Biology 1030 Winter 2009

Transcription

1 Animal Diversity Chapters 32, 33 and 34 (select pages) Living Organisms Three Domains of life Bacteria Archaea Eukarya True nucleus True organelles Heterotrophic Animals Fungi Protists Autotrophic Plants Protists Heterotrophic Protists Paraphyletic grouping Lack chloroplasts Protozoans Unicellular Animal-like like protists Diplomonads (Giardia) Ciliates (Paramecium) Unikonta Amoebozoans (Amoeba) Opisthokonta (Choanoflagelates) 1

2 Choanoflagelates Predecessor of all animals Colonial protists Collared cells What is an Animal? Animals are characterized by multiple traits: Multicellular Cells interconnected through various junctions Lack cell walls Heterotrophic Directional motion Diplontic life cycle Tissues develop from germ layers Animal Diversity Over 1.5 million described species of animals Insects Underestimate Two large, general groups of animals: 1. Invertebrates 2. Vertebrates 2

3 Phyla A large taxonomic grouping of related animals total phyla 10 major phyla Phyla You Need to Know Porifera Cnidaria Echinodermata Chordata Nematoda Arthropoda Platyhelminthes Brachiopoda Annelida Mollusca Animal Classification To classify animals, we ask the following questions: 1. Are there true tissues? 2. If yes, how many layers? 3. What is the pattern of development? 4. How do they grow? 4b. Special structure? 5. Is there body symmetry? 6. Is there a body cavity? 3

4 1. Are Tissues Present? What is a tissue? A group of cells If one or a few cells are removed: They cannot perform their task They will eventually die Two major groups Parazoa Phylum Porifera Eumetazoa Everything else Ph. Porifera The Sponges The first animals Colonial protists (Choanoflagellates) All are aquatic and benthic Poriferan Body Plan Sponges have no true tissues Three layers of cells only Pinacoderm Pinacocytes Porocytes Mesohyl Spongocytes Choanoderm Choanocytes But Why not true tissues? Totipotency 4

5 Poriferan Body Plan Each cell is totipotent Not dependent on each other Able to change Useful for asexual reproduction 2. How Many Tissue Layers? Animals with true tissues Invagination of a hollow ball of cells Ectoderm outside Endoderm inside = Diploblastic How Many Tissue Layers? In most animals Ectoderm Endoderm Mesoderm forms between Two major groups: Diploblastic Triploblastic 5

6 Phylum Cnidaria Jelly fish, anemones, corals Diploblastic Ectoderm (epidermis) Endoderm (gastrodermis) Space between is filled with mesoglea 2 basic body shapes Medusa Polyp Cnidocytes Nematocysts Specialized stinging cell Highly venomous Paralyzes prey Cnidarian Body Plan Colonial cnidarians All individuals are clones Corals Autozooids are similar in morphology 6

7 Cnidarian Body Plan Specialized colony members Dactylozooid Gastrozooid Gonozooid 3. What Type of Development? Animal development Diplontic life cycle The zygote Undergoes cleavage The morula A solid ball of cells The blastula A hollow ball of cells Gastrulation Arranges the tissue layers correctly Forms the primitive digestive tract or archenteron Creates an opening (blastopore) 7

8 3. What Type of Development? Fates of the blastopore: 1. Formation of the mouth Protostome development (mouth first) 2. Formation of the anus Mouth forms later Deuterostome development (mouth second) The Deuterostomes Radial cleavage Indeterminate development Enterocoelous Outpockets from archenteron Echinodermata Chordata The Protostomes Spiral cleavage Determinate development Schizocoelous Splitting of solid masses of mesoderm The remaining phyla 8

9 Phylum Echinodermata Divided into 5 major classes Class Crinoidea Class Asteroidea Class Ophiroidea Class Echinoidea Class Holothuroidea All species are marine Echinoderm Body Plan Larvae have bilateral symmetry Pentaradial (secondary) symmetry as adults Echinoderm Body Plan The water vascular system Locomotion Gas exchange Circulation Prey capture An adaptation of their coeloms! 9

10 Echinoderm Body Plan All have a calcareous endoskeleton of several plates or ossicles Microscopic remnants Echinoderm Regeneration Phylum Chordata Characteristics Dorsal hollow nerve cord Notochord Post-anal tail Pharayngeal gill arches /slits 10

11 Phylum Chordata Three major subphyla Subphylum Cephalochordata Subphylum Urochordata Subphylum Vertebrata Pharyngeal Gill Arches Highly modified in the more derived chordates Ancestral uses Form the jaws (arch 1) Form the inner ear (arches 1 & 2) Form the cartilages of the throat (arches 4 & 5) Subphylum Cephalochordata The lancelets Small, fish-like animals Only 25 species Filter-feeders, catching food in their 100+ gill arches Believed to be the earliest chordates Fossils found in the Burgess Shale and Chengjiang deposits 11

12 Subphylum Urochordata The tunicates Defining characteristics only in the larval stages of development Most are filter-feeders, but one is an active predator Subphylum Vertebrata Recall the Protostomes Spiral cleavage Determinate development Schizocoelous Splitting of solid masses of mesoderm The remaining phyla 12

13 4. What Type of Growth Pattern? Two different methods of growth Growth by continually extending their skeletons Growth by moulting body coverings The Lophotrochozoans Growth by extension of their skeletons A common larval form Trochophore larva Annelids & Mollusks A feeding structure Lophophore Brachiopods Neither Platyhelminths The Ecdysozoans These animals are covered by a hard covering Growth occurs by moulting or shedding their cuticle or exoskeleton Ecdysis Nematodes & Arthropods 13

14 Phylum Nematoda The round worms The most abundant group of the Eumetazoa Found in all habitats Free-living and parasitic forms Nematode Body Plan Free-living species are generally small, interstitial worms µm mm scale Parasitic species can be very large cm m scale! Dracunculus can grow over 1m! Nematode Body Plan Body covering is a cuticle A clear, tough but flexible, non-living covering Not an exoskeleton 14

15 Free-Living Nematodes Parasitic Nematodes Phylum Arthropoda Well over 1,000,000 species described! All arthropods are characterized by: Exoskeleton with jointed appendages 15

16 Arthropod Body Plan Segmentation is obvious Generally each segment has a pair of appendages Similar segments are grouped into body regaions or tagmata Phylum Arthropoda Divided into multiple Subphyla including: Subphylum Myriapoda Subphylum Cheliceriformes Subphylum Hexapoda Subphylum Crustacea Myriapod Body Plan Centipedes and millipedes Homonomous segmentation Except for the head region Legs are simple unbranched The major difference is the number of legs per segment ~30 segments 2 legs/segment = ~190 segments 4 legs/segment = 16

17 Cheliceriform Body Plan The spiders, mites, scorpions and ticks Segments are grouped into 2tagmata Anterior cephalothorax Posterior abdomen The chelicerae (chelicera sing.) 4 pairs of unbranched walking legs No antennae Hexapod Body Plan Over 1,000,000 described species! Dominate terrestrial environments Light-weight chitinous exoskeleton Three tagmata Head 5 segments Thorax 3 segments Legs and wings Abdomen up to 11 Crustacean Body Plan The crabs, lobsters, shrimp, barnacles, copepods Mostly aquatic with a few terrestrial species Heavy calcarious carapace Body divided into 2 tagmata Cephalothorax Biramous appendages Several pairs of antennae Abdomen or tail 17

18 The Lophotrochozoans Growth by extension of their skeletons A common larval form Trochophore larva Annelids & Mollusks A feeding structure Lophophore Brachiopods Neither Platyhelminths Phylum Platyhelminthes The flat worms Possess neither a trochophore larvae or a lophophore 3 major classes Class Turbellaria Class Cestoda Class Trematoda Platyhelminth Body Plan They have a solid body construction Acoelomate All flat worms exhibit bilateral symmetry Rudimentary light-sensitive iti eye-spots Flat worms have an incomplete, two-way gut The gastrovascular cavity 18

19 Phylum Platyhelminthes Phylum Brachiopoda The lamp shells One of a few lophophorate phyla Not clams! Different plane of symmetry Different mode of life Different musculature Brachiopod Body Plan Most are sessile - pedicle Some dig through the sand Valves are produced by a mantle as in the molluscs Predominant tin the fossil record 19

20 Protostome Development? Cleavage is radial The second opening becomes the mouth The blastopore disappears The third opening becomes the anus (if it forms) The Inarticulata have a complete, 1-way gut The Articulata have an incomplete, 2-way gut Phylum Annelida The segmented worms Three major classes Class Polychaeta Class Oligocaeta Class Hirudinea Annelid Body Plan Obvious segmentation In many, the segments are all similar homonomous Others have segments that are specialized heteronomous 20

21 Annelid Body Plan Trochophore larval Paired setae (chaetae) on nearly all segments Polychaetae Oigochaetae Hirudinea Polychaete Body Plan Predominantly marine worms with parapodia on each segment Multitasking Well-developed head with palps Multitasking Oligochaete Body Plan Mainly terrestrial (some freshwater) worms No parapodia, & small setae or bristles Streamline body shape Reduced head No palps 21

22 Hirudinean Body Plan Body is dorsoventrally flattened Anterior and posterior suckers Segmentation is reduced to accommodate large blood meals Phylum Mollusca All with a trochophore larval stage Can be found in all environments marine, freshwater and terrestrial (moist habitats) Four major classes Class Polyplacophora Class Gastropoda Class Bivalvia Class Cephalopoda Molluscan Body Plan Despite this variety all mollusks are variations on a common theme 1. Muscular foot 2. Mantle 3. Radula 4. Visceral mass A great example of adaptive radiation 22

23 Class Polyplacophora The chitons Muscular foot for crawling Flexible 8-piece shell Tongue-like radula Class Gastropoda The snails and slugs Crawling muscular foot Single spiral shell slugs Tongue-like radula Class Bivalvia The clams, scallops, mussels etc. Digging foot in some Shell in 2 hinged pieces No radula 23

24 Class Cephalopoda The squid & octopi Foot modified into tentacles Shell reduced or absent Beak-like radula 5. Type of Body Symmetry? Most sponges (parazoa) are asymmetrical A random growth of cells with no plane of symmetry 5. Type of Body Symmetry? The ancestral eumetazoan character trait is radial symmetry Where there are several planes of symmetry Radial animals are divided on an oral-aboral axis 24

25 5. Type of Body Symmetry? The more derived trait is bilateral symmetry Only a single plane creates two equal halves Bilateral animals have multiple axes or sides Anterior Posterior Dorsal Ventral Cephalization Two major groups of animals Radiata Bilateria The concentration of sensory organs at the anterior end Clustering of neurons Ganglia Brains Complex behaviours 6. Is There a Body Cavity? The body cavity is called the coelom The fluid-filled space around internal organs Room for internal organs to expand and move Only looked at in triploblastic animals 25

26 6. Is There a Body Cavity? Eucoelomate A cavity completely lined with mesoderm Pseudocoelomate A cavity partially lined with mesoderm (and endoderm) Acoelomate No cavity The space is completely filled with mesoderm Animal Phylogeny The traditional phylogenetic tree shared characters Anatomical features Developmental characters Embryological characters New technologies molecular data DNA and rrna sequencing Molecular phylogeny Read Concept