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

Mendel's Pea Plant Inheritance Studies

What is a Pure Race for a Character?

Pea flowers can be white or purple. When crossing two plants with purple flowers, some offspring plants had white flowers, and others had purple flowers. After repeating this process for several generations (remembering there is only one crop of peas per year), offspring were obtained solely from plants with purple flowers. This outcome persisted in subsequent generations. These purple-flowered plants represent a pure race for that specific character.

Character Study: Crossing Pure Breeds

Mendel studied several characters by crossing pure breeds (varieties):

• Seed Color

  • Dominant Alternative: Yellow
  • Recessive Alternative: Green

• Seed Aspect

  • Dominant Alternative: Smooth
  • Recessive

The Digestive System

Functions of the Digestive System

The digestive system performs the following vital functions:

• Breaks down food into molecules the body can use.
• Absorbs molecules into the blood and carries them throughout the body.
• Eliminates wastes from the body.

Types of Digestion

There are two main types of digestion:

• Mechanical Digestion: Foods are physically broken down into smaller pieces.
• Chemical Digestion: Chemicals produced by the body break foods into their smaller chemical building blocks. Most chemical digestion occurs in the stomach.

Key Components and Processes

Saliva

Saliva is the fluid released when your mouth waters. It is produced by salivary glands and plays an important role in chemical digestive processes.

Teeth

• Incisors: Central

The Immune System and Disease Prevention

The immune system is a set of organs, cells, and molecules whose primary function is to defend the body against infectious agents and abnormal cells within the organism.

It is responsible for defense once infectious agents have crossed the skin or mucous membranes, and it acts through:

Nonspecific Defenses

Nonspecific defenses, such as inflammation, are not dependent on the nature of the pathogen.

Specific Defenses

Specific defenses are based on the specific recognition of foreign substances, known as antigens, against which an immune response is triggered. This response has the following characteristics:

• Specificity: Lymphocytes, which are cells of the immune system, distinguish specific antigens from others

Vegetative Reproduction in Plants

Vegetative reproduction is a form of asexual reproduction in plants. A part of a single individual, a cell (e.g., spores), or a group of cells (fragmentation) develops into a duplicate of the progenitor. The offspring are identical to each other and identical to their preserved vegetative progenitor. Plants always have embryonic tissues, the meristems, which consist of totipotent cells. Therefore, they have a great capacity for regeneration, and asexual reproduction is common.

Structures Involved in Asexual Reproduction

• Stolons: Stems that run parallel to the ground, which occasionally produce roots and new stems and leaves. Example: Strawberries.
• Rhizomes: Underground stems that occasionally produce roots and

Immunology

By removing serum from pustules of the udder of a cow and injecting it into human skin, an individual suffered from a mild illness but never acquired smallpox. It was the first experiment of active immunization.

1. The Body's Defenses

All organisms have developed mechanisms of defense against the invasion of pathogens. These mechanisms may be nonspecific, preventing entry into the body or destroying them quickly, or very specific, which is known as the immune response.

1.1 Nonspecific Defense Mechanisms

These act against any organism or foreign substance. They are of three types:

a) Natural Barriers: Skin and secretions from the mucosal surfaces.

• Skin is a mechanical barrier because its outermost stratum corneum is fully keratinized.
• It

The Miller-Urey Experiment: Origin of Life

The Miller-Urey experiment represents the first demonstration that organic molecules can form spontaneously from simple inorganic substances under simulated early Earth conditions. This groundbreaking experiment provided crucial insights into the chemical origins of life.

In the experiment, a gaseous mixture (simulating Earth's early atmosphere) was introduced into a sealed flask, where water was kept boiling to mimic the primordial ocean. The resulting vapor then underwent condensation. Substances were circulated continuously through the experimental setup, while two electrodes consistently produced electric shocks, simulating lightning.

Crucially, samples were extracted from the apparatus for analysis.... Continue reading "Evolutionary Biology: Miller-Urey, Lamarck, and Natural Selection" »

Levels of Biological Organization

Living matter is organized into distinct levels, categorized as abiotic or biotic:

• Abiotic: Components that do not conform to living matter, such as inert substances.
• Biotic: Components exclusive to living organisms.

Hierarchy of Living Matter

• Subatomic: Particles and atoms.
• Atom: The smallest portion of a chemical element.
• Molecular: Molecules formed by the joining of two or more atoms.
• Macromolecules: Resulting from the binding of many molecules to form a polymer.
• Supramolecular Complexes: Aggregations of macromolecules.
• Subcellular Structures: Union of different supramolecular complexes, resulting in the cell's structure with characteristic functions.
• Cells: Comprised of various organelles and structures. (Biotic Level)

The Nervous System

The nervous system is a biological system that enables very complex beings to interact with what surrounds us. We can say that it is a huge network responsible for the collection of internal and external stimuli. It processes these stimuli to generate the response that the decision center (brain) considers optimal.

There are two main divisions:

• Central Nervous System: Consists of the brain and spinal cord.
• Peripheral Nervous System: Includes all the nerves of the body that connect internal and external stimuli to the central nervous system.

Peripheral Nervous System

The peripheral nervous system includes different types of nerves:

• Sensory Nerves: Transmit information from sensory receptors (like those for touch, pain, temperature)

Advances in Stem Cells and Regenerative Medicine

Recent breakthroughs in stem cell research offer immense potential for tissue regeneration, curing diseases like cancer, and even slowing the aging process.

Key Concepts in Cellular Biology and Genetics

• Cloning: The process of creating an exact genetic copy of an organism or cell.
• Embryonic Stem Cells: These remarkable cells possess the ability to reproduce and differentiate into various specialized cells and organs.
• Therapeutic Cloning: A technique where the development of an individual is intentionally halted to obtain stem cells from a very early-stage embryo, known as a blastocyst.
• Totipotent Stem Cells: Cells capable of dividing and differentiating into any cell type required by an organism.
• Pluripotent

The Origin of the Moon

• Sister. The Moon formed while the Earth did, but the Moon is 100 million years younger, and their densities are different.
• Adopted. Both formed, but the Moon formed in an area farthest from the Sun and would have been attracted to the Earth. This does not explain the difference in age.
• Daughter. A planet similar to Mars collided with the Earth. Part of the star that crashed formed a debris cloud that orbited around the Earth. The union of these materials created the Moon.

Prebiotic Synthesis

Hypotheses in which life would have originated on Earth as a result of a process:

• Formation of simple organic molecules. Radiation caused molecules to react, forming simple organic molecules.
• Formation of complex organic molecules.