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

Lamarckism: Key Principles

Jean-Baptiste Lamarck proposed a theory of evolution based on the following principles:

• There is a gradual progression from simpler organisms to more complex forms.
• The mechanism by which gradual changes occur is adaptation to the environment through the use and disuse of certain organs.
• The exercise of an organ produces its development and perfection.
• Inherited acquired characteristics can easily be adapted to environmental conditions.

Darwinism: The Theory of Natural Selection

The Voyage of the HMS Beagle

Charles Darwin embarked on the HMS Beagle for a trip around the world. His mission on board consisted of collecting exotic plants and animals. The trip lasted 5 years, and by the end, Darwin found evidence of the variability...

The Scientific Method

The scientific method involves a systematic approach to discovery:

• Ask a question and find information.
• Observe, describe, measure, and classify.
• Identify variables of a phenomenon.
• Formulate hypotheses.
• Design experiments to test the hypothesis.
• Select proper instruments, tools, and techniques.
• Analyze results and propose conclusions.
• Invent laws and theories.
• Verify the operation of those laws or models.
• Communicate results.

Cosmological Theories

1. Slipher: Analyzed the light spectrum from distant galaxies, finding that light waves showed a peculiar elongation (redshift).
2. Gamow: Proposed the "law of recession of the galaxies," stating that galaxies are expanding and cooling over time.
3. Penzias and Wilson: Discovered cosmic microwave background

Genetics: The Study of Gene Inheritance

Genes are transmitted according to defined rules or laws. Genes are located on chromosomes, which are cellular structures. Sex is determined by specific genes or chromosomes in most living organisms.

Key Genetic Terms

• Genotype: The genetic constitution of an individual, referring to a specific character or the entire set of genes.
• Phenotype: The external expression of the genotype; the observable characteristics of an individual.
• Alleles: Variants that a gene may present. For each gene, an individual has a pair of alleles, often represented by letters.
• Homozygous: An individual having two identical alleles for a specific gene.
• Heterozygous: An individual carrying two different alleles for a specific gene.

Mendelian

The Molecular Structure of DNA

The molecular structure of DNA was discovered by J. Watson and F. Crick in 1953. The double helix of DNA consists of two strands twisted together in the form of a helical spring. Each strand forms a chain that acts as the rails of a ladder, joined to the other strand through molecular steps.

Nucleotides and Base Pairing

Nucleotides: Each nucleotide consists of a specific nitrogenous base: Adenine (A), Thymine (T), Cytosine (C), and Guanine (G). In the DNA structure, Adenine always pairs with Thymine (A-T), and Guanine always pairs with Cytosine (G-C).

DNA Polymerase and Replication

DNA polymerase: This is the primary enzyme involved in DNA replication. It adds complementary nucleotides to the template strand to extend...

Radiography: First Imaging Technique

Radiography is the first imaging technique developed. It is based on the use of X-rays. X-rays are a type of radiation with much energy, which causes some objects to pass through easily. Abuse of X-rays poses a risk of producing cancer. This technique is not recommended for pregnant women and small children.

Computerized Tomography (CT)

Computerized Tomography (CT) is based on taking multiple X-rays of a body area with a special device where the X-ray rotates around the patient. All images are combined using a PC. This technique provides detailed images of the body's interior. Its major drawback is that it requires using large amounts of radiation.

Magnetic Resonance Imaging (MRI)

Magnetic Resonance Imaging (

DNA Replication

The process of DNA duplication, which allows identical genetic information to be shared between cellular daughters, consists of the following:

• The two strands of the double helix are separated.
• Free nucleotides can join the DNA nucleotides through their complementary bases. Only the nucleotides A can be combined with T, and C with G.
• The new nucleotides bind and form new DNA chains.
• Each of the two DNA chains serves as a template to create new strands.

Protein Synthesis

Proteins are formed by the joining of smaller molecules called amino acids. There are over 20 types of amino acids in different proteins. The order in which amino acids bind determines the type of protein.

Each cell produces thousands of proteins in its ribosomes, using...

Cytokinesis: Cytoplasmic Division

Cytokinesis is the process of cytoplasmic division that results in the formation of two daughter cells. It typically begins in late anaphase and concludes during telophase.

Differences Between Animal and Plant Cells

Cytokinesis occurs through distinct mechanisms in animal and plant cells.

Animal Cell Cytokinesis

In animal cells, cytoplasmic division is caused by the strangulation of the cytoplasm. This process begins at the end of anaphase or early telophase:

• A contractile ring of actin and myosin forms beneath the plasma membrane at the position of the metaphase plate.
• The ring contracts, creating a cleavage furrow.
• The furrow advances, contacts the interzonal microtubules, and cleaves the cytoplasm into two parts,

Deoxyribonucleic Acid (DNA) Structure

DNA molecules are linear biopolymers formed by the polymerization of deoxyribonucleotide-5'-monophosphate of adenine (A), guanine (G), cytosine (C), and thymine (T).

Primary Structure of DNA

The primary structure of DNA consists of long chains of polynucleotides formed by the union of deoxyribonucleotide-5'-monophosphate. In DNA, nucleotides are linked by ester bonds. Each DNA molecule is characterized by its specific base composition and sequence. The distribution of the four bases along the phosphate and polydeoxyribose backbone contains the essential information required for protein synthesis.

Secondary Structure: The Double Helix

The secondary structure is a double helix consisting of two polynucleotide...

Fertilization and Seed Formation

After fertilization, the ovules develop into seeds, and the ovary matures into a fruit.

The Fertilization Process

• Pollen Germination: The pollen grain lands on the stigma, leading to the formation of the pollen tube.
• Double Fertilization:
  • One sperm nucleus (male gamete) fuses with the oosphere (egg cell) to form a diploid zygote. This zygote develops into the embryo of the seed, which consists of a radicle, a plumule, and cotyledons (one in monocots, two in dicot plants).
  • The other male gamete fuses with the secondary nuclei to form a triploid endosperm (albumen), which serves as the nutrient reserve for the seed.
• Seed and Fruit Structure: The embryo and its endosperm are enclosed within the seed coat (derived from