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Edexcel GCSE Biology: Natural selection and genetic modification

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Edexcel GCSE Biology: Natural selection and genetic modification Evidence for Human Evolution Based on Fossils 1. Ardi (Ardipithecus ramidus) - 4.4 million years ago - Discovery: Found in Ethiopia. - Physical Characteristics: - Climbing adaptations evident in foot structure. - Long arms and leg...

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  • August 29, 2024
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  • 2024/2025
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Edexcel GCSE Biology: Natural selection and genetic modification
Evidence for Human Evolution Based on Fossils



1. Ardi (Ardipithecus ramidus) - 4.4 million years ago

- Discovery: Found in Ethiopia.

- Physical Characteristics:

- Climbing adaptations evident in foot structure.

- Long arms and legs indicating more ape-like than human traits.

- Brain size comparable to that of a chimpanzee.

- Leg structure suggests bipedalism, while hand bone structure indicates she did not walk on her
hands.



2. Lucy (Australopithecus afarensis) - 3.2 million years ago

- Discovery: Also found in Ethiopia.

- Physical Characteristics:

- Arched feet, suggesting better adaptation for walking rather than climbing.

- Arm and leg proportions similar to both apes and humans.

- Slightly larger brain than Ardi, but still indicative of early hominins.

- Leg bone structure is more efficient for upright walking compared to Ardi.



3. Leakey’s Discoveries - 1.6 million years ago

- Findings: Fossil hominids discovered by Louis Leakey and his team.

- Notable Specimen - Turkana Boy: A Homo erectus skeleton.

- Represents both ape-like and human-like features, more similar to Lucy.

- Shorter arms and longer legs, resembling modern human proportion.

- Brain size significantly larger than that of Lucy, indicating cognitive evolution.

- Leg and foot structure suggests enhanced adaptation for upright walking.



### Evidence for Human Evolution Based on Stone Tools

, 4. Dating Stone Tools: Methods

- Structural Features: Simpler tools are often older, allowing for chronological insights.

- Stratigraphy: The geology of rock layers; tools found in deeper layers tend to be older.

- Carbon-14 Dating: Stone tools frequently found with organic materials that can be carbon-dated,
further establishing age.



5. Development of Stone Tools Over Time

- Early Tools: Simple designs suitable for skinning animals or cutting meat.

- Advancements: More recent tools exhibit sophistication, being smaller and sharper, reflecting
improved human dexterity and cognitive skills.



### Principles of Evolution



6. Darwin's Theory of Evolution by Natural Selection

- Genetic Variation: Individuals exhibit genetic variation due to differences in alleles.

- Selection Pressures: Factors such as predation, competition for resources, and disease influence
survival and reproduction rates.

- Natural Selection: Individuals with advantageous traits are more likely to survive and reproduce,
leading to the propagation of beneficial alleles.

- Long-Term Trends: Over time, beneficial characteristics become common within populations.



7. Emergence of Resistant Organisms and Natural Selection

- Antibiotic Resistance in Bacteria: Mutations may confer resistance, offering a survival advantage in
the presence of antibiotics.

- Evidence of Evolution: Rapid reproduction of resistant bacteria demonstrates natural selection, as
advantageous alleles are passed down through generations.



### Contributions of Darwin and Wallace



8. Charles Darwin

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