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

Glial Cells (Glia) are responsible for maintaining the structure; they act as functional reservoirs, specialized barriers, and provide immune defense. Neurons are the structural and functional units of the nervous system, specialized to receive, carry, and transmit electrochemical signals called nerve impulses. Soma or Body is the part where the cellular organelles and the nucleus, mitochondria, Golgi apparatus, and lysosomes are located. You can find the Nissl substance here. Axon drives action potentials from the cell body to the synaptic terminal; the cytoplasm of the axon is called axoplasm, and the surrounding membrane is known as axolemma. Dendrites are short extensions of the cytoplasm of the neuronal soma. Sodium-Potassium Pump: for...

Neurons: Structure and Function

Neurons are cells that vary in size and shape and consist of three main parts: dendrites, the cell body, and the axon.

Types of Neurons

• Sensory Neurons: Feature long axons and short dendrites. Their function is to take messages from sensory organs and send them to the central nervous system.
• Motor Neurons: Possess long axons and dendrites. Their role is to take messages from the central nervous system and send them to muscle fibers and glands.
• Interneurons: Found only in the central nervous system. Their function is to transmit messages between various parts of the central nervous system, such as from one side of the brain or spinal cord to another, or between the brain and spinal cord.

The Spinal Cord

The spinal cord...

Cellular Components and Organelles

• Cytoplasm: A colloidal system consisting primarily of water and other cellular components. It contains organelles and the cytoskeleton, responsible for structuring and storing.
• Cytoskeleton: A complex network of actin filaments and microtubules composed of tubulin. It is responsible for cellular movement.
• Rough Endoplasmic Reticulum (RER): Composed of flattened sacs; its external surface presents many ribosomes. It synthesizes proteins and produces ribosomes.
• Smooth Endoplasmic Reticulum (REL): Composed of flattened sacs; it synthesizes lipids and carbohydrates and lacks ribosomes.
• Lysosomes: Membrane-bound vesicles containing digestive enzymes synthesized in the RER. They function in the degradation of nutritional

DNA and Genetic Information

The DNA molecule transfers information between living organisms with the capacity for self-replication. It contains genetic information encoded for the individual and belongs to the group of nucleic acids.

Nucleic Acids

A nucleic acid is a biomolecule consisting of a long chain that stores genetic information, built around the repetition of units called nucleotides.

Nucleotide Structure

Both DNA and RNA consist of three elements: 1) Nitrogenous base, 2) Sugar (ribose or deoxyribose), and 3) Phosphate group.

Nucleobases

The primary bases are adenine, thymine, cytosine, and guanine. In RNA, thymine is replaced by uracil. Base pairing follows the rule: AT / GC.

Chromosomes and Species

• The human species is diploid, possessing

Epithelial Tissue and Glandular Functions

Epithelial tissue covers and protects surfaces from external or internal body cavities. Key types include:

• Mucous: Covers the oral cavity, the pharynx, and other internal passages.
• Endothelium: The inside lining of blood vessels.
• The epidermis: The outer layer of the skin.
• Glandular epithelium: Tissue forming glands, which has the function of secreting substances.

Classification of Glands

• Exocrine glands: Produce substances discharged to the outside or inside the body cavities.
• Endocrine glands: Produce hormones that are discharged into the blood.
• Mixed glands: Act as both exocrine and endocrine glands at the same time.

Connective Tissue and Its Specialized Forms

Connective tissue is formed by cells immersed in...

Understanding the Process of Biological Evolution

Evolution is a gradual process that leads to the emergence of new species and causes adaptations. It accounts for the diversity of species originating from a common ancestor and is responsible for the appearance of new species.

Theories of Evolution

Evolutionary theories describe self-organizing processes occurring in living systems. Different schools of global thought exist to explain the processes through which living beings evolve.

Lamarck's Evolutionary Scenarios: Transformism

In this model, species transform gradually as one evolves into another. This theory is based on the principle that "the function creates the organ": organisms adapt, causing transformations through habit. Organs develop...

The Human Brain: Structure and Function

The brain is the organ with the greatest mass in the nervous system. Its surface is composed of a layer of gray matter, 2 to 4 mm thick, known as the cerebral cortex. Below this layer lies the subcortical white matter. During embryonic development, the cortex folds upon itself, creating convolutions. Due to this appearance, the cerebral cortex is often described as having a rough texture in mammals.

Cerebellum

The cerebellum controls skeletal muscle contractions, which are necessary for:

• Coordination
• Posture
• Balance
• Execution of precise movements

Diencephalon

The diencephalon contains the thalamus and the hypothalamus, serving as the main coordinator of the brain.

• Thalamus: The relay station where sensory information

Male Reproductive System Components

The Testes (Testicles)

The testes are two organs consisting of numerous coiled seminiferous tubules. The walls of these tubules are where sperm originate. Also, between the tubules, male sex hormones (androgens) are produced. The testicles are located outside the abdominal cavity within a fold of skin called the scrotum.

The Penis

The penis is the male copulatory organ. It consists primarily of erectile tissue:

• Two masses called the corpora cavernosa, which are positioned above the urethra.
• The corpus spongiosum, which surrounds the urethra.

The corpus spongiosum enlarges at its end to form the glans, which is covered by the foreskin (prepuce). During sexual arousal, arteries inject blood into the corpora cavernosa,...

Blood and the Circulatory System

Blood is a viscous, salty liquid that runs inside the ducts of the circulatory apparatus. Every human being has approximately 5.5 L of blood. This fluid has multiple roles:

• It carries nutrients and oxygen to all our cells.
• It collects waste products formed in cellular metabolism.
• It participates in the body's defense against infections.
• It carries hormones, molecules important in controlling the functions of the organism.
• It is involved in temperature regulation, as body heat is distributed similarly to a heating system, from warmer to cooler regions.

The yellow component, blood plasma, is mostly water in which several types of molecules are dissolved: proteins, minerals, nutrients and waste substances.

Blood Vessels

Monera: Prokaryotic Organisms

Monera are prokaryotic organisms lacking a defined nucleus. They utilize autotrophic nutrition through photosynthesis or heterotrophic nutrition by obtaining organic matter via parasitism or symbiosis. They reproduce asexually through binary fission.

• Ecological Role: Diverse roles, including cyanobacteria that produce oxygen and bacteria that act as decomposers to cycle matter.
• Pathogens: Some bacteria are pathogenic and cause diseases.
• Industrial Use: Bacteria are used in food production (yogurt, vinegar) and the manufacturing of antibiotics.

Protoctists: Eukaryotic Organisms

Protoctists are unicellular eukaryotes that exist as solitary or colonial organisms.

• Algae: Photosynthetic autotrophs that release significant