Evidence for Change Over Time
How scientists use multiple lines of evidence to demonstrate evolution from simple to complex organisms
In exams, this topic is easier if you group the evidence into four lines: fossils, anatomy, biogeography, and biochemical evidence. Your job is not just to name them, but to explain how each one supports the idea that organisms changed over time.
Fossil Record
Progression from simple to complex organisms in rock layers, transitional fossils, and evidence of mass extinctions.
Comparative Anatomy
Homologous structures (same basic structure, different functions) and vestigial structures (remnants with lost function).
Biogeography
Distribution of species influenced by continental drift, with related species found on different continents.
Biochemical Evidence
Shared DNA and protein structures across all living organisms suggest a common origin of life.
The Fossil Record
The fossil record serves as the cornerstone of evidence for evolutionary change, revealing the progression of life forms through time.
Rock Layer Progression
Transitional Fossils
A transitional fossil between reptiles and birds, providing evidence of the evolutionary transition from dinosaurs to avian species.
Reptile Features
- Teeth in jaws
- Long bony tail
- Claws on wings
Bird Features
- Feathers
- Wishbone
- Bird-like skull
A transitional fossil between fish and tetrapods (four-legged animals), showing features of both groups.
Fish Features
- Fish scales
- Fins
- Gills
Tetrapod Features
- Flat head
- Ribs
- Limb-like fins
1. What type of fossil shows characteristics of two different groups, providing evidence of evolutionary links?
Comparative Anatomy
The study of body structures across different species to identify evolutionary relationships.
Homologous Structures
Body parts that share a similar basic structure but serve different functions in various species.
Grasping
Flying
Swimming
Flying
Vestigial Structures
Remnants of organs or parts that have lost their original function through evolution.
Remnant of a larger cecum used for plant digestion
Remnants of hind limbs from land-dwelling ancestors
2. The human appendix and whale pelvic bones are examples of what?
Match the Structure Type
Match each example to the correct structure type.
Examples
Structure Types
Biogeography (Continental Drift)
Biogeography examines the distribution of species across different geographical areas and how this distribution has been influenced by continental drift.
Southern supercontinent that included Africa, South America, Antarctica, Australia, and India.
Found in Africa and Australia - evidence of common ancestry
Ostrich (Africa), Emu (Australia), Rhea (South America)
Northern supercontinent that included North America, Europe, and Asia.
Camels (Asia), Llamas (South America) - originated in North America
Found in Asia and North America
3. The presence of Proteas in both Africa and Australia is evidence for what?
Evolution Timeline Challenge
Arrange these events in the correct evolutionary order.
Biochemical Evidence (Introductory)
While explored in greater depth in Grade 12, this foundational knowledge highlights the shared characteristics of all living organisms.
All living organisms share the same basic DNA and protein structures, suggesting a common origin of life.
4. What does the high similarity in DNA between humans and chimpanzees suggest?
Key Terms
Exam Recap: Four Lines of Evidence
Fossil Record
- Progression from simple to complex in rock layers
- Transitional fossils (Archaeopteryx - reptile/bird)
- Mass extinctions followed by new species
Comparative Anatomy
- Homologous structures (pentadactyl limb)
- Vestigial structures (appendix, whale pelvis)
Biogeography
- Continental drift (Gondwanaland, Laurasia)
- Related species on different continents
- Proteas in Africa & Australia
- Flightless birds on southern continents
Biochemical Evidence
- Shared DNA and protein structures
- Humans share 98% DNA with chimpanzees
- All life shares common genetic heritage
