Biology - Animals: Classification, Evolution, Types

Animals: classification breakdown, evolution, types

1. Evolution of Animals Animals likely share most recent common ancestor with Choanoflagellates aquatic suspension feeders flagellated protists similar to a type of sponge cell reproduce by simple fission

2. Why Study Animals? Most species-rich and morphologically diverse lineage of multicellular organisms Humans depend on wild and domesticated animals for food and, in developing countries, for transportation and power Humans study our closest relatives to understand ourselves

3. Introduction to Animals Animals are distinguished by two traits: they eat they move They are the largest and most abundant predators, herbivores, and detritivores in virtually every ecosystem. Animals find food by tunneling, swimming, filtering, crawling, creeping, slithering, walking, running, or flying.

4. Introduction to Animals Animals are heterotrophs— they obtain the chemical energy and carbon compounds they need from other organisms. They are the dominant consumers in ecosystems. Multicellular Body no cell walls specialization of cells nervous & muscle tissue Diploid (2n) stage dominant sexual gametes are the only haploid (n) cells and produced via meiosis

5. Most morphological diversity in animals is based on differences in mouths and limbs.

6. Major Innovations in Animals Embryonic Germ Cell Layers 0, 2, 3 ectoderm, mesoderm, endoderm Symmetry none, radial, bilateral Cephalization increased development of head

7. Major Innovations in Animals Body Cavity = coelom fluid filled space none, pseudocoelom, coelom Segmentation none, present, present with fusion Gut none, incomplete, complete

8. Tissues All animals other than sponges have tissues ; tightly integrated structural and functional units of cells. Only two groups of animals (Cnidaria and Ctenophora) have two types of tissues or germ layers : the ectoderm and endoderm . Most animal embryos have three types of tissues: the ectoderm, endoderm, and mesoderm .

9. Sponges = Porifera Most ancestral animals Very simple multicellular animals No germ cell layers No body symmetry Only one tissue (epithelium) and no organs few cell types

10. Symmetry A basic feature of a multicellular body is the presence or absence of a plane of symmetry. Animals with radial symmetry have at least two planes of symmetry Organisms with bilateral symmetry have a single plane of symmetry and face their environment in one direction

11. Cephalization Bilateral symmetry allowed cephalization : the evolution of a head, or anterior region, where structures for feeding, sensing the environment, and processing information are concentrated rapid movement

12. Cnidaria Includes: jellyfish, corals, anemones 2 germ cell layers (ectoderm, endoderm) Radial symmetry True tissues or organs Gut with one opening

13. Evolution of a Body Cavity Animals may or may not have an internal, fluid-filled body cavity called a coelom . Advantages of a coelom are: movement: more flexible and hydrostatic skeleton in limbless animals space: internal organs size: increases surface area to volume ratio

14. The Coelom & Classification Animals with 3 germ cell layers, bilateral symmetry, and: no coelom = Acoelomates (e.g., flatworms) pseudocoelom = Pseudocoelomates (e.g., roundworms, rotifers) coelom = most animals

15. Coelomate Animals All have bilateral symmetry except echinoderms (reversal to radial symmetry) Protostomes molluscs, arthropods, and annelids Deuterostomes chordates and echinoderms

16. Molluscs

17. Segmentation Two independent origins arthropods & annelids (segmented worms) chordates Improved motility Greater cephalization

18. Annelids

19. Arthropods 4 groups: Trilobites (extinct) Arachnids (spiders, scorpions, ticks) Crustaceans (crabs, lobster, shrimp) Insects (beetles, flies, millipedes) Exoskeleton thick and rigid (protein & chitin) waterproof growth by periodic molting Jointed foot

20. Themes in the Diversification of Animals Within each animal phylum, the basic features of the body plan do not vary from species to species. Diversity arose in animals mostly because of the evolution of innovative methods for feeding and moving.

21. Feeding The feeding tactics observed in animals can be broken into five general types: suspension feeding deposit feeding herbivory predation parasitism

22. Suspension (Filter) Feeding Suspension feeders , or filter feeders , capture food by filtering out particles suspended in water or air. This method is found in a wide variety of animal groups and has evolved many times independently.

23. Deposit Feeding Deposit feeders eat their way through a substrate Food for deposit feeders consists of soil-dwelling bacteria, protists, fungi, and archaea, along with detritus —the dead and partially decomposed remains of organisms. Depending on what they eat, deposit feeders can also be considered herbivores (plant eaters), parasites, detritivores (detritus eaters), or predators.

24. Herbivory Herbivores are animals that digest algae or plant tissues They have complex mouths with structures that make biting and chewing or sucking possible. The radula of mollusks, for example, functions like a rasp or a file. The mandibles of grasshoppers are used to process leaves or stems.

25. Parasitism Parasites are much smaller than their victims and often harvest nutrients without causing death. Endoparasites live inside their hosts. They are often wormlike in shape and can be extremely simple morphologically. Ectoparasites live outside their hosts. They usually have grasping mouthparts that allow them to pierce the host’s exterior and suck the nutrient-rich fluids inside.

26. Movement Many animals are sit-and-wait predators, and some are sessile throughout their adult lives. But the vast majority of animals move under their own power either as juveniles or as adults. Movement has three functions in adult animals: finding food finding mates escaping from predators

27. Limbs A major innovation in animals—the limb —made highly controlled, rapid movement possible. Types of Limbs: unjointed limbs are saclike jointed limbs move when muscles that are attached to a skeleton contract or relax

28. Skeletons Although arthropods have an exoskeleton (external skeleton) and vertebrates have an endoskeleton (internal skeleton), the skeleton has the same function: it is a stiff structure that resists the forces exerted by muscles.

29. Reproduction and Life Cycles At least some species in most animal phyla can reproduce asexually (via mitosis), as well as sexually (via meiosis). Sexual reproduction can occur with internal or external fertilization

30. Early Embryology Eggs or embryos may be retained in the female’s body during development, or they may be laid outside the body. Species in the former group are viviparous ; those in the latter are oviparous .