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Evolution Evolution is descent with modification; the idea that living species are descendents of ancestral species that were different from present-day.

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Presentation on theme: "Evolution Evolution is descent with modification; the idea that living species are descendents of ancestral species that were different from present-day."— Presentation transcript:

1 Evolution Evolution is descent with modification; the idea that living species are descendents of ancestral species that were different from present-day ones Evolution describes the genetic changes in a population over time

2 Evolution Organisms are adapted to their environment; a good fit As descendents of a remote ancestor spread into various habitats over millions and millions of years, they accumulate diverse modifications (adaptations) that fit them to specific ways of life = descent with modification (evolution)

3 Evolution Natural variation among individuals is based on heredity (and mutation). These variations enable organisms to become adapted to their environment over time

4 Natural Selection Natural selection is the process by which favorable, inherited traits become more numerous in successive generations of a population of reproducing organisms Over time, natural selection leads to species that are well adapted (highly evolved) to their environments

5 Natural Selection Natural selection is the brain child of Charles Darwin; a naturalist who sailed around the world and noted the unique adaptations of animals in many diverse environments (most notably the Galapagos Islands)

6 The Principles of Natural Selection King Penguin Rookery © Momatiuk - Eastcott/Corbis Struggle for existence/Competition – More offspring are produced than can be supported by resources

7 The Principles of Natural Selection Variation – Some individuals, due to heredity or mutation, possess characteristics which make them better adapted to their environment

8 The Principles of Natural Selection Inheritance of Traits – Best-suited organisms will survive to produce more individuals that share same adaptation

9 “Survival of the Fittest” Organisms are adapted to their environment through natural selection Natural selection is a pessimistic process

10 Population with varied inherited traits 1 Elimination of individuals with certain traits 2 Reproduction of survivors 3 Certain individuals with a distinct, inherited characteristic will be selected against, while others with a (different) distinct, inherited trait will survive

11 Let’s look at an example… Normal allele; vulnerable to pesticides Alternate allele; resistant to pesticides Survivors ‘Resistant’ allele passed to next generation

12 Mechanisms of Evolution Remember evolution is dependent on genetics! Reproductive component – organisms must reproduce Heredity component – offspring must resemble parents (traits passed on to offspring) Variation component – there must be genetic variation among individuals of population Genetic variation must lead to variation in fitness (the ability to survive and reproduce)

13 Evolution Remember, evolution is the genetic change in populations over time Individuals do NOT evolve; evolution refers to generation-to-generation changes Evolution does not lead to perfectly-adapted organisms; natural selection results from environmental factors that vary from place to place and from time to time (a trait that is favorable in one situation may be detrimental in another)

14 Evolution Evolution is a gradual change over time

15 Evidence for Evolution Fossils!!! – the fossil record (the sequence in which fossils appear in layers of sedimentary rocks) provide some of the strongest evidence of evolution Sedimentary rocks form from sand and mud that settles to the bottom of seas, lakes and swamps; when organisms die, they settle along with the sediments and are preserved as fossils

16 Evidence for Evolution Trilobite: 230 mya Seed fern: 150 mya Allosaurus: 65 mya

17 Evidence for Evolution Microevolution – evolution can be observed in nature (pesticide-resistance in insects, Peppered moths/industrial melanism) A well-known example of microevolution is the case of the Peppered moths in England during the Industrial Revolution Known as “industrial melanism”

18 Microevolution Prior to the industrial revolution, light variants of the peppered moth survived better than dark variants because they blended well with the light colored trees (caused by the presence of a light-colored lichen) Pre-industrial era – only light variant known 1848 – first dark variant collected Mid-1900’s – dark variant made up 90% of population in industrial areas!

19 Microevolution Poor air quality killed the lichens which covered the otherwise dark trees and camouflaged the light moths against predation Light moths were predated on; dark moths were not (Prior to the industrial revolution, the reverse would be true)

20 Evidence for Evolution Artificial selection – the process by which humans have modified other species by selectively breeding for desired traits Darwin got the idea of natural selection from artificial selection! terryandchristine/ / /

21 Terminal bud Lateral buds Leaves Kale Stem Brussels sprouts Cauliflower Cabbage Kohlrabi Wild mustard Flower clusters Flowers and stems Broccoli

22 Artificial Selection All dogs are domesticated breeds of the Gray wolf, Canis lupus; “Fido” is actually a subspecies of the wolf!

23 Artificial Selection

24 Humerus Radius Ulna Carpals Metacarpals Phalanges HumanCatWhaleBat Evidence for Evolution Homologous structures – similar characteristics that result from a common ancestry

25 Evidence for Evolution A prime (and very amusing) example of homologous structures are vestigial organs; remnants of structures that have no apparent function, but served important functions in organism’s ancestors

26 Evidence for Evolution

27 Vestigial structures of a whale

28 Evidence for Evolution In contrast to homologous structures, analogous structures also provide evidence for evolution Analogous structures are structures that share similarities by a way of life, not by a common ancestry Analogous structures arise among unrelated organisms in response to similar needs or similar environmental factors

29 Analogous structures Examples: wings of insects (a) and birds (b); flippers of seals (c) and penguins (d)

30 Evidence for Evolution Remember, evolution uses the materials and processes that are already available (it fashions adaptations, rather than starting from scratch) Evolution is a tinkerer, not a master engineer (a tinkerer uses tools already there to improve) Adaptations are not perfect Evolution is constant; traits that are well- adapted for today may not be so tomorrow…

31 Evidence for Natural Selection Darwin’s fishes of the Galapagos 14 species of finch; 1 common ancestor (from the mainland); different beaks

32 Anatomical Evidence of Evolution Orchid petals - used as pollinator lure Snake with 2 leg bones (vestigal) Manatee fingernails (vestigal) Humans – muscles for wiggling ears

33 Developmental similarities reflect descent from a common ancestor

34 Ontogeny recapitulates phylogeny! Pop quiz time!!! Which of the bottom images shows a lemur? A pig? A human?

35 Mutations and sexual reproduction are the driving forces of evolution New alleles originate by mutation, a change in the nucleotide sequence of DNA Only mutations in cells that produce gametes can be passed along to offspring Most mutations are harmful, however a mutant allele may improve the adaptation of an individual to its environment and enhance its reproductive success

36 Mutations and sexual reproduction are the driving forces of evolution Mutation rates in animals and plants average ~1 in every 100,000 genes per generation (a slow process!) Sexual reproduction is a quick and easy (insert giggling here) means of increasing genetic diversity and variation, creating genetically- distinct individuals with new combinations of alleles (which may enhance adaptation and reproductive success!)

37 Evolution Evolution is a widely accepted scientific theory that describes the observed changes in living things over time Scientists use evolution to explain the great diversity of life, but some dispute its ability to describe the origins of life on Earth

38 Other theories out there Name Descent with modification? Common ancestor? Extinction? Creation (A) NoNoNo Transformism (B) YesNoNo Evolution (C) YesYesYes change extinction (A)(B)(C)

39 FSM And my personal favorite – The Church of the Flying Spaghetti Monster! Satirical protest to Kansas Board of Education’s decision to require the teaching of Intelligent Design, an alternative to Creationism which avoids specifying identity of ‘designer’ Founded in 2005 The FSM is invisible and undetectable; evidence of evolution planted by FSM to test “Pastafarian”’s faith

40 FSM

41 Evolution Remember, evolution is an accepted (and well-supported) scientific theory Scientific theories can never be proven (you cannot prove a hypothesis) but can be supported or rejected; must also be testable and falsifiable Distinct from religion, which is neither testable or falsifiable; nonetheless, debates over evolution linger on!


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