From First Cells to Modern Humans: Life’s Evolution
1. The Origin of Life
Spontaneous Generation Theory
- Aristotle (384–322 BC): Life can arise from nonliving matter (e.g., frogs from mud, mice from grain).
- Theory persisted until the 17th century.
Refutation of Spontaneous Generation
- Francesco Redi (1626–1697): Experiment with meat and maggots.
- Louis Pasteur (1822–1895): Swan-neck flask experiment disproved spontaneous generation.
Panspermia Hypothesis
- Anaxagoras (500–428 BC): Life exists throughout the universe and spreads via space.
- Svante Arrhenius
Understanding the Human Heart and Blood Vessels
The Heart’s Chambers and Valves
The heart, located between the lungs and slightly to the left within the chest cavity, comprises four chambers surrounded by thick muscular walls. The lower portion of the heart is divided into two chambers: the left and right ventricles, responsible for expelling blood. These ventricles are separated by a wall known as the intraventricular septum.
The upper portion of the heart consists of the right and left atria, which receive blood entering the heart. The atria
Classification and Diversity of Living Organisms
Concept and Use of a Classificatory System
Binomial System
A system of naming species in which the scientific name of an organism is made up of two parts showing the genus (starting with a capital letter) and species (starting with a lower case letter), written in italics when printed (therefore underlined when handwritten) e.g. Homo sapiens
Classes of Animals
Class Fish
Moist skin, fins, gills, scaly skin, poikilothermic (cold-blooded), lays eggs with jelly coat.
Class Amphibia
Poikilothermic (cold-blooded)
Read MoreHuman Body Systems: Functions and Diseases
Human Body Systems: Functions & Diseases
Apparatus and Their Functions
| Apparatus | Function |
|---|---|
| Digestive | Responsible for digesting food and converting it into simpler substances (nutrients) (digestion). |
| Respiratory | Provides for the exchange of gases, i.e., oxygen intake and carbon dioxide removal. |
| Circulatory | Transports oxygen and substances throughout the body via the blood. |
| Excretory | Removes waste substances carried by the blood. |
Anatomy of the Digestive System
Digestive Tract: Mouth, pharynx, esophagus, stomach,
Read MoreDNA Replication, Transcription, and Translation Explained
DNA Replication, Transcription, and Translation
Understandings:
The replication of DNA is semi-conservative and depends on complementary base pairing.
- Complementary base pairing ensures two identical DNA strands are formed after replication is complete.
- In replication, the original strands are used as templates, allowing complementary bases to be added according to base pairing rules.
- DNA replication is semi-conservative, meaning the new DNA that is created consists of one old strand (template) and one
Competitive and Non-Competitive Enzyme Inhibitors
Competitive Inhibitors
These are structurally similar to the substrate of the enzyme and bind to the active site. This means that when a competitive inhibitor binds to the active site of an enzyme, it prevents the substrate from binding. Only once the inhibitor has been released can the substrate bind. The inhibitor is called a competitive inhibitor as it competes with the substrate for the active site.
The effects of a competitive inhibitor can be reduced by increasing the substrate concentration.
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