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

Protozoa

Features:

• Microscopic and eukaryotic unicellular organisms.
• Exhibit movement.
• Aquatic, living in aquatic or terrestrial environments.
• Some are free-living; others are parasites.
• Reproduction may be sexual or asexual.

Classification:

• Mastigophora (Flagellates): Possess flagella for locomotion.
• Rhizopods (Sarcodina): Move via pseudopods, extensions of the cytoplasm.
• Ciliophora (Ciliates): Move using cilia.
• Apicomplexa (Sporozoa): Have a complex life cycle; all are parasites.
• Suctoria: Have cilia in their juvenile phase and tentacles in adulthood.

Locomotion: Move by extending cytoplasm externally (pseudopods), into which the rest of the cytoplasm flows.

Nutrition: Engulf organic particles via pseudopods, forming a digestive vacuole. Enzymes digest... Continue reading "Protozoa, Bryophytes, Gymnosperms, and Angiosperms: A Comparison" »

Nucleic Acids: Fundamental Molecules of Life

Nucleic acids contain the instructions necessary for life processes and are responsible for all basic functions of living beings. They are heritable, possess the characteristic of self-duplication, are stable, contain the hereditary material of living things, allow for changes (mutation and recombination), and produce various molecules.

Nucleotide Structure

Nucleotides are the fundamental units that form nucleic acids. They are composed of a pentose sugar, a nitrogenous base, and one or more phosphate groups. Both the nitrogenous base and the phosphate groups are attached to the pentose, which is always an aldopentose.

Nitrogenous Bases

Nitrogenous bases can be of two types: purines, derived from the... Continue reading "Nucleic Acids and Nucleotides: Structure, Function, and Biological Significance" »

Nervous Tissue

Nervous tissue cells produce responses sent to muscles and glands, leading to movements and secretions, respectively. These functions are performed through nerve impulses, which are common electrochemical signals. Nerve endings reach all body parts. Except for the simplest invertebrates, whose nervous tissue consists only of neurons, in other animals, it is also composed of a very different set of glial cells.

Neurons: Structure and Function

Neurons are the structural and functional units of the nervous system. They receive information from both the internal and external environments of an organism. Neurons have a high degree of specialization. Once mature, they cannot divide, and their numbers are definitively established from... Continue reading "Nervous Tissue: Components, Structure, and Roles" »

Meiosis: Diploid to Haploid Cell Division

Meiosis is a specialized cell division mechanism that produces haploid daughter cells (n) with distinct genetic combinations from a single diploid cell (2n). It involves two consecutive divisions: Meiosis I (the first meiotic division) and Meiosis II (the second meiotic division).

Essentially, Meiosis transforms one diploid cell (2n), which has already duplicated its genetic material, into four genetically different haploid cells (n) through these two divisions. Without meiosis, gametes would retain the same chromosome number as somatic cells. Consequently, after each fertilization event, the resulting zygote would have double the necessary chromosomes. This highlights the crucial role of meiosis in maintaining... Continue reading "Meiosis Explained: Diploid to Haploid Cell Division Process" »

Human Sensory Receptors and Body Systems

Sensory Receptors: Body's Information Gateways

Sensory receptors detect environmental changes, or stimuli, that can be captured by an organism. Our nerve cells are sensitive receptors, often denominated as such. These include:

Types of Sensory Receptors

• Interoceptors (internal)
• Exteroceptors (external)
• Mechanoreceptors
• Chemoreceptors
• Thermoreceptors
• Photoreceptors

The Skin: Our Largest Sensory Organ

The skin, our body's largest organ, consists of two primary layers: the epidermis, which is the outermost surface layer, and the dermis, located beneath the epidermis. The epidermis is composed of epithelial tissue and forms various appendages, including:

Skin Layers and Appendages

• Nails
• Hair
• Sweat glands
• Sebaceous glands

Tactile

Theories on the Origin of Life

Panspermia Hypothesis

Life originated from spores traveling through space from one planetary system to another.

Prebiotic Synthesis Hypothesis

Life emerged from organic molecules on Earth, which in turn formed from inorganic matter.

Oparin-Haldane Hypothesis (Prebiotic Synthesis)

In 1923, Oparin and Haldane proposed that simple organic molecules could form from gases present in the early atmosphere. This hypothesis is based on several key points:

• Millions of years ago, the planet had an atmosphere without oxygen.
• When the Earth's temperature decreased, water vapor condensed into clouds, resulting in rain and the formation of oceans.
• The energy from the sun and electric discharges caused inorganic compounds present in the

Mutations

Mutations: Sudden alterations in genetic material may go unnoticed or be a source of genetic variation. Mutations occurring in gametes are transmitted to offspring.

Types of Mutations:

1. Gene or Point Mutations:

   These replace one base pair with another. This can halt protein synthesis or cause the synthesis of a different protein.

2. Chromosome Mutations:

   These involve the loss (deletion) or duplication of a chromosome. They also include variations in the distribution of chromosome segments, such as translocation, where segments move to another chromosome.

3. Genomic Mutations:

   These include euploidies, which affect the entire set of chromosomes, leading to haploid (n) or polyploid (3n or 4n) conditions, often seen in plants. Aneuploidies involve

Cellular Biology

Synthesis of Cell Theory

• Each living organism is made up of one or more cells (structural unit).
• The smallest living organisms are single cells, and cells are structural units of multicellular organisms.
• All cells come from preexisting cells (the source drive).

Forms of bacteria:

• Bacilli
• Coccobacilli
• Vibrio
• Spirochetes / Spirilla

Prokaryotic and Eukaryotic Cells

Prokaryotic Cells: Are those that have no internal membranes or an organized nucleus (bacteria).

Eukaryotic Cells: They have internal membranes and an organized nucleus.

Difference Between Animal and Plant Cells

Plasma membrane: Structure that separates the intracellular from the extracellular... Continue reading "Cellular Biology: Prokaryotic and Eukaryotic Cells" »

Microbiology: The Science of Microorganisms

Microbiology, derived from the Greek words mikros ("small"), bios ("life"), and logos ("study"), is the scientific discipline dedicated to the study of microorganisms. These are living things too small to be seen with the naked eye. Microorganisms, often called germs, were discovered over 300 years ago. Their only common characteristic is their small size.

Microscopy depends on factors such as contrast, resolution, and magnification.

Taxonomy involves the study of nomenclature, classification, and identification of microorganisms.

Factors Influencing Microbial Growth

The number and types of microorganisms in an environment depend on factors like humidity, heat, nutrient availability, aeration, and pH.

• Soil

Animal Nutrition and Digestion

Animals have specific nutritional needs. Digested food cannot be used as it is ingested; animals need to extract nutritious substances, which are the components that must be digested. Most animals possess a digestive system, more or less complex, with a digestive tract divided into regions and various associated glands.

The Digestive System

Vertebrate Digestive Tract

The digestive tract of vertebrates is clearly differentiated into various regions, including the mouth, esophagus, stomach, and intestine. It also features several glands such as salivary glands, the liver, and the pancreas.

Variations in Stomach Structure

Avian Stomach

In birds, the stomach is divided into several cavities. The proventriculus is involved... Continue reading "Animal Body Systems: Digestion, Respiration, & Circulation" »