Notes, summaries, assignments, exams, and exercises for Biology for Baccalaureate

The Human Genome Project (HGP)

The Human Genome Project (HGP) aimed to map and sequence all the genes of human beings.

Key Genetic Concepts

• Genome: The complete set of genes of an individual organism.
• Proteome: The entire set of proteins originating from the genome.

The human genome contains fewer than 30,000 genes. The genetic differences between humans and other species are lower than initially expected.

Present and Future Applications of HGP Discoveries

The possibilities offered by these discoveries include:

• Genetic Testing: To determine the likelihood of developing specific diseases.
• Gene Therapy: Techniques used to correct defective genes.
• Genetic Diagnosis: Essential for pre-transplantation screening.
• Knowledge of Human Evolution: Providing deeper

Bone Tissue: Structure and Cell Types

Bone is a vital component of body mass in vertebrates. Bone tissue is an intercellular matrix that contains abundant minerals, predominantly calcium (Ca) and phosphorus (P). Bone contains three main cell types:

Bone Cell Types

• Osteocytes: Small, mature bone cells that reside in lacunae. They are the most important cells of bone tissue and are commonly grouped, typically between 4–6 cells, within bone lacunae.
• Osteoblasts: Large, bone-forming cells located on the outer surface of bones. Their primary function is to synthesize and deposit bone matrix.
• Osteoclasts: Large, multinucleated cells located on internal bone surfaces, especially along the medullary cavity of long bones. Their function is to resorb bone

Principles of Cell Theory

Living organisms consist of one or more cells. The cell is the fundamental structural and functional unit of all living things and represents the most basic life form capable of performing all biological functions.

Endosymbiotic Theory

This theory suggests that certain organelles evolved from bacteria phagocytosed by an ancestral cell:

• Mitochondria: Derived from aerobic bacteria.
• Chloroplasts: Derived from photosynthetic bacteria.

These organisms established a symbiotic relationship, eventually forming eukaryotic cells.

The Plasma Membrane

The plasma membrane is a continuous sheath that surrounds the cell, providing individuality and separating it from its environment. It is composed of a lipid bilayer embedded with proteins...

Proteins and Amino Acids

Proteins are formed by a union of linear amino acids (NH2-COOH). There are 20 amino acids that are part of proteins. Nucleobases form a triplet or codon, which determines a particular amino acid. There are 4x4x4 = 64 different triplets; this implies that there are different triplets that encode the same amino acid. The code is degenerate because the combination of 3 letters adds up to 64 possible triplets.

The Genetic Code

The genetic code is the relationship between the sequence of bases in DNA and the ratio of amino acids in protein. There are three special triplets coding for a stop sign:

• TAA
• TAG
• TGA

There is also a triplet (ATG) determining a beginning.

Functions of Proteins

Proteins perform various essential functions:

• Transport

Fundamentals of Genetics and Heredity

Deoxyribonucleic Acid (DNA)

DNA is the inherited material that carries genetic information in all living organisms, passed down from generation to generation. A DNA molecule is composed of nucleic acid nucleotides.

Nucleotides are formed by three essential components:

• A phosphate group.
• A pentagonal ring sugar (Deoxyribose).
• A nucleobase (nitrogenous base).

In DNA, there are four basic types of nitrogenous bases: Cytosine (C), Guanine (G), Thymine (T), and Adenine (A).

DNA Replication: Ensuring Genetic Continuity

The information contained within the sequence of DNA bases is the foundation of inheritance for every species. This information must be transmitted intact from cell to cell to ensure the continuity of that...

Central Dogma of Biology

Cells store information in the form of DNA. This information is relayed via an intermediary, RNA, which is manufactured using DNA as a template. The RNA leaves the nucleus for the cytoplasm, where its message is read by ribosomes to produce proteins, effectively executing the genetic order.

(Replication) DNA → (Transcription) RNA → (Translation) Proteins (Enzymes)

The message of DNA lies in the sequence of four nucleotides that form long chains: Adenine (A), Thymine (T), Cytosine (C), and Guanine (G). A gene is a specific segment of DNA that, when transcribed and translated, generates a protein or enzyme. If a gene undergoes an alteration in its sequence (a mutation), the consequences can be:

• Beneficial: Sometimes a

Functioning of the Mammalian Heart

Blood circulates through blood vessels to the heart, driven by coordinated movements of systolic contraction and diastolic dilation. Both movements occur simultaneously.

Circulatory Pathway

• Left side: Blood from the lungs enters the heart through the left atrium, passes into the left ventricle, and is distributed throughout the body via the aorta.
• Return: Blood returns to the heart through the superior and inferior vena cava, which flow into the right atrium.
• Right side: Blood passes into the right ventricle and travels to the lungs through the pulmonary artery.
• Completion: Blood returns to the heart through the pulmonary veins, which empty into the left atrium.

Heart Valves

The heart has four valves that open in...

Population Autoregulation

A population is constituted by a set of individuals of the same species living in a given location. Environmental resistance is a set of factors that prevent a population from reaching its maximum biotic potential. These factors include:

• External factors: These may be biotic (predators, parasites) or abiotic (climate change, food shortages, disasters, etc.).
• Internal factors: Increasing population density adversely affects individuals.

There are two forms of reproduction strategies:

• r strategists: These are simple organisms with very high biotic potential. They have many offspring with no parental care. Consequently, only a few manage to survive and reach adulthood. The population size remains relatively stationary (e.g.

How New Species Originate: The Speciation Process

All living things descend from a common ancestor. Evolution explains how a single species can diverge into two or more, leading to the current biodiversity. This process, known as speciation, typically occurs as follows:

• Geographic Isolation: Two populations of the same species become separated by a geographical barrier, such as a sea or a high mountain range.
• Independent Evolution: Both populations then undergo independent evolutionary paths. Mutations occur randomly in each, and since the number of genes is very high, these mutations will differ between the two populations.
• Accumulation of Differences: The accumulation of these genetic differences, combined with the pressures of natural selection,

Chloroplasts and Photosynthesis

Chloroplasts are the sites where photosynthesis occurs. These organelles are generally ovoid or discoidal in shape. They are composed of an outer membrane and an inner membrane; the latter is folded to form structures similar to columns called grana. Each granum is composed of a series of disc-shaped compartments known as thylakoids. Thylakoid membranes contain chlorophyll, the photosynthetic pigment responsible for photosynthesis. These structures are immersed in a liquid called stroma, which contains, in addition to the grana, DNA, ribosomes, and polyribosomes.

Obtaining Energy in Living Organisms

Regardless of how living things get their food—whether incorporated from the outside, like animals, or made by themselves,...