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" »

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" »

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

Genetic Transcription Process

TRANSCRIPTION: The process of copying a part of the genetic message from its original form (DNA) to another (RNA) that can be used directly for protein synthesis.

Transcription forms a strand of RNA whose sequence is complementary to the DNA template strand. Consequently, its sequence is the same as the non-template DNA strand (with uracil replacing thymine).

Transcription requires:

• A DNA strand serving as template
• Ribonucleotide triphosphates
• Enzymes (primarily RNA polymerase)

Stages of Transcription

Initiation

The RNA polymerase recognizes specific short sequences of nitrogenous bases (promoter) to which it binds. RNA polymerase opens the DNA double helix to allow incorporation of ribonucleotides.

Elongation

Addition of... Continue reading "Understanding Genetic Transcription & Code" »

Plant Anatomy: Roots, Stems, and Leaves

Root Structure

The root has a simple structure with no central bone. It contains vascular tissue in the phloem and wood beams, along with fundamental bark tissue. The endodermis clearly demarcates these areas. Two meristems are present: the cambium, which forms a ring of dividing cells between the phloem and wood, and the phellogen, which develops in the cortical parenchyma. The phellogen produces corky tissue layers for protection and cortical parenchyma internally.

Stem Structure

Stem structure differs between dicotyledonous and monocotyledonous plants. In dicots, vascular tissue forms a cylinder with the xylem inside and phloem outside. Fundamental tissue is located between the epidermis and vascular tissue... Continue reading "Plant Root, Stem, and Leaf Anatomy: Structure and Function" »

Internal Environment: The Body's Inner Sea

The internal environment refers to the set of fluids that surround the cells of an organism. From these fluids, cells extract the nutrients and oxygen they need.

Key Components of the Internal Environment

• Interstitial Fluid: This fluid, also known as tissue fluid, performs defensive and nutritive functions, remaining between the cells.
• Blood: Responsible for the transport of substances, blood circulates through blood vessels.
• Lymph: A fluid formed from plasma and interstitial fluid, lymph flows through lymphatic vessels.

The Blood Circulatory System

The blood circulatory system distributes nutrients and oxygen throughout the body while collecting waste products of cell metabolism.

Blood Vessels: Pathways of