Notes, summaries, assignments, exams, and exercises for Biology for Secondary education

The Nervous System

Cranial Nerves

Twelve pairs of cranial nerves enter and exit the brain, comprising sensory, motor, and mixed types. They innervate the head, upper torso, and some internal organs. Some cranial nerves are associated with the autonomic nervous system. Along their pathways, ganglia—groups of neuronal cell bodies—can be observed.

Spinal Nerves

Thirty-one pairs of mixed spinal nerves emerge from the spinal cord. Each nerve originates as two distinct roots—dorsal and ventral—which merge to form a single nerve cord. Sensory neurons enter the spinal cord through the dorsal root, while motor neurons exit through the ventral root.

The Autonomic Nervous System

The autonomic nervous system (ANS) regulates involuntary bodily functions....

Prokaryotes and Eukaryotes

Prokaryotes are small, simple cells with their genetic material dispersed throughout the cytoplasm. Eukaryotes are larger, more complex cells with their genetic material contained within a structure called the nucleus, separated from the cytoplasm by a membrane called the nuclear membrane.

• Animal Cell: Found in protozoa and animals.
• Plant Cell: Found in algae and plants.

Photosynthesis

Photosynthesis is the process by which organisms synthesize energy-rich organic molecules, such as glucose, from inorganic substances lacking energy. Sunlight provides the necessary energy. Photosynthesis occurs in leaves and green stems and takes place within chloroplasts.

Formula: H₂O + CO₂ + sunlight = Mineral salts = Glucose + O₂

Cellular

Genetic Material

Genetic information is stored in the DNA molecule and is composed of three elements:

• Silica
• A sugar phosphate group
• A nitrogenous base

Chromosome

Hereditary information for each individual is stored in the DNA. This is called the genome, and the protein formed by it is called chromatin.

Genes

A gene is the unit of living legacy and consists of a linear sequence of nucleotides in the DNA molecule.

Homologous Chromosome

In somatic cells, each chromosome has a companion, which constitutes a pair of homologous chromosomes.

Mutation

A mutation is an alteration or change of genetic information in a living being. Therefore, it will produce a change of features spontaneously and can be transmitted or inherited by the offspring.

Genetic Mutation

A...

Homeostasis and the Respiratory System

Homeostasis refers to the actions performed by the body to maintain a stable internal environment. The respiratory system plays a crucial role in this process.

Key Components of the Respiratory System

• Mucus: Contains water and lysozyme, an enzyme that kills bacteria.
• Trachea: A tube that carries air into the lungs, branching into bronchi and bronchioles.
• Diaphragm: A muscle that separates the chest from the abdominal cavity.
• Ribs: Protect the lungs, which have a spongy structure.

The trachea, bronchi, and bronchioles share similar anatomical characteristics. The trachea is horseshoe-shaped and located behind the liver.

Functions of the Respiratory System

• Gas exchange: The primary function, involving the intake

Fundamental Concepts in Ecology

Ecology and Ecosystem Definitions

Ecology: The study that examines the relationships between living organisms and their physical environment.

Ecosystem: A community of living organisms residing in a specific physical environment, including the relationships between them and that environment.

Ecosphere: Consists of all terrestrial ecosystems.

Biosphere: The set of all living beings on the planet.

Types and Components of Ecosystems

Ecosystems are composed of two main types of components: the Biocenosis (living part) and the Biotope (non-living part).

The Biotope (Abiotic Environment)

The Biotope is the physical environment or place where ecosystem creatures live. It is defined by environmental conditions. Key elements of...

Classification of Nerves

Classification of Nerves by Origin

Nerves can be classified based on their origin (where they exit the central nervous system):

• Cranial Nerves: Nerves exiting the brain. They are responsible for transmitting information regarding sight, hearing, smell, chewing, speech, and other vital functions.
• Spinal Nerves: Nerves exiting the spinal cord. They manage the transmission of information to control internal organs such as the heart, lungs, liver, kidneys, and so on.

Functional Classification of Nerves

According to their function, nerves can be classified as:

• Sensory (Afferent) Nerves: Receive the sensations perceived by receptor organs and transmit them to the Central Nervous System (CNS).
• Motor (Efferent) Nerves: Transmit impulses

Methods for Studying Cellular Composition and Function

Biochemical Methods: To understand the composition and function of cellular structures.

• Cell Fractionation: Homogenization and deep freezing.
• Chromatography and Electrophoresis: Used to separate macromolecules.

Isotopic Methods: Incorporating radioactive isotopes into molecules to track their evolution within the cell, followed by autoradiography. Fluorescent markers are also used.

Cytosol and Cytoplasmic Inclusions

Cytosol: The internal liquid medium composed of water, salts, organic molecules, and macromolecules.

Cytoplasmic Inclusions: Accumulations of substances in eukaryotic and prokaryotic cells. Functions include reserve storage (e.g., glycogen and fat in animal cells, vegetable oils and...

Fertilization Process

Ovulation occurs about fourteen days before menstruation. The egg released from the Graafian follicle is propelled along the fallopian tube to the uterus, taking over a week for this journey.

The egg can be fertilized for only 24 hours after ovulation while traveling along the fallopian tube.

Intercourse, or the sexual act, is the introduction of the penis into the vagina. At ejaculation, sperm are released inside the vagina.

Unlike the egg, sperm are very fast. They ascend through the vagina, traverse the cervix and uterus, and reach both fallopian tubes in a few hours. They can also survive for three to five days, so if intercourse occurs in the days before ovulation, the probability of pregnancy is very high.

If the egg...

Puberty: Hormonal Changes

Boys: Sperm production, increased bone thickness and muscle mass, voice deepening, beard growth, and the appearance of pubic and axillary hair.

Girls: First menstruation, breast growth, widened hips, and the appearance of pubic and axillary hair.

Female Reproductive System

Ovaries, Fallopian tubes, uterus, vagina, clitoris, labia majora, and labia minora.

Male Reproductive System

Testes, prostate, urethra, epididymis, vas deferens, seminal vesicles, penis, and scrotum.

Key Definitions in Human Development

• Embryo: The second phase of zygote development occurs when it attaches to the endometrium.
• Fetus: The third stage of embryonic development, starting in the second trimester.
• Nidation: The moment when the zygote attaches to

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