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

Legislation on Stem Cells and Cloning

UN Declarations on Cloning

Resolution adopted on 23 March 2005, stating that practices contrary to human dignity, such as reproductive cloning of humans, must be avoided.

Solemnly declares the following:

• The Member States shall take all measures necessary to adequately protect human life in the application of life sciences.
• Member States shall prohibit all forms of human cloning inasmuch as they are incompatible with human dignity and protection.
• Member States shall take the necessary measures to prohibit the application of genetic engineering techniques that may be contrary to human dignity.

Stem Cell and Cloning Law in Spain

In Spain, the Biomedical Law passed in 2007 allows therapeutic cloning and the obtaining... Continue reading "Biotechnology Legislation and Genetic Material Basics" »

The Cerebral Cortex and Synaptic Transmission

The cerebral cortex is the highest level of the brain, responsible for controlling the activities of other neurons at lower levels. This demonstrates the hierarchical nature of our nervous system. For instance, while the medulla oblongata (often referred to as 'the bulb' in older texts) controls automatic breathing movements, it also sends signals to the cerebral cortex. This explains why, when we enter water, we can consciously hold our breath, as the cerebral cortex can override the medulla's automatic control.

Understanding the Synapse

A synapse is the specialized space between two neurons that a nerve impulse must traverse to pass from one to another. This crucial process is known as synaptic transmission.... Continue reading "Neural Control and Vision: Brain and Eye Functions" »

Early Earth: The Cradle of Life

The conditions on early Earth, the stage upon which life emerged, are quite well-defined:

• Intense Volcanism and Submarine Activity

  The planet's interior was extremely hot, leading to intense volcanism. As most continents had not yet formed, the majority of this volcanism was submarine.

• An Anoxic Atmosphere and Global Ocean

  The proto-atmosphere lacked oxygen, and consequently, there was no ozone layer to shield the planet's surface from lethal ultraviolet rays, which could destroy any nascent signs of life.

Theories on Life's Genesis

Current scientific thought on the origin of life includes several prominent hypotheses:

• The Metabolic Hypothesis

  This hypothesis suggests that small, simple molecules from the environment

Sensory Receptors

The receptors are classified as:

• Chemoreceptors: Sensitive to chemicals.
• Mechanoreceptors: Sensitive to mechanical stimuli.
• Photoreceptors: Light-sensitive.
• Thermoreceptors: Sensitive to temperature variations.
• Nociceptors: Sensitive to internal pressures.

Sensory Receptors:

• Internal receptors: Report the condition of the body, e.g., hunger, thirst, need to urinate.
• External receptors: Collect stimuli from outside, e.g., light, sound, temperature.

The Senses of Touch, Smell, and Taste

Touch

• Epidermis: Epithelial tissue formed by several layers of cells. These cells contain keratin, a protein whose function is to waterproof the skin.
• Dermis: Formed by connective tissue, which provides elasticity to the skin. The dermis contains many blood

Human Heart: Structure and Function

The heart is a vital muscular organ responsible for pumping blood throughout the body. Its walls are primarily composed of a specialized muscle tissue called the myocardium.

Heart Anatomy: Key Components

The heart is divided into four main chambers:

• Two Atria: These are the upper chambers. They have thin, elastic walls and receive blood returning to the heart via veins.
• Two Ventricles: These are the lower chambers. They possess thick, powerful walls, especially the left ventricle, which pumps blood to the entire body. Arteries exit from the ventricles.

The left ventricle is connected to the left atrium, while the right side is separated by a partition (septum). Blood enters the atria from veins and leaves the ventricles... Continue reading "Human Heart: Structure, Circulation, and Health" »

Nervous System Actions: Reflexes and Voluntary Acts

Reflex acts are fast and automatic, and do not involve conscious brain processing. These acts occur when a quick response is needed.

Neurons Involved in Reflexes

• Sensory neurons: Come from the skin and their axons enter the spinal posterior roots.
• Interneurons: Synapse with sensory neurons and transmit nerve impulses to other neurons.
• Motor neurons: They leave the spinal cord by the anterior roots and reach muscles, causing contraction and reflex.

Voluntary acts are varied, changing, and more elaborate than reflexes, involving the cerebral cortex.

Autonomic Nervous System

Also called the involuntary nervous system, it is responsible for the proper regulation and coordination of internal organs.

Types

Carnitine: An Essential Nutrient

Carnitine is a nutrient synthesized in the liver, kidneys, and brain from two essential amino acids: lysine and methionine. Carnitine is responsible for transporting fatty acids into the mitochondria, cellular organelles responsible for energy production.

Some individuals need carnitine supplements to maintain normal metabolism, which indicates that carnitine should be considered an essential nutrient.

Carnitine Deficiency

Carnitine deficiency is classified into two major groups: systemic deficiency (rare) and myopathic (more common). The systemic form affects the whole body, while the myopathic form affects only muscle tissue.

Causes of Carnitine Deficiency

Known causes of carnitine deficiency include:

• Deficiency

Population, Community, and Ecosystem

A population is a group of individuals of the same species living in a specific area. A community is a set of populations inhabiting the same area. The biotope is the physical environment occupied by a community, characterized by specific environmental conditions. An ecosystem encompasses both the community (biocenosis) and the biotope, including the interactions of organisms with each other and their environment.

Habitat and Optimal Conditions

A habitat is the specific environment where an organism finds the necessary conditions for life. Optimal conditions, regarding a given environmental factor, are the values at which a species thrives, reproduces effectively, and experiences high offspring survival.... Continue reading "Understanding Ecosystems: Species, Niches, and Interactions" »

In the early 1990s, research on the human being began with the Human Genome Project. In April 2003, the entire nucleotide sequence of the human genome was completed. Today, we know that:

• Our haploid genome (all 23 different chromosomes that we possess) contains 3,000 million pairs of nitrogenous bases, which equates to about 30,000 genes.
• 99.9% of these genes are the same in all people: the differences between us do not represent more than 0.1% of the genome.
• 90% of the genome has no known coding function, which does not mean it has no function, such as gene regulation or various biological controls. It is thought that some of this DNA may correspond to genetic remains of our ancestors.

Applications of the Human Genome Project

The practical applications... Continue reading "Decoding the Human Genome: Applications and Biotechnology" »