Biology Lecture 10: Animal Diversity Part 3: PDF

BIOLOGY II LECTURE 10 ANIMAL DIVERSITY PART 3 ANIMAL DIVERSITY PART 3 Chapter 42 - Biology: How Life Works, Morris et al. (Sections 42.2 and 42.3; Pages 952 to 960) ANIMAL DIVERSITY PART 3 Objectives: Deuterostomes Hemichordates Cephalochordates Echinoderms...

BIOLOGY II LECTURE 10 ANIMAL DIVERSITY PART 3 ANIMAL DIVERSITY PART 3 Chapter 42 - Biology: How Life Works, Morris et al. (Sections 42.2 and 42.3; Pages 952 to 960) ANIMAL DIVERSITY PART 3 Objectives: Deuterostomes Hemichordates Cephalochordates Echinoderms Tunicates Vertebrates DEUTEROSTOME TREE Based on: shared features of larval development strongly supported by molecular sequence data Deuterostome tree includes three major phyla: Echinodermata (sea urchins and sea stars). Hemichordata (acorn worms) Chordata (vertebrates and invertebrate chordates) 4 VERTEBRATE CHARACTERS Vertebrates are named for their jointed skeleton running along the main axis of the body, forming vertebrae. Chordate characters = red Vertebrate characters = blue 5 VERTEBRATE PHYLOGENY 6  JAWLESS FISH: HAGFISH AND LAMPREYS Defining characters of both hagfish and lampreys No jaws and Cartilaginous cranium Hagfish Characteristics: Lamprey Characteristics: – Lack vertebrae – Cartilaginous vertebral – Notochord retained in column adult – Notochord retained in – Gill slits adult – Slime glands – Gill slits Hagfish s lime vide o 7 JAWLESS FISH: HAGFISH AND LAMPREYS Molecular data favor the view shown here, that hagfish and lampreys together form the sister group to all other vertebrates. 8 CARTILAGINOUS FISH (CHONDRICHTHYES) Monophyletic group Sharks, rays, and chimaeras All have jaws and a cartilaginous skeleton Form calcium phosphate minerals only in their teeth and in small toothlike structures called denticles embedded in the skin Can retain high levels of urea in tissues (fatal to other vertebrates)  adaptation to maintain salt balance 9 BONY FISHES (OSTEICHTHYES) 20,000–25,000 fresh and seawater species, these are the fish that we most commonly encounter. Have a cranium, jaws, and bones mineralized by calcium phosphate Fins with ray-like thin bones Moveable elements in jaws – diversified feeding Swim bladder – buoyancy Kidneys able to regulate water balance – can live in large range of water salinities 10 BONY FISHES (OSTEICHTHYES) Evolutionary importance of the swim bladder: Early vertebrates evolved a gut sac that enabled them to gulp air to obtain additional oxygen. In some fish, this sac evolved into an air bladder, but in one group (tetrapods) the sac was modified to become a lung Swim bladder and vertebrate lung are homologous organs! 11 LOBE-FINNED FISH Coelacanth Lungfish About a dozen species, related to ray-finned fishes but have paired, fleshy pectoral and pelvic fins (muscular bony stalk) Coelacanth and lungfish  the nearest relatives of tetrapods Tetrapods descend from same ancestor common to all four fish groups so “fish” are not monophyetic 12  THE TETRAPODS Movement to land Many fossils showing anatomical transition to land Changes in limbs, rib cage, skull Tiktaalik and other fossils link tetrapods to lobe-finned fishes Amphibians - Share many characteristics with early tetrapods Modern amphibians - about 4,500 species Most restricted to moist habitats: Simple lungs - they require gas exchange through the skin (toads exceptions) Reproduction in water 13 THE TETRAPODS: CLASS AMPHIBIA Order Urodela Includes salamanders, which retain their tails as adults Order Anura Includes frogs and toads, which lack tails Oder Apoda Includes caecilians- are legless; resemble worms Absence of legs = secondary adaptation – evolved from a legged ancestor 14 AMPHIBIAN LIFE CYCLE 15 AMNIOTES Amniotes are a group of tetrapods who evolved terrestrial eggs (amniotic egg) “Non- avian” reptiles – lizards, snakes, turtles, crocodilians “Avian reptiles” Mammals – birds 16 AMNIOTES The amniotic egg: Requires internal fertilization Advantages: Development on land Long development times – more complex body forms Other amniote adaptations to life on land: – waterproof skin – increasing use of rib cage to ventilate lungs 17 AMNIOTES: REPTILES Traditional reptile group is paraphyletic (excludes birds) Lizards, snakes, turtiles, crocodilians Reptile characters: Scales with keratin - waterproofing Shelled eggs (exception - some snakes bear live young) Ectothermic - absorb external heat as the main source of body heat one advantage - can survive on less than 10% of calories required by a mammal of equivalent size 18  AMNIOTES: BIRDS (AVIAN REPTILES) Almost every feature of their reptilian anatomy has undergone modification in their adaptation to flight A bird’s most obvious adaptations for flight: Wings and feathers: Modified scales: Feathers made of protein β-keratin (also found in scales of other reptiles) Shape/arrangement of feathers make wings into airfoils Loss of teeth Gizzard in digestive system to replace heavy jaws to grind food Hollow bones Respiration that extracts more oxygen from each breath 19 AMNIOTES: BIRDS (AVIAN REPTILES) 20 AMNIOTES: MAMMALS Most, but not all, mammals give birth to live young instead of laying eggs ~5,300 known species Mammalian characteristics: Hair and fat layer under skin (to retain body heat) Produce milk (mammary glands) Differentiated teeth 21 AMNIOTES: MAMMALS First true mammals that gave birth to live young originated in the Jurassic – many are now extinct but gave rise to marsupial and placental mammals During Mesozoic most mammals remained small (shrew sized) By early Cretaceous three major lineages arose: Monotremes (egg-laying mammals) Marsupials (pouched mammals) Placental mammals 22 Amniotes: Mammals Monotremes Lay eggs, have lower metabolic rates than other mammals (like reptiles) Consists of echidnas (spiny anteaters) and the platypus Have hair and females produce milk in specialized glands but have no nipples Marsupials Include opossums, kangaroos, and koalas Marsupials and placental mammals split from each other approximately 150 million years ago Secrete milk through nipples and give birth to live young A marsupial is born very early in development completes embryonic development while nursing within a maternal pouch called a marsupium Kangaroo development video 23 Amniotes: Mammals Placental mammals Compared to marsupials placental mammals have: longer period of pregnancy more complex placenta Young complete their embryonic development within a uterus, joined to the mother by the placenta Allows young to grow larger and become more quickly independent when born 24