General Features of Animals Animals are a diverse group that are characterized by several features animals are heterotrophs all animals are mul:cellular and lack cell walls most animals are able to move from place to place most animals reproduce sexually
Five Transi:ons in Body Plan The evolu:on of animals is marked by five key transi:ons to the body 1. Evolu(on of (ssues only the sponges (Parazoa) lack both defined :ssues and organs all other animals (Eumetazoa) have true :ssues 2. Evolu(on of bilateral symmetry sponges also lack any definite symmetry and grow as irregular masses virtually all of the Eumetazoa have a definite shape and symmetry radial symmetry means the parts of their bodies are arranged around central axis bilateral symmetry means that the body only has lef and right mirror images 3. Evolu(on of a body cavity a body cavity makes possible the evolu:on of efficient organ systems supports organs, distributes materials, and fosters complex developmental interac:ons 4. Evolu(on of deuterostome development bilateral animals can be divided into two groups based on differences in the pajern of embryonic development protostomes include flatworms, nematodes, mollusks, annelids, and arthropods deuterostomes include echinoderms and chordates 5. Evolu(on of segmenta(on segmented animals are assembled from a succession of similar segments
We will know this chart by the end of class today
Sponges: The Simplest Animals Sponges are members of the phylum Porifera They lack true :ssues and organs but instead are comprised of masses of specialized cells embedded in a gel like matrix the body of a sponge is perforated by :ny holes unique flagellated cells, called choanocytes, line the body cavity of the sponge and draw water in through the pores the sponge is a filter feeder that ingests any suspended food par:cles trapped by the choanocytes as the water flows by
Cnidarians and Ctenophora All animals other than sponges have symmetry and :ssues Two phyla exhibit radial symmetry (Radiata) bodies are organized around a central axis Cnidaria jellyfish, corals, and sea anemones» Carnivores first animals to use extracellular diges:on occurs in gastrovascular cavity» S:nging cells are called cnidocytes» Each s:nging cell or cnidocyte has a harpoon called a nematocyst» Exist in two forms Medusae free floa:ng umbrella shaped Polyps cylindrical shaped, usually ajached to a rock Ctenophora comb jellies Polyp Medusae
Bilateral symmetry From here on out, all organisms we describe have bilateral symmetry All bilateral animals have three embryonic layers that develop into the :ssues of the body Ectoderm, endorderm, mesoderm
Flatworms Flatworms are in the phylum Platyhelminthes They have a gut with only one opening called the pharynx Food taken in and waste expelled from here No other body cavity besides the diges:ve system acoelomates From here on out, all organisms have a body cavity. Important advance for 3 reasons Circula:on Movement Organ func:on Pseudocoelomate body cavity located between mesoderm and endoderm Coelomate body cavity located within mesoderm
Pseudocoelomates: Nematoda and Ro:fera All pseudocoelomates lack a defined circulatory system, but most have a oneway diges:ve tract (meaning mouth and anus now) In all pseudocoelomates, the pseudocoel serves as a hydrosta(c skeleton muscles can work against the rigidity of the fluidfilled cavity Nematodes unsegmented worms with a cylindrical (i.e., round) body covered by a flexible, thick cu:cle that is shed as they grow in a process called mol:ng About 50 species of nematodes regularly parasi:ze human beings Trichinella causes trichinosis afer consuming raw or undercooked pork From here on out, all organisms we discuss are coelomates
Mollusks The only major phylum of coelomates without segmented bodies are the mollusks (phylum Mollusca) Basic body design a head and foot the foot is muscular and may func:on in locomo:on, ajachment, or food capture a central visceral mass contains the body s organs a mantle a heavy fold of :ssue that surrounds the visceral mass respiratory organs are posi:oned on the inner surface of the mantle 3 major groups gastropods use the muscular foot to crawl and their mantle ofen secretes a single, hard protec:ve cell all terrestrial mollusks are gastropods bivalves secrete a two part shell with a hinge and filter feed by drawing water into their shell cephalopods have a modified mantle cavity that permits jet propulsion and, in most groups, the shell is reduced or absent
Pearls In mollusks with shells, the outer layer of the shell consists of horny material that is rich in protein the inner layer of the shell consists of pearly material that is used as mother of pearl pearls are formed in clams and oysters when a foreign object becomes lodged between the mantle and the inner shell the mantle coats the foreign object with layer upon layer of shell material to reduce irrita:on
Annelids The first segmented animals to evolve were the annelid worms (phylum Annelida) Segmenta(on is the building of a body from a series of similar segments a small change in an exis:ng segment can produce a new kind of segment with a different func:on This allows for two important advancements 1. specialized segments the anterior segments contain sensory organs and a brain 2. connec(ons circulatory system is required because the segments are divided by par::ons a nervous system allows for coordina:on
Arthropods All arthropods have jointed appendages, including legs, wings, antennae, and mouthparts Without jointed appendages, it is impossible to walk, fly, or grasp an object Arthropods also developed a rigid, chi:nous exoskeleton on the outside of their body provides points for muscle ajachment one drawback of a chi:nous exoskeleton was that it prevented arthropods from reaching immense sizes
Embryo development Up to this point, all coelomates develop the same way called protostomes From here on out, organisms will develop in a different way deuterostomes
Echinoderms Echinoderms (phylum Echinodermata) were the first deuterostomes to evolve their name means spiny skin, which refers to an endoskeleton composed of hard, calcium rich plates called ossicles that lies just beneath the skin all echinoderms are bilaterally symmetrical as larvae but become radially symmetrical as adults a key innova:on in echinoderms is a hydraulic system that aids in movement called the water vascular system it is a system of fluid filled canals that extend into numerous, hollow tube feet
Chordates Chordates (phylum Chordata) are deuterostome coelomates characterized by a flexible rod called a notochord that develops along the back of the embryo 4 principal features of chordates 1. notochord a s:ff but flexible rod that forms beneath the nerve cord in the early embryo 2. nerve cord a single dorsal hollow nerve cord 3. pharyngeal pouches a series of pouches behind the mouth that develop into slits in some animals 4. postanal tail a tail that extends beyond the anus, at least during embryonic development All vertebrates are chordates the only non vertebrate chordates are the tunicates and the lancelets vertebrates are dis:nguished by having backbone (comprised of a series of hollow bones) that replaces the notochord head with a skull and brain
Chordate phylogene:c tree
Fish Vertebrates first conquered the sea, then the land 4 characteris:cs that all fish share 1. gills fish use gills to extract dissolved oxygen from water 2. vertebral column all fishes have a skeleton made of either bone or car:lage 3. single loop blood circula(on blood is pumped from the heart to the gills, to the body, and then back to the heart 4. nutri(onal deficiencies fish are unable to synthesize the aroma:c amino acids and must consume them in their diet The first fishes to evolve were jawless Later, predatory fishes with jaws evolved, which eventually gave rise to the sharks and bony fishes At this point, we are talking about various classes not phyla anymore all organisms are part of the chordata phylum
Sharks and rays Sharks and rays are members of the class Chondrichthyes Sharks evolved into fast swimmers because their car:laginous skeleton is light and flexible
Bony fishes Bony fishes (class Osteichthyes) consist of about 30,000 species Have a heavy internal skeleton of bone but are s:ll buoyant because of a swim bladder the swim bladder is a gas filled sac that allows fish to regulate their buoyant density Have a gill cover called the operculum allows them to breathe without having to move
Amphibians Amphibians have five key characteris:cs that allowed them to successfully invade land 1. legs 2. lungs 3. cutaneous respira(on supplements the use of lungs 4. pulmonary veins returns oxygenated blood from the lungs to the heart for repumping 5. par(ally divided heart helps to prevent the mixing of oxygenated blood with deoxygenated blood must reproduce in water and are not completely terrestrial many have a tadpole or intermediate larval phase Major groups include Frogs and Toads Salamanders and newts Caecilians
Rep:les Rep:les replaced amphibians as the dominant terrestrial vertebrates because of important features amnio(c egg rep:les lay water:ght eggs with various layers that protect and nourish the embryo dry skin the skin of rep:les is covered by dry scales that prevent water loss thoracic breathing rep:les expand and contract the rib cage to move air in and out of the lungs Major groups Turtles and tortoises Crocodiles and alligators Snakes and lizards
Birds Birds evolved from small bipedal dinosaurs modern birds lack teeth and have only ves:gial tails they lay amnio:c eggs and have rep:lian scales on their feet and lower legs birds are unique from rep:les in having feathers lightweight and adapted for flight flight skeleton rigid for ajaching flight muscles; the bones are thin and hollow
Mammals Mammals share three major characteris:cs mammary glands female mammals have mammary glands that produce milk to nurse the newborns hair the primary func:on is insula:on hair is made up of dead cells filled with the protein, kera(n middle ear all mammals have three middle ear bones that evolved from bones in the rep:le jaw 3 major groups Monotremes lay eggs, duck billed platypus Marsupials kangaroos placental mammals most species of mammals today are placental mammals