Notes, abstracts, papers, exams and problems of Biology

The Nephron: Structure and Function

The nephron is the functional and anatomical unit of the kidneys. It is responsible for filtering the blood and reabsorbing essential substances.

Nephron Parts:

1. Bowman's Capsule: The end of the nephron is cup-shaped and surrounds a network of capillaries called the glomerulus. The glomerulus is connected to an afferent arteriole (input) and an efferent arteriole (output).
2. Proximal Convoluted Tubule: Named for its serpentine appearance.
3. Loop of Henle: A narrowed area of the proximal tubule, with a descending and an ascending branch.
4. Distal Convoluted Tubule: A continuation of the loop of Henle, it connects with the collecting duct.

The collecting duct empties into the renal pelvis.

Urine Formation

Urine formation takes... Continue reading "Nephron Function and Urine Formation: A Detailed Look" »

Types of Cells in Multicellular Organisms

Diploid Cells

They have two copies of each chromosome type. It is symbolized as 2n. In humans, somatic cells, which constitute the body, have 2x23 chromosomes = 46.

Haploid Cells

They have a single copy of each type of chromosome. It is symbolized as n. In humans, these are the reproductive cells (eggs and sperm) and have 23 chromosomes. n is the number of different types of chromosomes present in each cell.

Mitosis

Inside the life cycle of a cell, we can identify:

• The interphase or growth period, which is the interval between two successive divisions.
• The cell division, the stage where two daughter cells are formed from an initial cell.

Cell Division

Cell division comprises:

1. The division of the nucleus or mitosis,

Chromosomal Mutations

Chromosomal mutations translate into two types of abnormalities, visible by light microscopy: numerical and structural.

Numerical Alterations of Chromosomes

There are two main types:

• Euploidies: Numerical alterations affecting the entire genome. Individuals may have two, three, or four sets of similar chromosomes (monoploidy, triploidy, and tetraploidy, respectively).
• Aneuploidy: Affects only one pair of chromosomes, while the rest remain the same. Individuals are described as monosomic, trisomic, or tetrasomic, depending on the number of copies of the affected chromosome.

Structural Alterations of Chromosomes

• Deletions: Loss of a chromosome fragment, which can be interstitial (within the chromosome arm) or terminal (at the

Cell Biology: Key Processes and Concepts

Rough Endoplasmic Reticulum: An organelle responsible for protein synthesis and transport. Learn more about proteins.

Nucleolus: Responsible for the production and assembly of ribosomal components.

Ribosomes: Responsible for synthesizing proteins from genetic information transcribed from DNA in the form of Messenger RNA (mRNA).

Mitosis: The process of cell division by which the cell retains the genetic information contained in its chromosomes.

Meiosis: A type of cell division in sexually reproducing organisms.

Types of Cell Division

Sporulation, budding, pluripartition, and bipartition are all types of cell division.

Photosynthesis: A chemical process by which plants obtain their own food.

Carbohydrates: The... Continue reading "Cell Biology: Processes, Division, and Organization" »

Geological Ages

Precambrian (4600-1000 million years ago)

• The most extensive
• Evolution at the cellular level
• Domain prokaryotes
• Emergence of Eukaryotes
• Cell organisms of greater size and complexity
• First multicellular organisms

Paleozoic (544 to 245 million years ago)

• Appearance of life forms that gave rise to the current lifestyles
• Mainly aquatic organisms
• Invasion of terrestrial environments, first plants (vascular)
• Emergence of arthropods

Mesozoic (245-65 million years ago)

• Pangea begins to split, affecting the climate
• Emergence and domain of dinosaurs (Jurassic); origin of mammals
• Arise flowering plants (angiosperms) and Conifers (Araucaria pines)
• At the end of the Age, massive extinction of marine and some terrestrial species (dinosaurs)

Cenozoic (65 million... Continue reading "Earth's Geological Ages and Evolution of Life" »

Features of Living Things

• Nutrition: Processes by which living things obtain matter and energy.
  • Autotrophs: Organisms that transform inorganic matter into organic matter, such as plants and bacteria. Two types of autotrophic nutrition exist:
    • Photosynthesis (using light)
    • Chemosynthesis (using chemicals)
  • Heterotrophs: Organisms that obtain matter from organic compounds, such as animals and fungi. Two types of heterotrophic nutrition exist, depending on the:
    • Presence of oxygen: Cellular respiration (aerobic)
    • Absence of oxygen: Fermentation (anaerobic)
• Interaction: The capacity of living beings to interact with their environment.
• Reproduction: The process by which living beings produce descendants, leading to the perpetuation of life.
  • Asexual: Descendants

1. Vomer Bone

Shape: Part of the postero-inferior nasal septum. Anatomical Features: Alae (wings), ridge, and furrow for choanal articulation with the vomer.

2. Sutures and Fontanelles

The bones of the cranial vault are joined by synfibrosis. We distinguish:

• Coronal suture
• Sagittal suture
• Squamous sutures
• Metopic suture
• Lambdoid suture

Schindylesis: Vomer and sphenoid crest articulation.

In newborns, skull bones are not yet firmly united at the sutures, leaving spaces called fontanelles. There are six:

• Bregmatic: Diamond-shaped, between the parietal and frontal bones.
• Lambdoid: Triangle-shaped, between the sagittal and lambdoid sutures.
• Pterygoid: Located at the junction of the frontal, parietal, temporal, and sphenoid bones.
• Asteroid: Star-shaped, between

GREAT PLANTS (Metaphytes) belong to this group of photosynthesizing multicellular eukaryotic organisms whose cells have cell walls of cellulose. Plants have a biological cycle in which dipohaplonte diploid and haploid phases are distinguished with different development. There are two divisions: Bryophytes and Tracheophytes.

Bryophytes: Simple Plants

Bryophytes are the less evolved plants. They present a thallus-type organization, with no tissues or organs. This group includes mosses and liverworts, where the haploid body is more developed. Bryophytes are considered an evolution of algae.

Tracheophytes: Developed Plants

Tracheophytes are more developed plants; they have tissues and organs. Conducting structures of food substances are known as vascular.... Continue reading "Plant Kingdom: Classification, Characteristics, and Evolution" »

Facial Muscles

Occipitofrontalis muscle (frontal belly): Elevates the brow and wrinkles the forehead.

Procerus muscle: Depresses the medial angle of the eyebrow and wrinkles the root of the nose.

Corrugator supercilii: Draws the eyebrow medially and inferiorly, creating vertical wrinkles between the eyebrows.

Depressor supercilii: Depresses the eyebrow.

Orbicularis oculi: Has three parts: palpebral (gently closes the eyelid), orbital (forcefully closes the eye), and lacrimal (compresses the lacrimal gland, aiding tear production).

Levator labii superioris alaeque nasi: Elevates the upper lip and dilates the nostril.

Levator labii superioris: Elevates the upper lip.

Zygomaticus minor: Elevates the upper lip.

Zygomaticus major: Draws the corner of the... Continue reading "Facial Muscles, Spine Joints, and Ligaments: An Anatomical Study" »

Plant Tissues

Supporting Tissue

Supporting tissue is found in the interior of the plant body. These tissues form the plant skeleton, giving it rigidity and strength. Their cells have very thickened walls.

Types of Supporting Tissue

• Collenchyma: Found in younger parts, consisting of living parenchymal cells reinforced by cellulose in some areas.
• Sclerenchyma: Supporting tissue of the developed parts, consisting of dead cells with thickened walls and lignin. If they are elongated, they are called fibers, and if they are round, they are called stone cells.

Secretory Tissues

Secretory tissues are varied, modified epidermal cells, such as those that accumulate aromatic substances, resin canals, and lactiferous ducts.

Animal Tissues

Epithelial Tissue

Types