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What is evolution?

What is evolution?. Slow, gradual change over time. Just in the last few million years, hundreds of species have become extinct- while hundreds of others have developed. “Slow” means thousands to millions of years. How do we know evolution is happening?. The Evidence Fossil Evidence

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What is evolution?

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  1. What is evolution? Slow, gradual change over time Just in the last few million years, hundreds of species have become extinct- while hundreds of others have developed “Slow” means thousands to millions of years

  2. How do we know evolution is happening? The Evidence • Fossil Evidence • Anatomical Structures • Embryological Development • Molecular Similarities

  3. FOSSILS (Dead Things) The remains of a plant or animal that lived long ago may be used to compare how the organism has changed over time or even evolutionary relationships.

  4. ANATOMICAL SIMILARITIES (Body Parts of Living or Dead Things) Structural similarities and differences can indicate evolutionary relationships.

  5. Types of Anatomical Structures • Homologous- similar structure, embryos and function. • Analogous- similar external form & function, but different internal structure. • Vestigial- structures that are remnants of structures that were functional in ancestral forms (reduced in size and serve little or no purpose).

  6. Embryological Development(Living Things Before Birth) Comparing embryos at various stages of development may show similarities not present after birth. Fish Salamander Tortoise Chicken Rabbit Human

  7. MOLECULAR SIMILARITIES(Tiny Parts Inside Living or Dead Things) • DNA sequencing… comparing DNA or proteins of various species.

  8. Charles Darwin • Born Feb. 12, 1809 in England • 1831-1836 Served as a naturalist aboard the HMS Beagle • 1835 The Beagle arrived in the Galapagos Islands (off the coast of South America) • 1859 Published Origin of Species • 1882 He died and was buried at Westminster Abbey near Isaac Newton

  9. Darwin’s thoughts on Natural Selection explained a lot about evolution, but he didn’t explain HOW traits change over time. The field of genetics explains this…MUTATIONS (they are not always bad).

  10. DARWIN AND HIS THEORY OF EVOLUTION Most organisms give birth to more offspring than can survive. OVERPRODUCTION Living things must struggle to exist. COMPETITION The individuals in a species are somewhat different from one another. VARIATION

  11. Organisms with traits best suited to the environment have a better chance of survival. ADAPTATION Those organisms best suited to their environment will pass their traits along to offspring. NATURAL SELECTION New species will develop. SPECIATION

  12. Now, who wants to play a game? I wanna play! Click on the guy to play

  13. HOW FAST IS EVOLUTION OCCURRING? There are two theories…scientists cannot seem to agree which one is best. THEORY #1 (based on Darwin’s ideas) Gradualism- species arise through the gradual accumulation of small variations…evolution is slow and continuous and it takes millions of years to happen

  14. THEORY #2 (based on the ideas of more recent scientists) Punctuated Equilibrium- species remain the same (in equilibrium) for extended periods of time…evolution occurs quickly for short periods of time.

  15. Gradualism vs. Punctuated Equilibrium

  16. GENE POOL- the total of all the alleles present in a population

  17. SOURCES OF GENETIC VARIATION(differences) • MUTATION- actually a rare event, causes new traits to arise • GENETIC RECOMBINATION- crossing-over in sexual reproduction forms new genetic combinations

  18. MIGRATION- greatest effect on small populations, bringing new traits into a population or taking traits out of a population due to individuals moving • GENETIC DRIFT- affects small populations; changes in the gene pool due to chance (storm, catastrophe…) Harmful because it decreases variation. In large populations, it is less likely to occur because there are so many individuals (an entire trait will not get wiped out).

  19. ADAPTATIONS The Purpose: Protection & Survival The Types: Structrual- involves the parts of the body (wings for flying, fins for swimming)

  20. Physiological- involves metabolism of the organism (poison venom). Other adaptations are mating, behavioral, hibernation… Freshwater snake Fordonia leucobalia.

  21. Peppered Moth CLICK ON THE PICTURE TO SEE AN ANIMATION

  22. SPECIATION(the formation of a new species) CAUSES OF SPECIATION: Click on a button to learn more! ISOLATION POLYPLOIDY ADAPTIVE RADIATION

  23. ISOLATION • Geographic- an actual physical barrier prevents two groups of the same species from interbreeding. • Reproductive- the loss of the ability to interbreed by two isolated groups (changes in mating behavior, mating seasons, or structure of sex organs) See an example

  24. BACK

  25. POLYPLOIDY (mostly in plants) Changes occur suddenly as a result of abnormal mitosis or meiosis. Individuals are formed with more than the usual number of chromosomes. If the offspring can interbreed only among themselves, they are considered to be a new species. BACK

  26. ADAPTIVE RADIATION • a spreading of one species into different environments accompanied by adaptations (Darwin’s finches)

  27. The Beaks of Finches

  28. Imagine these are beaks…

  29. Some are great for big seeds…

  30. While others are best for little ones

  31. Without the best beak for the available food source… Some finches will not survive to pass their unfavorable traits on to offspring.

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