The Evolution and Classification of Species Darwin argued for adaptive radiation in which demes spread out in a given environment and evolved How related are organisms? Taonomy the science of classifying organisms into different categories according to their relationships and ordering them into hierarchies 1
Human Taonomy Domain Kingdom Phylum Class Order Family Genus Species Subspecies Eukaryota (nucleus in cell) Animalia (multi-celled; heterotroph) Chordata (backbone [mostly]) Mammalia (live young; warm-blooded) Primates (prosimians & simians) Hominidae (humans and great apes) Homo (humans and related ancestors) sapiens (all humans) sapiens (modern humans) Species A group of organisms that can interbreed to produce fertile offspring. Members of one species are reproductively isolated from members of all other species A bunch of -enys Phylogeny the relatedness of various groups of organisms. It includes the evolutionary history of an organism Ontogeny the development of an organism from fertilized egg to mature form 2
Ontogeny recapitulates phylogeny Humans 3 3 1 1 2 Major features: 1. Large brain 2. Non-honing chewing 3. Speech. Bipedalism 1 Problems with species This does not happen with comple organisms Anagenesis - where a single species eists at any given point in time but evolves over a period of time. This is straight-line evolution. Species 1???? Species 2 3
Cladogenesis It involves the formation of one or more new species (speciation) that branch from an original species. also called divergent evolution Species 1 Species 1??? Species 2 Genetic Divergence Mutation, genetic drift, and natural selection will produce genetic divergence. Time Slide 3 Mules are the offspring of a male donkey and a female horse 2011 by The McGraw-Hill Companies, Inc. All rights reserved.
Slide 5 a hinny! Male horse and female donkey 2011 by The McGraw-Hill Companies, Inc. All rights reserved. Zedonk Semi-species Horses and donkeys can breed, but their offspring is sterile. Horses and donkeys are therefore separate species. The concept of semi-species has been suggested for populations that are only partially isolated from each other reproductively. 5
today 2 species 50,000 years ago semi-species 100,000 years ago one species Hu-anderthal? We have found remains of humans with very strong Neanderthal-like traits from around 30,000 years ago 6
What we have to work with Evolution...fast or slow? stasis change change time time gradualism punctuated equilibrium The Death of Species More than 99% of all species that have ever eisted have become etinct. Permian etinction 251 million years ago 96% of land species die Cretaceous etinction 65 million years ago dinosaur etinction gives rise to mammals Mass etinction 7
doh! ok so... species evolve species adapt species die Classification of Species Biological classification reflects certain common characteristics between organisms. We have to distinguish between shared ancestry and coincidence 8
Analogy (homoplasy) Superficial similarity due to the independent evolution of the same trait (s) in both species. Types of Homoplasy Convergent evolution is the independent evolution of similar traits in more distantly related species (i.e., evolution of flight in birds and flies). Parallel evolution is the independent evolution of similar traits in closely related species (i.e., increase in dental size among early human ancestors). Homology Homology refers to similarity due to descent from a common ancestor. Animals may use their anatomical features for different purposes i.e., whale, bird, and humans have similar limb bones. 9
Homologous traits Primitive traits are those that are inherited from an earlier form. Homologous traits Derived traits are those that have changes from an ancestral state. Primitive & Derived Traits The concept of primitive and derived traits is relative. What might be considered primitive at one level of comparison might be considered a derived trait at another level. Monkey (has tail) Primitive Reptile (has tail) Gorilla (has no tail) Derived Monkey (has tail) 10
Classification of Species Cladistics Looks at only shared derived traits and classifies organisms based solely on their evolutionary relationship (shared / derived traits only) Which of these species are the most closely related? Baboons Projecting face Large canines Supraorbital bar Tail Narrow thora Chimpanzees Projecting face Large canines Supraorbital bar No Tail Wide thora Humans No facial projection Small canines No supraorbital bar No Tail Wide thora Which of these species are the most closely related? Baboons Projecting face Large canines Supraorbital bar Tail Narrow thora Chimpanzees Projecting face Large canines Supraorbital bar No Tail Wide thora Humans No facial projection Small canines No supraorbital bar No Tail Wide thora Primitive (ancestral) conditions 11
Parsimony things are usually connected in the most economical way traits are more likely to have evolved once Lungs Full body hair Legs Mammary glands Cat Dog Salama nder Cladistics What if we add a fish? Lungs Hair Legs Gland s no no no no Species diversity Ancestral species Time 12
Speciation Species diversity Time Species diversity Clade Time Species diversity Haplorhine Ancestor Monkeys and Apes Tarsiers Time 13
The reality of the fossil record Species diversity Fossil species Monkeys and Apes Tarsiers Time Modern species 1