Criteria of Organism Classification:
1. Homologous: common feature from same ancestor
2. Analogous: similar feature from different ancestor
1. Primitive: every individual in group has it
2. Derivative: not every individual in group has it
Systematics:
1. Phenetic System: groups organisms based on phenotypic similarities only
Homologous characteristics = analogous characteristics
Doesn’t reconstruct evolutionary history
2. Cladistic system: based on similarity of characteristics that reflect evolutionary relationships
Derived characteristics = more important > primitive characteristics
Only accepts monophyletic groups
3. Classic system: based on similarity of characteristics that reflect evolutionary relationships
All shared characteristics = primitive + derived
Accepts monophyletic + paraphyletic groups
Types of Phylogenetic Trees:
1. Cladogram: node position indicates relative time but branch lengths are arbitrary
• Doesn’t indicate amount of time between ancestor + descendant
• Branches of equal length
2. Phylogram: branch length represents amount of change
3. Dendrogram/Ultrametric: nodes associated with specific geological time
Groups in Phylogenetic Trees:
1. Monophyletic: ancestor + all descendants e.g. Mammalian class
2. Paraphyletic: ancestor + not all descendants e.g. Reptilia class
3. Polyphyletic: missing ancestor + some descendants e.g. algae
Blue-green ancestor = eubacteria
Green + blue ancestor = missing
Phylogenetic Tree Hypothesis:
Parsimonious: choose tree with fewest evolutionary steps
Body form changes at different rate to DNA/RNA
Morphological similarities different to genetic similarities
More molecular evolution = not expressed in body form
Estimating Evolutionary Timelines:
Radiometric dating: compares radioactive isotope + decay product concentration to estimate age
Stratigraphy: layering of deposited rocks
Molecular clocks: amount of genetic divergence separates related species e.g. mitochondria
Comparing ribosome structure = can separate larger groups
6 Kingdoms:
1. Eubacteria: unicellular, prokaryotic e.g. cyanobacteria
2. Archaea: unicellular, prokaryotic, no peptidoglycan in cell wall e.g. halophile bacteria
3. Protista: unicellular, eukaryotic e.g. Paramecium algae
4. Fungi: multicellular, heterotrophic, non-motile
, 5. Plantae: multicellular, photosynthetic, non-motile, cellulose cell
wall
6. Animalia: multicellular, heterotrophic, motile
Animalia Kingdom:
Choanoflagellates: evolutionary ancestor of all animals
• Cell differentiation -> 4 types = epithelial, nervous, muscle, skeletal
• Unique blastula stage of development
• Mostly sexual reproduction
55 Phyla, 34 phyla = invertebrates, vertebrates < 1 phyla
= Porifera, Cnidaria, Platyhelminthes, Mollusca, Annelida, Nematoda, Echinodermata, Arthropoda,
Chordata
Body Plans:
Body Symmetry:
1. Asymmetric = primitive e.g. Porifera
2. Radial = primitive e.g. Cnidaria
3. Bilateral = modern e.g. Anthropods
Body Cavities:
1. Acoelomates: no body cavity, organs surrounded by mesenchyma, mesoderm, ectoderm
2. Coelomates: cavity contains organs + is surrounded by mesoderm
3. Pseudocoelomates: internal cavity contains organs + organs not surrounded by mesoderm
Coelome Development:
1. Protostomes:
a. 8 cell stage
b. 2 cell layers = offset
c. Forms blastula
d. Blastospore: entrance to cavity
e. Coelome forms digestive tube
f. Mouth develops from blastospore = opening of embryonic gut
2. Deuterostomes:
a. 8 cell stage
b. 2 cell layers = aligned
c. Forms blastula
d. Outward bulges off developing digestive tract -> form coelom
e. Anus develops from blastospore
Life Styles:
Parasite: doesn’t kill host
Parasitoids: keeps host alive while feeding but final stage = host death
Predator: kills host
1. Porifera Phylum: Sea sponges
• Aquatic + mostly marine
• Acoelomates
• Sessile adults + free-swimming larvae
, • Mostly asymmetric – some are radial
• No tissues + organs
• Made of flagellated collar cells
• Filter feeders: collar cells create water currents -> trap food particles in mucus
• Mostly hermaphrodites: 1 individual has female + male sex organs = release sperm + eggs ->
fertilisation in water = asexual reproduction
2. Cnidaria Phylum: Stinging = sea anemones, corals, jelly fish
• Aquatic + mostly marine
• Radial symmetry
• Acoelomates – have 1 opening for gastrovascular cavity
• 2 cell layers = epidermis + gastrodermis -> no mesoderm
• Mesoglea: extracellular matrix = hydrostatic skeleton + gelatine structure
• 2 body forms: sessile polyps + mobile medusae
• Stinging Cells: Sacs in tentacles contain thread -> discharges into prey + releases venom
Life Cycle:
a. Polyp colony asexually reproduce -> medusae bud
b. Medusae sexually reproduce by releasing sperm + eggs into water
c. External fertilisation -> planula larva -> mature polyp
Cnidaria Classes:
1) Hydrozoa: medusae, polyp, hydra
2) Scyphozoa: medusae = jellyfish
3) Cubozoa: medusae = jellyfish
4) Anthozoa: polyp = sea anemones, corals
Coral Reefs:
• Stony corals = cnidaria polyps
• Symbiotic zooxanthellae: unicellular photosynthetic protist
3. Platyhelminthes Phylum: flat worms, flukes + tape worms
• Free-living, aquatic + parasitic
• Bilateral symmetry
• Parasites = anaerobic, non-parasites = aerobic
• Acoelomates – 1 mouth + no anus
o Release waste through skin
• Parenchyma: soft tissue
Platyhelminthes Classes:
a. Turbellaria: free-living flatworm
b. Trematoda: endoparasite flukes of mammals
c. Cestoda: endoparasite tapeworms of mammals
d. Monogenea: ectoparasitic flatworms of fish
Pre-adaptations: small, asexual reproduction – for repair (grow 2 if cut in half), flat +
cylindrical, hermaphrodites in planarian worms, reduced sensory organs
Adaptations: loss of sensory organs as don’t need to hunt, attachment organs, anaerobic
respiration – low O2 inside organism
Life Cycle of Pork Tapeworm: Taenia solium
Matures in humans = primary host
Larve in pigs = secondary host
