Evolution

 Definition of Evolution

• Evolution is the process by which living things change and adapt over a long period of time.
• These changes happen slowly, over many generations, and help plants and animals survive better in their environment.

Example:

• Giraffes with slightly longer necks could reach leaves on tall trees more easily. Over many generations, giraffes with longer necks survived better and had more babies, so most giraffes today have long necks.
• Another example is the peppered moth: Before factories, most moths were light-colored to blend in with trees. When pollution darkened the trees, darker moths survived better and became more common.

Origin of Life

·         Observing Stars and Universe:

o    Viewing stars is like looking into the past due to the time light takes to reach Earth.

o    Universe is vast and ancient (~20 billion years old); Earth is a tiny part of it.

·         Big Bang Theory:

o    Universe began with a massive explosion (Big Bang).

o    Expansion led to cooling; hydrogen and helium formed, later condensing into galaxies.

·         Formation of Earth:

o    Earth formed about 4.5 billion years ago in the solar system.

o    Early Earth lacked an atmosphere; surface covered by water vapor, methane, CO₂, and ammonia.

o    UV rays split water; lighter hydrogen escaped, oxygen formed water and CO₂.

o    Ozone layer developed; cooling led to rain and ocean formation.

·         Origin of Life:

o    Life appeared about 500 million years after Earth formed (~4 billion years ago).

o    Panspermia Hypothesis: Some believe life came from outer space via spores.

o    Spontaneous Generation Theory: Life from decaying matter (disproved by Louis Pasteur).

o    Pasteur’s experiments showed life only comes from pre-existing life.

·         Chemical Evolution Theory:

o    Oparin (Russia) and Haldane (England): Life arose from non-living organic molecules (e.g., RNA, proteins).

o    Early Earth conditions: High temperature, volcanic activity, reducing atmosphere (CH₄, NH₃).

·         Miller-Urey Experiment (1953):

o    S.L. Miller simulated early Earth conditions in the lab.

o    Electric discharge in a mixture of CH₄, H₂, NH₃, and water vapor at 800°C produced amino acids.

o    Other experiments produced sugars, nitrogen bases, pigments, and fats.

o    Meteorites also contain similar organic compounds.

·         First Life Forms:

o    First non-cellular life forms (giant molecules: RNA, proteins) may have appeared ~3 billion years ago.

o    First cellular life forms (single cells) appeared ~2 billion years ago, all aquatic.

·         Current Understanding:

o    Most scientists accept abiogenesis: life arose gradually from non-living molecules via chemical evolution.

o    The transition from simple molecules to complex biodiversity is a key topic for further study.

Theory of Special Creation 

• All species were created as they are today.
• Diversity of life has always remained the same and will not change.
• Earth is about 4000 years old.

Challenges to Special Creation

• 19th-century scientists questioned these ideas.
• Charles Darwin’s observations during H.M.S. Beagle voyage:
• Living forms share similarities with each other and with extinct species.
• Many life forms have gone extinct; new forms have appeared over time.

Other Contributors

• Alfred Wallace reached similar conclusions as Darwin.

Key Conclusions

• New types of organisms have appeared over time.
• All life forms share similarities and common ancestors.
• Ancestors lived during different geological periods (epochs, eras).
• Earth is billions of years old, not just thousands.