Biodiversity and Patterns in Life

Biodiversity and Patterns in Life

Classifying life Carl von Linne (1707-78) Botanist and naturalist Began to classify organisms based on observed characteristics

Turn in your diagram/classification for 5pts extra credit Classification activity Lion Magnolia Crab Tiger Sea Lion Fish Orangutan Cat

What traits do they share? Lion Plant Crab Cat Tiger Fish Cells with nuclei, no cell walls, backbone, produces milk, large canine teeth, long tail, ability to roar Cells with nuclei, cell walls Cells with nuclei, no cell walls Cells with nuclei, no cell walls, backbone, produces milk, large canine teeth, long tail Cells with nuclei, no cell walls, backbone, produces milk, large canine teeth, long tail, ability to roar, dark vertical stripes Cells with nuclei, no cell walls, backbone Orangutan Cells with nuclei, no cell walls, backbone, produces milk Sea Lion Cells with nuclei, no cell walls, backbone, produces milk, large canine teeth

Nested hierarchy of shared characteristics Species Kingdom Phylum Class Order Family Genus Felidae Panthera Carnivora Animals Mammals Chordates (vertebrates) All living things

Linnaean system of classification Use observable shared or divergent characteristics to classify organisms in a nested hierarchical system Organism grouped at high levels of classification share a few, very general traits. Organisms grouped at lower levels of classification share many, very specific traits with each other. Give unique binomial name to each species (Genus species; e.g. Panthera tigris) Genus Panthera Phylum Chordata

Whence diversity? Why do organisms share characteristics? Where does diversity of life come from?

Two major hypotheses H1. Species were fixed, had always been the way they are. The assumption there is balance in nature. H2. Life on earth has changed over time Both hypotheses had been postulated in many different cultures, Ancient Greece, Rome, China, Medieval Islam Scientific evidence to test these hypotheses began to be collected in the age of exploration (1600-1800s)

Puzzling Observations Homologous structures: structures that have underlying similarities but very different functions

Puzzling Observations Vestigial traits: structures or traits that do not serve a function and are degenerated in form.

Puzzling Observations Similarities in embryo development

Why is bear species size correlated with latitude? Biogeography Why is the highest biodiversity around the equator? Why do animals at the North pole look like animals at the South Pole? Why do you find big flightless birds that look similar to each other on totally different continents?

Analogous traits Traits that are similar in function, but not necessarily sharing an underlying structure (e.g. wings of bats, birds and bees) Cactus Euphorbia

Fossils -Where are these organisms? -Why do some of them resemble extant (alive) organisms? - Extinction was not a widely accepted concept before the 1800s

Reflection (10 points) Observations Hierarchy of shared characteristics Homologous structures Vestigial traits Biogeography Adaptations Analogous traits Fossils Embryology Question Based on the observations we ve discussed, does one hypothesis seem to be more valid than the other? (H1. Life is fixed, H2. Life has changed) Explain your reasoning. And which of the observations support the hypothesis If both hypotheses are equally valid at this point, explain which evidence supports each and discuss what other evidence would be important in deciding.

Developments in Geology Understanding the history of life on earth went hand in hand with understanding the history of the earth (advances in the science of geology) Leading understanding at the time was catastrophism (earth generally fixed except for a few catastropic events) Uniformitarianism: Many geological formations can be explained by the accumulation of gradual changes over many many many years Conclusions: Earth has been around for a long time (millions of years, not thousands) The earth has changed over time. Charles Lyell (1797-1875)

Charles Darwin & Alfred Wallace HMS Beagle (1831) chart the coast of South America Darwin was offered job as naturalist, collecting specimens and recording observations Naturalist 1848 expedition to Amazon 1854-1862 travelled through Malay Archipelago studying island biogeography Known as the father of biogeography

Evolution Change over time Biologically: Descent with modification Small scale: changes in gene frequencies in a population from one generation to the next Large scale: accumulation of changes over thousands/millions of years leads to the descent of different species over many generations Thus... All organisms share common ancestors Some are more distant than others Classification is really study of genealogy

Look back on taxonomy Common mammal ancestor Common vertebrate ancestor Common animal ancestor Common ancestor of all living organisms Common panthera ancestor Common felis ancestor Common carnivora ancestor

Second cousin Geneaology Siblings Cousin Great grandma Grandma Mom

Development of taxonomy

What evidence is there that all living organisms share a common ancestor? What traits do al living organisms share?

Next time More on evolution The mechanism driving change Is there a conflict between science and religion?