Ls2 afet unit 4 biodiversity of animals invertebrates
UNIT 4: BIODIVERSITY OFANIMALS:INVERTEBRATES( Campbell and Reece, 2010:Chapter 32 and 33)
Welcome to Your Kingdom• The animal kingdom extends far beyondhumans and other animals we mayencounter• 1.3 million living species of animals havebeen identified• Invertebrates (animals that lack abackbone) account for 95% of knownanimal species.
EARLY EMBRYONICDEVELOPMENT IN ANIMALS Most animals reproduce sexually, with thediploid stage usually dominating the lifecycle After a sperm fertilizes an egg, the zygoteundergoes rapid cell division calledcleavage Cleavage leads to formation of a blastula The blastula undergoes gastrulation,forming a gastrula with different layers ofembryonic tissues.
EARLY EMBRYONICDEVELOPMENT IN ANIMALSFig. 32-2-1ZygoteCleavageEight-cell stage
EARLY EMBRYONICDEVELOPMENT IN ANIMALSFig. 32-2-1ZygoteCleavageEight-cell stageFig. 32-2-2ygoteCleavageEight-cell stageCleavageBlastulaCross sectionof blastulaBlastocoel
EARLY EMBRYONICDEVELOPMENT IN ANIMALSFig. 32-2-1ZygoteCleavageEight-cell stageFig. 32-2-2ygoteCleavageEight-cell stageCleavageBlastulaCross sectionof blastulaBlastocoelFig. 32-2-3ZygoteCleavageEight-cell stageCleavageBlastulaCross sectionof blastulaBlastocoelGastrulationBlastoporeGastrulaArchenteronEctodermEndodermBlastocoel
• Many animals have at least onelarval stage.• A larva is sexually immature andmorphologically distinct from theadult; it eventually undergoesmetamorphosis.
2. RELATIONSHIP BETWEENBODY PLAN AND GROUPINGOF ANIMALS IN PHYLA• Zoologists sometimes categorize animalsaccording to a body plan.• A body plan is a set of morphologicaland developmental traits, integrated intoa functional whole living animal.
CHARACTERISTICS WHICHCHARACTERISTICS WHICHEXPLAIN BODY PLANEXPLAIN BODY PLAN• Symmetry• Cephalization• Tissues)• Body cavities• Protostome and Deuterostomedevelopment
A. SYMMETRY• Animals can be categorizedaccording to the symmetry of theirbodies, or lack of it• Some animals have radial symmetry• Two-sided symmetry is calledbilateral symmetry
Bilaterally symmetricalanimals have:–A dorsal (top) side and a ventral(bottom) side–A right and left side–Anterior (head) and posterior (tail)ends
B. CEPHALIZATION• Cephalization, the development ofa head
C. TISSUES• Animal body plans also varyaccording to the organization of theanimal’s tissues• Tissues are collections of specializedcells• During development, three germlayers give rise to the tissues andorgans of the animal embryo
• Ectoderm is the germlayer covering theembryo’s surface• Endoderm is theinnermost germ layer andlines the developingdigestive tube, called thearchenteron• Mesoderm: middle layerof some body plansGERM LAYERS ARE:
• Diploblastic animals haveectoderm and endoderm• Triploblastic animals have anectoderm, endoderm and interveningmesoderm layer.
D. BODY CAVITIES• Most triploblastic animals possess a bodycavity• A true body cavity is called a coelom and isderived from mesoderm• Coelomates are animals that possess a truecoelom• A pseudocoelom is a body cavity derived fromthe mesoderm and endoderm• Triploblastic animals that possess apseudocoelom are called pseudocoelomates• Triploblastic animals that lack a body cavity arecalled acoelomates
E. PROTOSTOME ANDDEUTEROSTOME DEVELOPMENT• Based on early development, manyanimals can be categorized as havingprotostome development ordeuterostome development• These two types of developments differ inregard to:• Different cleavage• Different coelom formation• Fate of the blastopore
CLEAVAGE• In protostome development, cleavage isspiral and determinate• In deuterostome development, cleavageis radial and indeterminate• With indeterminate cleavage, each cell inthe early stages of cleavage retains thecapacity to develop into a completeembryo
COELOM FORMATION• In protostome development, thesplitting of solid masses of mesodermforms the coelom.• In deuterostome development, themesoderm buds from the wall of thearchenteron to form the coelom.
FATE OF THE BLASTOPORE• The blastopore forms duringgastrulation and connects thearchenteron to the exterior of thegastrula• In protostome development, theblastopore becomes the mouth• In deuterostome development, theblastopore becomes the anus
Phylum: Porifera (sponges)• Sedentary animals (fixed in oneposition)• They live in both fresh and marinewaters• Cellular level of development• Lack true tissues and organs• Asymmetrical
Phylum:Cnidaria (Hydra, sea anemones)• True tissue – Eumetazoa• Both sessile and motile forms including jellies,corals, and hydras• Diploblastic body plan• Radial symmetry• The basic body plan of a cnidarian is a sac witha central digestive compartment, thegastrovascular cavity• A single opening functions as mouth and anus
• Carnivores that use tentacles to capture prey• The tentacles are armed with cnidocytes,unique cells that function in defense andcapture of prey• Nematocysts are specialized organelleswithin cnidocytes that eject a stinging thread.
Phylum: Platyhelminthes (flat worms)• Live in marine, freshwater, and dampterrestrial habitats.• Triploblastic development• Acoelomates• Flattened dorsoventrally and have agastrovascular cavity• Gas exchange takes place across the surface• Protonephridia regulate the osmotic balance
Phylum: Nematoda (round worms)• Found in most aquatic habitats, in the soil, inmoist tissues of plants, and in body fluids andtissues of animals• They have an alimentary canal, but lack acirculatory system• Sexual Reproduction• Internal fertilization• Some species are parasites of plants andanimals.
Phylum: Annelida (earthworms, leeches)• Bodies composed of a series of fusedrings or compartments - Metamerism
Phylum: Arthropoda (crabs, insects)• Found in nearly all habitats of the biosphereThe arthropod body plan consists of a segmented body, hard exoskeleton (made of layers of proteinand the polysaccharide chitin jointed appendages• The body is completely covered by the cuticle• When it grows, it molts its exoskeleton.• Includes: insects, crabs, spiders, millipedes,centipedes, mites…
Phylum: Mollusca (slugs, snails)• Includes snails and slugs, oysters and clams,and octopuses and squids• Most are marine, some inhabit fresh water andsome are terrestrial• Soft bodied animals, but most are protected bya hard shell.
Phylum: Echinodermata(sea stars, sea urchins)• Shared characteristics define deuterostomes(Chordates and Echinoderms)–Radial cleavage–Formation of the mouth at the end of theembryo opposite the blastopore• Echinoderms have a unique water vascularsystem, a network of hydraulic canalsbranching into tube feet that function inlocomotion, feeding, and gas exchange
Phylum: Chordata (vertebrates)• Phylum Chordata consists of two subphyla ofinvertebrates as well as hagfishes andvertebrates• Vertebrates are a subphylum within thephylum Chordata• Chordates are bilaterian animals that belongto the Deuterostomia.• All chordates share a set of derived characters• Some species have some of these traits onlyduring embryonic development
Four key characteristics ofchordates–Notochord–Dorsal, hollow nerve cord–Pharyngeal slits or clefts–Muscular, post-anal tail