Introduction to animals Introduction to Animals

Characteristics of Animals All multicellular Eukaryotes Heterotrophs (take in food and internally digest it) Store food reserves in the liver as glycogen

Support Systems Have some type of skeletal support Endoskeleton inside and made of cartilage &/or bone Exoskeletons found in arthropods –Cover the outside of the body –Limit size –Must be molted making animal vulnerable to predators

Cicada Molting Exoskeleton

Support Systems Worms and echinoderms (starfish) have fluid-filled internal cavities giving them support Called hydrostatic skeletons

Movement Animals such as sponges may be sessile (attached & non-moving) Animals that move very little are said to be sedentary (clam) Animals that can move are motile Have muscular tissue to provide energy for movement

SESSILESEDENTARY MOTILE Sponge Chiton Cheetah

Reproduction in Animals All animals are capable of sexual reproduction Some animals like sponges and earthworms are hermaphrodites producing both eggs and sperm Hermaphrodites may exchange sperm and NOT fertilize their own eggs

Leeches Exchange Sperm During Mating Mating leech

Reproduction in Animals Females of some animals produce eggs, but the eggs develop without being fertilized Called Parthenogenesis New offspring will be all female Parthenogenesis occurs in some fishes, several kinds of insects, and a few species of frogs and lizards

Parthenogenesis in the Komodo Dragon

Mating and Mating Behaviors Beetles Mating Male Female Young Courtship

Levels of Organization Sponges are the ONLY animals that have just the cellular level All other animals show these levels – cell, tissue, organ, and system Cells may specialize (take own different shapes and functions) Cells are held together by cell junctions to form tissues

Atom Molecule or compound Organelle CELL Levels of Organization Tissue Organ Organ system Organism Life begins

Invertebrate groups

Characteristics of Invertebrates Simplest animals Contain the greatest number of different species Most are aquatic (found in water) Do NOT have a backbone Includes sponges, cnidarians, flatworms, roundworms, annelids, mollusks, arthropods, and echinoderms

1. Phylum Porifera (Sponges)

Sponge - Porifera Osculum of Sponge

Phylum Porifera (Sponges) (exit for water) (digest and distribute food) (skeleton) Choanaocyte *** Sponges are Parazoans: they contain NO true tissues *** Sponges are filter feeders

2. Phylum Cnidaria Jellyfish, Corals, and other Stingers

General Characteristics Simple body plan-bag shaped organism Radially symmetrical organization Consists of a mouth and a sac-like cavity Lacks an anus The mouth is surrounded by a ring of tentacles The cavity in the center of the gut, called the gastrovascular cavity.

Two Body Forms Polyps - attached to a surface - ex: sea anemones - mouth points up Medusae - free floating -ex: jellyfish -mouth points down

Sea Anemone - Cnidaria Tentacles of Sea Anemone

More Cnidarians Brain Coral Red jellyfish

3. Phylum Platyhelminthes (Flatworms) Platyhelminthes consists of three kinds of acoelomate flatworms. 1. Free-living Flatworms: such as planarians, which are carnivorous scavengers. 2. Flukes: are internal, or external, parasites that suck tissue fluids or blood. 3. Tapeworms: internal parasites that live in the intestinal tracts of vertebrates.

Flatworms - Platyhelminthes Planarian Marine Flatworm

Planaria

Tapeworm Scolex (head) Young Proglottids Old Proglottids ** tapeworms appear to be segmented, but they are not true “segmented” worms

4. Phylum Nematoda (Roundworms) Found in fresh water, marine, moist soil, tissues of plants, and tissues and body fluids of animals A complete digestive tract is present and nutrients are transported through the body in the pseudocoelomic fluid. Free-living forms are important in decomposition Animal parasitic forms can be hazardous to health.

(Trichinella spiralis in humans via undercooked infected pork)

Nematode

7. Phylum Annelid (Segmented Worms: includes leeches, earthworms and polychaetes) Leeches are freshwater but some are terrestrial in moist vegetation. Many are carnivorous and feed on small invertebrates, while some attach temporarily to animals to feed on blood. They have 2 suckers, one at each end.

leech

Earthworms ingest soil, extract nutrients in the digestive system and deposit undigested material (mixed with mucus from the digestive tract) as casts through the anus. Important to farmers as they till the soil and castings improve soil texture

Polychaetae drift and swim in the plankton, some crawl along the sea floor, and many live in tubes they construct by mixing sand and shell bits with mucus. Tube-dwellers include the fanworms that feed by trapping suspended food particles in their feathery filters which are extended from the tubes.

Phylum Annelid Fanworm Polychaete Worm

6. Phylum Mollusca (snails, bivalves, octopuses and squids) In Squids, the shell is reduced and is internal. In octopuses, the shell is entirely absent. Octopuses have a highly developed nervous system with a large, complex brain.

Snails

Mollusca (With and Without Shells) snailscallop nautilus nudibranch octopus

8. Phylum Arthropoda (spiders, insects, crustaceans, and various related organisms) Arthropods have two kinds of life cycles…(1) complete metamorphosis, (2) incomplete metamorphosis. Arthropods have: * jointed appendages, * a well-developed nervous system, * specialized body segments, and * an exoskeleton made of chiton.

The specialized body segments are the: Head, Thorax and Abdomen

Incomplete Metamorphosis (immature forms are often called nymphs) Nymphs resemble the adult in form except for being smaller and lacking fully developed wings and sexual organs. Life Cycle: Egg nymph adult

Complete metamorphosis Immature forms are called larvae (larva, singular). The pupal stage is a transition stage, when the larva is transformed to the adult. Pupa molts to the adult form. Life Cycle: Egg --> larva --> pupa --> adult

Arthropoda (insects, spiders, crustaceans, horseshoe crab) Dung beetle Horseshoe crab crayfish spider

9. Phylum Echinodermata (sea stars (starfish), sea urchins and sand dollars) Echinoderms are Coelomates Deuterostomes Echinoderms have complete digestive systems Although some adults exhibit radial symmetry, some features are bilateral, as are the body shapes of their larvae.

Echinoderms Sea cucumber Sand dollar starfish Brittle star Sea fan (crinoid)

Vertebrate Groups

10. Phylum Chordata The Phylum Chordata consists of animals that exhibit the following four features. In many cases, these features are temporary, appearing only during embryonic development.

1. A Notochord A notochord provides support for the body. It is a flexible cord located on the dorsal surface. In most cases, the notochord is replaced by bone during development. Notochord

2. A Dorsal Hollow Nerve Cord A dorsal hollow nerve cord forms the basis of the nervous system. In some chordates, the nerve cord becomes the brain and spinal cord.

3. Pharyngeal Gill Slits Pharyngeal Gill Slits provides channels across the pharynx to the outside of the body. In some chordates, the slits become gills for oxygen exchange, or for filter feeding, while in others, the slits disappear during embryonic development.

4. A Muscular Tail A muscular tail extends beyond the digestive system. In many chordates, such as humans, the tail is lost during embryonic development.

There are Two Groups of Chordates 1. Invertebrate Chordates: includes lancelets and tunicates. 2. Vertebrate Chordates: includes sharks, fish, amphibians, reptiles, birds and mammals. Vertebrate Chordates are characteristics by a series of bones, the vertebrae, that enclose the spinal cord.

Vertebrata More complex animals Most have a backbone made up of individual bones called vertebrae From simplest to most complex, the phylum includes: fish, amphibians, reptiles, birds, and mammals

Vertebrate Backbone

Vertebrata Vertebrates have endoskeletons (internal) Some vertebrates have skeletons of cartilage (sharks, rays, and skates) Other vertebrates have skeletons of bone and cartilage (reptiles, birds, & mammals)

Bone & Cartilage in Fetus

Fish lancelet ray anglerfish damselfish

Amphibia toad newt frog salamander

Reptilia Turtle Snake Alligator Lizard

Birds - Aves hummingbird ostrich lovebirds

Mammalia

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

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

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 & spicules (sponges) Limestone cases (corals) Exoskeletons of Chitin (arthropods) –Must be shed or molted to grow Inner Calcium plates or Test (echinoderms) Bone/cartilage endoskeleton (vertebrates)

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

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