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

Operation of the Nephron

Filtration of blood occurs as it passes through the glomerulus. Substances pass into the renal tubule, small molecules but not large molecules or cells. This process forms the primary urine.

Reabsorption of useful substances, such as glucose, amino acids, and over 90% of the water, takes place along the renal tubule.

Secretion of noxious substances, such as urea or some mineral salts, from the capillaries into the renal tubule, continues along the entire duct, so that inside it, concentrated urine is formed. This is drained into a collecting duct, common to many nephrons, which flows into the renal pelvis. As a result of the process, blood from the kidneys, via the renal veins, is cleansed of waste products.

Average Domestic

Interstitial

Chemistry of Life

The universe is mainly composed of Hydrogen (H) and Helium (He). The Earth's crust is composed of Silicon (Si), Iron (Fe), Magnesium (Mg), and carbon (C). Living organisms form organic macromolecules. Oxygen and Hydrogen constitute 68-70% of living matter (Water = H₂O). Nitrogen (N) is part of proteins.

Properties of Living Beings

Living beings are complex materials that can interact with the world around them and reproduce.

Features

• Made mostly of Carbon and H₂O
• Their reactions inside cells are governed by the laws of physics and chemistry.
• They reproduce

Interaction with the Environment

Living beings evolve and react to external or internal stimuli, creating responses through the nervous and endocrine systems (hormones).

Nutrition

Living... Continue reading "Chemical Composition and Functions of Living Beings" »

Skeletons: Types and Functions

Exoskeletons

External systems support proportionally less weight than endoskeletons of the same size, which is why larger animals such as vertebrates have internal skeletal systems.

Key developments in exoskeletons are found among arthropods and some invertebrates, where the exoskeleton forms a shell or outer structure that protects the internal organs.

Given the limitations on animal growth imposed by exoskeletons, species with this feature have evolved various solutions. Most molluscs have calcareous shells that grow along with the animal, maintaining a consistent growth morphology. Other animals, such as arthropods, shed their old exoskeleton to grow, a process known as "molting." The new... Continue reading "Skeletons: Exoskeletons, Endoskeletons, and Hydrostatic Systems" »

Gram Staining: Positive and Negative Bacteria

In bacteria, the cell wall is a determinant of cell shape and has also served as a classification criterion. In 1884, French bacteriologist Christian Gram developed a method to observe bacteria under light microscopy using specific staining. However, not all bacteria are stained with this method, which led to their classification into two groups: Gram-positive bacteria, which retain the stain, and Gram-negative bacteria, which do not retain the stain.

This distinction reflects structural differences in the bacterial cell wall. In Gram-positive bacteria, the wall is mainly composed of peptidoglycan and teichoic acid. In contrast, Gram-negative bacteria have, in addition to peptidoglycan, an outer membrane... Continue reading "Bacterial Basics: Gram Staining, Morphology, and Reproduction" »

Understanding Diet and Nutrition

What is Diet?

Diet: The amount and type of food we consume.

Types of Diets

Balanced Diet: A healthy diet provides the body with the right amount of energy and different types of nutrients.

Mediterranean Diet: This is a balanced diet that combines all foods properly.

Genetically Modified Organisms

GMO Foods: These are produced from organisms that have had genetic material from another living being introduced.

Food Preservation and Additives

Food Preservation Methods

Food can be preserved using chemical and physical methods:

• Heating foods to high temperatures for a few seconds can eliminate a number of bacteria.
• Preservation by cold (refrigeration/freezing).
• Freeze-drying eliminates water from food.
• Chemical preservation uses

Sun Energy and Life

The ecosphere is a hypothetical spherical zone located around any star, such as the Sun, where temperatures and appropriate conditions exist to allow living things to originate and evolve.

What is an Ecosystem?

An ecosystem is a particular area where environmental conditions allow some organisms to develop concretely.

• Biotope: The physical environment in which an ecosystem is stable.
• Biocenosis: All living beings inhabiting a biotope.

Factors of an Ecosystem

They fall into two types:

• Abiotic factors: All environmental factors in an ecosystem.
• Biotic factors: Establishing relationships between living things in an ecosystem.

What Effect do Abiotic Factors Have on Living Beings?

They can be:

• Climatic factors (temperature, rainfall, and

Asexual Reproduction in Animals

This is a reproductive process in which new individuals arise from the somatic cells of a single parent. It is common in less evolved animals.

Budding

This consists of the formation of a multicellular outgrowth (bud) on the parent animal's body. Later, these buds may separate to form an independent adult, or they may remain attached, giving rise to colonies, as seen in corals.

Fragmentation (Excision)

The parent body divides into two or more parts, each capable of regenerating into a new animal. Fragmentation can be:

• Longitudinal: Division occurs parallel to the main body axis.
• Transverse: Division occurs perpendicular to the main body axis.

Strobilation

This is a form of multiple transverse fragmentation found in some... Continue reading "Animal Reproduction: Asexual and Sexual Methods" »

A gene is the carrier of an inherited feature that is passed from generation to generation.

Alleles are possible alternatives for a character. Alleles stand at the same site on two chromosomes in an individual, one from each parent. Alleles are equal when it is said that the individual is homozygous or pure-bred for the character. If different, they are heterozygous or hybrid.

A dominant allele is the character that is always represented (capital letters).

A recessive character emerges only in homozygous individuals (lowercase).

Genotype is the joint of the genes, half from one progenitor and the other half from the other.

Phenotype is the set of characters that manifests externally. This is particular, but the genotype influences the environment.... Continue reading "Understanding Genes, Alleles, and Inheritance" »

Cellular Foundations and Body Tissues

Understanding Cell Components

• Cell Membrane: The thin layer that wraps the cell and separates it from the external environment.
• Cytoplasm: The contents of the cell, excluding the nucleus.
• Nucleus: A structure bounded by a double membrane, traversed by pores that allow substance exchange between the nucleus and the cytoplasm. Contains DNA.

Metabolic Processes

• Catabolism: A set of reactions that break down complex molecules to provide energy for cellular activities.
• Anabolism: A set of reactions that build complex molecules from simpler ones, requiring energy.
• Diffusion: Small molecules like oxygen and carbon dioxide freely pass through the plasma membrane.

Cell Specialization and Organization

• Cell Specialization:

Biotechnology and Genetic Innovations

Biotechnology

A set of techniques that leverage biochemical transformations to improve the performance of certain food processes, create substances with therapeutic activity, or resolve environmental alterations.

Genetic Engineering

Technology involving the manipulation and transfer of DNA from one organism to another, enabling the creation of new lineages of a given species.

Transgenic Organism

Hereditary material that has been modified by inserting a foreign gene or deleting one of its own.

Creating Transgenic Animals

The most commonly used technique is microinjection. It consists of obtaining the fertilized egg of the animal before it splits, and injecting DNA (containing the desired gene) into it.

Stem Cells

Embryonic... Continue reading "Biotechnology, Genetics, and Earth's Vital Systems" »