Animal structure and function. Invertebrates -Introduction

Transcription

1 Animal structure and function Invertebrates -Introduction

2 Lectures Introduction Organ systems Seminars Invertebrates Reproduction: November 8 Morphological adaptation: November 11 Lab seminars Laboratory practicals (print pdfs for Lab 1) Final exam November 21

3 What is an animal? Definition: Multicellular Heterotrophic eukaryotes: ingestion Lack cell wall: structural protein: collagen Nerve and muscle cells Most animals reproduce sexually Embryonic development: zygote to blastula to gastrula Regulatory genes: Hox gene

4 Animal classification Body plan Body symmetry Tissue organization Body cavities Early embryonic development

5 Classification by characteristics of body plan: symmetry PARAZOA (near animals, no tissue) asymmetry EUMETAZOA (true animals, tissue) radial symmetry =RADIATA bilateral symmetry =BILATERA

6 Three polarity axes

7 Bilateria: cephalization Evolutionary trend towards the concentration of sensory equipment on the anterior end.

8 Body symmetry - lifestyle

9 Classification by characteristics of body plan: Tissue organisation TISSUE: Collection of specialized cells isolated from other tissues by membranous layers

10 The embryo become layered through the process of gastrulation

11 Germ layers 1. Ectoderm -covering the surface of the embryo -gives rise to the outer covering of the animal -gives rise to central nervous system in some phyla 2. Endoderm -the innermost layer which lines the archenteron -gives rise to the lining of digestive tract -gives rise to the liver and lungs of vertebrates =DIPLOBLASTIC (Cnidaria) 3. Mesoderm -located between ectoderm and endoderm -forms muscles and most of the organs =TRIPLOBLASTIC (all bilaterians)

12 Triploblastic animals can be further classified into three basic plan of body cavities A. Coelomate- with a true body cavity (coelom) that is completely lined by tissues derived from mesoderm B. Pseudocoelomate-with a body cavity but is not completely lined by tissue derived from mesoderm C. Acoelomate-without a body cavity

13 Triploblastic animals (coelomates) can be divided into two distinct grades A. Protostomia B. Deuterostomia

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15 Two views of animal phylogeny. Which is right? Both are useful? Tree based on morphological and developmental comparisons Tree based mainly on molecular data

16 Invertebrates

17 Life Without a Backbone Invertebrates Are animals that lack a backbone Account for 95% of known animal species >30 phyla Figure 33.1 Figures are mainly from the book Biology (ch 32&33) by Campbell & Reece Black&white figure are from Invertebrate zoology by Ruppert, Fox, & Barnes

18 Phylum Porifera (Phyla Calcarea and Silicea) Porifera, sponges (svampdjur) Non-moving (sessile) animals No nerves or muscles (no tissue differentiation) Mostly marine Most sponges are hermaphrodites.

19 Phylum Porifera Sponges are suspension feeders -Capturing food particles suspended in the water that passes through their body Choanocytes, flagellated collar cells -Generate a water current through the sponge and ingest suspended food pinacoderm Pinacoderm= epithelioid tissue Pinacocytes and porocytes Lab 1:I

20 Phylum Cnidaria corals, jellies, hydras, sea anemones (nässeldjur) One of the oldest groups in clade Eumetazoa Simple diploblastic epidermis gastrodermis mesoglea (gelatinous extracellular matrix) Radial symmetry

21 Phylum Cnidaria Both sessile and floating forms (Polyp or medusa form) One opening in the gastrovascular cavity serves as both mouth and anus.

22 Phylum Cnidaria Carnivores Phylum name comes from specialized cells called cnidocytes Cnidocytes are stinging cells used for defense and to capture prey Hydra

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24 Phylum Cnidaria Polyp and medusa mainly medusa only as polyps Lab 1:II Hydrozoa & Anthozoa

25 Phylum Acoela Basal bilaterians A simple nervous system No body cavity (coelom) Lacks many organ systems Were classified with other flatworms in the phylum Platyhelminthes

26 Phylum Platyhelminthes tapeworms, flukes and flatworms (plattmaskar) Simple, sift, ribbon-like body Acoelomates with organ systems Inefficient gas exchange across body walls Gastrovascular cavity Asexual and sexual reproduction Marine, freshwater and damp terrestial Most free living but many parasites Eat microbes and invertebrates Tapeworm Planarians Lab 1:III

27 Phylum Mollusca snails, slugs, clams, oysters, squids, octopuses (Blötdjur) There are at least known species All molluscs have similar body plan Muscular foot Visceral mass with organs Mantle (that secretes the shell) The life cycle of many molluscs includes a ciliated larval stage called a trochophore Lab1:IV

28 Gastropods About three-quarters of all living species of molluscs Belong to class Gastropoda (a) A land snail Figure 33.18a, b (b) A sea slug. Nudibranchs, or sea slugs, lost their shell during their evolution.

29 The most distinctive characteristic of this class Is a developmental process known as torsion, which causes the animal s anus and mantle to end up above its head Anus Mantle cavity Stomach Intestine Mouth Figure 33.19

30 Cephalopods Class Cephalopoda includes squids and octopuses and nautiluses Carnivores with beak-like jaws surrounded by tentacles of their modified foot (a) Octopuses are considered among the most intelligent invertebrates. (b) Squids are speedy carnivores with beaklike jaws and welldeveloped eyes. (c) Chambered nautiluses are the only living cephalopods with an external shell.

31 Phylum Annelida Segmented worms (Ringmaskar) Have bodies composed of a series of fused rings Divided into three classes: Oligocheata - has bristles of chitin (earth worm) Polychaeta - has paddlelike parapodia Hirudinea- blood sucking parasites (leeches) Marine, freshwater and terrestrial Asexual and sexual reproduction Parapodia Figure Figure Lab 1:III,IV & 3

32 Segmentation The annelid body is composed of three regions: Prostomium-brain and sense organs Truck-consists of a longitudinal series of similar body units- the segments. First segmentlike part= peristomium Growth zon: teloblast cells that divide and differentiate Pygidium- anus

33 Phylum Nematoda Roundworm (rundmask) small Marine, freshwater and terrestrial Nonsegmented pseudocoelomates Covered by a tough coat-cuticle Eat microbes, predaceous, or parasitic on plants/animals Encysted juveniles Muscle tissue 50 µm

34 Phylum Arthropoda crustaceans, spiders, insects (leddjur) Three sub-phyla: Chelicerata, Crustacea and Tracheata Hard exoskeleton, segmented bodies, jointed appendages Arthropods are the most successful of all animal phyla based on diversity, distribution, and numbers. More than one million species identified so far, mostly insects

35 Phylum Arthropoda crustaceans, spiders, insects (leddjur) The exoskeleton, or cuticle, is composed of protein and chitin. Molting of the cuticle is called ecdysis. Open circulatory systems in which a heart pumps hemolymph through short arteries and into open spaces (sinuses). A variety of organs specialized for gas exchange have evolved in arthropods Lab 1:III,IV, 2, 4, 5

36 Arthropod body-segmented Acron=anterior end (prostomium) First segment-mouth Growth zon Telson= posterior end (post anal) (pygidium)

37 Evolution of the arthropod body is characterised by tendencies to -tagmosis -heteronomy -fusion of segments -cephalization

38 Tagmosis Tagmosis: tendency to organize segments into region having similar structure. Three tagmata: Head, Thorax, Abdomen Secondary tagma: cephalothorax: some or all of the thoracic segments unite with head

39 Evolution of the arthropod head (cephalization) headancestor acron truck A L L L L L L Chelicerata 0 C P L L L L Crustacea Tracheata A1 A2 Mnd Mx1 Mx2 L L L L L A1 0 Mnd Mx1 Mx2 L L L L L A: antenna C:Chelicera chelicerer L:leg Mnd:mandible Mandibler, överkäkar Mx: maxilla Maxiller, underkäkar P: pedipalp maxillarpalper 0: lost segment Each higher taxon of modern arhropods has a characteristic set of head appendages Fig 16-3

40 Ecdysis (ömsning) Arthropoda and other animal taxa: Nematoda, Nematomorpha, Kinorhyncha, Loricifera and Priapulida have a cuticle that is molted under hormonal (ecdysone) control. Exoskeleton is incapable of stretching Intermolt Proecdysis Ecdysis Postecdysis new instar For Nematoda ecdysis see fig 22-9

41 Phylum Arthropoda Sub-phylum Classes Example Chelicerata Arachnida spiders, scorpions, mites, ticks Xiphosura horseshoe crab Pantopoda sea spiders Crustacea Remipedia elongated undersea caves crustaceans (10 species) Cephalocarida undifferentiated crustacean(9 species) Anostraca fairy & brine shrimps Phyllopoda water fleas, clam shrimps Malacostraca crabs, lobster, crayfishes, shrimps, krill Maxillopoda (SC) (8 classes Copepoda) small or micro crustaceans-krill Tracheata Myriapoda (SC) Chilipoda centipedes Diplopoda millipedes Pauropoda small soft-bodied nocturnal animals Symphyla small white elongated animals found in litter Hexapoda (SC) Insecta (C) (Entognatha (C)) insects

42 Sub-phyla Chelicerata Are named for clawlike feeding appendages called chelicerae Include spiders, ticks, mites, scorpions, and horseshoe crabs Figure 33.30

43 Class Arachnida 50 µm (a) Scorpions have pedipalps that are pincers specialized for defense and the capture of food. The tip of the tail bears a poisonous stinger. Figure 33.31a c (b) Dust mites are ubiquitous scavengers in (c) human dwellings but are harmless except to those people who are allergic to them (colorized SEM). Web-building spiders are generally most active during the daytime.

44 Arachnids have an abdomen and a cephalothorax Which has six pairs of appendages, the most anterior of which are the chelicerae Digestive gland Intestine Heart Stomach Brain Eyes Ovary Poison gland Anus Figure Spinnerets Silk gland Gonopore (exit for eggs) Book lung Sperm receptacle Chelicera Pedipalp

45 Sub-phyla Crustacea Most diverse arthropod group Head, thorax and abdomen-may fuse these parts 2 pairs of antennae, 1 pair of compound eyes, 3 pairs of mouthparts (1 pair of mandibles+ 2 pair of maxillae). Some breathe over body surface, but larger species have gills

46 Decapods are all relatively large crustaceans And include lobsters, crabs, crayfish, and shrimp Three basic body shapes Fig 19-24

47 Super-class Myriapoda (Tracheata) Millipedes, class Diplopoda Have a large number of legs Each trunk segment Has two pairs of legs dubbelfotingar Centipedes, class Chilopoda Are carnivores with jawlike mandibles Have one pair of legs per trunk segment enkelfotingar

48 Class Insecta (Hexapoda, Tracheata) Outnumber all other forms of animals. Flight was followed by an explosion of diversity. Coevolution of flowering plants and insects. Well-adapted terrestrial organisms Many orders of insects

49 The external anatomy of an insect Truck divided into thorax (prothorax, mesothorax, metathorax) and abdomen (9-11 segments) adults (imago) and usually immatures (juveniles) have 3 pairs of legs (6 parts) (hexapods) (on thorax) 2 pair of wings (forewings and hindwings on meso- and metathorax, respectively) 1 pair of antenna

50 The internal anatomy of an insect Includes several complex organ systems Figure The insect body has three regions: head, thorax, and abdomen. The segmentation of the thorax and abdomen are obvious, but the segments that form the head are fused. Abdomen Thorax Head Compound eye Antennae Heart. The insect heart drives hemolymph through an open circulatory system. Ovary Malpighian tubules. Anus Metabolic wastes are removed from the Vagina hemolymph by excretory organs called Malpighian tubules, which are outpocketings of the digestive tract. Tracheal tubes. Gas exchange in insects is Nerve cords. The insect accomplished by a tracheal system of branched, nervous system chitin-lined tubes that infiltrate the body and consists of a pair of carry oxygen directly to cells. The tracheal ventral nerve cords system opens to the outside of the body with several through spiracles, pores that can control air segmental ganglia. flow and water loss by opening or closing. Cerebral ganglion. The two nerve cords meet in the head, where the ganglia of several anterior segments are fused into a cerebral ganglion (brain). The antennae, eyes, and other sense organs are concentrated on the head. Dorsal artery Crop Insect mouthparts are formed from several pairs of modified appendages. The mouthparts include mandibles, which grasshoppers use for chewing. In other insects, mouthparts are specialized for lapping, piercing, or sucking.

51 Development Basic life stages are: egg, juvenile and adult Substages: instars-separated by molts Unually only one adult stage: imago (sexually mature, wings) Life cycle of many hexapods includes a diapause 4 basic developmental pattern: A. Ametabolous development: young are identical to adults except in size and sexual maturity. silverfish

52 Development B. Hemimetabolous development: aquatic juveniles (nymphs) have wing pads that gradually increase in size and become functional wings only with the final molt. Adults (aerial) have wings and are sexually mature. Mayfly dagslända

53 Development C. Paurometabolous development (gradual or incomplete metamorphosis): Similar to hemimetabolous development except that adults and juveniles (nymphs) are similar morphologically. The adult form is reach gradually through a series of molts. For ex. grasshopper, cockroaches, bugs Fig 21-13

54 Development D. Holometabolous development (complete metamorphosis): The life cycle incudes an additional stage-the pupa Imagos are winged, sexually mature and do not molt The wormlike juveniles (larvae, maggots, grubs, or caterpillar) do not resemble the adults. At the end of the sequence of larval instars, the juvenile becomes a nonfeeding pupa- larva undergoes metamorphosis: larval organs are destroyed and adult structures develop anew from clusters of embryonic reserve cells known as imaginal discs Fig Larva (a) (caterpillar) (b) Pupa (c) Pupa (d) Emerging adult Figure 33.6a e (e) Adult

55 Phylum Chordata vertebrater, lancettfiskar, manteldjur (urochordater) (ryggsträngsdjur) Consists of two subphyla of invertebrates, Cephalochordata and Tunicata (Urochordata), as well as the hagfishes (pirål) and the vertebrates. Shares many features of embryonic development with echinoderms having, at some time in their life cycle, A) a notochord korda (fexible londitudial axial rod), B) a hollow dorsal nerve cord, nervrör C) a filterfeeding pharynx with gill slit (organ for feeding and gas exchange) and an endostyle (mucous net cast) gältarm D) a post-anal tail. svans Vertebrata: the dorsal hollow nerve cord has been surrounded with cartilaginous or bony vertebrae Fig 29-1 Lab1:III