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

Body Types can be graded on three components:

• Endomorphy: Refers to the predominance of curves and visceral development.
• Mesomorphy: Refers to the predominance of muscle and bone. Subjects are relatively strong.
• Ectomorphy: Highlights the prevalence of poor muscle development, resulting in greater fragility. Subjects typically have long and thin limbs.

In relation to the question of heritage concerning body type, there seems to be a consensus to accept its inherited character, manifesting at an early age.

The Growth of Different Body Systems

Nervous System

The nervous system shows growth and maturity very quickly. It is likely that after 7 months of age, nerve cell formation has not yet completed; however, there seems to be a predetermined sequence... Continue reading "Understanding Body Types and Their Developmental Growth" »

Major Theories of Biological Evolution

Lamarckism: Inheritance of Acquired Characteristics

Lamarckism is a theory of evolution proposing that species are the result of a long process of gradual change, progressing from simple to complex forms. Its key principles include:

• Tendency toward Improvement: All organisms strive for improvement through an inherent vital impulse.
• Law of Use and Disuse of Organs: Environmental changes necessitate an increase or a diminution in the use of certain organs. These organs develop more or less depending on their use.
• Function Creates the Organ: Environmental changes give rise to new needs, which can develop an organ shaped in response to that function.
• Inheritance of Acquired Characteristics: Changes acquired by an

Carl Linnaeus: The Father of Modern Taxonomy

Although a practicing physician, Carl von Linnaeus had a deep interest in botany. He developed a revolutionary system to classify plants using a binomial method of scientific nomenclature. This simplified classification system organized plants and animals into meaningful groups based on their physical similarities.

Linnaeus also described and classified numerous animal species. His descriptions and classifications were so accurate that many of them have remained unchanged to this day.

Systema Naturae: Linnaeus's Most Important Work

Linnaeus's most important work is his Systema Naturae (1735), which saw numerous later editions. In each subsequent edition, he improved and completed his system. From the... Continue reading "Linnaeus's Binomial System: Foundations of Modern Taxonomy" »

Ecological Succession: Ecosystem Transformation

Ecological succession is the sequence of changes that occur in an ecosystem, resulting from its own internal dynamics. It is a slow and gradual process, leading to the evolution of an ecosystem from an initial state of low biological diversity towards a final state of greater diversity.

General Changes in Succession Sequences

In all ecosystems, as the succession sequence progresses, the following phenomena generally occur:

• Increased species diversity
• Increased structural complexity
• Increased biomass
• Increased efficiency in energy use
• Lower net productivity (as more energy is used for maintenance)
• Increased ecosystem stability

The Climax Community Concept

The climax community is considered the ideal state... Continue reading "Ecosystem Dynamics: Succession, Populations, and Growth" »

Blood Tissue

Blood is a tissue fluid that flows through the veins and arteries of all vertebrates. Its characteristic red color is due to the presence of the pigment hemoglobin in red blood cells.

Blood has a solid phase and a liquid phase, represented by the plasma. Its main function is the logistics of distribution and systematic integration.

Blood consists of formed elements and blood plasma.

Platelets

Platelets are small cell fragments (2-3 um in diameter), oval and without nuclei. They are produced in the bone marrow from the fragmentation of the cytoplasm of megakaryocytes. Their normal quantitative value is between 150,000 and 450,000 platelets per mm3.

They serve to plug injuries that could affect blood vessels. Platelets contribute to clot... Continue reading "Understanding Blood, Cartilage, Muscle, and Nervous Tissue" »

The Golgi Apparatus: Structure and Function

The Golgi Apparatus (GA) is found in all eukaryotic cells, essential in the transfer and packaging of products from the Endoplasmic Reticulum (ER), and involved in the synthesis of glycoproteins and mucopolysaccharides.

Distribution and Morphology

Its distribution depends on microtubules and motor proteins in secreting cells. In protein-secreting cells, the GA is located between the nucleus and the apical pole. In ganglion nerve cells, it is located around the nucleus with expansions to the cell surface. In Leydig cells, it is an ovoid mass located at one pole of the nucleus. In hepatocytes, it is distributed throughout the cytoplasm.

Its form differs from one cell to another and also within the same... Continue reading "Golgi Apparatus: Structure, Function, and Cellular Roles" »

Sensory Receptors

Sensory receptors are structures formed by nerve cells specialized to capture and transform stimuli into nerve impulses. The receptors are classified as:

• Chemoreceptors: Sensitive to chemicals.
• Mechanoreceptors: Sensitive to mechanical stimuli such as touch, pressure, sound, or gravity.
• Photoreceptors: Sensitive to light.
• Thermoreceptors: Sensitive to changes in temperature.
• Nociceptors: Sensitive to heavy pressure and responsible for pain.

Receptors can also be classified according to their location:

• Internal receptors: Located inside the body, particularly in the viscera. Responsible for collecting information from internal organs.
• External receptors: Located on the surface of the body. Responsible for collecting external stimuli

Milk and Dairy

Provides protein, vitamins, and calcium. Recommended serving: 250 mL of milk and 80g of dairy products.

Meat, Fish, and Eggs

Excellent sources of protein, vitamins, and iron. Recommended serving: 100g of meat and 150g of fish.

Legumes and Potatoes

Offer carbohydrates and protein. Recommended serving: 80g of pulses and 180g of potatoes.

Vegetables

Rich in vitamins, minerals, and fiber. Recommended serving: 125g.

Fruits

Packed with vitamins, fiber, minerals, and carbohydrates. Recommended serving: 125g.

Cereals and Grains

Provide carbohydrates. Recommended serving: 80g of pasta or rice, 50g of bread.

Fats, Oils, and Butter

Sources of lipids.

Carbohydrates

Nutrients that provide energy. Simple sugars, like glucose, are the primary source of cellular... Continue reading "Nutrition Essentials: Building a Balanced Diet" »

Cell Membrane Differentiations: Junctions

Some areas of the cell membrane may have specific adaptations, such as invaginations (e.g., microvilli) to increase surface area, or structures that form unions between cells. These junctions are essential for stabilizing tissues and providing mechanical adhesion. They are particularly prevalent in tissues under heavy strain, like epithelial tissues or heart muscle, where their primary function is to provide mechanical strength to the union. These junctions are classified into:

Adherens Junctions (Bands of Adhesion)

• These junctions are formed by transmembrane proteins that bind cells together.
• On the intracellular side, these proteins are associated with actin filaments, which are part of the cytoskeleton.

The Vital Role of Algae in Aquatic Life

Algae are a very large group of photosynthetic protoctists dependent on the aquatic environment. They all possess chlorophyll pigments, which give them their coloration, and their cells have a cell wall composed of cellulose. Algae colonize all aquatic habitats.

Ecological Importance and Reproduction

Through photosynthesis, algae form the first link in the food chain in ecosystems, discharging large amounts of O₂ into the atmosphere.

Reproduction is typically:

• Asexual: By binary fission or fragmentation.
• Sexual: Involving the interference of gametes and meiospores.

Most algae are microscopic, unicellular, or colonial, forming phytoplankton that floats in the upper, illuminated layers of the oceans and is of... Continue reading "Algae Classification: Types, Pigments, and Aquatic Role" »