⚡ Quick Revision: Evolution Fundamentals
🔹 Basic Concepts
- ✔ Evolution: A slow, progressive, and irreversible change in the characteristics of organisms over generations.
- ✔ Speciation: The process of formation of new species from existing ones due to evolution.
- ✔ Variation: Small differences between individuals of the same species that provide the raw material for evolution.
Adaptation: The adjustment of an organism to its environment to improve its chances of survival and reproduction.
Acquired Traits with Inherited Traits. Remember: Acquired traits (e.g., muscles) cannot be passed to offspring; only inherited traits (in DNA) drive evolution.
⚡ Quick Revision: Lamarckism vs. Darwinism
🔹 Lamarck’s Theory (Inheritance of Acquired Characters)
- ✔ Use and Disuse: Organs used frequently become developed; those not used degenerate.
- ✔ Inheritance: Traits acquired during a lifetime are passed to offspring (e.g., long neck of giraffe).
🔹 Darwin’s Theory (Natural Selection)
- ✔ Struggle for Existence: Overproduction of offspring leads to competition for limited resources.
- ✔ Survival of the Fittest: Individuals with favorable variations survive and reproduce.
- ✔ Natural Selection: Nature selects the best-adapted individuals to pass on their genes.
Vestigial Organs: Non-functional organs in the body which were functional in ancestors (e.g., Vermiform Appendix, Wisdom Tooth).
Natural Selection with Artificial Selection. Remember: Natural Selection is driven by environmental factors; Artificial Selection is done by humans for desired traits (e.g., dog breeds).
⚡ Quick Revision: Evidence for Evolution
🔹 Homologous Organs (Divergent Evolution)
- ✔ Definition: Organs with the same basic structure but different functions.
- ✔ Example: Forelimbs of a human, wing of a bird, and flipper of a seal (all have the same bone pattern).
- ✔ Indication: Suggests a common ancestry.
🔹 Analogous Organs (Convergent Evolution)
- ✔ Definition: Organs with different structures but performing the same function.
- ✔ Example: Wings of an insect (membranous) and wings of a bird (feathery).
- ✔ Indication: Suggests adaptation to a similar environment, not common ancestry.
Palaeontology: The study of fossils which provide direct evidence of past life and evolutionary links.
Connecting Links with Missing Links. Remember: Connecting links are living organisms with traits of two different groups (e.g., Duck-billed Platypus); Missing links are fossils (e.g., Archaeopteryx).
⚡ Quick Revision: Stages of Human Evolution
🔹 The Evolutionary Timeline
Human evolution is characterized by bipedalism (walking on two legs), increased cranial capacity, and use of tools.
| Stage | Cranial Capacity | Key Features |
|---|---|---|
| Australopithecus | 450 - 600 cm³ | First to walk upright; "Ape-man." |
| Homo habilis | 650 - 800 cm³ | "Handy Man"; first tool maker. |
| Homo erectus | 800 - 1100 cm³ | Used fire; Java Man & Peking Man. |
| Neanderthal Man | 1450 cm³ | Buried their dead; heavy brow ridges. |
| Cro-Magnon Man | 1600 cm³ | Cave paintings; direct ancestors. |
| Homo sapiens | 1350 - 1500 cm³ | Modern Man; developed culture/language. |
🔹 Major Evolutionary Changes
- ✔ Posture: Shift from semi-erect to Perfect Bipedal Gait.
- ✔ Hands: Development of opposable thumbs for precise gripping.
- ✔ Face: Reduction in jaw size and loss of simian shelf (chin development).
Anthropology: The scientific study of humans, human behavior, and societies in the past and present.
Cranial Capacity trend. Note: Neanderthals actually had a *larger* average cranial capacity than modern humans, but Homo sapiens developed higher cognitive regions (frontal lobe).