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

1. Human Beings and Health

The World Health Organization (WHO) defines health as 'the complete physical, mental and social well-being, not only the absence of disease'.

The Environment

Healthy surroundings should be free of biological, physical or chemical elements that are harmful to your health.

Personal Characteristics

Genetic factors, age and gender predispose people to suffer from certain types of illnesses.

Lifestyle

Healthy habits and lifestyles are very important for staying healthy.

Healthcare

It is essential to have an efficient healthcare system to guarantee public health.

Vital Signs

Vital signs are physiological parameters that inform us of our state of health or the evolution.

Cause -> Organic Alteration -> Symptoms and Signs ->

Darwin’s Theory of Evolution

Darwin’s theory posits that the world is not static; it is constantly changing. The process of change is gradual and continuous, and similar organisms are related and descended from a common ancestor. Evolutionary change is the result of natural selection.

The Mechanism of Natural Selection

Darwin explained natural selection through the following principles:

• In any population, individuals have variations, which are produced randomly.
• In the fight for existence, only the fittest survive.

Darwin’s explanation for this fact is that, when resources are limited, individuals in a population must compete for them. In this fight for existence, only those with favourable variants survive, as they are best adapted to the...

The Nervous System: Stimuli, Response, and Effectors

Stimuli are detected by the sensory organs: sight, touch, hearing, taste, and smell.

The information is transmitted, and a response is created by the nervous system. This response is transmitted to the effector organs:

• Locomotor system: Responsible for movement.
• Endocrine system: Responsible for hormone release.

The Neuron: Anatomical and Physiological Unit

The nervous system's anatomical and physiological unit is the neuron.

Supporting Cells

• Schwann cells: They isolate the axon, ensuring that the nerve impulse is transmitted faster.

Types of Neurons Based on Function

• Sensory neurons: Transmit information from the receptors to the nerve centers.
• Motor neurons: Transmit signals from the nerve centers

Sensory Receptors and Human Senses

Types of Sensory Receptors

• Chemoreceptors: Located in the nose and tongue, sensitive to chemical substances.
• Mechanoreceptors: Located in the skin and ears, sensitive to physical stimuli, such as touch.
• Photoreceptors: Located in the retina, sensitive to light.
• Thermoreceptors: Located in the skin, sensitive to temperature changes.
• Nociceptors: Located throughout the body, sensitive to stimuli that cause pain.

The Five Sense Organs

• Sense of Sight (Eyes): Detected by the eyes. Each eye consists of the eyeball and accessory structures.
• Sense of Touch (Skin): The skin has two layers: the epidermis (the outer layer) and the dermis (the inner layer).
• Sense of Smell (Nose): Enables the body to detect chemical molecules in

Four Types of Animal Tissues

1. Epithelial Tissue

• Squamous:
  • Simple: One cell thick; forms solid layers of cells.
  • Stratified: Multiple layers; forms the epidermis.
• Cuboidal:
  • Simple: One cell thick, roughly cube-shaped. Lines ducts where absorption and secretory activities take place.
• Columnar:
  • Simple: One cell thick, column-shaped. Lines the digestive tract.
  • Pseudostratified: Gives the appearance of more than one layer of columnar epithelial organs.

2. Connective Tissue

• Adipose: Honeycomb or chicken wire appearance. Stores energy, insulates, and supports and protects organs.
• Dense: Forms ligaments and the outer protective covering for bone.
• Bone: Tree ring-like appearance. Supports and protects, stores minerals and fat, and aids in blood cell production.

Key Concepts in Evolution

Species: A set of individuals that can reproduce with each other and create fertile offspring.

Speciation: A process driven by several factors:

• Natural selection: Natural selection favors some individuals over others.
• Genetic isolation: Members of two different populations within the same species can no longer reproduce with the other population.
• Gradual differentiation: After isolation, populations become increasingly different.
• Speciation: Over time, genetic changes produce such significant differences that it's no longer possible for two populations to produce fertile offspring.

Human Ancestors

• Australopithecus (6 million years ago): The first hominid, walked upright.
• Homo habilis (2.5 million years ago): Used rudimentary

1. Central Nervous System

• Brain: Protected by the cranium and divided into:
  • Cerebrum: Interprets information from sense organs, controls language, memory, and thought. It produces voluntary responses.
  • Cerebellum: Controls basic movements and helps maintain balance.
  • Brain Stem: Controls involuntary movements.
• Spinal Cord: Protected by the vertebral column. It sends signals to and from the brain and facilitates involuntary responses or reflexes.

2. Autonomic Nervous System

• Sympathetic: Stimulates organs in case of emergency.
• Parasympathetic: Maintains the functioning of the body.

3. Neurons

Neurons are specialized cells of the nervous system that transmit nerve impulses.

4. Synaptic Transmission

The nerve impulse is transmitted from one neuron to another...

Essential Genetics and Cell Biology Vocabulary

• Alleles: Different forms of a gene.
• Cell Cycle: The series of events that take place in a cell leading to its division and duplication (replication) that produces two daughter cells.
• Chromosome: A structure of DNA, protein, and RNA found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements, and other nucleotide sequences.
• Codominance: A phenomenon in which a single gene has more than one dominant allele.
• Cytokinesis: The process in which the cytoplasm of a single eukaryotic cell is divided to form two daughter cells.
• Dominant Allele: A genetic trait that always shows or is expressed.
• Fertilization: The fusion of gametes to initiate the development of a new individual

Sexual Reproduction in Plants

Understanding the Process

Sexual reproduction is typical of plants with seeds. The reproductive organs are inside the flower, where gametes are produced. After pollination, fertilization and the formation of embryos and seeds take place. Pollination is the transfer of pollen grains from the anther of the stamen to the stigma of the pistil.

Flower Structure

A flower is the reproductive unit of a plant. It consists of the following parts:

• Calyx: Green sepals which protect the developing flower.
• Corolla: Brightly colored petals.
• Stamen: The male reproductive organ of the flower. It consists of a stalk (filament) and sacs (anthers), where pollen is stored.
• Pistil: The female reproductive organ of the flower. It consists of

Sensory Receptors

The receptors are classified as:

• Chemoreceptors: Sensitive to chemicals.
• Mechanoreceptors: Sensitive to mechanical stimuli.
• Photoreceptors: Light-sensitive.
• Thermoreceptors: Sensitive to temperature variations.
• Nociceptors: Sensitive to internal pressures.

Sensory Receptors:

• Internal receptors: Report the condition of the body, e.g., hunger, thirst, need to urinate.
• External receptors: Collect stimuli from outside, e.g., light, sound, temperature.

The Senses of Touch, Smell, and Taste

Touch

• Epidermis: Epithelial tissue formed by several layers of cells. These cells contain keratin, a protein whose function is to waterproof the skin.
• Dermis: Formed by connective tissue, which provides elasticity to the skin. The dermis contains many blood