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

Nervous System: The Body's Control Center

The Nervous System controls, processes, and responds to information, coordinating the body's activities.

Neuron: The Basic Unit of the Nervous System

The neuron is the basic structural unit of the nervous system. Neurons conduct impulses throughout the nervous system and consist of three regions:

• Axon
• Dendrites
• Cell Body

Dendrites and Axons: The Neuron's Extensions

Dendrites are extensions of the neuron that receive impulses and carry them toward the cell body.

The axon is an extension of the neuron that carries impulses away from the cell body toward other neurons, muscles, or glands.

Three Categories of Neurons

Neurons are categorized into three types:

1. Sensory Neurons: Carry impulses from the body to the spinal

MICROEVOLUTION

Changes that lead to the appearance of new species and groups that are closely related to each other.

MACROEVOLUTION

Leads to large groups of organisms after drastic change.

PUNCTUATED EQUILIBRIUM

The appearance of major groups of organisms took place as a result of drastic changes and the accumulation of gradual variations.

PHYSIOLOGICAL TREES

Visual representation of the evolutionary history of a group of organisms. A simplified diagram that, using a series of branches, shows the relationship between organisms.

SPECIATION

Two or more distinct species.

GEOGRAPHICAL BARRIERS

Examples are lakes, mountain ranges, and seas.

SEXUAL BARRIERS

Caused by anatomical changes that prevent mating from occurring.

PHYSIOLOGICAL BARRIERS

Incompatibilities... Continue reading "Evolutionary Processes and Theories: A Comprehensive Overview" »

Introduction

Humans are heterotrophs, meaning they cannot create their own organic matter. They obtain energy by ingesting substances from other organisms.

Food: Substances from other living things that are ingested.

Nutrients: Simple molecules contained in foods, necessary for life.

Eating: Conscious, voluntary process by which foods are taken from the outside environment.

Nutrition: Complex, unconscious, and mostly involuntary process by which foods are transformed into nutrients.

Carbohydrates (Glucides)

Energy-providing nutrients.

Monosaccharides

Formed only by one molecule.

• Examples: Glucose (cane sugar), fructose (fruit sugar)

Disaccharides

Formed by two molecules.

• Examples: Sucrose (cane sugar), lactose (sugar of milk)

Mono and disaccharides are sweets,... Continue reading "Nutrients: Essential Substances for Life" »

Describe the sources, targets, and primary effects of the hormones of calcium metabolism

The parathyroid gland is the hormone that affects Ca2+ concentration. When Ca2+ concentration is too low in the plasma, the parathyroid hormone secretion is stimulated, and vice versa. This parathyroid hormone can have several effects. It can send a signal to the bones and the osteoblasts will break down and more Ca2+ enters the blood. It can also stimulate the formation of 1,25 (OH)₂D to reabsorb Ca2+ in the intestines and kidneys so less Ca2+ is excreted, it also increases the excretion of phosphate ions. It also stimulates the reabsorption of Ca2+ in the GI tract. Calcitonin is a peptide hormone secreted by parafollicular cells in the thyroid gland. Calcitonin... Continue reading "Hormones of Calcium Metabolism and Stress Response Pathways" »

Infectious Diseases

Pathogenic Bacteria and Associated Diseases

Compare and contrast the morphological characteristics of various pathogenic bacteria given below and explore their role in human diseases.

• Bacillus anthracis: Anthrax
• Clostridium botulinum: Botulism
• Clostridium tetani: Tetanus
• Corynebacterium diphtheriae: Diphtheria
• Haemophilus influenzae: Influenza (flu); Bacterial Meningitis
• Mycobacterium tuberculosis: TB (Tuberculosis)
• Neisseria gonorrhoeae: Gonorrhea
• Salmonella Typhi: Typhoid Fever
• Shigella Dysenteriae: Dysentery
• Staphylococcus aureus: Boils and Pimples
• Streptococcus pneumoniae: Pneumonia
• Streptococcus pyogenes: Strep Throat; Scarlet Fever; Rheumatic Fever

Microbiology Concepts and Tests

Hemolytic Activity

Describe how hemolytic activity is... Continue reading "Key Pathogenic Bacteria and Tests" »

Pollination and Fertilization in Plants

Pollination is the mechanism to achieve the objective of transferring pollen grains, shed from the anther, to the stigma of a pistil. This transfer is termed pollination.

Kinds of Pollination

Depending on the source of pollen, pollination can be divided into three types:

• Autogamy
• Geitonogamy
• Xenogamy

Double Fertilization

After entering one of the synergids, the pollen tube releases two male gametes into the cytoplasm of the synergid. One of the male gametes moves towards the egg cell and fuses with its nucleus, thus completing the syngamy. This results in the formation of a diploid cell, the zygote. The other male gamete moves towards the two polar nuclei located in the central cell and fuses with them to produce... Continue reading "Pollination, Fertilization, and Reproduction in Plants and Humans" »

Biology Study Guide

Cellular Biology and Genetics

Cell Growth and Reproduction

Benign vs. Malignant Tumors

Benign tumors are characterized by slow growth, non-invasive behavior, and the absence of metastasis. Malignant tumors, on the other hand, exhibit rapid growth, invasiveness, and the ability to spread to other parts of the body through a process called metastasis.

Cancer Terminology

A carcinogen is a substance that can cause cancer. Genetics is the study of genes and their inheritance patterns. Inheritance refers to the transmission of genetic information from parents to offspring. Alleles are alternative versions of a gene. A homozygous individual has two identical alleles for a particular gene, while a heterozygous individual has two different... Continue reading "Biology Study Guide: Key Concepts and Definitions" »

Human Circulatory System: Double Circulation

The human circulatory system performs double circulation, meaning that the blood passes through the heart twice in order to complete a full circuit. The two loops are completely separate from one another, which prevents the mixing of deoxygenated blood.

• Blood passes through the lungs.
• All the organs receive blood that is equally rich in oxygen and nutrients.

Right Half of the Heart

• Vena cavae carry blood back to the heart.
• Blood enters through the right atrium and moves to the right ventricle.
• Blood exits through the pulmonary artery and goes to the lungs.

Left Half of the Heart

• Pulmonary veins bring blood from the lungs to the heart.
• Blood enters through the left atrium and moves to the left ventricle.
• Blood

Cell Structure and Function

1. Cytoplasm

   The cytoplasm is the internal "soup" of the bacterial cell, bounded on the outside by the cell envelope. It is mostly water, but contains bacterial inclusions.

2. Cell Membrane

   The cell membrane protects the cell from its surroundings. It controls the movement of substances in and out of cells and consists of the phospholipid bilayer with embedded proteins.

3. Nucleus

   The nucleus is located in the very center of the cell and serves as the control center. It is made up of the nucleolus, chromosomes, and is surrounded by the nuclear envelope.

4. Nuclear Envelope

   The nuclear envelope surrounds the nucleus with a double membrane and multiple pores. The pores regulate the passage of macromolecules but permit free passage of