Deuterostomes

Developmental patterns of Deuterostomes

• cleavage - initial first divisions in development

• Coelom development - how coelom develops

• Fate of blastopore - butt of mouth

Deuterostome 3 traits

• Triploblastic

• Coelomate

• internal skeletons (when they have one)

Clades

• Echinoderms

• Hemichordates

• Chordates

Ambulacraians

Echinoderms and Hemichordates

Ambulacrarian traits

Ciliated and bilaterally symmetrical larvae

Hemichordate adults

bilaterally symmetrical

Echinoderms adults

pentaradial symmetry

Echinoderms

• Internal skeleton of fused calcified plates

• Water vascular system: network of water-filled canals leading to extensions called tube feet

  • functions in gas exchange, locomotion, and feeding

  • water enters through madreporite

Crinoids

• Sea lilies attach to the substrate by a stalk

• feather stars grasp substratum for movement

Echinozoans

Sea urchins

• Lacks arms, uses spines to move

• catches plankton with tube feet

Sea cucumbers

• lacks arms

• has a front (mouth) and a back (anus)

• tube feet used for movement but more to anchor to substrate

Asterozoans

Sea stars

• Gonads and digestive organs located in the arms

• tube feet have suction cups for locomotion, gas exchange, and attachment

Brittle starts

• flexible arms

• gonads and viscera are in central disc

• tube feet lack suction cups

Hemichordates

Bilateral symmetry ​

• A three-part body plan—proboscis, collar (containing mouth), and trunk (contains other body parts).

Acorn worms:​

• Up to 2 m long​

• Burrow ( proboscis ) in soft marine sediments

Pterobranchs: ​

• Up to 12 mm long​

• Live in tubes secreted by the proboscis.​

Chordates derived characteristics at some stage

• Dorsal, hollow nerve cord​

• Tail that extends beyond the anus- post anal tail​

• a notochord – dorsal supporting rod - rigid and flexible​

Lancelets

cephalochordates)

• Very small, less than 5 cm​

• Notochord is retained throughoutlife.​

• Enlarged pharynx forms apharyngeal basket for filtering preyfrom the water.​

Tunicates

urochordates

• Sea squirts

• Adult body is enclosed in atough “tunic” of proteins andpolysaccharides secreted by theepidermis.​

• Adults are sessile​

• Pharyngeal basket filters preyfrom the water (like lancelets).​

​

Vertebrates

Type of chordate that is broken down into more parts

• Vertebral column replaces notochord

• Anterior skull enclosesa large brain.​

• Rigid Internal skeleton​

• Internal organs suspended in acoelom​

• Well-developed circulatory systemdriven by a ventral heart​

Vertebrates tree

Vertebrates:

• Jawless fishes

  • Lamprey

  • hagfish

• Gnathostomes

  • Chondrichthyans

  • Bony Vertebretes

    • Rayfinned fish

    • Lobe-limbed vertebrates

      • Coelacanths

      • lung fish

      • amphibians

      • amniotes

hagfish

• Marine​

• A partial cranium, and no jaws.​

• Skeleton is cartilage; no vertebrae; some biologists don’t consider hagfishes to be vertebrates.​

• Blind; produce large amounts of slime as a defense.​

Lamprey

• complete skull and vertebrae (cartilaginous).​

• Adults of many species are parasitic; the round mouth is used to attach to fish and rasp at the flesh

• Some adults are nonfeeding.​

• Anadromous

anadromous

Move to freshwater to reproduce

Gnathostomes

Fish with jaws

• Jaws and teeth improved feeding efficiency and prey capture

• Most jawed fishes have paired fins for stabilization and swimming.

Chondrichthyans

• Skeletons of cartilage​

• Flexible, leathery skin ​

• Sharks swim using lateral undulations of the body​

• Skates and rays swim by vertically flapping enlargedpectoral fins​

Ray-finned fish

• Most are covered by scales.​

• Have a swim blatter for buoyancy​

• Gills open to a chamber covered by the operculum -Movement of the operculum enhances water flow over thegills.​

• Ray-finned fishes exploit all types of food​

Lobe-limbed vertebrates

• lung-like sacs in fishes allowed for breathing air

• lobed-limb vertebrates and more muscular pelvic and pectoral fins allowed for walking on land

• Some aquatic lobe-limbed vertebrates began to use terrestrial food sources, became adapted to life on land, and evolved to become ancestral tetrapods.

• Tetrapods split into amphibians and amniotes.

Coelocanths

• Were thought to have become extinct 65 mya, but living ones were found off South Africa in 1938.​

• They have a cartilaginous skeleton that is a derived feature.​

Lungfishes

• have lungs and gills

• burrow in mud when ponds dry up

• can survive many months in an inactive state while breathing air

Amphibians

• Most remain tied to moist habitats; they lose water easily through the skin; eggs dry out if exposed to air.​

• Some species are entirely aquatic. ​

• In others, adults live on land but must return to water to lay eggs; larvae develop in the water

• complex social behaviors

Three groups of amphibians

• Caecilians—wormlike, limbless, tropical burrowing animals​

• Tailless frogs and toads (anurans)​

• Tailed salamanders

Anurans

Frogs

• Some have tough skins and other adaptations for dry habitats.​

• Many are arboreal; some completely aquatic.​

• All have a short vertebral column and pelvic region modified for hopping/leaping or kicking in the water

Salamanders

• Many live in moist soil and rotting logs. ​

• One major group has lost the lungs and relies on gas exchange through skin and mouth lining.​

• Completely aquatic species – they develop through neoteny

Neoteny

Retention of juvenile features

Amniotes Features

features help them conserve water and exploit terrestrial habitat

• Amniote egg

  • Relatively impermeable to water

  • Leathery or brittle shells

  • Amniote eggs store food in the form of yolk

  • Extraembryonic membranes

Extraembryonic membranes

protect the embryo from drying and assist gas exchange and excretion of nitrogen.​

Amniotes two major groups

Reptiles and mammals

Adult amniotes

tough skin with scales, feathers, or hair to prevent drying

• Kidneys allow excretion of concentrated urine

Reptiles

• Squamates​- lizards, snakes​

• Turtles​

• Crocodilians – crocodiles and alligators​

• Birds

Squamates

• Skin covered with horny scales. ​

• Gas exchange is only through the lungs.

• Most lizards are insectivores, some are herbivores and predators

• snakes are limbless squamates

Turtle

• Dorsal and ventral bony plates form a shell

• Dorsal shell is a modification of the ribs

Crocodilians

• Carnivores; mostly stay in water in tropical and warm temperate regions.​

• Build nests on land or floating piles of vegetation—heat from decaying organic matter warms the eggs

Birds

• Bipedal stance​

• Hollow bones​

• A furcula

• group of dinos

• no teeth

Living bird species fall into two groups

paleognaths (flightless/weak flyers) and neognaths (flying birds)

bird feathers

• Are lightweight but strong​

• Provide flying surface​

• Provides insulation​

• Helps attract mates

Mammals

• Coexisted with dinosaurs.​​

• Range in size from tiny shrews to blue whales, the largest animal on Earth

• Highly differentiated teeth reflect their varied diets

• Sweat glands​

• Mammary glands ​

• Hair ​

• Four-chambered heart

• eggs are fertilized internally

Purpose of the placenta

• Nutrient and gas exchange​

• Wast elimination​

• Both, via the female’s circulatory system.​

Two groups of mammals

Prototherians and Therians

Prototherians

• duck-billed platypus and echidna

• Lay shelled eggs

• Provide milk to their young

Therians

All other mammals

• Marsupials

• Eutherians​

Marsupials

• Carry and feed young in a ventral pouch.

  • Young are born early, and crawl into pouch for further development. ​

• Most are in Australia and South America.​

• Virginia opossum is the only marsupial in North America north of Mexico.

• Marsupials are herbivores, insectivores, and carnivores.​

• None can fly, but some arboreal species are gliders. ​​

Eutherians

• Have well developed placentas

• young are more developed at birth than marsupials

• Several eutherian lineages returned to aquatic habitats

Major adaptation to arboreal life and distinguish the primates

Grasping limbs with opposable digits

2 primate clades

• Wet-nosed primates

• Dry-nosed primates

New world monkeys

arboreal, many have long prehensile tail

Old world monkeys

Some are arboreal, others are terrestrial; none have prehensile tails

• Asian apes

• African apes

Asian apes

gibbons and orangutans

African apes

gorillas, chimpanzees, and humans

hominin

lineage gave rise to the genus Homo