Chapter 23 Part I Animal Characteristics Animal Characteristics

Chapter 23 Part I Animal Characteristics

Animal Characteristics § § Multicellular Eat other organisms Can move Break down food for energy and to build tissue § Cells have no cell walls

Food getting § Some animals hunt § Some animals are sessile and wait for food to come to them § Movement is directly related to method of getting food

Animal digestion § § § Some digest food internally Some digest food inside individual cells Digested food is stored as fat or glycogen and used for energy when food is scarce § Digestive cavities can have one opening (mouth) or two openings (mouth and anus)

Animal development § § § Blastula Gastrula Protostomes Deuterostomes Mesoderm

Blastula development § Most animals develop from a single fertilized egg (zygote) § Zygote undergoes cell division to produce a hollow ball of cells (blastula) § Blastula – a single layer of cells surrounding a fluid filled space § Develops about 10 hours after fertilization

Gastrula development § Cells on one side of the blastula fold inward to form the gastrula § Outer surface is ectoderm (develops into skin and nervous tissue) § Inner surface is the endoderm (develops into the digestive tract)

Protostomes § The indented space in the gastrula develops into the mouth § Have one opening in their digestive tract

Deuterostomes § The indented space in the gastrula develops into the anus; mouth develops from cells in another location § Complex animals § Two openings in the digestive tract

Mesoderm § Third layer of cells that develops between the endoderm and ectoderm § Develops into muscles, reproductive organs, and circulatory vessels

Body plans: symmetry § § § Asymmetry Radial symmetry Bilateral symmetry

Asymmetry § § § Irregular body shapes Usually sessile organisms Ex: sea sponge

Radial symmetry § Can be divided along any plane, through a central axis, and produce roughly equal right and left halves § Detect and capture prey from any direction § Ex: hydra, starfish

Bilateral symmetry § Divided down the length into right and left halves that form mirror images § Anterior is head § Posterior is tail § Dorsal is the back § Ventral is the belly § Find food/mates more efficiently due to better muscle control

Body Cavities § § § Acoelom Pseudocoelom

Acoelom § Three cell layers (ectoderm, endoderm, mesoderm) § Digestive tract § NO body cavity § Organs embedded in tissues § Water/digested food travel through body by diffusion § Ex: flatworms

Pseudocoelom § Fluid-filled body cavity partially lined with mesoderm § Develops between endoderm and mesoderm § More efficient movement § Two openings in digestive tract § Ex: roundworms

Coelom § Body cavity completely lined with mesoderm § Internal organs suspended in fluid-filled space § Allows space for complex organs § Ex: humans

Adaptations § Exoskeleton § Endoskeleton

Exoskeleton § Hard, waxy covering on outside of the body § Provides support, protection § Prevents water loss § Place for muscle attachment in invertebrates

Endoskeleton § § § Internal skeleton found in vertebrates Protects internal organs Place for muscle attachment

26. 2 Sponges § Phylum Porifera § Sessile (attached to a single spot as adults) § Multicellular § Heterotrophic § No cell walls § Few specialized cells

Sponge body plan § § § No mouth, gut, tissues, or organs Use only specialized cells Asymmetrical No dorsal, ventral, left or right sides Body is tubular and arranged around a central opening through which water flows

Body plan cont. § Choanocytes (cells with flagella) keep steady current of water flowing § Water enters through pores in body wall but flows out through osculum (hole at top of sponge) § Movement of water through sponge allows feeding, respiration, circulation, and excretion § Spicules-structure made of Ca. CO 3 or silica make up internal skeleton in some sponges

Sponge feeding § Filter feeders – sift microscopic food from water § Intercellular digestion occurs in choanocytes that take in the food and then pass it to archaeocytes that transport digested food throughout the sponge

Sponge response § No nervous system § Protect themselves with toxins that make them taste bad or make them poisonous to predators

Sponge reproduction § Sexual – figure 26 -9 § Sperm release into water by one sponge are carried on currents to another sponge § Sperm are carried to egg by archeocytes § After fertilization, zygote develops into a larva (immature form; looks different) § Larva are motile (usually use flagella) so swimming and currents carry them to new areas on sea floor

Sponge reproduction cont § Asexual budding – a piece of a mature sponge breaks off, settles on sea floor, and develops into a new sponge § Asexual gemmules – groups of archeocytes surrounded with spicules; used to withstand unfavorable conditions; good conditions allow the gemmules to develop into a new sponge

Ecology § Sponges provide habitat for other organisms (commensalism) § Sponges pair up with photosynthetic organisms providing their habitat, while the photosynthetic organism gives food (mutualism); also helps productivity at coral reefs

26. 3 Cnidarians § § § Soft-bodied Carnivorous Stinging tentacles arranged in a circle around the mouth (cnidocytes- stinging cells that contain nematocysts or darts with poison to kill prey) § Simplest animals with symmetry and specialized tissues

Cnidarian body plan § § § Radial symmetry Central mouth surrounded with tentacles Life cycle includes the polyp (sessile) and medusa (motile) stages Body wall surrounds the gastrovascular cavity (digestion occurs in gastroderm) Outside layer is epidermis Middle layer is meoglea

Cnidarian feeding § Paralyze prey before pulling it in to the gastrovascular cavity § Extracellular digestion (outside of cells) § Digested food is absorbed by gastroderm § Digestion completed inside cells of gastroderm § Undigested materials are expelled through the mouth

Cnidarian response § Use a nerve net – loosely organized network of nerve cells that allow detection of stimuli (touch) § Usually distributed evenly throughout body but can be centrally located around mouth § Statocysts help determine direction of gravity § Ocelli – are eyespots that help detect light

Cnidarian movement § Some use hydrostatic skeleton – layer of circular muscles and layer of longitudinal muscles, with water in gastrovascular cavity, enable movement § Medusas use jet propulsion – muscle contractions that force water out of the “bell” of the organism which pushes the organism forward

Cnidarian reproduction § Sexual – figure 26 -15 § Eggs and sperm released into water by separate sexes § External fertilization occurs producing the zygote that grows into a free swimming larva § Larva eventually attaches to hard surface to develop into polyp § Polyp buds and releases the medusa

Cnidarian reproduction cont § Asexual – budding § Budding can occur in polyps, producing a genetically identical organism

Jellyfishes § § § Class Scyphozoa Live primarily as medusas Polyp is small larva stage that does NOT produce colonies § Reproduce sexually

Hydras and relatives § Class Hydrozoa § Polyps grow in branching colonies, can be specialized for specific functions § Portuguese man-of-war § § § One polyp produces the “balloon” or float Others produce tentacles to catch prey Some also undergo digestion § Hydras – freshwater, lack a medusa stage; solitary; reproduce both sexually and asexually and may have symbiotic relationship with photosynthetic protists

Sea anemones and corals § § § Class Anthozoa Only a polyp stage Central body surrounded by tentacles Many are colonial Sea anemones § Live at all depths § Usually solitary § Can by symbionts with photosynthetic organisms

Corals § Most colonial § Hard corals develop after a motile larva attaches to a solid surface § New polyps produced by budding § Produce skeleton of Ca. CO 3 or limestone § Can live for hundreds-thousands of years § Sexual reproduction § External fertilization (eggs and sperm are released into water)

Ecology of corals § Distribution determined by temperature, water depth, light intensity § Hard corals need high levels of light § Rely on mutualistic relationships with algae (provide 60% of energy needed by corals) § Corals provide habitat to a variety of marine organisms (commensalism)

Damage to corals § Human activity § § § Logging Divers that damage corals Silt Farming / mining Release of chemicals § High temperatures § Kill algae and cause bleaching § May be due to global warming