, water vapor, methane, and hydrogen.
2. The energy for the first chemical reactions to occur came from volcanic eruptions, radiation from the sun, and storms.
3. The temperature of the Earth fell, so the water vapor condensed and formed seas.
4. Organic molecules, synthesized by the reactions, accumulated in the water and joined together to form bigger molecules.
5. Coacervates were structures formed by organic molecules insulated from the water.
6. The first cell appeared when the coacervates started to reproduce.

The Endosymbiotic Theory

The Endosymbiotic Theory of Margulis explains the appearance of the first eukaryotic living things from the symbiotic relationships...

Gene Regulation and Molecular Insights

Goal: To organize gene orientation and understand gene regulation involving 25,000 Protein-Coding Genes (PCG) and 40,000 non-coding RNA (ncRNA) to advance knowledge and medical insight.

Key Mechanisms of Gene Expression

• 3D Chromosome Territories: mRNA looping and open chromatin.
• Epigenetic Marks:
  • Little to no methylation on DNA.
  • Histone marks.
  • Chromatin modification coactivator complexes and ncRNA coactivators.
• Transcription Factor Activators: Usually heterodimers.
  • Transactivation Domain (TD): Interacts with the mediator.
  • Binding Domain (BD): Binds to DNA.
• RNA Polymerase and Factors at the Promoter:
  • Elongation process.
  • Production of multiple mRNA molecules.
  • Presence of many promoters.
• Maternal and Paternal Expression: