Introduction to animals Introduction to Animals Copyright cmassengale

Traits

Characteristics of Animals All multicellular (metazoans) Eukaryotes (cells with nucleus & organelles) Ingestive heterotrophs (take in food and internally digest it) Store food reserves as glycogen Have some type of skeletal support

Characteristics of Animals Diploid (means they have 2 sets of chromosomes) Form a blastula (embryo) during gastrulation Have specialized tissues

Tissues

Tissue Development Zygote (fertilized egg) undergoes rapid cell divisions called cleavage Forms a hollow ball of cells called the blastula

Blastula The blastocoel is the center cavity of the blastula with 1 germ layer (blastoderm)

Tissue Development The blastula INVAGINATES (folds inward at one point) Called Gastrulation The opening is called the blastopore The center is the primitive gut or Archenteron blastopore Archenteron

Tissue Development Blastopore may become the mouth (Protostome) or anus (Deuterostome) Protostomes (mollusks, arthropods, & annelids) Deuterostomes (echinoderms & vertebrates) Some animals form a middle germ layer called mesoderm

Embryonic Development

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

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

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

Embryonic Cleavage

Cleavage Cleavage – rapid mitosis (cell division) of zygote Radial Cleavage – cells divide parallel or perpendicular to axis to each other

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

Body Areas

Surfaces Dorsal – back or upper surface Ventral – belly or lower surface Anterior – head or front end Posterior – tail or hind end opposite the head Oral surface (echinoderms) – is where the mouth is located (underside) Aboral surface (echinoderms) – is opposite the mouth (top side)

DORSAL VENTRAL Surfaces (Most Animals) ANTERIOR POSTERIOR

Surfaces (Echinoderms) ORAL ABORAL mouth

Symmetry

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)

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)

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

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)

Segmentation

Segmentation Occurs whenever animal bodies are divided into repeating units or segments Found in more complex animals Earthworms show external segmentation Humans show internal segmentation (backbone) Segments may fuse (cephalothorax)

Segmentation cephalothorax

Stages of Development

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

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

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

Metamorphosis COMPLETE INCOMPLETE

Body Cavities

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

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

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

Animal Systems

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

Support Systems Hydrostatic skeletonHydrostatic skeleton – fluid filled body cavity (worms) Calcium plates or TestInner Calcium plates or Test (echinoderms) Bone cartilage endoskeletonBone and/or cartilage endoskeleton (vertebrates)

Exoskeletons Must Be Molted

Endoskeletons Grow with the Animal

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

Gastrovascular Cavity with Mouth Only (Cnidarians)

Two-Way Digestion

Digestive Systems Animals with a one-way digestive system have a mouth and an anus Food enters the mouth, continues in one direction through the digestive tract, and wastes leave through the anus Includes annelids, arthropods, & vertebrates

One-Way Digestion Mouth anus

Circulatory Systems Transports oxygen & nutrients to cells Carries away wastes & carbon dioxide from cells Sponges, cnidarians, & flatworms do NOT have circulatory systems

Circulatory Systems In closed circulation, blood remains inside blood vessels until it reaches cells (annelids & vertebrates) In open circulation, blood is pumped out of blood vessels to bathe tissues in the body cavity or hemocoel (arthropods & mollusks)

Open Circulation Closed Circulation

Respiratory System Taking in O 2 & releasing CO 2 diffuseGases can diffuse across moist surfaces (earthworms) GillsGills filter O 2 from water (aquatic animals) LungsLungs take O 2 from air (terrestrial animals)

Skin breather Lungs Gills

Nervous System Coordinates the activities of the animal’s body NeuronsNeurons – nerve cells that transmit electrochemical signals Nerve net -Nerve net - network of neurons, very little coordination GanglionGanglion – clusters of neurons; may serve as a simple brain BrainBrain – control center at anterior end

Excretory System ExcretionExcretion is the removal of nitrogen wastes from the body DiffusionDiffusion is used by simple aquatic animals Flame cellsFlame cells remove wastes in flatworms

Excretory System nephridiaCoiled tubules called nephridia remove nitrogen wastes in arthropods KidneysTerrestrial animals remove wastes with Kidneys paired –May be paired (most vertebrates) single –May be single as in birds

Reproductive System ReproductionReproduction is the process by which organisms make more of their own kind sexual reproductionAll animals reproduce by sexual reproduction (produce eggs and sperm) asexual reproductionSome animals also use asexual reproduction creating identical offspring

Types of Animal Asexual Reproduction Regeneration FragmentationRegeneration or Fragmentation is the breaking off of pieces and the re- growth of a new organism Sponges FlatwormsFound in simple animals like Sponges and Flatworms

BuddingBudding occurs in hydra whenever a growth on the parent is released cloneCreates a clone

ParthenogenesisParthenogenesis – females produce eggs that develop unfertilized into female organisms Komodo dragonKomodo dragon is an example

Hermaphrodite BOTHHermaphrodite are animals like earthworms that produce BOTH eggs and sperm NOTMost hermaphrodites do NOT fertilize their own eggs Mate to exchange spermMate to exchange sperm

Fertilization ExternalExternal – sperm and eggs are released into water where they are fertilized InternalInternal – sperm and egg are fertilized inside the female animal’s body