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

Arthropod Characteristics

Arthropods exhibit bilateral symmetry and a ventral nervous system. Their heart is positioned dorsally, and they have an open circulatory system. They possess an external chitinous exoskeleton, which they shed and replace with a new one during growth, a process called molting. The sensory organs of arthropods are highly developed, primarily located in the head and legs.

Chordate Features

• The alimentary canal includes glands that aid digestion, such as salivary glands, the pancreas, and the liver.
• The cerebrospinal nervous system consists of a thick dorsal nerve cord, forming the brain and spinal cord, with nerves branching out.
• Most chordates have separate sexes. Development typically occurs in eggs, although mammals and

Core Biological Processes

Gametogenesis: Formation of Gametes

Gametogenesis is the process involving the formation of two types of propagating phase gametes.

Oogenesis (Egg Formation)

The germ cells reach sexual maturity via mitosis, leading to the subsequent rise of oogonia (2n). The growth phase involves some oogonia increasing in size due to the accumulation of cytoplasm, transforming them into primary oocytes (2n).

Each maturing primary oocyte undergoes Meiosis I, resulting in:

• A secondary oocyte (n)
• The first polar corpuscle (n)

The secondary oocyte then undergoes Meiosis II, generating an ovotid (n) and the second polar corpuscle.

Spermatogenesis (Sperm Formation)

When the organism reaches sexual maturity, cells in the testes multiply via mitosis,... Continue reading "Fundamentals of Gametogenesis, Genetics, and Cell Biology" »

Levels of organization refer to the different degrees of complexity in organized matter.

• Subatomic level: Particles that make up atoms (protons, neutrons, electrons).
• Atomic level: Formed by atoms; the smallest constituents of matter that retain their properties.
• Molecular level: Molecules resulting from the binding of different atoms. There are two types:
  • Inorganic: Found in non-living or dead material (water and mineral salts).
  • Organic: Found only in living matter, usually polymers, chains formed by the union of a similar type of monomer molecules.
• Cellular level: The first level with life.
• Tissue level: Groups of cells with the same function and similar structure.
• Organ level: Different tissues are grouped for a particular function.
• System level:

Mitochondria: Structure and Function

In mitochondria is where cellular respiration occurs (specifically the Krebs cycle, beta-oxidation, electron transport, and oxidative phosphorylation), whose ultimate objective is to obtain energy in the form of ATP. Mitochondria also generate precursors of the major anabolic routes.

The mitochondria are structured as follows: a double membrane formed by an external and an internal membrane, which delimits two different compartments: the intermembrane space and the mitochondrial matrix.

The Outer Mitochondrial Membrane

The outer mitochondrial membrane is in continuous contact with the cytosol. It contains numerous proteins that regulate trade in chemicals with it, including channel proteins (porins) that form... Continue reading "Mitochondrial Structure and Function in Cellular Respiration" »

The Central Nervous System: Brain and Spinal Cord

The Central Nervous System (CNS), comprising the brain and spinal cord, receives information to process and control bodily functions.

The Brain

Located within the braincase, the brain is divided into two hemispheres. Its outermost part, the gray matter, has convolutions (gyri) and grooves (sulci). This area receives information and develops responses. The innermost zone is white matter.

The Cerebellum

Situated below the brain, the cerebellum is also divided into two hemispheres and features convolutions. It coordinates movements such as walking and maintains balance.

The Medulla Oblongata (Bulb)

This vital part links the encephalon with the spinal cord. It controls automatic bodily functions, including... Continue reading "Understanding the Nervous System: Components and Health" »

Female Reproductive Anatomy

The Uterus

The uterus is a pear-shaped organ, inverted. Its walls are formed by a muscular layer lined by an epithelial layer, the uterine lining or endometrium.

The Vagina

The vagina is an elastic conduit connected to the uterus.

Sperm and Spermatogenesis

Sperm Structure

Sperm cells are tiny, highly specialized cells. The front portion, known as the head, contains the nucleus with the parental genetic material. They also have a long thread called the flagellum (or scourge).

Formation of Sperm

Sperm are formed within the testes in small tubes called seminiferous tubules. Each testis contains many seminiferous tubules inside.

Ovules and Oogenesis

Ovules (Egg Cells)

Ovules are large cells containing hereditary information and... Continue reading "Human Reproduction: Gamete Formation and Fetal Development" »

Noncyclic Phosphorylation

The arrangement of the pigment-protein complexes, Photosystems I and II, both electron carriers in the electronic transport chains and ATP synthase enzymes, is necessary to maintain a specific spatial arrangement in the thylakoid membrane, which enables ATP synthesis. The mechanism of ATP synthesis is nearly identical to that of the mitochondria; it depends on the existence of the ATP synthase enzyme complex on the stromal face of the thylakoid membrane. Proton pumping into the thylakoid, performed by several protein complexes of the light phase, generates a proton-motive force gradient necessary for synthesis. In the chloroplast, it is known that each ATP synthesis catalyzed by the stromal portion F1 is associated... Continue reading "Mechanisms of Photophosphorylation in Chloroplasts" »

Forest Ecosystems: A Comprehensive Look

Forest: A natural ground dominated by trees. Vegetation: Various species of plants with 3 strata: arboreal, shrubby, and herbaceous. Conditions: Light, heat. Virosta: Composition of residue that accumulates sun.

Plant Types

• Bryophytes (moss, liverwort)
• Pteridophytes (fern, horsetail)
• Spermatophytes (seed plants)

Gymnosperms (not enclosed seeds). Angiosperms (enclosed seeds). Vegetation Zones: Forest (arboreal), thicket (tall shrub), springs (low shrub), meadow (herbaceous).

Revolt: Perennial, deciduous. Mineral salts (active absorption via PX transport - against gradient, sometimes with gradient). Concentration: Hypotonic (-), isotonic (=), hypertonic (+).

Osmosis and Photosynthesis

Osmosis: Process of water absorption... Continue reading "Understanding Forest Ecosystems: Flora, Soil, and Life Cycles" »

Biological Contaminants in Indoor Environments

Biological contaminants are living or once-living organisms that can negatively affect indoor air quality and human health. Key types include:

• Bacteria: Carried by people, animals, soil, and plant debris.
• Viruses: Primarily transmitted by people and animals.
• Moulds: Grow on water-damaged materials or wet surfaces.
• Pollens: Originate from plants.
• Animal Dander: Sources include household pets.
• Saliva: Mainly from cats and rabbits.
• Dust Mites: Thrive in damp, warm environments.
• Insects and Pests: Including ants, cockroaches, mice, and rats.

Humans as Sources of Indoor Contamination

Human activities significantly contribute to indoor biological contamination:

• During sneezing, between 4,000 and 40,000 small drops

Carbohydrates: Primary Energy Source

Carbohydrates are chemical compounds of oxygen, carbon, and hydrogen, synthesized by plants through the action of solar energy. Sugars are found in bread, grains, fruits, and vegetables.

They serve as the first major energy substrate, providing between 50% and 60% of the total energy necessary for movement and basic functions. They are also essential to feed the brain.

Fats (Lipids)

Fats (lipids) consist of hydrogen, oxygen, and carbon that form a chain, categorized as saturated or unsaturated fatty acids.

Sources of Fats

• Saturated Fats: Meat, eggs, and dairy.
• Unsaturated Fats: Olive oil or sunflower oil.

Fats are indispensable; they serve as an energy source, help regulate body temperature (Tª), and transport... Continue reading "Essential Nutrients: Macronutrients, Vitamins, and Diet" »