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Announcements: 1. Labs meet this week 2. Lab manuals have been ordered 3. Some slides from each lecture will be on the web 4. Study questions will be posted after each lecture Prokaryotes Eukaryotes Protozoa Autotrophic Metazoa Heterotrophic Absorptive Monera Protista Plantae Fungi Ingest/digest Animalia What is an Animal ? 1. Animals are multicellular, heterotrophic, eukaryotes that ingest and digest their food. 2. Animals lack a cell wall. 3. Are capable of moving (during some point in their lives). 4. All animals have regulatory genes called Hox genes. •To date > 1.5 million species of animals have been described by biologists • ~ 10, 000 new species are described each year •Estimates of the total number of animal species are around 10 million. What is a Species? Species Concepts: 1. Typological species concept: species are distinct, unchanging entities defined by unique, morphological features. This concept has been abandoned by biologists. Some Problems with the Typological Species Concept It ignores evolution: species are not “unchanging entities” 1. Artificial selection: artificial selection for oil content in corn High oil Low oil Natural selection: Trinidadian guppies Some Problems with the Typological Species Concept Sexual Dimorphism: the sexes differ morphologically male female Sailfin molly Some Problems with the Typological Species Concept Alternative morphs: Hornless morph Horned morph e.g. horn polymorphisms in beetles Some Problems with the Typological Species Concept Cline: a change in in morphology along an environmental gradient Size in yarrow Some Problems with the Typological Species Concept Drosophila subobscura Latitude Some Problems with the Typological Species Concept Cryptic species: some species are similar morphologically but differ in other important ways Western meadowlark Eastern meadowlark What is a species? Species Concepts: 2. Biological species concept: a species is a population or group of populations that can potentially interbreed and produce viable,fertile offspring, but that is reproductively isolated from other populations. There is tremendous morphological variation within Homo sapiens. But all humans can potentially interbreed. In contrast, some species are very similar morphologically but can not interbreed… Western meadowlark Eastern meadowlark Mechanisms of reproductive isolation: 1. Prezygotic barriers: prevent mating or fertilization •Behavioral Western meadowlark Eastern meadowlark Mechanisms of reproductive isolation: 1. Prezygotic barriers: prevent mating or fertilization •Behavioral •Temporal Western spotted skunk: summer breeder Eastern spotted skunk: winter breeder Mechanisms of reproductive isolation: 1. Prezygotic barriers: prevent mating or fertilization •Behavioral •Temporal •Habitat isolation Aquatic garter snake Terrestrial garter snake Mechanisms of reproductive isolation: 1. Prezygotic barriers: prevent mating or fertilization 2. Postzygotic barriers: prevent hybrid from developing into a viable, fertile adult Some problems with the biological species concept: 1. It is hard to apply especially to fossil data. 2. Species exist in time and space: the biological species concept has no time component. 3. What do we do with asexual organisms? •Bdelloid Rotifers haven’t reproduced sexually for > 80 million years- each individual is reproductively isolated ! •An estimated 2000 species are completely asexual. Species Concepts: 1. Typological species concept 2. Biological species concept 3. Evolutionary species concept • Incorporates time 4. Ecological species concept • Incoporates niche 5. Phylogenetic species concept • Incorporates unique, evolved traits These have all been proposed to solve some of the problems of the other concepts •To date > 1.5 million species of animals have been described by biologists • ~ 10, 000 new species are described each year •Estimates of the total number of animal species are around 10 million. •How do biologists organize all of this diversity? Classification and Phylogeny of Animals •Taxonomy: the branch of biology that deals with the systematic classification and naming of species (or groups of species) (long pre-Darwinian history). Taxonomy Carolus Linnaeus (1707- 1778) •Swedish botanist •Systema Naturae: a classification scheme that used morphology to group organisms into hierarchical categories Taxonomy Linnaean Classification Kingdom •In this scheme the major categories are called taxa Phylum Class Order Family Genus species •Higher taxa are increasingly inclusive •Each species is given a unique binomial name: Binomial nomenclature Taxonomy Linnaean Classification: an example Kingdom: Animalia Phylum: Chordata Class: Aves Order: Piciformes Family: Picidae Genus: Melanerpes species: carolinus Taxonomy Linnaean Classification: another example Kingdom: Animalia Phylum: Chordata Class: Aves Order: Piciformes Family: Picidae Genus: Melanerpes species: erythrocephalus Taxonomy Linnaean Classification: another example Kingdom: Animalia Phylum: Chordata Class: Aves Order: Piciformes Family: Ramphastidae Keeled toucan Genus: Ramphastos species: sulfuratus Taxonomy Linnaean Classification Kingdom: Animalia Phylum: Chordata Subphylum: Vertebrata Class: Mammalia Subclass: Eutheria Order: Primates Suborder: Anthropoidea Family: Pongidae Subfamily: ~ Genus: Gorilla species: gorilla Classification and Phylogeny of Animals •Taxonomy: the branch of biology that deals with the systematic classification and naming of species (or groups of species) (long pre-Darwinian history). •Systematics: the branch of biology that seeks to understand the evolutionary relationships between groups of organisms (post-Darwinian). -One of the major goals of systematics is the construction of phylogenies Systematics Phylogeny: an evolutionary tree that depicts the relationships between living and extinct species (or higher taxonomic groups) A Most recent common ancestor of A and B B C D Most recent common ancestor of C and D Most recent common ancestor of A, B, C and D Systematics What kind of information is used to construct phylogenies? •Characters: organismal features that vary among species (morphological or molecular characteristics) Morphological characters used to construct phylogenies- •Levels of organization: 1. Cellular level: an aggregation of cells that are functionally differentiated, but that are not organized into tissues 2. Tissue level: cells are organized into tissues that have a specific function 3. Organ level: tissues are aggregated into organs that have specialized functions sponges jellyfish, corals, etc. other animals organ level tissue level cellular level Morphological characters used to construct phylogenies •Type of symmetry: the arrangement of body structures relative to some axis of the body 1. Asymmetrical: 2. Radial symmetry: 3. Bilateral symmetry: Asymmetrical No plane can divide the body into two symmetrical halves Bilateral Radial > 1 plane can divide the body into two symmetrical halves 1 plane divides the body into two symmetrical halves sponges jellyfish, corals, etc. other animals bilateral symmetry radial symmetry asymmetrical Characters used to construct phylogenies •The presence of different body structures •Developmental patterns •Molecular data: DNA / RNA sequence data What kind of information is used to establish these relationships? •Characters: organismal features that vary among species (morphological or molecular characteristics) •Homologous characters: characters that are similar to one another due to shared ancestry (not necessarily shared function) Examples of homologous characters: Vertebrate forelimbs •Analogous characters: characters that are similar to one another in function, but not ancestry. •Analogous characters are not useful in determining the evolutionary relationships between organisms. Examples of analogous characters: bat wings and insect wings Bat wing Fly wing Classification and Phylogeny of Animals •Taxonomy: the branch of biology that deals with the systematic classification and naming of species (or groups of species) (long pre-Darwinian history). •Systematics: the branch of biology that seeks to understand the evolutionary relationships between groups of organisms (post-Darwinian).