Regents Biology Insect eaters Bud eater Seed eaters Cactus eater Warbler finch Tree finches Ground finches Darwin & Evolution by Natural Selection

Regents Biology Charles Darwin …  born into a fairly wealthy family.  Had a father who was a medical doctor and grandfather was Josiah Wedgewood (the  started medical school, but lost interest.  attended theologian school, but was more interested in biology and geology.

Regents Biology Charles Darwin  Proposed a way how evolution works  How did creatures change over time?  by natural selection  Collected a lot of evidence to support his ideas   British naturalist

Regents Biology Darwin’s influences  Charles Lyell- wrote Principles of Geology (1830). Believed in uniformitarianism which states that the earth was shaped entirely by slow-moving forces still in operation today, acting over a very long period of time.

Regents Biology Thomas Malthus- (1797 )wrote Essay on the Principle of Population which argued that because of the natural human urge to reproduce, human population increases geometrically (1, 2, 4, 16, 32, 64, 128, 256, etc.). But food supply increases arithmetically (1, 2, 3, 4, 5, 6, 7, 8, etc.). Therefore, since food is necessary to human life, population growth in any area or on the planet, if unchecked, would lead to starvation. Darwin thought, this would apply to plants and animals too.

Regents Biology  les-Darwin les-Darwin  Check out the videos.

Regents Biology Robert Fitzroy Voyage of the HMS Beagle  Invited to travel around the world  (22 years old!)  makes many observations of nature  main mission of the Beagle was to chart South American coastline

Regents Biology Voyage of the HMS Beagle  Stopped in Galapagos Islands  500 miles off coast of Ecuador

Regents Biology Galapagos Recently formed volcanic islands. Most of animals on the Galápagos live nowhere else in world, but they look like species living on South American mainland. 800 km west of Ecuador

Regents Biology Many of Darwin’s observations made him wonder… Why? Darwin asked: Why were these creatures found only on the Galapagos Islands? Darwin found…many unique species

Regents Biology present day Armadillos Darwin found: that creatures have changed over time Evidence that creatures have changed over time ancient Armadillo Darwin asked: Why should extinct armadillos & modern armadillos be found on same continent? Darwin found…clues in the fossils

Regents Biology Darwin found: Different shells on tortoises on different islands Darwin asked: Is there a relationship between the environment & what an animal looks like?

Regents Biology Finch?Sparrow? Woodpecker? Warbler? Darwin found… birds Finch?Sparrow? Woodpecker? Warbler? Darwin found: Many different birds on the Galapagos Islands. He thought he found very different kinds…

Regents Biology Darwin was amazed to find out: All 14 species of birds were finches… Finch?Sparrow? Woodpecker? Warbler? Finch?Sparrow? Woodpecker? Warbler? But Darwin found… a lot of finches Large ground finch Small ground finch Warbler finchTree finch But there is only one species of finch on the mainland! Darwin asked: If the Galapagos finches came from the mainland, why are they so different now?

Regents Biology Finch?Sparrow? Woodpecker? Warbler? The finches cinched it! Large ground finch Small ground finch Warbler finchTree finch Big seed eaterSmall seed eater Insect eaterLeaf & bud eater Darwin said: Ahaaaa! A flock of South American finches were stranded on the Galapagos… Darwin found: The differences between species of finches were associated with the different food they ate. different beaks are inherited variations serve as adaptations that help birds compete for food these birds survive & reproduce pass on the genes for those more fit beaks over time nature selected for different species with different beaks

Regents Biology Relationship between species (beaks) & food

Regents Biology Darwin’s finches  Darwin’s conclusions  variations in beaks  differences in beaks in the original flock  adaptations to foods available on islands  natural selection for most fit  over many generations, the finches were selected for specific beaks & behaviors  offspring inherit successful traits  accumulation of winning traits: both beaks & behaviors  separate into different species

Regents Biology Warbler finch Woodpecker finch Small insectivorous tree finch Large insectivorous tree finch Vegetarian tree finch Cactus finch Sharp-beaked finch Small ground finch Medium ground finch Large ground finch Insect eaters Bud eater Seed eaters Cactus eater Warbler finch Tree finches Ground finches variation natural selection for best survival & reproduction From 1 species to 14 species…

Regents Biology  LaMarck  evolution by acquired traits  creatures developed traits during their lifetime  give those traits to their offspring  example  in reaching higher leaves giraffes stretch their necks & give the acquired longer neck to offspring  not accepted as valid Earlier ideas on Evolution

Regents Biology Darwin’s view of Evolution  Darwin  giraffes that already have long necks survive better  leave more offspring who inherit their long necks  variation  selection & survival  reproduction & inheritance of more fit traits

Regents Biology present day Sloth Darwin found… more fossils Darwin asked: Why should extinct sloths & modern sloths be found on the same continent? (extinct) Giant ground sloth Darwin found: that creatures have changed over time Evidence that creatures have changed over time

Regents Biology Darwin Publishes His Results  On the Origin of Species By Natural Selection  Alfred Wallace also came to the same conclusions as Darwin and they published their results together.

Regents Biology Not a lot was known in the 1840s  the basic mechanism for speciation was unknown  there were (and still are) gaps in the fossil record  little known about genes and inherited traits  age of the earth was still disputed  people believed each species was a distinct and unchanging entity.

Regents Biology Natural selection was based on the following observations.  1) Species have great fertility. They make more offspring than can grow to adulthood.  2) Populations remain roughly the same size, with modest fluctuations.  3) Food resources are limited, but are relatively constant most of the time.  From these three observations it may be inferred that in such an environment there will be a struggle for survival among individuals.  4) In sexually reproducing species, generally no two individuals are identical. Variation is rampant.  5) Much of this variation is heritable.

Regents Biology  To summarize Darwin's Theory of Evolution;  1. Variation: There is Variation in Every Population. 2. Competition: Organisms Compete for limited resources. 3. Offspring: Organisms produce more Offspring than can survive. 4. Genetics: Organisms pass Genetic traits on to their offspring. 5. Natural Selection: Those organisms with the Most Beneficial Traits are more likely to Survive and Reproduce.

Regents Biology  The End  Adapted from Regents Biology