Animals 1) General Characteristics of Animals a) Multicellular i) Cells are arranged in varying levels of organization (1) Cell- fundamental unit (2) Tissue- groups of cells working together (3) Organ- groups of tissues working together b) Heterotrophic i) Cannot make their own food and therefore must eat autotrophs or other heterotrophs in order to gain nutrients c) Require Oxygen i) Use aerobic respiration to convert compounds into energy d) Reproduction i) Animals reproduce sexually, and in many cases, asexually e) Motility i) Most animals are motile during at least part of the life cycle. f) Embryonic Development i) The life cycle includes stages of embryonic development ii) Embryonic cells give rise to primary tissue layers (1) Ectoderm-outer layer (2) Endoderm-inner layer (3) Mesoderm- middle layer g) Body symmetry and cephalization i) Animals are radial or bilateral in symmetry (1) Radial symmetry- body parts arranged regularly around a central axis, like the spokes of a bike wheel. (2) Bilateral symmetry- right half and left half are mirror images of each other ii) Cephalization- tendency for sensory structures to be located in a head region (1) Associated with bilateral symmetry (2) Implies a certain level of behavioral ability h) Gut- tubular, sac-like region in which food is digested and absorbed into the internal environment. i) Sac-like guts- one opening acts as mouth and anus. ii) Tube-like guts- two openings, complete with mouth and anus. i) Body Cavities- region between the gut cavity and the epidermis (outer skin). i) Coelom- one type of body cavity that has a unique tissue lining called a peritoneum (1) Coelomate animals- have a coelom with a peritoneum (2) Pseudocoelomate animals- have a pseudocoel, a body cavity w/o peritoneum (3) Acoelomate animals- lack a body cavity j) Segmentation i) Segmented animals have a repeating series of body units that may or may not be similar to one another (1) Earth worms- all the segments are very similar
(2) Insects- Segments are very different and are even grouped into body regions: head, thorax and abdomen. 2) Animal Evolution a) Most likely evolved from protistans i) Hypothesis 1 (1) Animals evolved from ciliates, like Paramecium and had multiple nuclei in a one-celled body. (2) As they evolved, the different nuclei became different cells. ii) Hypothesis 2 (1) Evolved from spherical colonies of a number of flagellated cells. (2) Certain cells evolved particular functions 3) Vertebrates vs. Invertebrates a) Vertebrates have a backbone. Invertebrates do not. i) 1.95 million species of invertebrates (1) 50,000 species of vertebrates 4) Invertebrate Phyla a) Simplest animal i) Trichoplax adhaerens only known placozoan ( plate - animal ) ii) Consists of several thousand cells arranged in two layers. iii) Has no symmetry and no mouth iv) Slides along the sea floor and briefly humps up when it gets to food, which it digests externally absorbs food into its cells. b) Porifera- The Sponges i) Lack symmetry, tissues and organs (1) Organization is at the cellular level. ii) Mostly marine, though some live in freshwater. iii) Body is stiffened by silica or calcium carbonate spicules iv) Filter feeders (1) Water flows into the sponge body through many microscopic pres and chambers by way of beating collar cells, which have little collars that trap food. v) Reproduction (1) Sexual (a) Release sperm into the water and retain eggs until after fertilization (2) Asexual (a) Somatic embryogenesis- a whole new sponge can grow from fragmented bits of another. c) Cnidaria- Sea anemones, corals, hydroids and jellyfish i) Mostly marine, though some are freshwater ii) Radially symmetric iii) Cells are arranged into tissue layers iv) Feed by using nematocysts- poisonous, stinging cells that that are shot out when touched v) Sac-like gut with one opening vi) Common body forms are the polyp and medusa (1) Medusae float- think of a jellyfish
(2) Polyps attach themselves to the bottom vii) Each lining in the body has an epithelium, a tissue having a free surface that faces the environment of some type of fluid inside the body viii) They have nerve cells within the epithelia that send signals to the contractile cells that cause the body to move ix) Mesoglea- layer of gelatinous secreted material that acts as a gelatinous, hydrostatic skeleton. (1) Hydrostatic skeleton- volume of the body remains the same when contracted and therefore the shape changes. d) Ctenophora- Comb Jellies i) Used to be part of the Cnidaria ii) Instead of using nematocysts, the use coloblasts, which are sticky cells iii) Propel by using cilia, not contracting their bells. e) Platyhelmenthes- The Flaworms i) Bilaterally symmetric ii) Cephalized iii) Have simple organ systems with a sac-like gut iv) Hermaphrodites- both male and female simultaneously v) Turbellarians (1) Mostly marine (2) Ex: Planaria (3) Reproduce asexually through transverse fission vi) Cestoda (1) Tapeworms (2) Parasitize the intestines of vertebrates (3) Attach by means of a scolex, a structure with suckers, hooks or both f) Nemertea- The Ribbon Worms i) Bilateral ii) Acoelomate iii) Soft-bodied and elongated iv) Mostly marine v) They have a complete gut, circulatory system and separation of the sexes. vi) Have a proboscis, which is a tubular, prey-piercing, venom-delivering device. g) Nematoda- The round Worms i) Pseudocoelomate ii) Bilaterally symmetric iii) Covered by a touch cuticle outer covering. iv) Simplest animal with a complete digestive system v) Most are free-living, but some are serious parasites (1) Hosts include: humans, cats, dogs, sheep, potatoes, sperm whales and others. h) Rotifera- The Rotifers i) Bilateral and cephalized ii) Mostly live in freshwater iii) <1mm iv) Have pharynx, esophagus, digestive glands, stomach, intestine and anus
v) Some have eyes vi) Two toes exude substances that attach free-living individuals to substrates at feeding time. vii) Have a crown of cilia on the head that assists in swimming and wafting food toward the mouth. 5) Coelomate Animals a) Protostomes vs. deuterostomes i) Protostome (1) In embryos cleavage is oblique to the original body axis (2) First opening to form is the mouth (3) Coelom arises from spaces in the mesoderm (4) Examples (a) Mollusks, annelids and arthropods ii) Deuterostome (1) In embryos cleavage is parallel and perpendicular to the original body axis. (2) First opening to form is the anus (3) Coelom arises from the gut wall (4) Examples (a) Echinoderms and Chordates b) Mollusca- Mollusks: Clams, squid, octopus and snails (molluscus means soft in latin, referring to their soft bodies) i) Bilateral, coelomate animals with a complete digestive system ii) Have a mantle, which secretes the calcium carbonate shell found in snails. iii) Most mollusks have a fleshy foot. iv) Many have a radula, a rasping tongue v) Examples: (1) Chitons: (a) Most ancestral (b) Have 8 plates on their backs (c) Rocky intertidal grazers (2) Bivalves two - shells (a) Clams, scallops, oysters and mussels (b) Filter feeders with incurrent and excurrent siphons. (c) Live buried in sand or wedged between rocks. (3) Cephalopods- squid and octopus (a) Have mostly lost their shells, though squid have a remnant piece internally. (b) Very fast and very intelligent (i) Use jet propulsion to move through the water (ii) Largest brain-to-body ratio of any mollusk 1. Octopus are smarter than cats. (4) Gastropods- Stomach - Foot : snails and slugs (a) Slugs are snails that have lost their shells (b) Eat with a radula
(c) Snails have this weird thing, where their intestines have gotten all twisted around because of their shell, and they consequently excrete on their own heads. c) Annelida- Means Ringed Forms - The Segmented Worms, e.g. the earth worm i) Bilateral symmetry, complete digestive system ii) Hermaphroditic iii) Hydrostatic Skeleton iv) Segmentation has great evolutionary potential (1) Individual parts can undergo modification for specialization of tasks (2) Polychaetes are a great example of this (a) Jaws (b) Tentacles (c) Paddles v) Many have bristles on the segments that grip the substrate as the worm pushes its way through. vi) They have a rudimentary brain, with a paired nerve cord vii) System of nephridia, which regulates the composition of internal fluids, much like kidneys. viii) Closed circulatory system d) Arthropods- Jointed - feet i) Evolutionarily, the most successful of all living organisms (1) Most species, most habitats, exploiting the mostdifferent types of food. ii) Bilateral, ceolomates with complete digestive and circulatory systems. iii) Six Important Adaptations (1) Hardened exoskeleton made of chitin (a) Used in defense against predation (b) Evolutionarily, it has been molded into a myriad of different forms. Think of it like nature s plastic. (c) Restricts water loss. (d) Arthropods must grow by molting (2) Jointed appendages (a) Allows the hardened exoskeleton to move (b) Led to the evolution of things such as antennae, wings, and legs (3) Fused and modified segments (a) Ancestral arthropods were similar to annelids (b) The fusing and modification of segments into regions of the head, thorax and abdomen allowed for more morphological diversification. (4) Respiratory structures (a) Many aquatic arthropods depend on gills for gas exchange. (b) Land dwellers have tubes that bring oxygen directly to the tissues. (5) Specialized sensory structures (a) Intricate eyes and other sensory organs contributed to arthropod success (6) Division of Labor (a) The job of surviving is divided amongst different stages of development.
(b) Many undergo metamorphosis (i) Egg-larva-adult (ii) Each stage may be adapted to a specific, and different lifestyle 1. Ex: Caterpillars and moths 2. Dragonfly nymphs and dragonflies iv) Major groups of arthropods (1) Chelicerates (a) Marine: (i) Sea spiders, horseshoe crabs, some mites (b) Terrestrial (i) Arachnids 1. Spiders, scorpions, ticks and chiggers 2. Segments fused into a forebody and a hindbody 3. Four pairs of legs, a pair of pedipalps for sensing and a pair of chelicerae that inflict wounds and discharge venom. 4. Hindbody spins out threads for webs and egg cases 5. Open circulatory system (2) Crustaceans: called so because they have a flexible, yet hard crust. (a) Mostly marine (i) Shrimp. Crabs, lobster, copepods, barnacles (b) Some terrestrial (i) Millipeds, centipeds, pill bugs (c) Many have 16 or 20 segments (d) In shrimp, crabs and lobsters, the head and throrax are fused into the cephalothorax. (3) Insects (a) Head, thorax and abdomen (b) Three pairs of legs and usually two pairs of wings (c) Three part gut (d) Only winged invertebrates (e) Life stages include a nymph and pupal, as well as a larval stage. e) Echinodermata- Spiny - Skin : Sea stars, sea urchins, sea cucumbers, sand dollar and brittle stars i) Number of spines with a rigid calcium carbonate endoskeleton ii) Radially symmetric. iii) No brain, but a decentralized nervous system that responds to information from all directions. iv) Move by using tube feet, which have suckerlike adhesive disks v) Water vascular system acts as a hydraulically driven musculature vi) Sea stars pry open their prey, insert their stomachs and then digest. 6) Phylum Chordata- The Vertebrates a) Deuterostomes b) Characteristics i) Notochord a long rod of stiffened tissue, not cartilage or bone, helps support the body.
ii) The nervous system develops from a tubular dorsal nerve cord, which runs parallel to the notochord and gut. iii) The embryos have distinctive lits in the wall of the pharynx, a muscularized tube iv) A post anal tail in the embryos c) Three Subphyla i) Urochordata- Tunicates ii) Cephalochordata- Lancelets iii) Vertebrata- Vertebrates d) Urochordata ( Tail Cord ) i) Tunicates (Sea Squirts) ii) Have a gelatinous or leathery tunic that adults secrete around themselves iii) Marine animals, attached to the substrate. iv) In the juvenile phase they are tadpoles free-swimming with a notochord, but settle on their heads, lose the notochord and begin filter feeding. e) Cephalochordates ( Head Cord ) i) Lancelets ii) Translucent animals that live in nearshore marine sediments iii) Burrow into the sand and filter feed with the pharynx 7) Vertebrates a) Have a backbone b) Most ancestral form is the fish. c) Major evolutionary steps i) Jaws ii) Gills iii) Lungs d) First vertebrates i) Early jawless fish had a notochord and hard, external armor plating ii) Placoderms: Earliest fish with jaws and paired fins (1) Extinct in the carboniferous iii) Extant Jawless Fish (1) Hagfish (a) Live together in groups on sediments of continental shelves. (b) Prey on worms or scavenge for weakened or dead organisms (c) Defend themselves through a sticky, smelly slime (2) Lampreys (a) Mostly parasitic predators (b) Latch onto other fish and destroy the tissue. (c) Their introduction into the great lakes has wiped out many fish there. iv) Extant Jawed Fish (1) The world s dominant vertebrate (2) Cartilaginous Fish (Chondricthyes) (a) Skates, sharks and chimeras (b) Have fins, a skeleton of cartilage and 5 to 7 gill slits (c) Scales are small bony plates on the body (3) Bony fish (Osteichthyes)
(a) Most numerous of all vertebrates. (b) Ray Finned fishes (i) Have rays that project from the dermis (skin s inner layer) to support the paired fins, which are quite maneuverable (ii) Sacs evolved into swim bladders, which aid in buoyancy and help hold a fish at its depth (iii)teleosts (Hard boned) are the most abundant fish, includes salmon, tuna, rockfish, catfish and a bunch of others v) Amphibians (1) Believed to have evolved form a lobed-fin fish. (a) The bony and cartilaginous structures that make up the fin evolved into appendages. (b) Lungfish, a potential link, gulp air, and encase themselves in mud during dry seasons to keep from drying out. (c) This may be similar to the first steps amphibians made. (d) Amphibians are vertebrates with a body plan and reproductive mode somewhere between fishes and reptiles. (e) All salamanders, frogs, toads and caecilians evolved from those first amphibians and none have escaped the water entirely. Even species adapted to land lay eggs in moist places. (f) Salamanders 380sp. (i) Live in North temperate zones and tropical areas of Central and South America (ii) Have a walking style similar to the first vertebrates and resembles a swimming fish (g) Frogs and Toads- 4,000 sp (i) Most successful amphibians (ii) Frogs are aquatic, while toads are more terrestrial. (iii)some have very poisonous skins (h) Caecilians (i) Have lost their limbs and most of their scales (ii) Almost all burrow in soft mud and they pursue earthworms (iii)almost all of the adults are blind. vi) Reptiles (1) First vertebrates to escape dependency on standing water with four adaptations. (a) Tough dry, scaly skin. (b) Internal fertilization. (c) Kidneys good at conserving water (d) Amniote egg, which protects the developing embryo (2) Cold-blooded, adjust their body temperature based upon activity (3) Tend to be fast moving, with big muscles and teeth. (4) Crocodillians, which diverged from the reptilian lineage, were the first to develop a four chambered heart (5) Early reptiles adapted to many different conditions, including land, sea and air.
(6) Most notable of the reptiles were the dinosaurs, which became extinct about 64mya and the end of the cretaceous (7) Crocodillians (a) Closest relatives of birds and dinosaurs (b) Big, sharp-toothed predators (8) Turtles (a) Have a shell (b) Instead of teeth turtles, have horny plates that are suitable for gripping and chewing food (9) Lizards and Snakes (a) Have a third eye that is covered with skin and registers day length. (b) Most are small, but some snakes can reach 30 (c) Most lizards are insect eaters (d) Some, like the gecko, have special adaptations for escaping prey. (e) All snakes are carnivores, with a flexible skull and highly movable jaws, using either venom or constriction (10) Tuataras (a) Similar to amphibians in how they walk (b) Body plan has not changed in 140 years. (c) Also have third eye like lizards vii) Birds-10,000 sp (1) Evolved from reptiles (2) Unique adaptation: The Feather (a) Used in flight (b) Used for insulation (3) Archeopteryx was the missing link (4) Warm blooded with a four chambered heart (5) Very diverse and live in all habitats on earth. viii) Mammals (1) Have hair and mammary glands (2) Tend to have extended care for their young (3) Mammals have varied teeth with secure, cut and chew food before swallowing (4) Evolution (a) >200 mya, small, hairless reptiles called synapsids gave rise to the therapsids, the ancestors of the mammals. (b) Therians, small (mouse sized) evolved legs under the body, which allowed for walking erect. (c) After the extinction of dinosaurs, three lineages of mammals emerged (i) Monotremes- egg layers (ii) Marsupials- pouched (iii)eutherians- placentals 1. Had the advantage 2. Higher metabolism 3. More precise way of regulating temperature 4. A new way of nurturing embryos
(iv) The breakup of Pangea led to the isolation of monotremes and marsupials. ix) Trends Among Primates (1) Prosimians (a) Lemur, Loris (b) Tree dwellers (c) Displaced by monkeys and apes in northern forests (2) Tarsioids (a) Tarsiers of southeast Asia are the only living tarsioids (b) The are somewhere between prosimians and anthropoids (3) Anthropoids (a) Monkeys, apes and humans (4) Key Adaptations (a) Enhanced daytime vision (i) Eyes moved to the front of the head (ii) And allowed to respond to variations in light (b) Upright Walking (i) Bipedalism 1. Frees up the hands to do other things 2. Saves on energy (c) Power grip and precision grip (i) Prehensile movement of digits allows for grasping (ii) Allowed to make and use tools (d) Teeth (i) Rectangular jaw and varied teeth allow for a wide variety of food types (e) Expansion of the Brain (i) More complicated behaviors and communications x) A Case Study in Mammalian Evolution (1) Cetaceans: Whales, Dolphins and Porpoises 8) From whom did whales evolve? a) Suborder Archaeoceti ( first - whale ) i) Aquatic elongated mammals up to 21m with reduced hindlimbs and strong snouts, adapted to life in shallow coastal fringes as well as open seas ii) Had long tail, short neck, reduced hindlimbs, paddle-shaped front limbs, and a point of flexion in the tail vertebrae that allowed up and down movement. iii) Pakicetus most primitive archaeocete b) Members of the terrestrial Condylarthra gave rise to the archaeocetes i) Condylarthra- primitive ungulates (cows, hippos, etc.). c) Cetaceans thus share common ancestry with Artiodactyla, (Cows, Hippos, Etc.) that gave rise to modern ungulates i) Supported by the following evidence (1) Blood composition (2) Fetal blood sugar (3) Chromosomes (4) Insulin
(5) Uterine morphology (6) Tooth enamel microstructure d) Cetacean adaptations i) Loss of limbs ii) Moving of nostrils back on the head iii) Telescoping of skull iv) More streamlined shape v) Loss of hair vi) Baleen in some