Biodiversity 2 PDF

Eumetozoa This group contains all animal life except sponges and placozoa. Tissue is organized into 2, or 3 germ layers. Neurons present. Embryo goes through a gastrula stage. Originated in the Ediacaran, Dickinsonia might have been eumetazoan…  It is tempting to consider t...

Eumetozoa This group contains all animal life except sponges and placozoa. Tissue is organized into 2, or 3 germ layers. Neurons present. Embryo goes through a gastrula stage. Originated in the Ediacaran, Dickinsonia might have been eumetazoan…  It is tempting to consider that our embryology reflects our evolution here. All animals begin as a zygote that divides rapidly into a ball of cells. This ball of cells organizes to be a blastula, a hollow structure, with an interior blastocoel. – Human blastula (right)  Sponges develop directly from the blastula stage. In eumetazoa, the blastula invaginates to form a gastrula. The gastrula has a blastopore, and two layers of cells. It is configured much like a hydrazoan.  The interior arechenteron gives rise to the gut. The blastocoel is now sandwiched, and the blastopore can serve as a mouth/anus.  Hox genes Hox genes are a group of related homeotic genes common to nearly all animals (sponges and ctenophores lack them) In segmented animals, they confer the identity of each segment along a head to tail axis. – Their produce a transcription factor – They contain a Homeobox DNA sequence. – In many animals, the organization of the Hox genes in the chromosome is the same as their orientation on the anterior axis – The fact that all animals have such similar Hox genes strongly suggests that the last common ancestor of all bilaterians had similar Hox genes. – Evolution of Hox genes may have paved the way for the development of complex body forms.  Ground Plan Each phylum has a ground plan, deeply ingrained in its developmental biology, that determines the general layout of its body cavities and organ systems. These body plans are very evolutionarily conservative, though in some organisms, they have been progressively modified by natural selection so many times that the original layout is hard to see. – Examine your own body for a tail-a key feature of the chrodate body plan. Ground plan for Phylum Arthropoda (example): segmented body, chitinous exoskeleton, periodic molts, and jointed appendages  Cnidaria This group is radially symmetric, even as embryos. Only two layers of tissue, surrounding a jelly like inner layer.  Phylum cnidaria…Jellyfish, Anemones, hydras, gorgonians, and corals. This is a major animal phylum, with over 10,000 species. Exclusively aquatic. Portuguese Man O’ War  Cnidarian Body Plan Cnidarian bodies consist of a jellylike, nonliving mesoglea, sandwiched between two layers of epithelium, one cell thick. Interior body cavity used as a gut and for respiration Lose nerve net Radially symmertic  The Cnidaria include: – 1) Hydrozoa – 2) Anthozoa-corals and sea anemones – 3) Scaphyzoa- jellyfish – 4) Cubozoa-box Cnidarians have jellyfish specialized Many groups cells, alternate between cnidocytes, that polyp and entangle or medusoid forms. harpoon prety.  The Bilatera Includes eumetazoa other than radiata=ctenophores+cnidaria Have 3 tissue layers. – Ectoderm, endoderm, mesoderm=triploblastic Differences in how tissue layers form: – Protostome-mouth forms first, sprial cleavage, determinate development, coelom forms from splitting of mesoderm. – Deuterostome-anus forms first, radial cleavage, coelom forms from inpocketing of mesoderm.  A coelom is an interior body cavity that is an Coeloms essential to the body plan of most animal phyla. – Lined with mesoderm – This fluid filled space separates the gut from the rest of the animal, allowing specialization of the gut. Gametes storage – It can also serve as hydrostatic skeleton  Lophotrochozoa The lophotrochozoa are group of animal phyla that share a very ancient common ancestor. – Members have a lophophore (a feeding structure), trochophore larvae, or 18s RNA sequences suggesting they are related to the others.  Phylum Platyhelminthes Flatworms – Unsegmented – No body cavity-aceolomate – Three tissue layers – Digestive cavity has only one opening – Nutrients and gasses move via diffusion-thus, flat shapes-no respiratory or circulatory system Ladderlike nervous system – Free living and parasitic Eye spots in some species members.  Ribbon Worms – Marine, freshwater, some Phylum terrestrial. Nemertea important marine predators and scavengers – Coelom serves to store proboscis, which can be everted for prey capture. Mouth and anus – Vessels for circulation – Flame cells for excretion – Brain + paired ventral nerve cords “pigment cup” ocelli chemosensory organs  Phylum Mollusca Chitons, Clams, Snails, Slugs, Squids, and Octopi A major animal phylum-85,000 extant species, about 23% of named marine species Freshwater, Banana marine, terrestrial Slug  “Typical” mollusk features: – A coelom that may function as a hydrostatic skeleton – A mostly open circulatory system with a heart – An excretory system with nephridia – A muscular “foot” on underside of animal – A shell – A mantle cavity – A radula – Paired nerve cords with ganglia – Metamorphosis from planktonic trochophore larvae.  Major mollusk groups: – Cephalopoda-foot modified into arms, closed circulatory system, cell lost in most contemporary species. – Gastropoda-torision, the visceral mass twisted – Bivalva-two valves (left and right, not top and bottom, to shell.  Segmented Worms Marine, freshwater, Phylum Annelida terrestrial species. Coelom forms hydrostatic skeleton Closed circulatory system. – Polychetes-marine – Oligochetes-mostly terrestrial burrowers – Hirudinea-leeches – Others..including pogonophores…  Phylum Brachiopoda Lamp shells, another lophophorate  Phylum Bryozoa Bryozoans, the largest phylum in the superphylum Lophophorata  Phylum Rotifera Wheel bearers. A very abundant group. Many asexual lineages. Uncertain affinities Many acellular forms.  Ecdyzoa Another large group of protostomes, discovered by 18s RNA analysis. – All members, in one way or another, shed their cuticles or exoskeletons.  Phylum Nematoda Roundworms. An abundant and ecologically important group of ecdyzoans. Pseudocoelomate Caenorhabditis elegans Ascaris lumbricoides  Phylum Tardigrada Water Bears. Amazingly tough cryptobiota  Phylum Arthropoda Horseshoe Crabs, Arachnids, Crustaceans, Myriapods, and Insects. – More species than all the other groups combined  Arthropods have a segmented body plan with jointed appendages and a cuticle made of chitin. – This confers ecological advantages and limitations. – They may be a sister Arthropoda originate group to the during the Cambrian onychophora, which explosion and quickly are specialized become numerous and segmented creatures ecologically important. that lack an Marella, above, a exoskeleton Cambrian arthropod.  Arthropods have a segmented body plan that allows the evolutionary specialization of certain segments – Ventral nerve cord – Dorsal gut – Open circulatory system. – Tagmosis-the progressive specialization and fusion of segments.  Crustacea – Biramous appendages Most have gills as one ramet of leg. – Marine, freshwater, terrestrial. – Antennae+antennules  Insecta – Terrestrial. – Uniramous appendages – Three segmented body plan. – Six legs, two antennae. – Evolved from crustacean ancestor – Trachae as respiratory structures. – Many winged forms. – Many undergo metamorphosis. – Mantispid lacewing, a neuropteran insect.  Deuterostomes Obvious developmental differences from other animal phyla. Includes Chordates, Hemichordates, Echinoderms  Phylum Echinodermata Starfish, Brittle Stars, Urchins, and Sea Cucumbers Major deuterostome phylum Secondary radial symmetry Water vascular system  Phylum Chordata Phylum Chordata is the only phylum containing vertebrate animals, however, there are some invertebrate chordates  Chordates At at least some point in their life, all have a skeletal structure called a notochord. – a flexible rod located between the digestive tube and nerve chord. – Provides skeletal support. – In most vertebrates, it’s replaced by a jointed skeleton. Remains of the notochord exist as disks between the vertebrae. At least some development of a dorsal hollow nerve cord In some, like humans, it into the brain and spinal cord of the adult. Pharyngeal slits – At least some point in development, these appear. Water enters through the mouth and passes out through the slits in the pharynx, without going through the digestive system. Slits function as suspension-feeding devices in many invertebrate chordates – In most vertebrates, these slits have been exapted for: Gas exchange Hearing Jaw support Postanal tail – Provides propulsion for swimming  Subphylum Subphylum Cephalochordata Urochordata Adult form shows chordate features. Adult is sessile and feeds via pharyngeal Adults feed and slits swim. Marine fiolter feeders Lancet-below Tunicate-below Four anatomical features that characterize the phylum Chordata Subphylum Urochordata: a tunicate Subphylum Cephalochordata: the lancelet Branchiostoma More recent data suggest that urchordates are a little closer to us. This seems a little less bizarre if you consider that some urchordates have neotenic larvae that never settle and lose their tails.  Polling Question Which of the following organisms is a deuterostome? A) A human B) A coral C) A sea star D) A and C E) All of the above  Vertebrates- subphylum vertebrata Vertebrate features Neural crest https://dos.uic.edu/student-legal/ Enhanced cephalization Vertebral column A closed circulatory system  Neural Crest Embryonic feature that allows for many unique vertebrate characteristics, e.g. bones and cartilage are formed from the neural crest cells throughout the body. Forms along the dorsal side of the embryo  Skeletal elements, such as the cranium (braincase), allow for the big evolutionary feature of vertebrates, cephalization. This gives us the term “Craniates” – Hagfish are probably craniates, but not vertebrates. – Likely, so were conodonts Vertebral column is the main support for the body axis. It allows for large size, fast movement, and protection of the nerve cord. The closed circulatory system pumps oxygenated blood to cells and allows rapid metabolism, rapid movement to search for food, escape predators.  Jawless Vertebrates First radiation of vertebrates was jawless Surviving groups include hagfish (no skeleton, no notochord in adult) Lamprey (early Early fish, a version of a cephalaspidomorph vertebral column).  Gnathostomes Gnathostomes have jaws – Vertebrate jaws evolved from skeletal supports of pharyngeal slit. – Members of group have two pairs of fins (or limbs) – Jaws and fins allowed fish to diversify ecologically Acanthodians and placoderms-early gnathostomes Hypothesis for the evolution of vertebrate jaws  Three groups of gnathostomes make up what we collectively call “fish” Chondricthyes: Sharks and rays have cartilaginous skeletons Osteichthes-bony fish. The most diverse group of vertebrates. 28,000 species in 435 families Sarcopterygii-lobe finned fish. Tetrapod relatives  Tetrapods Evolved from lobe finned fish. Early tetrapods were mostly aquatic air breathers. An assemblage of “amphibians” radiate in the Carboniferous period. Many groups, probably tied to water for reproduction  Bony fish have undergone multiple, spectacular adaptive radiations. The teleosts account for 98% of bony fish. Suzuki, D., Brandley, M.C. & Tokita, M. The mitochondrial phylogeny of an ancient lineage of ray-finned fishes (Polypteridae) with implications for the evolution of body elongation, pelvic fin loss, and craniofacial morphology in Osteichthyes. BMC Evol Biol 10, 21 (2010). https://doi.org/10.1186/1471- 2148-10-21  Tetrapods Evolved from lobe finned fish. – Early tetrapods were mostly aquatic air breathers. – An assemblage of “amphibians” radiate in the Carboniferous period. – There were many groups, including lepospondyls, stereospondyls, etc. – Most were probably tied to water for reproduction. – Contemporary amphibians and amniotes evolved from two separate groups. Acathoseega, an early tetrapod, aquatic and air breathing, prob not an ancestor to terrrestrial tetrapods. Early tetrapods diversify into a bewildering variety of groups. Amniotes and amphibians arise from two separate surviving branches Amemiya, C., Alföldi, J., Lee, A. et al. The African coelacanth genome provides insights into tetrapod evolution. Nature 496, 311–316 (2013). https://doi.org/10.1038/nature12027 A simplified tetrapod phylogenetic tree Surviving amphibians fall within a monophyletic group called the lissamphibia. They are in NO WAY ancestral to amniotes, but rather, originated during the Mesozoic Skin a major gas exchange Gerobatrachus, above. organ Nearly all amphibians Order Urodela – need to return to water Salamanders. to lay eggs and for Order Anura – Frogs development of larvae. Order Apoda – Caecilians.  Amniotes Includes reptiles, mammals, and birds) – The amniotic egg is a key adaptation to life in arid terrestrial environments. Specialized extra- embryonic membranes that function in gas exchange, waste storage, and transfer of nutrients. Membranes develop from tissues derived from the embryo. Amnion Chorion Allantois Amniotic eggs require internal fertilization. Shell forms around fertilized egg in the reproductive tract.  Gastrulation in Amniotes Amniotes, often having a large amount of yolk, have evolved modifications of the gastrulation process to cope with the huge amount of yolk sitting over a tiny embryo, and to create the amniotic membranes. (other high-yolk vertebrates have analogous adaptations) The embryonic cleavages do not penetrate the mass of egg. What had formerly been a hollow ball is now a disk, with endoderm pressed against a huge mass of yolk. Embryonic membranes Note that the grow over the embryo, blastopore is incorporating multiple more of a germ layers. groove, called the “primitive streak” Amniotes split into several groups early on. A few stem groups retained the anapsid condition. One group, the synapsids (whose descendants include mammals) split off early. Another group, the Limnoscelis was originally described sauropsids (whose as an amphibian, but likely was a descendants include birds very early amniote. Whether it laid and reptiles) split off amniotic eggs, we do not know. slightly later. TY - JOURAU - Martin, AnthonyPY - 2023/08/18SP - T1 - Dinosaur Evolution: From Where Did They Come and Where Did They Go?  Reptiles “Reptiles” are a paraphyletic assemblage of sauropsid amniotes. Scales of keratin, waterproof skin - prevent water loss. Lepidosaura, – Unlike amphibians, (monophyletic) which reptiles cannot breathe includes lizards and through skin, so all gas exchange occurs snakes, has overlapping via lungs. scales. All surviving reptiles descend from diapsids- turtles have secondarily lost these openings and have restored the anapsid condition.  Nearly all “reptiles” are ectothermic, using behavior and external sources of heat to regulate their body temperature. Reptiles are able to survive on about 10% of calories required by mammals.  Archosaurs Archosaurs are a major group of saurposids. Archosaurs include crocodilians, birds, and nonavian dinosaurs, and some other extinct groups. They diversified during the Triassic Early archosaurs Birds, class Aves, are the sole surviving dinosaur lineage. Porous skeletons with air spaces are light and strong. Unidirectional air flow in lungs. Avian wing and feather-unlike dinosaur Dinosaur feathers, feathers, good for flight. above, lack the vanes All contemporary birds needed to support are toothless flight  All contemporary birds are endotherms and egg layers. Feathers provide insulation. Efficient circulatory system supports high rate of metabolism necessary for flying. – Flight was a key evolutionary adaptation during the Jurassic-enabled birds to colonize many ecological niches alongside the pterosaurs (who also flew) Toothed birds were once fairly common. Mass extinction took them out.  Synapsids Synapsids originate very early, soon after the origin of amniotes. – They diversify as “mammal-like reptiles” and become ecologically dominant in the Permian, before the age of dinosaurs – Early synapsids had differentiated teeth and were likely homeothermic.  Mammals originate in the early Jurassic. They were actually quite abundant during the Mesozoic. They diversified into new ecological niches following the KT extinction. – Mammary glands – Large brains – Hair and subcutaneous fat – Endothermic – Dentary bone Morganucodon, early mammal  Three surviving groups of mammals. – Monotremes – lay eggs and produce milk, but have no nipples. Survivors of a very ancient, Southern, group. – Marsupials – born early in embryonic development; climb to mother’s pouch and attach to a nipple. Platypus- an Very diverse in Cretaceous, egg laying lost ground due to mass extinction. mammal with – Eutherians – long pregnancy with many unique embryonic attachment to mother adaptations in uterus via placenta. Two ossicles in the mammalian inner ear are an excellent example of exaptation. They arise from jaw bones. They probably confer a greater range of pitches to our hearing The adaptive radiation of mammals produced our own group, the primates. The early branching of the tree follows continental breakup of the Mesozoic continents, but dispersal has moved species  You are: a homonoid, a primate a placental mammal a synapsid tetrapod a gnathastome a vertebrate a deuterostome a bilaterian a eumetazoan an animal Primates diversify in the Eocene, about 50 million years ago. an ophistocont One group gave rise to the apes, a eukaryote which include humans.  Polling question Which of the following is an amniote? a). A trout a) A fly b) A human c) An ostritch d) C and D