Introduction to Animals

1. Introduction to Animals

2. Characteristics • All multicellular & eukaryotic • Cells lack cell walls and come in a variety of shapes. • Ingestive heterotrophs (take in food and internally digest it).

3. Characteristics cont’d • Have some type of skeletal support • Exoskeletons found in arthropods cover the outside of the body but limit size. • Endoskeletons found in all vertebrates are found inside the body and are made of cartilage and/or bone.

4. Characteristics Cont’d • Worms have fluid-filled internal cavities giving them skeletal support. • Sponges have the simplest skeleton. • May be sessile (attached and non-moving) or motile (able to move around).

5. Characteristics Cont’d • Muscular tissue provides energy for movement. • Reproduces sexually. • Shows levels of organization including cell, tissue, organ, and system.

6. Characteristics Cont’d • Most show division of labor among cells. • Cells are specialized for particular functions. • Cell junctions hold individual cells in a tissue together. They link neighboring cells. • Most vertebrates have a backbone or spine made of repeating bones called vertebrae that protect the spinal cord. • Some show cephalization (have a head with sensory organs concentrated there).

7. Invertebrate Groups • Simplest animals • Contains the greatest number of animal species • Most found in water • Do not have a backbone • Includes sponges, cnidarians, flatworms, roundworms, annelids (segmented worms), mollusks, arthropods, and echinoderms.

8. Vertebrate Groups • More complex animals • Most have a backbone • Includes fish, amphibians, reptiles, birds, and mammals.

9. Body Areas • Dorsal is the back or upper surface • Ventral is the belly or lower surface • Anterior head or front end • Posterior is the tail or hind end opposite the head • Oral surface in echinoderms is where the mouth is located (underside) • Aboral surface in echinoderms is the surface opposite the mouth

10. Body Areas: (Most Animals) DORSAL POSTERIOR ANTERIOR VENTRAL

11. Symmetry

12. Body Symmetry Also called asymmetrical

13. Body Symmetry • Symmetry is the arrangement of body parts around a central plane or axis • Asymmetry occurs when the body can’t be divided into similar sections (sponges)

14. Body Symmetry • Radial symmetry occurs when body parts are arranged around a central point like spokes on a wheel(echinoderms) • Most animals with radial symmetry are sessile(attached) or sedentary(move very little)

16. Body Symmetry • Bilateral symmetry occurs when animals can be divided into equal halves along a single plane • Organisms will have right and left sides that are mirror images of each other • More complex type of symmetry

17. Body Symmetry • Animals with bilateral symmetry are usually motile • Animals have an anterior and posterior ends • Show cephalization(concentration of sensory organs on the head or anterior end)

19. Segmentation

20. Segmentation • Occurs whenever animal bodies are divided into repeating units or segments • Found in more complex animals • Earthworms show external segmentation, while humans show internal segmentation (vertebrae of the backbone) • Segments may be fused together such as cephalothorax covering chest & head of a crayfish

21. Segmentation cephalothorax

22. Tissue Development

23. Tissue Development Cont’d • All animals reproduce sexually, but some also reproduce asexually (sponges bud & flatworms fragment) • Zygote is the fertilized egg all animals form from • Zygote undergoes rapid cell divisions known as cleavage to become hollow ball of cells called blastula • Blastocoelis the central cavity of the blastula

24. Tissue Development Cont’d • Blastulafolds inward at one point to form an opening & two cell or germ layers; process called gastrulation • New cup-shaped structure with 2 cell layers is called the gastrula • Archenteron is the deep cavity of the gastrula that forms the primitive gut Blastula

25. Tissue Development Cont’d • Inner germ layer called endoderm & outer germ layer called ectoderm • Opening may become the mouth or the anus • Protostomes(mollusks, arthropods, & annelids)develop mouth from blastopore, whiledeuterostomes (echinoderms & vertebrates) develop an anus from blastopore

26. Tissue Dev. Cont’d • Some animals form a third germ layer in the middle called mesoderm • Cells differentiation during development changing their shapes to fit their function ( neurons or nerve cells become long to conduct messages)

27. Germ Layers • Form tissues, organs, & systems • NOT present in sponges • Ectoderm (outer) – forms skin, nerves, sense organs • Endoderm (inner) – forms liver and lungs • Mesoderm (middle) – forms muscles & other systems

28. Body Layers • Sponges have NO tissues or organs, only specialized cells • Cnidarians like jellyfish & coral have only two body layers & one body opening (mouth/anus) into gastrovascular cavity • Cnidarians have outer epidermis & inner gastrodermis with jelly-like mesoglea between the layers

29. Body Layers • All worms, mollusks, arthropods, echinoderms, and vertebrates have three cell layers • Ectoderm • Endoderm • mesoderm

30. Embryonic Cleavage

31. Cleavage • Cleavage – rapid mitosis (cell division) of zygote • RadialCleavage – cells divide parallel or perpendicular to axis to each other

32. Cleavage • Spiral Cleavage – cellular divisions occur diagonally, in a twisting pattern

34. Stages of Development

35. Larval Forms • Animals with Indirect development • Go throughimmature (larval) forms • Larva does NOT resemble adult • Cnidarian (jellyfish, coral, & sea anemone) larva called Planula

36. Larval Forms • Mollusk (squid & octopus) larva called trochophore • Echinoderm (starfish) larva is called Dipleurula

37. Metamorphosis • Usually found in arthropods • May be complete or incomplete • Incomplete Metamorphosis: egg nymph adult • Complete Metamorphosis: egg larva pupa adult

38. Metamorphosis COMPLETE INCOMPLETE

39. Body Cavities

40. Coelom - Body Cavity • Internal body cavity fully lined with mesoderm • Body organs suspended in this cavity

41. Coelom - Body Cavity • Acoelomate animals have solid bodies filled with cells • Acoelomate animals include sponges, cnidarians, & flatworms

42. Coelom - Body Cavity • Pseudocoelomate animals (roundworms) have a functional body cavity NOT fully lined with mesoderm

43. Animal Systems

44. Support Systems • Spongin & spicules(sponges) • Limestone cases(corals) • Exoskeletons of Chitin(arthropods) • Limits size • Must be shed or molted to grow • Animal vulnerable to predators during molting

45. Support Systems • Hydrostatic skeleton – fluid filled body cavity (worms) • Inner Calcium plates or Test(echinoderms) • Bone and/or cartilage endoskeleton (vertebrates)

46. Exoskeletons Must Be Molted

47. Endoskeletons Grow with the Animal

48. Digestive Systems • All animals are ingestive heterotrophs • Choanocytes (specialized cells) capture & digest food for sponges • Gastrovascular cavity with one opening in cnidarians and flatworms for food to enter & leave; called two-way digestive system

49. Gastrovascular Cavity with Mouth Only (Cnidarians)

50. Two-Way Digestion