ICSE 10 Biology Human Evolution Basic

1.0 Theories of Biological Evolution

Evolution is the gradual change in the heritable characteristics of biological populations over successive generations. Two major theories paved the way for our modern understanding.

Lamarckism vs. Darwinism

Feature	Lamarckism	Darwinism
Main Concept	Inheritance of Acquired Characters.	Natural Selection.
Key Idea	Use and Disuse of Organs.	Survival of the Fittest.
Example	Giraffes stretched necks to reach leaves.	Long-necked giraffes survived better.

Darwin's Core Concept

Natural Selection: The process by which organisms with favorable variations survive, reproduce, and pass those traits to the next generation.

⚠️ Exam Note:

Lamarck's theory was eventually disproved because acquired traits (like muscle building or scars) do not affect the DNA of germ cells and therefore cannot be inherited.

2.0 Morphological Evidences

Scientists use structural similarities between different organisms to prove common ancestry. This is a favorite topic for "Identify the odd one out" questions.

Homologous Organs

Organs with same basic structure but different functions.

Example: Forelimbs of a human, wing of a bird, and flipper of a whale.

Evidence of: Divergent Evolution.

Analogous Organs

Organs with different structure but performing same functions.

Example: Wings of a butterfly and wings of a bird.

Evidence of: Convergent Evolution.

Vestigial Organs

These are organs that are non-functional in the possessor but were functional in ancestors.
Examples in Humans: Vermiform Appendix, Wisdom teeth, Pinna muscles, and the Coccyx (tailbone).

3.0 Stages in Human Evolution

Human evolution is characterized by several key anatomical changes: an increase in Cranial Capacity (brain size), the development of Bipedal Locomotion (walking on two legs), and the use of tools.

The Evolutionary Timeline

Stage	Cranial Capacity	Key Characteristics
Australopithecus	450 – 600 cm³	"First ape-man"; bipedal but ape-like face.
Homo habilis	650 – 800 cm³	"Handy man"; first to use chipped stone tools.
Homo erectus	800 – 1100 cm³	"Upright man"; discovered Fire and lived in caves.
Neanderthal Man	1400 – 1450 cm³	Used animal hides; buried their dead.
Cro-Magnon Man	~1600 cm³	Direct ancestor of modern man; cave paintings.
Homo sapiens	1350 – 1500 cm³	Modern Thinking Man; developed agriculture.

Significant Physical Changes in Humans:

• Bipedalism: Upright posture on two legs, freeing the hands for tool use.
• Opposable Thumb: Allows for a "precision grip" to handle tools.
• Binocular Vision: Stereoscopic vision for depth perception.
• Chin: Development of a prominent chin (unique to Homo sapiens).

⚠️ High-Frequency Question:

In the "Chronological Order" section of the exam, ensure you place Cro-Magnon after Neanderthal and before modern Homo sapiens. Note that Cro-Magnon had a slightly larger cranial capacity than us!

💡 Did You Know?

Scientific naming uses Binomial Nomenclature. For humans, it is Homo sapiens. "Homo" is the Genus (Capitalized) and "sapiens" is the Species (lowercase), and both should be underlined when handwritten!