What is science and how is it done? What is science? - Science is the systematic investigation of phenomena

Transcription

1 What is science and how is it done? What is science? - Science is the systematic investigation of phenomena How is it carried out? - The SCIENTIFIC METHOD is the systematic process by which such investigations are conducted

2 Scientific Method Make an observation Ask questions about causes Develop testable hypotheses Make predictions based on hypothesis Perform experiments to test hypothesis

3 We need repeated observations replicates! Select 1 marble = blue Assumption: all marbles are blue Sampling error can result from too few observations! Select 10 marbles - 3 marbles blue Assumption: 30% of marbles are blue

4 A Case Study in Scientific Inquiry: Investigating Mimicry in Snake Populations Observation: 1. Dangerous creatures have warning coloration 2. Benign creatures mimic the dangerous Question: Why? Hypothesis: Mimicry evolved in harmless species as an evolutionary adaptation that reduces their chances of being eaten (Henry Bates)

5 Fig Scarlet kingsnake (nonpoisonous) Key Range of scarlet kingsnake only Overlapping ranges of scarlet kingsnake and eastern coral snake South Carolina North Carolina Eastern coral snake (poisonous) Scarlet kingsnake (nonpoisonous)

6 Field Experiments with Artificial Snakes Experimental Design fake snakes An experimental group resembling kingsnakes A control group resembling plain brown snakes Equal numbers of both types were placed at field sites, including areas without poisonous coral snakes After four weeks, the scientists retrieved the artificial snakes and counted bite or claw marks Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

7 A Case Study in Scientific Inquiry: Investigating Mimicry in Snake Populations Hypothesis: Mimicry evolved in harmless species as an evolutionary adaptation that reduces their chances of being eaten (Henry Bates) Hypotheses for this experiment: H1: The ringed snakes will be attacked less frequently in the geographic region where coral snakes were found Null Hypothesis H0: There will be no difference

8 Fig (a) Artificial kingsnake (b) Brown artificial snake that has been attacked

9 Percent of total attacks on artificial snakes Fig RESULTS % 84% Artificial kingsnakes Brown artificial snakes % 16% 0 Coral snakes absent Coral snakes present

10 Fig Scarlet kingsnake (nonpoisonous) Key Range of scarlet kingsnake only Overlapping ranges of scarlet kingsnake and eastern coral snake South Carolina North Carolina Eastern coral snake (poisonous) Scarlet kingsnake (nonpoisonous)

11 A Case Study in Scientific Inquiry: Investigating Mimicry in Snake Populations Hypotheses for this experiment: H1: The ringed snakes will be attacked less frequently in the geographic region where coral snakes were found Null Hypothesis H0: There will be no difference Result: The prediction is upheld. The null hypothesis is not supported, the hypothesis is not rejected.

12 Limitations of Science repeatable peer review Old science is replaced by new science when there is a huge mountain of evidence, not before. Science cannot support or falsify supernatural explanations, which are outside the bounds of science Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

13 Theories in Science In the context of science, a theory is: Broader in scope than a hypothesis General, and can lead to new testable hypotheses Supported by a large body of evidence in comparison to a hypothesis Vetted EXAMPLE: Evolution the central unifying theory of Biology and one of the central theories of Geology Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

14 Fig. 22-UN1 Observations Individuals in a population vary in their heritable characteristics. Organisms produce more offspring than the environment can support. Inferences Individuals that are well suited to their environment tend to leave more offspring than other individuals and Over time, favorable traits accumulate in the population.

15 Fig Big new ideas occur from many smaller breakthroughs Linnaeus (classification) Hutton (gradual geologic change) Lamarck (species can change) Malthus (population limits) Cuvier (fossils, extinction) Lyell (modern geology) Darwin (evolution, natural selection) Wallace (evolution, natural selection) American Revolution French Revolution U.S. Civil War Hutton proposes his theory of gradualism Malthus publishes Essay on the Principle of Population Lamarck publishes his hypothesis of evolution Lyell publishes Principles of Geology Darwin travels around the world on HMS Beagle Darwin begins his notebooks Darwin writes essay on descent with modification Wallace sends his hypothesis to Darwin The Origin of Species is published.

16 Fig GREAT BRITAIN EUROPE NORTH AMERICA ATLANTIC OCEAN The Galápagos Islands Fernandina Isabela Pinta Marchena Santiago Pinzón Santa Cruz Florenza Genovesa Daphne Islands Santa Fe San Cristobal Española PACIFIC OCEAN SOUTH AMERICA Tierra del Fuego Cape Horn Cape of Good Hope AFRICA Equator AUSTRALIA Tasmania New Zealand

17 Fig (a) Cactus-eater (c) Seed-eater (b) Insect-eater

18 Evolution Evolutionary change is based on the interactions between populations and their environment A population is the smallest unit that can evolve Individuals are selected Populations evolve

19 Fig (a) A flower mantid in Malaysia (b) A stick mantid in Africa

20 Organisms are adapted to their environments How does this happen?

21 Evolution via Natural Selection Over production: Organisms produce more offspring than can survive Limited Resources: There usually isn t enough to go around. Observations

22 Fig Spore cloud

23 Evolution via Natural Selection Variation: Individuals vary extensively (phenotype) Inheritance of Variation: Much of this morphological variation is inherited (genotype) Observations

24 Fig

25 Evolution via Natural Selection Inference #1 Struggle for existence: production of more individuals than can be supported leads to competition for recourses

26 Evolution via Natural Selection Inference #2 Survival of the best adapted: Individuals with traits that give them an advantage in the struggle for limited resources will survive. These individuals are more likely to leave offspring than individuals that are less fit

27 Evolution via Natural Selection Inference #3 Accumulation of adaptations:the unequal ability of individuals to survive and reproduce will lead to a gradual change in populations

28 To sum up 1. Individuals within species vary (phenotypic variation) 2. Some of this variation is heritable (genetic variation) 3. Survival and/or reproduction are non-random (natural selection) The individuals that survive & reproduce the most are those with variations most suited to their environment Hawaiian honeycreepers

29 Evolution is supported by an overwhelming amount of scientific evidence argued for 250+years New discoveries continue to fill the gaps identified by Darwin in The Origin of Species Direct evidence in the lab and in the field Fossil Record Molecular Homology Convergent Evolution Ontogeny

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

31 Fig Layers of deposited sediment Younger stratum with more recent fossils Older stratum with older fossils

32 Fig Fossils (a) Pakicetus (terrestrial) (b) Rhodocetus (predominantly aquatic) (c) Dorudon (fully aquatic) Pelvis and hind limb Pelvis and hind limb (d) Balaena (recent whale ancestor)

33 Molecular evidence includes: Direct sequence similarity Regulatory genes Hox gene 6 Hox gene 7 Hox gene 8 Ubx About 400 mya Drosophila Artemia

34 Fig Morphology: Homologous Structures in mammals Humerus Radius Ulna Carpals Metacarpals Phalanges Human Cat Whale Bat

35 Fig Morphology: Ontogeny Pharyngeal pouches Post-anal tail Chick embryo (LM) Human embryo

36 Fig b Morphology: Ontogeny Chimpanzee fetus Chimpanzee adult Human fetus Human adult

37 Fig Sugar glider NORTH AMERICA AUSTRALIA Convergent Evolution Flying squirrel

38 Fig Pigmented cells (photoreceptors) Epithelium Pigmented cells Nerve fibers (a) Patch of pigmented cells (b) Eyecup Nerve fibers Fluid-filled cavity Epithelium Cellular mass (lens) Cornea Optic nerve (c) Pinhole camera-type eye Pigmented layer (retina) Optic nerve (d) Eye with primitive lens Cornea Lens Optic nerve Retina (e) Complex camera-type eye

39 The pace of scientific change