Early ideas about evolution

1. Theory of Evolution:a theory to explain CHANGE in a population’s genetic makeup that takes place OVER MANY GENERATIONS A theoryis: a broad range of data that has been scientifically tested and supported but not proven.

2. Early ideas about evolution • Until the end of the 18th century, in general scientists did not believe that species change over time (Robins have always been Robbins, Oak trees have always been Oak trees and so on). LAMARCK • In 1809, the French scientist, Jean Baptiste Lamarck proposed (like Darwin) that organisms change over time as they adapt to changing environments. • He noticed that organisms are usually well adapted to their environment.

3. Lamarck’s hypothesis of how organisms change over time • Use and Disuse: body parts used regularly become larger and stronger • He said that giraffes stretched their necks to reach leaves high in the trees. Their offspring, therefore would have longer necks. • Today, we know Lamarck’s hypothesis is wrong. Acquired traits, such as large muscles, are not passed down to the offspring

4. Modern Evolution: Charles Darwin • Charles Darwin lived from 1809-1882 • Modern evolutionary theory began when Charles Darwin presented evidence that evolution happens and offered an explanation of how it happens.

5. The Voyage of the Beagle: on Darwin’s voyage he collected many specimens.

6. Galapagos Islands • Darwin collected several different species of birds called finches. • Each of the finches are very similar, but have different bills. • Each bill is suited to a particular food available on the individual islands.

7. The Theory of Evolution by Natural Selection

8. Natural Selection • Darwin suggested that nature “selects” which organisms survive and reproduce. • Survival of the Fittest: an organism that is well adapted to it’s environment is more likely to survive and pass on those traits to their offspring.

9. 4 Steps to Natural Selection 1. Overproduction – Every population is capable of producing more offspring than can possibly survive. Therefore, there is competition for survival.

10. 2. Variation – Variations exist within every population. Much of this variation is in the form of inherited traits. Some traits are better adapted than others.

11. Meiosis and Mutations are the leading cause for variation. • A mutation happens when a mistake occurs during the replication of DNA • Mutations can be harmful but not always. Sometimes a mutation produces a trait that makes one individual slightly more fit for its environment than other individuals in its population.

12. Types of mutations • Point mutations: involves a substitution. One nucleotide is substituted for another. Only one nucleotide is affected so only one amino acid will be changed in the protein.

13. Types of mutations cont. • Frame shift mutations: a deletion or insertion occurs causing all the other nucleotides to shift. This affects all amino acids and can cause profound damage. Deletion mutation Insertion mutation JEN PET THE WET DOG  JZE NPE TTH EWE TDO

14. 3. Selection – In a given environment, having a particular trait can make certain individuals more likely to survive & have successful offspring than others.

15. 4. Adaptation – Over time, those traits that improve survival & reproduction will become more common in a population.

16. Adaptation: any inherited characteristic that increases an organisms chance for survival 3 types of adaptations • Structural: the form the organism takes. Ex: The arctic fox has small ears; the fennec fox has large ears. The small ears of the arctic fox are close to its body and insulated by fur. The large ears of the fennec fox, in contrast, help to expel heat from its body

17. Types of adaptations cont. • Behavioral: the innate actions that individuals of the species perform. Ex: the arctic fox can be active at any time of the day. This means that the fox is ready to find food whenever it’s available. The fennec fox is nocturnal. It sleeps in a burrow during the hottest part of the day and hunts in the evening.

18. Types of Adaptations cont. • Physiological:this adaptation is related to the biochemical processes at work within the organism’s body. Ex: in the winter food is scarce so the arctic fox stores food energy as fat. The fennec fox on the other hand lives in an environment with little free water so its body is adapted to getting all the water it needs from roots, fruit and leaves.

19. Adaptive Radiation • Adaptive radiation is a process in which organisms diversify rapidly into a multitude of new forms, particularly when a change in the environment makes new resources available and opens environmental niches.An example of adaptive radiation is the variety of creepers on the Hawaiian islands. It is believed that an ancestor of the modern honeycreepers arrived on the islands and eventually, new species emerged, each a different color and with a different beak shape. • When Charles Darwin was in the Galapagos islands, one of the first things he noticed is the variety of finches that existed on each of the islands. All in all, there were many different species of finch which differed in beak shape and overall size. This is adaptive radiation and natural selection at work.

20. SPECIATION • Specie: a group of organisms that can breed and produce fertile offspring • Speciation:speciation occurs when a species separates into two genetically separate groups which are isolated from one another. A physical barrier, such as a mountain range or a waterway, makes it impossible for them to breed with one another. Each species develops differently (adapts) based on the demands of their unique habitat.

21. When Arizona's Grand Canyon formed, squirrels and other small mammals that had once been part of a single population could no longer contact and reproduce with each other across this new geographic barrier. They could no longer interbreed. The squirrel population underwent speciation. Today, two separate squirrel species, the Kaibab and Aberts, inhabit the north and south rims of the canyon.

22. Speciation cont. Another example of speciation is the Galápagos finch. Different species of these birds live on different islands in the Galápagos. The finches are isolated from one another by the ocean. Over millions of years, each species of finch developed a unique beak that is especially adapted to the kinds of food it eats. Some finches have large, blunt beaks that can crack the hard shells of nuts and seeds. Other finches have long, thin beaks that can probe into cactus flowers without the bird being poked by the cactus spines. Still other finches have medium-size beaks that can catch and grasp insects. Because they are isolated, the birds don’t breed with one another and have therefore developed into unique species with unique characteristics.

23. Punctuated Equilibrium and Gradualism: are two ways in which the evolution of a species can occur. • Gradualismis selection and variation that happens more gradually. Over a short period of time it is hard to notice. Small variations that fit an organism slightly better to its environment are selected for: a few more individuals with more of the helpful trait survive, and a few more with less of the helpful trait die. Very gradually, over a long time, the population changes. Change is slow, constant, and consistent.

24. Punctuated Equilibrium and Gradualism • Punctuated equilibrium, change comes in spurts. There is a period of very little change, and then one or a few huge changes occur, often through mutations in the genes of a few individuals. Because these mutations are so different and so helpful to the survival of those that have them, the proportion of individuals in the population who have the mutation/trait and those who don't changes a lot over a very short period of time. The species changes very rapidly over a few generations, then settles down again to a period of little change.

25. How did the tiger get it’s stripes? • We don't know whether the tiger got its stripes through gradualism or punctuated equilibrium, here is how it could have happened through each. Let's assume that stripes are helpful because they help the tiger to camouflage, blend in with the tall grasses where it lives, so that it can sneak up on its prey and not be noticed. • Gradualism: A long time ago, there were a lot of tiger-like animals, but without stripes. Most of them were unmarked, but a few had light markings in their fur. These few blended in with the tall grasses a little bit better, so they were generally able to catch more food, so more of them were able to reproduced. Unmarked ones died of hunger. In the next generation, more animals were marked than in the previous generation. Very gradually, over many, many generations, stripes over the tigers' whole bodies formed and appeared in the whole population.

26. How did the tiger get its stripes cont. • Punctuated equilibrium: A long time ago, there were a lot of tiger-like animals, but without stripes. One time, a mutation occurred in a few of the animals, causing a huge change: they were born with stripes! This was so helpful to survival that out of the whole population, none or almost none of those with stripes died of hunger. They lived to reproduce, and their striped offspring also did very well. Over only a few generations, the whole population was born striped.

27. Natural Selection Animation • http://www.mhhe.com/biosci/esp/2001_gbio/folder_structure/ev/m2/s1/evm2s1_6.htm