Classifying Living Things

1. Classifying Living Things Thousands of years ago, Aristotle arranged a “chain of being.” Other scientists used this strategy to arrange living things from “simple” to “complex.” Humans were at the top of the chain.

2. King Phillip Comes Over For Good Spaghetti • Kingdom • Phylum • Class • Order • Family • Genus • Species

3. Classifying Living Things In the 18th century, Linnaeus developed a system for classification that emphasized the shared similarities of organisms. This system classified organisms using a number of hierarchical levels, from domain to species.

4. Diversity on Earth • Diversity: variety of living organisms • Estimated between 5-15 million species • Only 1.5 million have been described

5. Common vs. Scientific Names • Scientific names eliminate confusion • Binomial nomenclature is the universal language for the organization of species. • Different areas use different common names for the same species. • The same common name is also used for different species.

6. gray silk mangrove snapper mangrove pargue mango snapper pargue black pargue black snapper lawyer silk snapper Common Names for Lutjanus griseus

7. Linnaeus’s Classification System • Swedish botanist (1707-1778) • Binomial Nomenclature – two-part scientific name  Genus species • Why Latin? • Latin was the language known universally by the educated • Also used as a descriptor

8. Classifying Living Things Biologists now classify life based on its evolutionary history. This system: • Is more exact • Allows scientists to make predictions • Helps biologists study the evolution of specific features

9. Classifying Living Things The evolutionary history of living things can be diagrammed in a cladogram.

10. Classifying Living Things Some well-known Linnaean groups are also clades. However, other Linnaean groups are not clades. For example, the cladistic system places birds among the reptiles, while the Linnaean system does not.

11. Classifying Living Things CHECK YOUR NEIGHBOR Why would Linnaeus separate birds from reptiles? Why would the cladistic system put them in the same clade?

12. Classifying Living Things CHECK YOUR ANSWER The Linnaean system grouped organisms using shared characteristics. It seemed natural to separate feathered, flying, “warm-blooded” birds from scaly, terrestrial, “cold-blooded” reptiles. But the cladistic system groups organisms according to shared ancestry, which puts birds in the reptile clade.

13. The Three Domains of Life Life is classified into three domains: • Bacteria • Archaea • Eukarya

14. Domains

15. The Three Domains of Life Domain Eukarya is divided into four kingdoms: • Plants • Fungi • Animals • Protists (everything that doesn’t fit into the other three kingdoms)

16. Bacteria Bacteria are diverse: • Some bacteria are autotrophs that photosynthesize. Others are heterotrophs. • Most bacteria are single celled, but others gather in clusters. • Bacteria reproduce asexually by dividing, but most occasionally exchange some genetic material. • Bacteria vary in shape, and some have flagella for locomotion.

17. Bacteria Important functions of bacteria from a human’s point of view: • They break down organic matter, releasing carbon for photosynthesis. • They help make nitrogen available to living things. • Some produce vitamins in the bodies of humans. • Some prevent harmful bacteria from infecting our bodies. • Some are essential for making cheese, yogurt, and some drugs.

18. Archaea Archaea are not bacteria. They are a distinct domain of prokaryotic organisms. Some archaea are “extremophiles” that thrive in harsh, salty, or very hot environments. Others are chemoautotrophs that make food using chemical energy from molecules such as hydrogen sulfide.

19. Protists Protists are eukaryotes that are not plants, fungi, or animals. They may be single celled or multicellular, reproduce through asexual or sexual means, be autotrophs or heterotrophs.

20. Protists Protists are diverse. They include: • Many seaweeds • Diatoms • Amoebas • Disease-causing organisms such as Plasmodium, which causes malaria

21. Plants Plants are autotrophic, multicellular, terrestrial eukaryotes that obtain energy through photosynthesis.

22. Plants Plant adaptations to the terrestrial world include: • Roots • Shoots • Leaves • Vascular system

23. Plants Plant reproduction occurs through alternation of generations. The plant life cycle alternates between a haploid stage (gametophyte) and a diploid stage (sporophyte). The details vary by type of plant.

24. Plants—Mosses Mosses are small, seedless plants with no vascular system. Every part of the moss has to absorb water directly via diffusion.

25. Plants—Ferns Ferns are seedless plants with feathery leaves. Most live in moist, shady habitats.

26. Plants—Seed Plants Seed plants have two key features that make them successful in many habitats: • Pollen—immature male gametophytes that can be transported to female gametophytes by wind or animals • Seeds—embryonic plants that are encased in a tough outer coating with a food supply. Flowering plants surround their seeds with a fruit. The two major types of seed plants are flowering plants and conifers.

27. Plants—Seed Plants

28. Fungi Fungi are more closely related to animals than to plants. They are heterotrophs. Fungi may be single celled or multicellular and may reproduce sexually or asexually. Many fungi are decomposers—they play a crucial role in terrestrial ecosystems.

29. Animals Animals: • Multicellular, heterotrophic eukaryotes that obtain nutrients by eating other organisms. • Most reproduce sexually and are diploid during most of their life cycle. • The gametes—sperm and egg—are the haploid stage of the life cycle.

30. Animals This drawing shows the evolutionary relationships among the various animal groups.

31. Animals—Sponges Sponges are sedentary marine animals. Special cells in the sponge beat flagella that move water through the sponge, allowing cells to capture food, digest it, and then distribute nutrients to other cells.

32. Animals—Cnidarians Cnidarians: • Include jellies, sea anemones, corals, and hydras • Have two distinct tissue layers separated by a jelly-like middle layer • Use tentacles to catch prey • Alternate between a sedentary polyp stage and a bell-shaped medusa stage, although some groups exist primarily in one form (corals are polyps, jellyfish are medusae)

33. Animals—Flatworms • Flatworms feature distinct head and tail ends and back and belly sides. • A single opening serves as mouth and anus. • The flat shape allows the animal to obtain oxygen across the skin via diffusion.

34. Animals—Roundworms Roundworms: • Small, slender bodies • Both a mouth and an anus • Tough outer cuticle • Longitudinal muscles • Move like flailing whips

35. Animals—Arthropods Arthropods include crustaceans, chelicerates (ticks, spiders), and uniramians (centipedes, millipedes, and insects). All feature: • An exoskeleton • Segmented bodies and jointed legs • A brain • Developed sense organs

36. Animals—Mollusks Mollusks: • Soft-bodied animals • Most have a protective shell • Use a muscular foot for locomotion • Visceral mass holds the digestive and reproductive organs • Mantle secretes the shell

37. Animals—Mollusks Mollusks include: • Bivalves (clams, scallops) • Cephalopods (squids, octopuses) • Gastropods (snails, abalones)

38. Animals—Annelids Annelids are segmented worms, such as earthworms and leeches. The muscles of earthworms are oriented both circularly and longitudinally, providing flexibility in motion.

39. Animals—Echinoderms Echinoderms (sea stars, sea cucumbers) have endoskeletons and tube feet.

40. Animals—Chordates Chordates include tunicates, lancelets, and vertebrates.

41. Animals—Chordates All chordates have, at some point in their life history, • A brain and spinal cord • A notochord that supports the back • Gill slits • A tail Some of these features are not apparent in adults. Human embryos do go through a tailed stage.

42. Animals—Chordates Vertebrates include: • Many groups of fishes • Amphibians • Reptiles • Mammals

43. Animals—Chordates Amphibians: • Include salamanders, frogs, and caecilians • May have aquatic larvae and terrestrial adults • Must live in moist environments to protect their skin and eggs • Are vulnerable to pollution and environmental contamination

44. Animals—Chordates Reptiles and mammals are amniotes: • Skin made of dead cells • Shelled eggs • Well adapted to diverse terrestrial habitats

45. Animals—Chordates Reptiles include birds. All reptiles other than birds are ectotherms. Ectotherms regulate their body temperature behaviorally. Birds and mammals are endotherms. They maintain a constant body temperature by metabolizing large amounts of food.

46. Animals—Chordates Mammals: • Have hair • Feed milk to their young • Are endotherms • May be terrestrial, aquatic, or able to fly • Include monotremes (egg layers like the platypus), marsupials (kangaroos), and placentals (humans).