EVOLUTION OF ANIMALS CHAPTERS 18 & 19: ANIMAL EVOLUTION AND DIVERSITY ANIMALS. Honors Biology Fig Fig. 18.2

Transcription

1 CHAPTERS 18 & 19: ANIMAL EVOLUTION AND DIVERSITY Honors Biology ANIMALS Egg Fig Sperm 2 Eukaryotic, multicellular heterotrophs whose cells lack cell walls Most animal cells are diploid Haploid gametes fuse to form a zygote Most animals have a blastula, gastrula, and larval stage Key Haploid (n) Diploid (2n) Meiosis Adult Metamorphosis Larva Endoderm Internal sac Digestive tract Zygote (fertilized egg) Ectoderm Eight-cell stage Blastula (cross section) 6 Future mesoderm Later gastrula (cross section) Early gastrula (cross section) 2 EVOLUTION OF ANIMALS About 550 million years ago Cambrian explosion produced many animal fauna (adaptive radiation) Ecological causes: Evolution of hard body coverings led to complex predatorprey relationships Geological Causes: Atmospheric O2 reached high enough concentration to support metabolism of active animals Genetic causes: Variations in Hox genes produced diversity Somatic cells Digestive cavity Reproductive cells Colonial protist, Hollow sphere Beginning of cell Infolding an aggregate of identical cells of unspecialized cells specialization Gastrula-like proto-animal Fig

2 BODY PLANS Top Anterior end Dorsal surface Posterior end Bottom Ventral surface Radial symmetry - any slice through the central axis divides the animal into mirror image halves Bilateral symmetry - have mirror image right and left sides, distinct head and tail, and a back (dorsal) and belly (ventral) surface Body plans vary in organization of tissues Sponges lack true tissues Tissue layers organized into ectoderm, endoderm, and mesoderm 4 BODY PLANS Fig Body covering (from ectoderm) Tissue-filled region (from mesoderm) Body cavities (coeloms) Digestive sac (from endoderm) No coelom (ex. flatworms) Body covering (from ectoderm) Muscle layer (from mesoderm) Pseudocoelom - partially lined with mesoderm tissue True coelom - completely lined by mesoderm tissue Coelom Digestive tract (from endoderm) Digestive tract (from endoderm) Pseudocoelom Body covering (from ectoderm) Tissue layer lining coelom and suspending internal organs (from mesoderm) 5 PHYLOGENETIC TREES No true tissues Sponges Hypothesis for the evolutionary history of the groups involved Based on comparative morphology Ancestral colonial protist True tissues Radial symmetry Eumetazoans Fig Bilateral symmetry Bilaterians Deuterostomes Protostomes Cnidarians Echinoderms Chordates Flatworms Molluscs Annelids Arthropods Nematodes 6

3 Pores Choanocyte Amoebocyte Phylum Porifera (sponges) - no true tissues Water flow Skeletal fiber Central cavity Suspension feeders - filter food particles from water Flagella Choanocyte in contact with an amoebocyte Sessile - cannot escape from predators Phylum Cnidaria (Cnidarians) - have two tissue layers (epidermis and inner cell layer) Capsule (nematocyst) Coiled thread Tentacle Trigger Discharge of thread Use tentacles to capture prey and push them into their mouths Prey Cnidocyte Figs & 18.6 Radial symmetry Polyp and medusa stages 7 Gastrovascular cavity Phylum Platyhelminthes (flatworms) - simplest bilateral animals Planarians have heads with light-sensitive eyespots Flukes and tapeworms are parasitic flatworms Nerve cords Mouth Eyespots Nervous tissue clusters Bilateral symmetry Units with reproductive structures Scolex (anterior end) Hooks Sucker Phylum Nematoda (roundworms) - bilateral symmetry and three tissue layers 8 Phylum Mollusca (molluscs) - have a true coelom and a circulatory system Gastropods - largest group of molluscs (include snails and slugs) Bivalves - shells divided into two halves (clams, oysters, mussels, and scallops) Cephalopods - have large brains and sense organs including image-focusing eyes 9

4 Phylum Annelida (annelids) - have a closed circulatory system; nervous system with a simple brain and nerve cord; true coelom Earthworms Polychaetes - largest group Leeches 10 Cephalothorax Head Phylum Arthropoda (arthropods) segmented bodies, exoskeleton, jointed appendages, open circulatory system Abdomen Thorax Antennae (sensory reception) Includes crayfish, lobsters, crabs, barnacles, spiders, ticks, and insects Swimming appendages Walking legs Pincer (defense) Mouthparts (feeding) A scorpion (about 8 cm long) A black widow spider (about 1 cm wide) A dust mite (about 420 µ m long) 11 Insects 70% of all animal species Successful because of jointed appendages, exoskeleton, flight, waterproof cuticle Some undergo a complete metamorphosis 12

5 Tetrapods Jawed vertebrates Vertebrates Chordates Phylum Echinodermata (echinoderms) - slowmoving and sessile, radial symmetry, water vascular system, exoskeleton Phylum Chordata (chordates) - dorsal, hollow nerve cord Tunicates and lancelets use pharyngeal slits for suspension feeding Stomach Adult (about 3 cm high) Excurrent siphon Anus Canals Dorsal, hollow nerve cord Mouth Pharyngeal slits Post-anal tail Notochord Larva Muscle segments Spines Head Mouth Pharynx Tube feet Pharyngeal slits Digestive tract Water exit Notochord Segmental muscles Anus Dorsal, hollow nerve cord Post-anal tail 13 No true tissues Sponges Ancestral colonial protist Radial symmetry Cnidarians True tissues Eumetazoans Bilateral symmetry Bilaterians Deuterostomes Lophotrochozoans Echinoderms Chordates Flatworms Molluscs Annelids Ancestral chordate Tunicates Lancelets Ecdysozoans Nematodes Arthropods Brain Hagfishes Lampreys Craniates Head Sharks, rays Vertebral column Jaws Lungs or lung derivatives Lobed fins Ray-finned fishes Lobe-fins Amphibians Legs Amniotic egg Reptiles Mammals Amniotes Milk 14 VERTEBRATE DIVERSITY All contained within Phylum Chordata Hagfish and lampreys Craniates that lack a hinged jaw and paired fins Hagfish only have the notochord for support, but lampreys have a notochord and rudimentary vertebral structures (vertebrates) Hagfish produce slime as an antipredator defense Lampreys are parasites that penetrate the sides of fish 15

6 VERTEBRATE DIVERSITY Some vertebrate features arose 470 million years ago Paired fins and tails and hinged jaws Jaws arose from a modification of the pharyngeal gill slits that were used for trapping suspended food particles Gill slits Skeletal rods Skull Hinged jaw Mouth 16 JAWED FISH Class Chondrichthyes (sharks and rays) Flexible skeleton made of cartilage Electrosensors on the heads of sharks heads help them locate prey Gill openings Rays are adapted for life on the bottom of the sea with flat bodies and eyes on the tops of their heads Lobe-fins Have muscular pelvic and pectoral fins supported by rod-shaped bones 17 Gills JAWED FISH Bony skeleton Dorsal fin Ray-finned fish Have an internal skeleton reinforced with CaPO3 Have flattened scales covered with mucus Buoyant swim bladder (derived from ancestral lung) Operculum Pectoral fin Heart Rainbow trout, a ray-fin Anal fin Swim bladder Pelvic fin Includes more than 27,000 species 18

7 TETRAPODS Carboniferous Devonian Eusthenopteron Pandericthys Tiktaalik Lobe-fin fish gave rise to the tetrapods (jawed vertebrates with limbs and feet Acanthostega Ichthyostega Tetrapod with no gills, limbs better-adapted for bearing weight Time known to exist 420 Scientists have collected fossils of many transitional forms Millions of years ago Bones supporting gills Tetrapod limb skeleton 19 AMPHIBIANS Class Amphibia (frogs, salamanders, and caecilians) First tetrapods to be able to move on land (most have tadpole larvae) Salamanders walk on land with side-to-side bending Frogs hop with powerful hind legs Caecilians are blind and legless (burrow in tropical soil) 20 REPTILES Reptiles (including birds) and mammals are amniotes Amniotic egg provides a specialized membrane that protects the embryo Reptiles (lizards, snakes, turtles, crocodilians, and birds) Terrestrial adaptations include scales that are waterproofed with keratin Ectothemic - must absorb heat from the environment (most reptiles) Endothemic - use metabolism to produce heat (birds) 21

8 REPTILES (BIRDS) Wing claw (like dinosaur) Teeth (like dinosaur) Birds evolved from two-legged dinosaurs called theropods Archaeopteryx - oldest bird (150 million years ago) with feathered wings Birds are reptiles with feathers, endothermic metabolism, and adaptations for flight Long tail with many vertebrae (like dinosaur) Feathers Flight adaptations: loss of teeth, feathers with hollow shafts, strong and light bones Flight is costly in terms of metabolism 22 MAMMALS Mammals are endothermic amniotes with hair and mammary glands Generally have larger relative brain size Generally have a long period parental care First mammals arose 200 million years ago as nocturnal insectivores Marsupials diverged from eutherians (placental mammals) 180 million years ago Underwent adaptive radiation after the Cretaceous extinction 23 MAMMALS Monotremes - egg-laying mammals (ex. duck-billed platypus) Only mammals whose embryos are not nourished by a placenta within the uterus Marsupials - have a brief gestation and give birth to tiny, embryonic offspring Offspring complete development attached to mother s nipple in a pouch or marsupium Eutherians - give birth to fully developed young Commonly referred to as placental mammals because their placentas are more complex than marsupial placentas 24

9 Millions of years ago PRIMATES Includes lemurs, tarsiers, monkeys, and apes Adaptations include: shoulder and hip joints that allow for climbing, grasping hands, forward pointing eyes (allows for better depth perception) Phylogenetic trees show primates are composed of three groups: 1st group - lorises, lemurs, and pottos 2nd group - tarsiers (small, nocturnal tree-dwellers with flat faces and large eyes) 3rd group - anthropoids (monkeys, apes, and humans) Large brains, rely more on eyesight, have opposable thumbs 25 Often called apes PRIMATES (HOMINOIDS) Include gibbons, orangutans, gorillas, chimpanzees, and humans Have relatively large brain size and high degrees of social organization Gibbons are the only fully arboreal apes Orangutans are shy and solitary and live in trees and on land Gorillas (largest of the apes) are fully terrestrial Chimpanzees are able to make use of tools Diverged from a common ancestor with humans between 5 and 7 million years ago (share 99% of their genes) 26 PRIMATES (HOMINIDS) Oldest hominid discovered was Sakelanthopus tchadensis (lived 6-7 million years ago) Adaptation of hominids Bipedalism (arose about 4 million years ago) Australopithecus anamensis Paranthropus boisei Australopithecus africanus Australopithecus afarensis Kenyanthropus platyops Ardipithecus ramidus Orrorin tugenensis Sahelanthropus tchadensis Paranthropus robustus Homo? ergaster Homo erectus Homo habilis Homo sapiens Homo neanderthalensis Homo habilis - fossils found with stone tools (2.4 million years ago) Homo ergaster - more sophisticated stone tools, long legs for long-distance walking ( million years ago) Ancient footprints Homo erectus - first to leave Africa 27

10 PRIMATES (HOMINIDS) Neanderthals - lived in Europe until about 30,000-40,000 years ago Brain was smaller but the same shape as human Diverged from human ancestors about 500,000 years ago Mitochondrial DNA analysis shows that all living humans inherited their mitochondrial DNA from a woman who lived 160, ,000 years ago in Africa Africa Atlantic Ocean Europe 40,000 BP 100,000 BP Original discovery Neander Valley Africa Asia 50 60,000 BP >40,000 BP (50 60,000?) Europe Mediterranean Sea Australia 15 35,000 BP Black Sea Key North America <30,000 years ago 30,000 35,000 years ago >35,000 years ago Approximate range of Neanderthals South America 28