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

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

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

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)

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

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

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

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

Fig Artificial kingsnakes Brown artificial snakes 83% 84% 17% 16% Coral snakes absent Coral snakes present Percent of total attacks on artificial snakes RESULTS

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

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.

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

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

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

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

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

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

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

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

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

Evolution via Natural Selection Over production: Organisms produce more offspring than can survive Limited Resources: There usually isn’t enough to go around. Observations

Fig Spore cloud

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

Fig

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

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

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

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

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

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

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

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

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

Fig Humerus Radius Ulna Carpals Metacarpals Phalanges HumanWhale Cat Bat Morphology: Homologous Structures in mammals

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

Fig b Chimpanzee fetusChimpanzee adult Human fetusHuman adult Morphology: Ontogeny

Fig Sugar glider Flying squirrel AUSTRALIA NORTH AMERICA Convergent Evolution

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

The pace of scientific change