COULD YOU HAVE RIDDEN A HORSE MILLIONS OF YEARS AGO? Horse evolution goes back more than 55 million years

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1 NATURAL SELECTION C I D E N T I F Y S O M E C H A N G E S I N T R A I T S T H A T H A V E O C C U R R E D O V E R S E V E R A L G E N E R A T I O N S T H R O U G H N A T U R A L S E L E C T I O N A N D S E L E C T I V E B R E E D I N G

2 COULD YOU HAVE RIDDEN A HORSE MILLIONS OF YEARS AGO? Horse evolution goes back more than 55 million years

3 EVOLUTION OF THE HORSE THE ECOLOGICAL PRESSURES FACING THE SPECIES DETERMINED THE TYPE OF DIFFERENCES, OR VARIATION The development of larger limbs and hooves allowed horses to spread out and become more successful in grassland habitats as they developed.

4 HOW DO GENETICS CHANGE OVER SEVERAL GENERATIONS? Changes occur over time from either natural selection or selective breeding You now know that when DNA is copied, mutations (mistakes) can occur Sometimes those mistakes are fatal, some times they make no difference in survival, and sometimes, every once in a great while, that mutation becomes critical to survival

5 WHY CAN YOU RIDE ONE NOW? Natural selection caused some changes in horses, and humans participated in selective breeding which both domesticated the horse and made specialized organisms.

6 WHAT EXACTLY IS NATURAL SELECTION? The process by which individuals that are better adapted to the environment survive and reproduce more successfully than other members of their species These are changes in genetics traits over many generations

7 WHO FIGURED THIS OUT? CHARLES DARWIN Most people in the world did not become aware of the theory of evolution until 1859, when Charles Darwin published his book On the Origin of Species by Means of Natural Selection.

8 DARWIN S OBSERVATIONS This book described the observations and evidence that he collected over 20 years of intensive research, beginning with a five-year voyage around the world on a British research ship, the HMS Beagle. During this five-year voyage, Darwin was able to make observations about plants and animals spread around the world, and to collect specimens to study when he returned to England.

9 DARWIN S JOURNEY Each time the Beagle stopped at a port to do some trading, Darwin went on land to explore and look for the local plants, animals, and fossils. One of the most important things Darwin did was to keep a diary. He took extremely detailed notes and drawings about everything he saw as well as his thoughts.

10 THE GALAPAGOS ISLANDS Darwin s best known discoveries were made on the Galápagos Islands, a group of 16 volcanic islands near the equator about 600 miles from the west coast of South America. Allowed geographical isolation to take place

11 GEOGRAPHIC ISOLATION Species evolved differently in on the islands than on the mainland Darwin was amazed by the array of life he saw on the Galápagos Islands. He saw animals unlike anything he had ever seen before. For example, the iguanas (large lizards) differed between islands. The members of one iguana species spent much of their time swimming and diving underwater for seaweed, while those of another iguana species lived on land and ate plants.

12 SIMILARITIES AND DIFFERENCES Marine Iguanas Marine Iguanas of the Galapagos Large claws for gripping slippery rocks, eat seaweeds Green iguanas in South America Smaller claws for climbing trees, eat leaves

13 WHAT DOES THIS MEAN? Key understanding: mainland species were still related to the island species - Curiously, they looked different, ate different foods, and behaved differently, but still had some similarities So how did this happen? Answer: gradual changes over many generations

14 Darwin s observations Of particular interest were the finches on these islands They had varied sizes and shapes of the beaks. This observation made him wonder. WHY?

15 FROM ONE FINCH There are now at least 13 species of finches on the Galapagos Islands, each filling a different niche on different islands. All of them evolved from one ancestral species, which colonized the islands only a few million years ago.

16 WHAT DARWIN LEARNED FROM THESE FINCHES The one species of finch gradually evolved into separate species because of food sources and other environmental factors such as amount of water available For example: Beaks highly adapted to food source Large beaks - meant there was little rainfall because the seeds were large & tough Small beaks - Heavy rainfall seeds small & soft Other adaptations were sharp beaks for finding and eating insects, wide beaks for cracking seeds

17 THE FINCHES ALSO EVOLVED TO EAT A VARIETY OF FOODS -

18 MORE ADAPTATIONS Darwin studied hundreds more animal and plant species. After nearly 20 years of research, he proposed his theory of evolution by natural selection. Another example of what he studied:

19 THE GALAPAGOS TORTOISE The giant tortoises (Geochleone nigra) in the Galapagos 2 m long Saddle-shaped shell, long necks more prone to standing upright to forage on cactus Nearest relative- Chacos Tortoise (Geochelone chilensis) in Argentina just 20cm long Dome-shaped shell, short necks graze on ground level vegetation

20 Theory of Natural Selection (Darwin s Conclusions) Species have changed over generations through adaptations The changes allow them to survive and reproduce in a new environment. Darwin proposed that evolution occurs by means of natural selection New species may form when a group of individuals is isolated from the rest of the population

21 Darwin s 5 key points in the Theory of Natural Selection: 1. Populations have (genetic) variations. 2. Some variations are favorable. 3. More offspring are produced than survive 4. Those offspring that survive have favorable traits. 5. A population will change over time.

22 NATURAL SELECTION - QUICK EXPLANATION How is this an example of natural selection? Green bugs are more visible to its predator Green bugs get eaten more easily Brown bugs not as visible, they survive Brown bugs reproduce, the helpful alleles for the brown color are passed on to the next generation After many generations, more members will be brown The environment has selected organisms with the helpful traits, hence the term natural selection Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College.

23 MYTHBUSTING! Survival of the fittest what does that mean? Fitness is the key to natural selection. We're not talking about how many reps you can burn through at the gym -- biological fitness is an organism's ability to successfully survive long enough to reproduce. Beyond that, it also reflects an organism's ability to reproduce well. It isn't enough for a tree to create a bunch of seeds. Those seeds need the ability to end up in fertile soil with enough resources to sprout and grow.

24 DARWIN S CONTEMPORARIES Jean-Baptiste Lamarck, Lamarck and Wallace had similar findings as Darwin Wallace called the changes in species over time evolution. Alfred Russell Wallace, (with Darwin)

25 YOU MAY HAVE HEARD OF Lamarckism (or Lamarckian inheritance) is the idea that an organism can pass on characteristics that it acquired during its lifetime to its offspring.

26 FACTORS AFFECTING NATURAL SELECTION 1. Overproduction 2. Competition 3. Variations

27 OVERPRODUCTION What s the point of so many offspring? Only the fittest survive, not all of your offspring will survive long enough to reproduce and pass on genetic heredity but some will!

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29 COMPETITION Resources are limited! There is only so much food, space, water and shelter Members of the same species must compete with each other, only the fittest survive

30 AND VARIATION. Any genetic difference between individuals of the same species very important in natural selection the stronger individuals survive and reproduce offspring with helpful traits will survive and then pass along those traits to their offspring What might those traits be?

31 EXAMPLE 1 OF VARIETY OF TRAITS: COUNTER-SHADING IN FISH Upper side of the animal is darker than the lower side, blends in with sea floor Lower side of organism is lighter, organism blends in with its surroundings in this case the sky Which do you think is better for the survival of these species?

32 EXAMPLE 2 OF VARIETY OF TRAITS: BEAKS IN BIRDS

33 EXAMPLE 3 OF VARIETY OF TRAITS: CLAWS IN BIRDS Variation in talon size and shape due to hunting technique.

34 TO SUM IT UP Watch this: Natural Selection video

35 HW NATURAL SELECTION WKSHT