Evolution and Adaptation

Early Theories, Darwin & Natural Selection

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.

Jean-Baptiste LamarckMechanisms 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

Jean-Baptiste LamarckImportant contributions to evolutionary theory:Organisms change over timeOrganisms adapt to their environmentTraits found in parents are passed to offspringWhat Lamarck got wrong:Evolution tends towards perfection & complexityOrganisms are constantly evolving Acquired characteristics are passed on

Pre-Darwinian Ideas About Evolution:

Life has existed on Earth for a long timeOrganisms have changed since the dawn of lifeMany extinctions have happened since life

beganFossil 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

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

Voyage of the Beagle

Galapagos IslandsGroup of Volcanic Islands off the coast of South

AmericaDarwin observed variation between the animals

species on each of the islands and the mainlandFamously, he observed, collected and measured

the many different species of finches found on the islands

Darwin’s Finches

Darwin’s FinchesNoticed huge variation in beak type and sizeBeak type correlated with the type of food

source on each islandHypothesized the beak type had adapted to the

type of food available in the finch habitatLed to theory of Natural Selection

Alfred Russell WallaceDarwin wasn’t the only one putting all the pieces

together…https://www.hhmi.org/biointeractive/origin-speci

es-making-theory

(30 min)