Notes, abstracts, papers, exams and problems of Biology

Excretion is the elimination of waste products (such as carbon dioxide and nitrogenous wastes) and is a crucial part of the broader processes aimed at maintaining homeostasis, which is essential for an organism's survival. Homeostasis is the process of maintaining constant internal conditions. The two pillars that maintain homeostasis in animals are excretion and osmoregulation.

Excretory Structures

Excretory systems use tubes to collect fluid from the blood, hemolymph, or extracellular fluid to adjust its composition through the reabsorption of useful substances and the active secretion of waste products.

• Sponges, Cnidarians, Nematodes, and Echinoderms: These organisms lack specialized excretory structures and eliminate waste through diffusion

Respiration: Concepts and Types

There are two types of respiration:

• A) Cellular or Internal Respiration: This is the use of oxygen by cells. It involves oxidizing complex organic molecules to obtain energy. This process produces CO2 and water as byproducts. Cellular respiration occurs in the mitochondria of the cell.
• B) External Respiration: This is the intake of oxygen and the output of carbon dioxide from the body. It occurs due to gas exchange across specialized respiratory surfaces. These surfaces must be very thin to allow for gas passage. They must also be wet, as gases dissolve in liquid before crossing. These surfaces are typically coated with a network of blood capillaries to facilitate the entry of oxygen and the exit of carbon dioxide.

Respiratory System

This system oxygenates the blood and removes carbon dioxide. It consists of the lungs and airways.

Components of the Respiratory System

• Nostrils: Two cavities that warm and humidify the air.
• Pharynx: Common tube leading to the larynx.
• Larynx: Contains the vocal cords.
• Trachea: Carries air to the lungs.
• Lungs: Facilitate gas exchange.
• Bronchi: Two conduits that branch into smaller bronchioles, eventually forming pulmonary alveoli.

Oxygen and carbon dioxide exchange occurs in the pulmonary alveoli by diffusion, moving from areas of high concentration to low concentration.

The Internal Environment

The fluids surrounding the cells of an organism provide nutrients and oxygen to the cells and remove waste products. These fluids consist of:... Continue reading "Respiratory and Circulatory Systems in the Human Body" »

Linnean Binomial Nomenclature

Linne-binomial nomenclature (genus-species) in the animal kingdom: chordate phylum, class, mammals, primate order, family Hominidae, genus Homo, Homo sapiens species.

Arthropods

3 main groups of animals: arthropods: exoskeleton made of chitin, articulated appendages. Insects are an example.

Mollusks

Mollusks: shell, visceral mass, and mantle body (head and foot), e.g., snails.

Chordates

Chordates: Notochord and cephalization. Includes vertebrates: fish and tetrapods (amphibians, birds, mammals).

Animal Nutrition Strategies

• Filter feeders: Consume organic particles or organisms in suspension (e.g., zebra mussels).
• Substrate feeders: Live permanently in their food source (e.g., earthworms).
• Fluid feeders: Feed exclusively on

What is Nutrition?

Nutrition is the set of processes by which the body obtains the substances it needs to live. It involves several stages:

• Collection of nutrients through digestion.
• Collection of oxygen through breathing.
• Distribution of nutrients and oxygen through the bloodstream.
• Elimination of waste through excretion and expulsion of carbon dioxide in the breath.

What is Digestion?

Digestion is the process by which foods are broken down into simple substances that can be used by the body. It has these phases:

• Digestion
• Absorption
• Waste Removal

Apparatus Involved in Nutrition

The digestive, respiratory, circulatory, and excretory systems are involved.

Parts of Dentition

Molars, canines, and incisors.

Digestive Tube

It is a muscular tube of different thicknesses... Continue reading "Human Nutrition, Digestion, and Body Systems" »

Mollusks

Triploblasty, coelomates, not segmented. Bilateral symmetry. Soft body (head, visceral mass, foot). Limestone shell. Complete digestive tube (mouth-anus). Radula (in most). Open circulatory system (closed in cephalopods). Excretory system: 1 or 2 metanephridia. Ganglionic nervous system. Asexual or larval reproduction.

• Bivalves: Mussels
• Gastropods: Snails
• Cephalopods: Cuttlefish

Annelida

Triploblasty, coelomates. Bilateral symmetry. Elongated cylindrical body with rings or metamerism. Closed circulatory system. Ganglionic nervous system. Cutaneous respiration. Excretory system: metanephridia. Sexes separate or hermaphrodites. With or without a larval stage.

• Polychaetes: Marine worms
• Oligochaeta: Earthworms
• Hirudinea: Leeches

Arthropods

Triploblasty,... Continue reading "Animal Kingdom Classification: A Comprehensive Guide" »

Cellular Immune Response

The cellular immune response occurs against: microorganisms with intracellular growth and development (bacteria, fungi, viruses, protozoa); cells that are foreign to an organism from another individual (e.g., transplanted organs); and tumor cells. This response involves cytotoxic T cells and helper T cells, which collaborate with antigen-presenting macrophages.

Activation Process

Recognition of Antigen: T lymphocytes recognize antigens only when they are bound to MHC molecules on cell surfaces. When a macrophage detects an extracellular antigen, it activates, phagocytoses the antigen, and processes its proteins into linear peptides. These peptides bind to MHC class II molecules, which are then transported to the macrophage... Continue reading "Cellular and Humoral Immune Responses: Mechanisms & Activation" »

Medications by System

Nervous System Medications

Adrenaline (SNA): Used in cases of asthma, allergies, and premature births (fenoterol). Also used in Parkinson's disease (dopamine) and inhibition of milk secretion (bromocriptine). Dopamine increases blood pressure.

• Parasympathetic Cholinergic Drugs: Produce parasympathetic stimuli.
• Acetylcholine: Causes vasodilation in the heart.
• Indirect Cholinergics: Prevent acetylcholine from being metabolized (e.g., Physostigmine, Neostigmine). Used in glaucoma, crosses the blood-brain barrier (BBB), and can be lethal in high doses.
• Anticholinergics: Block the effects of acetylcholine (e.g., Atropine, Scopolamine).

Respiratory System Medications

Most commonly used drugs include oxygen and cough modifiers. They... Continue reading "Medications: Nervous, Respiratory, Circulatory & Digestive Systems" »

Primary Meristem

Located at the tips of juvenile plant organs such as roots, shoots, and buds, the primary meristem is responsible for the plant's growth in length.

Root

The root has several distinct parts: the suberized zone, the zone of absorption, the growth area, and the root cap.

The growth zone, located near the root tip, contains meristematic tissue. This tissue can have one, two, or three meristematic cells. If there is one cell, it gives rise to all other cells. If there are three cells, they multiply and differentiate into the root cap and epidermis (lower cells), the cortex (middle cells), and the vascular cylinder (upper cells).

Shoot

Shoots do not grow in the opposite direction of roots. Shoots have nodes, internodes, and buds.

Buds... Continue reading "Plant Growth and Anatomy: Meristems, Tissues, and Structures" »

Catabolic and Anabolic Metabolism

Catabolic metabolism is oxidized when it loses electrons. It is a set of molecular processes that transform complex molecules into simpler ones. The energy molecule ATP stores energy. Energy is released during the oxidation of molecules, especially if O₂ is the ultimate acceptor (aerobic) or if another acceptor is used (anaerobic). Fermentation is the incomplete oxidation of energy molecules. For example, glucose activates Bacillus, and the initial product in the muscles is lactic acid. Alcohol fermentation starts with glucose in yeast, and the final product is ethyl alcohol. Putrefaction of proteins into simpler molecules is performed by some organisms.

Anabolism is a set of reduction reactions in which it is... Continue reading "Cellular Metabolism and Biodiversity: From Molecules to Ecosystems" »