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

Genetics and Heredity

Genetics is the science that studies how traits are inherited. Besides hereditary traits, external factors, including the environment, cause changes. Species variation is the manifestation of differences between individuals of the same species. The main causes are genetic variations.

Continuous and Discontinuous Variation

Continuous variation occurs when a trait has slightly different manifestations, like hair or skin color. Discontinuous variation occurs when a trait is clearly expressed as different and is genetically determined, not changing during an individual's life.

Phenotypic and Genotypic Variations

Phenotypic variations are observable traits (weight, height, color) resulting from the environment and genotype. Genotypic

Main Characteristics of Mammals

In general, mammals are characterized by the following:

• They are warm-blooded; their body temperature is constant.
• Mothers have mammary glands that produce milk for their young.
• The mouth is surrounded by lips, allowing young to suckle.
• They have abundant glands (sebaceous, sweat, and odoriferous) and are generally covered in fur, which they shed periodically.
• They have teeth to chew food.
• They have pulmonary respiration.
• Circulation is double (pulmonary and general).
• Most are viviparous: The embryo develops inside the mother and is nourished through the placenta.

Mammals are among the most highly evolved animals. They can live on land, fly, or live in the water.

Here, we will examine in more detail some common characteristics... Continue reading "Key Characteristics and Evolution of Mammals" »

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" »

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" »

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.

English Vowels

Short Vowels

• /ɪ/ (as in: sit): Front, unrounded, between close and half-close.
• /ɛ/ (as in: dead): Front, unrounded, between half-close and half-open.
• /æ/ (as in: cat): Front, unrounded, between half-open and open.
• /ʌ/ (as in: does): Between front and central, unrounded, half-open.
• /ɒ/ (as in: dog): Back, rounded, between half-open and open.
• /ʊ/ (as in: good): Between back and central, rounded, near-close.

Long Vowels

• /i:/ (as in: sweet): Unrounded, almost fully closed.
• /ɜ:/ (as in: bird): Central, unrounded, between half-close and half-open.
• /ɑ:/ (as in: fast): Almost fully back, unrounded, fully open.
• /ɔ:/ (as in: hawk): Back, rounded, between half-close and half-open.
• /u:/ (as in: shoe): Almost fully back, rounded, almost fully