Classification Chapter 18
The domain system Prokaryotic domains Bacteria and Archaea Eukaryotes Are in the domain Eukarya Bacteria Archaea Eukarya Earliest organisms Prokaryotes Eukoryotes Figure 15.10B
Two patterns of evolutionary change (a) Anagenesis (b) Cladogenesis
Hierarchical classification Species Panthera pardus Genus Panthera Family Felidae Order Carnivora Class Mammalia Phylum Chordata Kingdom Animalia Domain Eukarya
Order Family Genus Species The connection between classification and phylogeny Panthera pardus (leopard) Mephitis mephitis (striped skunk) Lutra lutra (European otter) Canis familiaris (domestic dog) Canis lupus (wolf) Panthera Mephitis Lutra Canis Felidae Mustelidae Canidae Carnivora
Monophyletic, paraphyletic, and polyphyletic groupings Grouping 1 Grouping 2 Grouping 3 D E G H J K D E G H J K D E G H J K C F I C F I C F I B B B A A A (a) Monophyletic. In this tree, grouping 1, consisting of the seven species B H, is a monophyletic group, or clade. A monophyletic group is made up of an ancestral species (species B in this case) and all of its descendant species. Only monophyletic groups qualify as legitimate taxa derived from cladistics. (b) Paraphyletic. Grouping 2 does not meet the cladistic criterion: It is paraphyletic, which means that it consists of an ancestor (A in this case) and some, but not all, of that ancestor s descendants. (Grouping 2 includes the descendants I, J, and K, but excludes B H, which also descended from A.) (c) Polyphyletic. Grouping 3 also fails the cladistic test. It is polyphyletic, which means that it lacks the common ancestor of (A) the species in the group. Furthermore, a valid taxon that includes the extant species G, H, J, and K would necessarily also contain D and E, which are also descended from A.
CHARACTERS Lancelet (outgroup) Lamprey Tuna Salamander Turtle Leopard Constructing a cladogram TAXA Hair 0 0 0 0 0 1 Amniotic (shelled) egg 0 0 0 0 1 1 Four walking legs 0 0 0 1 1 1 Hinged jaws 0 0 1 1 1 1 Vertebral column (backbone) 0 1 1 1 1 1 (a) Character table. A 0 indicates that a character is absent; a 1 indicates that a character is present. Lancelet (outgroup) Lamprey Turtle Leopard Hair Salamander Amniotic egg Tuna Four walking legs Hinged jaws Vertebral column (b) Cladogram. Analyzing the distribution of these derived characters can provide insight into vertebrate phylogeny.
Trees with different likelihoods Human Mushroom Tulip Human 0 30% 40% Mushroom 0 40% Tulip 0 (a) Percentage differences between sequences 25% 15% 15% 20% 15% 5% 5% 10% Tree 1: More likely Tree 2: Less likely (b) Comparison of possible trees
Arranging life into kingdoms is a work in progress In the five-kingdom system Prokaryotes are in the kingdom Monera Eukaryotes (plants, animals, protists, and fungi) are grouped in separate kingdoms Monera Protista Plantae Fungi Animalia Earliest organisms Figure 15.10A Prokaryotes Eukoryotes
Prokaryotes (Monera) Bacteria live EVERYWHERE! Bacteria live in all ecosystems on plants & animals in plants & animals in the soil In EXTREMES (hot, cold, acid, salt, deep) on the living on the dead Microbes always find a way to make a living!
Prokaryote Structure eukaryote cell Unicellular prokaryote cell bacilli, cocci, spirilli Size ~1/10 size of smallest eukaryotic cell 1 micron (1um) Internal structure no internal compartments no membrane-bound organelles only ribosomes circular chromosome, naked DNA not wrapped around proteins
Protista: General characteristics Classification criteria eukaryotes not animal, plant or fungi That s more of what they re not & not what they are!
Protist Diversity The full spectrum of modes of life unicellular to multicellular autotrophic to heterotrophic asexual to sexual reproduction pathogenic to beneficial sessile to mobile
Problems with Protist Classification Too Diverse! doesn t reflect any evolutionary relationship amongst all kingdom members paraphyletic Something s not right here!
Plantae: Bryophytes non-vascular land plants mosses Pteridophytes seedless vascular plants ferns Gymnosperm pollen & naked seeds conifers pollen & seeds Angiosperm flowers & fruit flowering plants flowers vascular system = water conduction Tracheophytes colonization of land Ancestral Protist xylem cells = tracheids
Fungi: General characteristics Classification criteria eukaryotes heterotrophs Absorb nutrients mostly multicellular EXCEPT unicellular yeasts cell wall chitin rigid polysaccharide sexual & asexual reproduction
Fungal body mycelium Cells Fungal Structure thread-like cells hyphae multiple nuclei Cell wall chitin just like crab shells
Ecological Roles Decomposers recycle nutrients Symbiotic Relationships lichen fungi + algae cyanobacteria or green algae pioneer species in ecosystems makes soil from bare rock mycorrhizae fungi + plants enables plants to absorb more water Lichens are fungi that have discovered agriculture!
Fungal Diversity Fungi
Animal Characteristics Heterotrophs must ingest orgnaisms ( food ) for nutrients Multicellular complex No cell walls Allows quickmovement Sexual reproduction no alternation of generations no haploid gametophyte
Animal Evolution Porifera Cnidaria Platyhelminthes Nematoda sponges jellyfish flatworms roundworms mollusks redundancy, specialization, mobility Annelida Echinodermata Mollusca Arthropoda Chordata segmented worms segmentation insects spiders starfish body size body & brain size, mobility endoskeleton vertebrates backbone coelom digestive sys radial body cavity body complexity digestive & repro sys bilateral symmetry distinct body plan; cephalization tissues specialized structure & function, muscle & nerve tissue multicellularity Ancestral Protist specialization & body complexity bilateral
Review Questions
1. The temperature at which hybrid DNA melts is indicative of the degree of homology between the DNA sequences. The more extensive the pairing, the higher the temperature required to separate the strands. You are trying to determine the phylogenetic relationships among species A, B, and C. You mix single-stranded DNA from all three species (in test groups of two) and measure the temperatures at which the hybrid DNA melts (separates). You find that hybrid BC has the highest melting temperature, AC the next highest, and AB the lowest.
(cont.) From these data you conclude that * A. species A and B are most closely related, whereas B and C are least closely related. B. B and C must be the same species, and A is more closely related to C than to B. C. species B and C must have diverged most recently, and A is more closely related to C than to B. D. A hybridizes most easily with B, and they must have a more recent common ancestor than do A and C. E. these tests are inconclusive and you had better go back and check the fossil record.
2. According to this dichotomous phylogenetic tree created using cladistic analysis, C and D are most closely related because they A. do not share a common ancestor with O, A, or B. B. are monophyletic. C. evolved from a common ancestor a long time ago. D. have the most shared derived characters in common. E. have the greatest number of anatomical similarities as shown by statistical analysis.
3. A biologist discovers two new species of organisms, one in Africa and one in South America. The organisms resemble one another closely. Which type of evidence would probably be least useful in determining whether these organisms are closely related or are the products of convergent evolution? A. the history and timing of continental drift B. a comparison of DNA from the two species C. the fossil record of the two species D. analysis of the behavior of the two species E. comparative embryology
Use Figure 25.1 to answer the following questions. 4. A common ancestor for species C and E could be at position number A. 1. B. 2. C. 3. D. 4. E. 5.
E. The two extant species that are most closely related to each other are 1. A and B. 2. B and D. 3. C and B. 4. D and E. 5. E and A.
5. If this evolutionary tree is an accurate depiction of relatedness, then which of the following should be correct? A. The entire tree depicts anagenesis. B. If all species depicted here make up a taxon, this taxon is monophyletic. C. The last common ancestor of species B and C occurred more recently than the last common ancestor of species D and E. D. Species A is the ancestor of both species B and C. E. The species present at position number three is ancestral to three extant species. 1. B only 2. A and C 3. C and D 4. B, C, and D 5. B, C, and E
A researcher compared the nucleotide sequences of a homologous gene from five different species of mammals. The sequence homology between each species' version of the gene and the human gene are presented as a percentage of similarity. Species Percentage Chimpanzee 99.7 Orangutan 98.6 Baboon 97.2 Rhesus Monkey 96.9 Rabbit 93.7
6. What conclusion can be validly drawn from these data? A. Humans and other primates evolved from rabbits. B. All organisms have similar DNA. C. Among the organisms listed, humans shared a common ancestor most recently with chimpanzees. D. Humans evolved from chimpanzees. E. Both A and D are correct.
7. Which statement represents the best explanation for the observation that the nuclear DNA of wolves and domestic dogs has a very high degree of homology? A. Dogs and wolves have very similar morphologies. B. Dogs and wolves belong to the same genus. C. Dogs and wolves are both members of the family Canidae. D. Dogs and wolves shared a common ancestor relatively recently. E. Convergent evolution has occurred.