The document discusses early theories of evolution, including those proposed by Jean-Baptiste Lamarck and Charles Darwin. Lamarck believed that organisms could pass on traits acquired during their lifetime to their offspring, and that evolution progressed towards greater complexity. His ideas were later disproven. Darwin's observations of finches during his voyage on the HMS Beagle, including variation between island populations, helped lead him to develop the theory of natural selection.

1. Evolution and
Adaptation
Early Theories, Darwin & Natural Selection

2. Jean-Baptiste Lamarck
(France - 1744-1829)
 Based theories on observations of
similarities between ancient fossils
and modern animals, vestigial
structures and passing on of desired
traits by selective breeding
 Proposed than an individual gains
or loses traits during its lifetime
which are then passed on to its
offspring.
 Believed evolution is a constant
process striving toward greater
complexity and perfection.

3. Jean-Baptiste Lamarck
Mechanisms of Change:
 Law of Use and Disuse
 Body parts most frequently used become stronger and more
developed and parts used less are reduced.
 Ex. Penguins wings – Small due to disuse.
 Transmission of Acquired Characteristics
 Qualities acquired during an organisms life time are passed down to
offspring
 Ex. Parents who develop strong muscles will pass strong muscles down
to offspring

4. Jean-Baptiste Lamarck
Important contributions to evolutionary theory:
Organisms change over time
Organisms adapt to their environment
Traits found in parents are passed to offspring
What Lamarck got wrong:
Evolution tends towards perfection & complexity
Organisms are constantly evolving
Acquired characteristics are passed on

5. Pre-Darwinian Ideas About Evolution:
Life has existed on Earth for a long time
Organisms have changed since the dawn of life
Many extinctions have happened since life began
Fossil evidence, embryology and comparative anatomy
show similarities between related species and suggest a
common ancestor.
Mendel’s work with genetics showed how genetic
elements are passed through generations

6. Charles Darwin
(England 1809-1882)
 Naturalist
 1831: Embarked on 5 year
around the world voyage
aboard the HMS Beagle.
 Studied the diversity of life
with a particular focus on the
Galapagos Islands
 Returned home to continue
his research
 1859: Published On the
Origin of Species

7. Voyage of the Beagle

8. Galapagos Islands
Group of Volcanic Islands off the coast of South America
Darwin observed variation between the animals species
on each of the islands and the mainland
Famously, he observed, collected and measured the
many different species of finches found on the islands

9. Darwin’s Finches

10. Darwin’s Finches
Noticed huge variation in beak type and size
Beak type correlated with the type of food source on
each island
Hypothesized the beak type had adapted to the type of
food available in the finch habitat
Led to theory of Natural Selection

12. Alfred Russell Wallace
Darwin wasn’t the only one putting all the pieces
together…
https://www.hhmi.org/biointeractive/origin-species-making-
theory
(30 min)