Chapter 7 Animal Classification, Phylogeny & Organization

Classification and Phylogeny of Animals Aristotle Greek Philosopher and Biologist First to classify organisms according to structural similarities Carolus Linnaeus Swedish botanist (collected flowers) Designed current system of classification Binomial nomenclature

Binomial nomenclature: a two name system for writing Written in Latin Genus: Noun Written first Capitalized Species (specific epithet) adjective written second lowercase Italicized if typed, underlined if hand written "Formal" scientific names - have a third part, the authority. (The authority is not italicized or underlined) The authority - abbrev of last name of person who named the organism. Ex: Carolus Linnaeus, the first person to name many plants, the L. for Linnaeus is common in most plant scientific names and some animal names. Ranunculus ficaria L.

Example: The scientific name for the common robin Turdus migratoriuos L. Turdus = thrush (definition of thrush… birds which are mostly of a plain color often with spotted underparts and many of which are excellent singers migratorius = of migratory habit

Some history… When Linnaeus developed his system of classification, there were only two kingdoms, Plants and Animals. But the use of the microscope led to the discovery of new organisms and the identification of differences in cells. A two-kingdom system was no longer useful. Today the system of classification includes three domains. We will be focusing on the Domain Eukarya and Kingdom Animalia.

Classification Species – groups of interbreeding natural populations reproductively isolated from other groups

Cladistics System of Arranging Animals Clades organisms that share characteristics (Gr. klados = branch) Synapomorphy the term for the characteristic shared by members of a clade Gr. Synapsis = joining together + morphe = form Example: Clade = Birds Synapomorphies that identify birds as a clade = Amniotic egg, no teeth, presence of feathers

Cladogram Cladogram – nested hierarchy of clades presented as a branching diagram Outgroup – phylogenetically close, but not within the group being studied/compared

Cladogram vs. Phylogenetic Tree Phylogenetic Tree – Branches represent real lineages that occurred in the evolutionary past. To obtain a phylogenetic tree … add to the cladogram info about ancestors, durations of evolutionary lineages, or amounts of evolutionary changes in the lineages. In the phylogenetic tree on the right: numbers represent the numbers of expected mutational changes in a specific gene along different evolutionary lineages.

Can you “read” a cladogram Can you “read” a cladogram? Can you identify an outgroup and a “nested” group?

Animal Body Plans Metazoa – multicellular organism Animal Symmetry – orientation of body parts around a point or axis -Asymmetry: absence of point around which part are equally distributed (example: sponge) Radial: divided into many parts

Directional Terms Bilateral symmetry – divided into TWO mirrored halves, advantage = forward movement Anterior – head end Posterior – tail end -Cephalic – toward head -Caudal – toward tail -Dorsal – back Ventral – belly Medial – middle Lateral – side * Distal – part far away from trunk * Proximal – part close to trunk *appendages/arms/legs/fin

Planes of Symmetry Frontal – div into dorsal and ventral halves Sagittal (median)– div into right and left halves Transverse – div into anterior and posterior halves

Cephalization Nervous tissue – concentrated in head Primarily in bilaterally symmetrical animals Cephalized Uncephalized

Developmental Sequence Gastrulation – forming of germ layers (cell layers) We start as 1 cell, 2 cells, 4 cells… to become Blastula – hollow ball of cells The only multicellular animal that stays in this form is the sponge. Blastopore (indentation)

3. Forms Gastrula (two layers of cells… endoderm and ectoderm) 4. Complete gut forms Animals with only two germ layers are called diploblastic (Gr. Diplos, twofold, + blastos, germ) FYI: The word “germ” also means source Ex: Sea Anemones, comb jellies 5. Most animals are triploblastic and add a third germ layer. The third layer, the mesoderm, forms between the endoderm and ectoderm. Longitudinal section below:

Body Cavities Coelom – membrane lined fluid filled space surrounding the gut (ex: humans) Acoelomate – no coelom, no body cavity flatworms Pseudocoelomate – have a cavity, NOT lined round worms Eucoelomate- have a lined cavity humans

Cross section

Now they take different paths… Mollusks, Annelids, Arthropods The blastopore becomes the mouth They are called PROTOSTOME (“first mouth”) Echinoderms, Chordates (Vertebrates) The blastopore becomes the anus, mouth develops later They are called DEUTEROSTOME (“second mouth”)

How the cells divide Deuterostomes – cells divide equally All cells are same size Stacked, radial cleavage Protostomes – cells divide obliquely Spiral cleavage

Development Deuterostomes – all cells are identical, if separated all parts will become a new individual (identical twins). This is also why they use these cells for stem cell research. Protostomes – cells are pre-programmed, developmental fate is fixed, cannot separate and survive

Let’s see how you did… What side of this cat do we see, dorsal or ventral? Are the pads on her paws distal or proximal to the trunk? Are we protostomes or deuterostomes? Which type of cells develops in a spiral fashion, protostomes or deuterostomes?

5. What kind of plane is this image showing? 6. What do we call an organism that has a body cavity, but it isn’t lined? 7. What does it mean to call something cephalized?

8. What kind of plane would be going through the waist of something? 9. What is a Metazoan? 10. What term is used to describe something that is on an appendage close to the trunk? 11. How many germ cell layers do WE have? 12. What are the names of our germ cell layers?

Answers What side of this cat do we see, dorsal or ventral? ventral 2. Are the pads on her paws distal or proximal to the trunk? distal 3. Are we protostomes or deuterostomes? deuterostomes 4. Which type of cells develops in a spiral fashion, protostomes or deuterostomes? protostomes

5. What kind of plane is this image showing? Frontal 6. What do we call an organism that has a body cavity, but it isn’t lined? Pseudocoelomate 7. What does it mean to call something cephalized? It has a concentrated nervous region (usually in the head)

8. What kind of plane would be going through the waist of something? Transverse 9. What is a Metazoan? Multicellular organism 10. What term is used to describe something that is on an appendage close to the trunk? proximal 11. How many germ cell layers do WE have? three 12. What are the names of our germ cell layers? Endoderm, ectoderm, mesoderm

How did you do? 1. How many kingdoms are there? 2. Which kingdom do humans belong to? 3. What kind of plane is being shown in the picture? 4. What is wrong with this scientific name? homo sapien

5. What language are scientific names written in? 6. What is wrong with this scientific name for a Blue Whale? Balaenoptera Musculus 7. What is this diagram called? 8. What is the main purpose of the diagram in question #7?

Answers? How many kingdoms are there? Six 2. Which kingdom do humans belong to? Animalia 3. What kind of plane is being shown in the picture? Transverse 4. What is wrong with this scientific name? homo sapien Genus needs to be capitalized

5. What language are scientific names written in? Latin 6. What is wrong with this scientific name for a Blue Whale? Balaenoptera Musculus Not in italics 7. What is this diagram called? Cladogram 8. What is the main purpose of the diagram in question #7? Classifying/organizing animals

Dichotomous Key A key to five classes of Vertebrates 1 a hair present Mammalia b hair absent 2 2 a feathers present Aves b feathers absent 3 3 a paired fins present Osteichthyes b paired fins absent 4 4 a scales present Reptilia b scales absent Amphibia