• Evolution: gradual change over time

– Gradual Change—small changes along the way

– Over Time—doesn’t happen over night

Charles Darwin

Charles Darwin• The Author of the On the Origin of Species

• The most notable evolution theorist of our time

• Known for his famous voyage on “The Beagle”

• Arrived at the Galapagos Islands on September 15th, 1835

• 5 week stay – was on land 19 days collecting & observing

In 1831, the young naturalist Charles Darwin set off on a five-year sail around the world that would profoundly change not just his life, but the course of science as well.  Commissioned to collect samples of flora and fauna from the HMS Beagle’s ports of call, Darwin left England firmly believing, like everyone else, that God had created every living thing on Earth exactly as it appeared.  His specimens told him otherwise, however, and when the Beagle docked in England, core tenets of the theory of evolution had been shaped.  Yet it would be 20 years before he would make his ideas public; Darwin feared that disclosing his radical views would be the equivalent of committing career suicide and was moved to publish only when another scientist independently arrived at the same conclusions as he.  That event sparked a debate that continues to this day.

Charles Darwin

• In 1831 he sailed to the Galapagos Islands in the HMS Beagle

• He left England on this voyage at 22 yrs. Old

• He published his theory of evolution 30 years later

The HMS Beagle

Darwin Left England in 1831

Darwin returned 5 years later in 1836Darwin returned 5 years later in 1836

13 major islands, 6 minor islands, & 40 smaller rock formations & reefs – 3000 square miles of land covering 17,000 miles of ocean located 600 miles west of Ecuador

Galapagos Islands

• Volcanic in origin – oldest are 325 million years old

• Hot spot formation theory

• Still active volcanoes

• Never connected to the mainlands

Galapagos Islands

• Until their discovery in 1535, life here evolved in isolation producing strange & marvelous species

• 8 Habitats to accommodate a large variety of species:

Open sea Rocky islets

Rocky shores Sandy beaches

Mangrove coasts Arid zone

Transitional zone Highlands

Bartolome Island – arid zone

North Seymour Island – transition zone

Rocky Islets

Black Sand Beach

Flamingos on the mangrove coasts

Rocky shores

Red Sand Beach

Highlands

View atop a inactive volcano

Darwin and the Galapagos

• He focused evolutionary principles on populations

• Why were there so many different plants and animals found in the Galapagos?

Animals of Galapagos

Galapagos Penguins

Land Iguana Pink Flamingo

Frigate Bird

Galapagos Tortoise

There are currently only 11 subspecies Left in the world today.

Tortoise nesting video

Lonesome George

• George is a Pinta Island Tortoise

• He is the very LAST one known in existence

• There is a reward of $10,000 offered by the zoo association if a female is found

The BoobysBlue Footed booby

Red footed booby

Masked booby

Blue Footed Booby

• http://www.youtube.com/watch?v=oYmzdvMoUUA

• Mating Dance

Waved Albatross

Animals of the Galapagos

Marine iguana Sally Lightfoot Crabs

Sea Lions

Darwin’s Ideas

• Evolution is due to genetic variation and natural selection on heritable characters

• Recognized natural selection as the mechanism in 1838

Darwin at 31

Sketch of genetic line

Evidence used in Darwin’s Natural Selection Theory• 1. Biogeography: Distinct features of cosmopolitan species and

the presence of endemic species (Darwin's finches: of the 14 finch species of the Galapagos islands, 13 are endemic)

• 2. Morphology and embryology: Homologous structures among related species; similarities in the embryos of related species – Homologous Structure-features that are similar in structure but appear in

different organisms and have different functions; offers support for common ancestor

– Analogous Structure-perform a similar function but are not similar in orgin

• 3. Palaeontology: Gradual change in the fossil record, evident extinctions

• 4. Taxonomy and systematics: Morphological similarities among related taxa

 

Natural Selection

• Darwin is credited with the theory of evolution by natural selection.

• Natural selection is that the strongest survive and propagate and therefore increase the strength of the species

Darwin Finches

• Once on the islands, various species established themselves and determined territories

• Evolution then set in and many unique species, such as Darwin’s finches resulted

Speciation• Formation of a new species• As new species evolve, populations become

reproductively isolated from each other (they cannot interbreed) called reproductive isolation

• Behavioral isolation occurs when 2 populations are capable of interbreeding but have differences in courtship rituals & are then not attracted to each other

• Geographic isolation – 2 populations are separated by geographic barriers such as rivers, or mountains

• Temporal Isolation occurs when 2 organisms reproduce at different times

Darwin’s Finches and Natural Selection

• The finches probably descended from one type of ancestor and due to isolation and through chance, different climates, natural forces, and food type, evolved into the 13 different types of finches

Finch Beaks

• Finch’s beaks vary based on their diet– some eat fruit and seeds– other insects– some can even suck the blood from marine

birds on the islands when they can't find their usual food.

– Certain varieties of finch clean the ticks from the shells of the giant tortoises.

Peppered Moths

http://www.biologycorner.com/worksheets/pepperedmoth.html

Natural Variation

• Some cows give more milk• Some plants bear larger fruit• Some humans are taller than others

Much of this variation is inherited & passed on to the next generation

Humans may take advantage of this variation by breeding certain organisms together with the desired trait (artificial selection)

Natural selection -

• Something like artificial selection occurs in nature – called natural selection

• However, the traits being selected contribute to an organism’s fitness without human control

• There is always a struggle for existence & the “fitness” of an organism depends on its survival & its reproductive success (“Survival of the Fittest”)Example:faster = better predatorcamouflagebehaviorbetter protection from extremes

Adaptation

• These changes increase the chance of survival & thus the traits that allow for survival are passed on the next generation