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

Energy and Matter Dynamics

The flow of energy: It is an open process. The cycle of matter: It is a closed cyclic process.

Trophic Parameters

• Biomass: The amount of organic matter accumulated in an individual, a trophic level, or an ecosystem population.
• Production: The amount of energy stored as biomass in each trophic level per unit of time.
• Productivity: Expresses the profitability and status of a trophic level by linking production with biomass.

Biogeochemical Cycles

These are specific elements that perform chemical cycles through the biocenosis and biotope of an ecosystem.

Ecological Succession

The sequence of changes that occur in an ecosystem as a result of its internal dynamics.

General Changes in Succession

• Increased species diversity.
• Increased

Virus Characteristics

Viruses are unique pathogens, not classified as living organisms. A virus particle, a submicroscopic infectious agent, has a single nucleic acid type (DNA or RNA) within a protein coat called the viral capsid, forming the nucleocapsid.

Some viruses have a lipid-protein envelope. The capsid's protein organization determines the virus's shape, usually helical or polyhedral. Viruses are genetic elements in transit, switching between extracellular and intracellular states.

Extracellular Phase (Virion)

In the extracellular phase, the virion is metabolically inert. It carries viral genetic material from one cell to another.

Intracellular Phase

Inside a cell, the virus replicates, using the cell's machinery to synthesize new viral...

Cranial Bones

Frontal Bone

The Frontal Bone is an unpaired, flat bone located on the top and front of the head. It forms the "roof" of the orbits and the root of the nose.

Sphenoid Bone

The Sphenoid Bone is an unpaired bone located in the anterior base of the skull. It has a body and six extensions: two greater wings, two lesser wings, and two pterygoid processes. Through these, it is inserted like a wedge between the other bones of the skull.

Occipital Bone

The Occipital Bone is an unpaired bone located posteroinferiorly in the skull. Its lowest part, which forms part of the skull base, features the foramen magnum. This opening connects the cranial cavity, housing the brain, to the spinal canal, which contains the spinal cord, thus allowing the...

Neuronal Structure: External Anatomy

1. The Soma (Cell Body)

The soma serves as the metabolic center of the neuron. It performs three primary functions:

• Maintenance: Preserves anatomical and functional integrity; contains the nucleus and most organelles (excluding centrioles).
• Structural Origin: Acts as the site where cellular extensions originate.
• Synthesis: Produces chemical messengers, specifically neurotransmitters.

2. Neuronal Extensions

• Axon: A long extension that carries impulses away from the soma, terminating in a branching structure known as the telodendron. Length varies significantly.
• Dendrites: Short extensions that receive and transmit impulses toward the soma. Most neurons possess these, with the exception of monopolar structures.

Internal

The Biosphere and Characteristics of Life

The biosphere is the layer of Earth where living beings exist, encompassing land and aquatic habitats. It is not continuous, making its limits difficult to specify, yet it exhibits both diversity and uniformity.

Features of Living Beings

Living beings are characterized by the following:

• They are made of biomolecules.
• They are highly organized structures.
• They perform vital functions (reproduction, nutrition, and relationship/response to stimuli).

Molecular Composition

Organic Molecules: These are exclusive energy sources and storage units.

Inorganic Molecules: These are found in the physical environment and do not provide energy.

Vital Functions

Nutrition

Living beings exchange matter and energy with their environment....

Limiting Factors in Aquatic Ecosystems

In aquatic ecosystems, the following are the limiting factors:

Salinity

• Freshwater, as in rivers.
• Seawater, as in seas and oceans.
• Brackish water, as in marshes.

Living things are adapted to the salinity value of their aquatic environment. Very few species, such as salmon, can live in all of them.

Light Penetration

Filtered light entering the water decreases in intensity with depth. There are three zones:

• Photic zone: Sufficient light for photosynthesis.
• Oligophotic zone: Low light levels.
• Aphotic zone: Total darkness.

Temperature

Temperature determines the amount of dissolved oxygen; less oxygen at higher temperatures. Changes in ocean temperature are responsible for ocean currents that distribute nutrients.

Biotic

Understanding Excretion

Excretion is the process of eliminating substances produced by our body that are toxic due to cellular activity.

The Urinary System Components

• Kidneys: The organs responsible for cleaning the blood of waste substances.
• Ureters: The ducts connecting the kidneys with the bladder.
• Urinary Bladder: A hollow organ that serves to accumulate urine. Its muscular walls dilate as it fills. At the bottom, a sphincter opens and closes voluntarily to release urine.
• Urethra: A tube that leads urine from the bladder to the outside during urination.

Anatomy of the Kidneys

The kidneys are dark red, bean-shaped organs measuring about 10 cm, located on both sides of the spinal column.

Internal Structure

• Cortex (Bark): The outermost layer, dark in

Genetics: Basic Concepts

• Locus: The position of a gene on a chromosome.
• Alleles: Alternative forms that a single gene can have.
• Homozygote: An individual who possesses two identical alleles for a specific character.
• Heterozygote: An individual who possesses two different alleles for a specific character.
• Genotype: The set of genes belonging to an organism.
• Phenotype: The observable characters within an organism's body.

Mendel's Laws

1. 1st Law: Law of Uniformity. In the crossing of two pure lines, the resulting offspring are identical to each other.
2. 2nd Law: Law of Segregation. When crossing the F1 hybrids obtained previously, the two alleles for a character separate during the formation of gametes.
3. 3rd Law: Law of Independent Assortment. Alleles for different

The Human Skin and Sensory Receptors

The skin consists of two layers: the epidermis (the superficial layer) and the dermis (the deep layer). The epidermis is an epithelial tissue made of several layers. Its cells are dead and impregnated with substances like keratin; these cells continually divide to renew those that are lost. In this layer, melanocytes are also found, which are cells containing a pigment called melanin that gives the skin its color.

Touch Receptors

Free nerve endings are located throughout the skin:

• Meissner's corpuscles: Sensitive to light pressure and contact.
• Pacinian corpuscles: Sensitive to heavy pressure and vibration.
• Ruffini endings: Sensitive to touch, pressure, and heat sensations.
• Krause corpuscles: Sensitive to a decrease

The Human Excretory System

To carry out their functions, cells perform chemical reactions called cellular metabolism. During this process, waste substances are produced, the main ones being:

• Carbon Dioxide: It originates from the metabolic reactions that produce energy.
• Urea and Uric Acid: These proceed from the destruction of proteins and nucleic acids.
• Toxic Ingested Substances: Various harmful substances taken into the body.

Anatomy of the Kidney

The kidneys are two bean-shaped organs located in the back of the abdomen. Each kidney is composed of an outer part called the renal cortex and an internal cavity called the renal pelvis.

Each kidney is made up of more than one million nephrons, which are small tubes closed at one end and surrounded by...