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

Nutrients and Cellular Function

Nutrients are the raw materials from which cells produce their own components. They allow the body to replenish lost components, grow, and produce new cells. Furthermore, nutrients provide the fuel cells require for energy to perform their essential functions.

Balanced Diet Composition

A balanced diet should ideally consist of:

• Carbohydrates: 55% of energy intake
• Lipids: 30% of energy intake
• Proteins: 15% of energy intake

Basal Metabolism and Energy Needs

Energy requirements depend on activity levels, age, sex, and environmental temperature. Basal metabolic formulas are as follows:

• Women: (7.4 x weight in kg) + (428 x height in meters) + 572
• Men: (16.6 x weight in kg) + (77 x height in meters) + 572

An adult with an appropriate...

Punctuated Equilibrium

The fossil record, while incomplete, reveals periods of stability punctuated by the sudden appearance of new species. These species often remain unchanged for extended periods before disappearing abruptly. In 1972, Gould and Eldredge proposed punctuated equilibrium to explain these sudden shifts, suggesting that not all evolutionary changes are gradual. Periods of stasis, where species remain unchanged, alternate with short bursts of rapid change (speciation), during which new species emerge from existing ones.

Gradualism vs. Punctuated Equilibrium

Gradualism

Species evolve along a single lineage, transforming slowly and continuously through small changes over long periods. The entire population transforms, not just isolated...

Tissues represent an organizational level above the cellular level. They are a set of similar cells that specialize in a particular function and are classified into four basic groups: epithelial, connective, muscular, and nervous.

1. Epithelial Tissue

Formed by epithelia, epithelial tissue has two main types based on its features:

• Epithelial tissue lining: Lines the body's surface and internal body cavities. This is further divided into two types:
  • Simple: Just one layer of cells.
  • Stratified: Many layers of cells.
• Glandular epithelial tissue: Builds secreting cells that are exchanged or clustered epithelial cells to form glands.

Examples of Epithelial Tissue:

• Simple squamous epithelium: Flattened cells, wider than they are high. Lines the heart and

Cell Structures and Their Functions

The cell is composed of various structures, each with specific functions vital to its survival and operation. Here's a breakdown of key cell components:

Cell Membrane

The cell membrane is a lipid bilayer that protects the cell, regulates the passage of materials, and helps maintain cell shape.

Endoplasmic Reticulum (ER)

The endoplasmic reticulum is a network of internal membranes forming tubes and vesicles that transport materials. There are two types:

• Smooth ER: Lacks ribosomes; produces steroids and aids impulse conduction in muscle cells.
• Rough ER: Contains ribosomes; synthesizes and transports proteins.

Ribosomes

Ribosomes are granules made of RNA and proteins (not membrane-bound). They synthesize proteins.

Golgi

DNA, Genes, and Proteins: The Blueprint of Life

DNA is the key to inheritance. Its structure allows it to carry a code of instructions that directs and regulates the synthesis of enzymes and other specific proteins. As discussed in Chapter 1, proteins consist of polypeptides, and a polypeptide is composed of amino acids linked together by peptide bonds. Natural proteins are formed by 20 different amino acids.

The piece of DNA whose function is encoding the amino acid sequence of a polypeptide chain is called a gene. Genes are hereditary units found in the chromosomes of the cell nucleus. They are passed from parents to children, empowering common traits that identify its kind.

Protein Synthesis

Transcription

The information in the DNA molecule is...

History of Cell Theory

Early Microscopy and Discoveries

• 1591 Zacharias Janssen: The first person to manufacture a microscope. By coupling a convex lens with another in a tube, he created a device that magnified objects.
• 1660-1661 Marcello Malpighi: He discovered that arteries and veins were connected by capillaries, which later led to the discovery of red blood cells.
• 1665 Robert Hooke: He examined thin slices of cork and observed numerous empty cavities resembling the cells of a honeycomb, separated by walls. He named these cavities "cells" due to their similarity to honeycomb structures.
• 1671-1677 Anton Van Leeuwenhoek: He was the first in history to observe free-living cells, magnifying images up to 300 times using a microscope he manufactured

DNA, Genetic Code, and Translation

Classical genetics is devoted to studying the mechanisms of heredity. In the 1930s, questions were raised, and geneticists began to explore the nature of the gene. Even earlier, there were no doubts about the existence of genes.

The Discovery of DNA Structure

The first chemical analysis of genetic material showed that the eukaryotic chromosome consists of deoxyribonucleic acid (DNA) and proteins. Both DNA and proteins were good candidates for the molecule that carries the genetic material.

In 1953, James Watson and Francis Crick gathered data from different studies on DNA. They postulated a model for DNA structure and were able to deduce that DNA is a double helix, an intertwined and long structure. An essential...

Geological Ages

Precambrian (4600-1000 million years ago)

• The most extensive
• Evolution at the cellular level
• Domain prokaryotes
• Emergence of Eukaryotes
• Cell organisms of greater size and complexity
• First multicellular organisms

Paleozoic (544 to 245 million years ago)

• Appearance of life forms that gave rise to the current lifestyles
• Mainly aquatic organisms
• Invasion of terrestrial environments, first plants (vascular)
• Emergence of arthropods

Mesozoic (245-65 million years ago)

• Pangea begins to split, affecting the climate
• Emergence and domain of dinosaurs (Jurassic); origin of mammals
• Arise flowering plants (angiosperms) and Conifers (Araucaria pines)
• At the end of the Age, massive extinction of marine and some terrestrial species (dinosaurs)

Cenozoic (65 million...

Levels of Biological Organization

The human body is organized into several levels of complexity:

• Atoms: These are chemical elements that form living beings, such as Carbon, Hydrogen, and Oxygen.
• Molecules: These are the components from which cells build their own structures, including Proteins, Carbohydrates, and Lipids.
• Cell: The basic unit of structure and functioning within the human body.
• Tissue: A set of cells that specialize and associate to accomplish a specific function.
• Body (Organ): These are formed by different tissues and are assigned a specific function.
• Apparatus or System: A partnership or relationship of organs working together to perform a vital role.

Key Components and Parts of the Cell

The cell contains various organelles and structures...

Essential Biological Molecules

Carbohydrates and Energy

Carbohydrates are our greatest source of energy. Some have structural functions and backup functions; carbohydrates are also called hydrates of carbon.

Lipids and Functional Roles

Lipids are substances with a unique chemical composition. These substances perform multiple functions, both energetic and functional.

Proteins and Amino Acids

Proteins are made up of amino acids; there are 20 types that combine to form proteins. Proteins perform many functions in our body, such as:

• Structural function
• Hormonal regulation (regulating blood sugar levels)
• Transport (carrying O2 in the blood)
• Defense
• Contractile proteins
• Enzymes: Involved in all chemical reactions in the body.

Nucleic Acids: DNA and RNA

Nucleic