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

Eukaryotic Cell Organelles: Structure and Function

Cell Membrane

All cells are covered by the cell membrane. It supports and protects the cell, forming a barrier between the cell and its environment. It also controls the movement of materials into and out of the cell, helping to maintain homeostasis.

Cell Wall

The Cell Wall is found only in plant cells and is primarily made of cellulose. Its functions include:

• Providing structural support and protection.
• Allowing the diffusion of gases into and out of the cell.

The strength provided by the cell walls enables plants, such as trees, to stand tall and grow against gravity.

Nucleus

The Nucleus is a spherical, membrane-bound organelle. It directs most of the cell's activities and contains the cell's hereditary

Heterotrophic Invertebrates

Heterotrophic organisms cannot produce their own food. They ingest their food. There are different types of symmetry.

Symmetry in Organisms

Symmetry is when one shape becomes exactly like another at any position. Symmetry can be divided into three groups:

• Asymmetrical: Organisms that lack symmetry and therefore are sessile, having no definite shape.
• Radially Symmetrical: Organisms that can be divided into similar halves by passing a plane at any angle along a central axis.
• Bilaterally Symmetrical: A body plan in which the left and right sides of the organism can be divided into approximate mirror images of each other.

Invertebrates

Invertebrates are organisms that do not have a backbone. 98% of animals are invertebrates....

Cellular Biology

Synthesis of Cell Theory

• Each living organism is made up of one or more cells (structural unit).
• The smallest living organisms are single cells, and cells are structural units of multicellular organisms.
• All cells come from preexisting cells (the source drive).

Forms of bacteria:

• Bacilli
• Coccobacilli
• Vibrio
• Spirochetes / Spirilla

Prokaryotic and Eukaryotic Cells

Prokaryotic Cells: Are those that have no internal membranes or an organized nucleus (bacteria).

Eukaryotic Cells: They have internal membranes and an organized nucleus.

Difference Between Animal and Plant Cells

Plasma membrane: Structure that separates the intracellular from the extracellular...

Cellular Functions

Cellular functions are basic units of life and conduct nutrition, relationships, and reproduction. Unicellular cells perform all these functions within a single cell, while multicellular organisms have specialized cells.

• Nutrition: Molecular intake from the external environment provides energy to renew cellular structures. This process inside the cell is known as metabolism.
• Relationships: Cells communicate with the outside environment, adapting to changes and maintaining stability.
• Reproduction: New cells are formed from existing ones. In unicellular organisms, this leads to a new being. In multicellular organisms, it replaces dying cells and increases cell numbers during growth. Cells pass their genetic material to their daughter

Male Reproductive System

• Glands: The seminal vesicles and prostate gland produce substances that are dumped into the vas deferens. These secretions, along with sperm, constitute semen.
• Genital Tracts:
  • Epididymis: A folded tube where spermatozoa are stored.
  • Vas deferens: Tubes leading sperm from the epididymis to the urethra.
  • Urethra: The evacuation duct of the bladder where the vas deferens also flows.
• Penis: A cylindrical cone with an enlarged tip called the glans, covered by a fold of skin called the foreskin.
• Testes: Two organs contained in a bag called the scrotum. They produce sperm and testosterone.

Stages of Labor

• Dilation Phase: Spontaneous contractions of the uterine wall begin. These contractions push the child toward the exit of the uterus,

The Human Digestive System

The digestive process begins in the **mouth**. The first processes are chewing, conducted by teeth (*incisors, canines, molars, and premolars*), and salivation, managed by a muscular organ called the tongue. The **tongue** moves food during chewing and contains **taste buds** for sensing flavor. During salivation, food is broken down by teeth and moistened by **saliva**, a watery secretion produced by the **salivary glands**. Saliva production can be triggered by the sight or smell of food. Saliva contains **mucin**, which gives it viscosity, and enzymes such as **salivary amylase** and **lingual lipase** (which hydrolyzes milk fat).

The ground food and saliva form the **bolus**, which is pushed into the **esophagus*...

Water: Properties and Cycle

Properties of Water

Freshwater: Salinity below 35g/L.

Saltwater (Ocean Water): Salinity over 35g/L.

General Properties: Colorless, odorless, tasteless. Higher density in liquid state than solid state. Universal solvent. High heat capacity. Facilitates many chemical reactions. Exhibits adhesive capacity.

States of Water

• Solid (S)
• Liquid (L)
• Gas (G)

Transitions: S --(fusion)--> L --(vaporization)--> G --(condensation)--> L --(solidification)--> S S --(sublimation)--> G --(inverse sublimation)--> S

Water as a Thermal Regulator

Water's high heat capacity means significant temperature changes require large amounts of energy. This explains why coastal regions experience milder climates compared to inland areas.

The

White Matter:

Formed by neurons' axons, white matter acts as communication cables and the connection between control centers.

Brain:

Part of the central nervous system found within the cranium, the brain weighs 1.4kg and is the largest organ in our body. It serves as the center of integration and consciousness. The brain is organized with grey matter making up the outer surface and white matter in the interior. Cranial nerves emerge directly from the brain, which is part of the peripheral nervous system.

Parts of the Brain:

• Cerebellum:

  The largest part of the brain, consisting of hemispheres, the corpus callosum, the hippocampus, the thalamus, and the hypothalamus.

• Hypothalamus:

  The master gland of the endocrine system, controlling most of its activity.

Food and Nutrients

Food is our primary source of nutrients. But what are nutrients exactly?

Nutrients: The Essentials for Life

NUTRIENTS are biomolecules that our bodies need to sustain vital functions. They are the chemical components of food, acting as the building blocks and energy sources our cells need to survive.

Why We Need Nutrients

Cells require nutrients to fulfill three fundamental requirements:

1. Energetic: Certain nutrients, like lipids and carbohydrates, are broken down in our mitochondria to release energy. This energy powers essential functions such as movement, temperature regulation, and more.
2. Structural: Some nutrients, including proteins, lipids, and mineral salts, serve as the building blocks for various body structures. These structures