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

Tracheophytes: The Vascular Plants

Key Features of Tracheophytes

• Also known as vascular plants due to their specialized conducting vessels (xylem and phloem).
• Possess true roots, stems, and leaves.
• Exhibit autotrophic nutrition, producing their own food through photosynthesis.
• Develop three primary tissue systems: vascular, ground, and dermal tissues.
• Many species reproduce via seeds, though some reproduce by spores.

Classification of Tracheophytes

• Lycopsida
• Sphenopsida
• Psilopsida

Ferns: Non-Seed Vascular Plants

Characteristics of Ferns

• Comprise approximately 10,000 known species.
• Typically herbaceous and rhizomatous (possessing underground stems).
• Often thrive in warm, humid environments, particularly in tropical forests.
• Possess true roots, stems, and leaves

Chromatin

Chromatin consists of strands of DNA at different degrees of condensation associated with proteins and scattered throughout the nucleoplasm. When the cell is going to divide, the chromatin filaments are organized and condensed to form thicker structures called chromosomes.

Genes

A gene is a unit of hereditary material. It is a fragment of nucleic acid that carries genetic information for a character, a protein, or a polypeptide chain. It corresponds to what Mendel called a hereditary factor.

Centriole

In animal cells, centrosomes present two small cylinders and consist of protein tubules.

Mitotic Spindle

The mitotic spindle forms when the nuclear membrane and nucleolus disappear.

Karyotype

A karyotype is a set of chromosomes from one species.... Continue reading "Cell Biology: Chromatin, Genes, Karyotype, and Cell Types" »

Changes achieved through the development, acquisition, or loss of organs are maintained and transmitted to offspring, which preserves and increases these traits through successive generations. This concept is known as the inheritance of acquired characteristics. However, analysis of these proposals has not demonstrated any inherent tendency or impulse towards complexity in living things. In light of developments in genetics, the inheritance of acquired characteristics is not supported.

Natural Selection: Darwin and Wallace

Darwinian theory posits that in a changing world, organisms also change over time. Some features disappear, and new ones emerge. This process of change is gradual and continuous. Organisms with similarities are related and... Continue reading "Evolutionary Theories: Darwinism, Neo-Darwinism, and Hominid Origins" »

The Small Intestine: Structure and Function

Structure

It is divided into three parts: the Duodenum, Jejunum, and Ileum. The small intestine represents the largest portion of the digestive tube. Its length varies with the type of feed: it is longer in herbivores and shorter in carnivores.

Function

Its primary function is to perform most of the chemical digestion and absorption of nutrients. For this, it requires that the secretions discharged by the pancreas, liver, and intestinal glands are mixed with chyme through sawing motions and peristaltic waves. After this mixture, chyme becomes chyle, consisting of H₂O, mineral salts, monosaccharides, and amino acids, which are absorbed by the intestinal mucosa to be incorporated into the circulatory... Continue reading "Human Digestive System: Stomach and Intestine Functions" »

The Circulatory System: Blood and Its Components

Composition of Blood

Blood is a red liquid that constantly circulates through blood vessels. It transports cells, nutrients, and oxygen, while collecting carbon dioxide and other waste products that must be expelled. Blood is formed by plasma and blood cells.

• Plasma: Transports nutrients and supports the blood cells.
• Blood Cells:
  • Red Blood Cells (Erythrocytes): Responsible for oxygen transport.
  • White Blood Cells (Leukocytes): Including neutrophils, monocytes, and lymphocytes, crucial for the immune system.
  • Platelets (Thrombocytes): Essential for blood clotting.

Blood Vessels

Blood vessels form a network of channels that distributes blood throughout the body, comprising three main types:

• Arteries: Carry

Central Nervous System (CNS) Components and Protection

The Central Nervous System (CNS) is composed of the brain and spinal cord. It is protected by membrane layers, called the meninges, and bone structures: the skull (for the brain) and the vertebrae (for the spinal cord).

Major CNS Structures Housed in the Cranium

The brain structure housed in the cranium includes the Cerebrum, Cerebellum, and Medulla.

The Cerebrum Structure and Function

The Cerebrum is divided into two hemispheres. Its surface features include protrusions called gyri and depressions called sulci or fissures. The cerebral cortex is the outer part, made up of gray matter that receives information from sense organs, produces response orders, and stores and processes information.... Continue reading "Understanding the Central and Peripheral Nervous Systems" »

Key Components of the Immune System

Immune Cells

The immune system relies on various specialized cells to identify and eliminate pathogens:

• Neutrophils: These are phagocytic cells (microphages) that can pass through blood vessel walls in a process called diapedesis.
• Monocytes: These cells can collaborate with macrophages and lymphocytes in immune reactions.
• Lymphocytes: A crucial category of white blood cells, central to the specific immune response.
• Basophils: Contain histamine granules, which, when released, dilate blood vessels and increase capillary permeability.
• Eosinophils: Capable of performing both phagocytosis and diapedesis.

Immune Protein Molecules

Immune protein molecules are synthesized by certain immune cells and are essential for defending... Continue reading "The Body's Defense: Immune Cells, Proteins, and Responses" »

Biological Foundations

Photosynthesis: Energy Capture

Photosynthesis is a vital process that enables plants to convert light energy into chemical energy. This fundamental process, crucial for life, relies on the presence of leaves and pigments to capture solar energy.

Cellular Structures & Nutrient Transport

Unicellular vs. Multicellular Organisms

Unicellular organisms are in direct contact with their external environment. In contrast, multicellular organisms do not have all their cells in direct contact with the outside world, facing challenges in spreading nutrients across individual cells.

Therefore, multicellular organisms require internal transport systems (like 'pipes' or circulatory systems) to distribute nutrients to all cells not in... Continue reading "Biological Foundations and Wastewater Treatment Essentials" »

Core Concepts in Biotechnology and Genetics

Genetic Code

The genetic code is the set of rules by which information encoded in messenger RNA (mRNA) sequences is translated into amino acid sequences during protein synthesis. It dictates which amino acids correspond to each codon, allowing them to join together in the correct position to form a protein.

Biotechnology

Biotechnology involves the use of living organisms, or parts of organisms, or modified products derived from them, to improve plants or animals, or to develop microorganisms for specific objectives.

Plasmids

Plasmids are circular DNA molecules, independent of the chromosomal DNA, that often carry genetic information useful to the host organism, typically found in bacteria and yeasts.

Bacteriophage

The Digestive System: Functions and Anatomy

The digestive system is responsible for several key functions:

• Food intake: Consuming food.
• Nutrient preparation: Breaking down nutrients through mechanical and chemical digestion.
• Absorption: Absorbing nutrients into surrounding tissues.
• Elimination: Eliminating undigested waste.

Components of the Digestive System

The digestive system consists of the following organs:

• Mouth
• Pharynx
• Esophagus
• Stomach
• Intestines:
  • Duodenum
  • Jejunum
  • Ileum
  • Large Intestine (Cecum, Appendix, Ascending Colon, Transverse Colon, Descending Colon, Sigmoid Colon, Rectum, Anal Canal, Anus)

The entire system is lined with the peritoneum, a serous membrane.

Accessory Glands

Several accessory glands aid in digestion:

• Minor and major salivary glands