Diversity of Animal Reproduction and Evolutionary Traits

Viviparous

Embryo develops inside the mother, nourished directly by her, born alive.

Ovoviviparous

Embryo develops in an egg inside the mother; nourished by yolk, hatches internally or right before birth.

Oviparous

Lays eggs outside; embryo nourished by yolk.

Tetrapods

Vertebrates with four limbs (or limb-like structures), evolved from lobe-finned fishes.

Amniotes

Tetrapods that have an amniotic egg adapted for terrestrial life.

Amnion

Cushions and protects the embryo in fluid.

Chorion

Gas exchange.

Yolk sac

Nutrients.

Allantois

Waste storage and gas exchange.

Cambrian Explosion

Sudden appearance of most major animal phyla about 541 million years ago.

Chordates

Bilaterians in the deuterostomia clade, includes vertebrates and some invertebrates.

Notochord

Flexible support rod found in all chordates at some point.

Dorsal hollow nerve cord

Becomes spinal cord in chordates.

Pharyngeal slits/clefts

Gills or jaw/ear structures in chordates.

Post-anal tail

Extends beyond anus in chordates.

Mammal Traits

Hair/fur, mammary glands (milk), endothermic, 4-chambered heart.

Swim Bladder

Controls buoyancy with gas-filled sac in bony fish.

Fish Breathing

Use gills: Water flows over gill membranes → oxygen in, CO₂ out.

Mammal Breathing

Use lungs, not gills; air pulled in by diaphragm, gas exchange in alveoli.

Sharks

Cartilaginous fish (Class Chondrichthyes) with gills, no swim bladder; rely on liver oil + movement for buoyancy.

Book Lungs

Stacked, plate-like structures for gas exchange in air found in arachnids.

Arthropods

Exoskeleton (chitin), segmented bodies, jointed appendages

Open circulatory system

Hemolymph

Chelicerates

Sea spiders, horseshoe crabs, arachnids

Chelicerae

Feeding appendages

Pedipalps

Sensing, feeding, defense, reproduction

Cladograms

Diagrams showing evolutionary relationships via shared traits

Nodes

Common ancestors

Derived Characters of Vertebrates

Multiple sets of Hox genes (more than in lancelets/tunicates)

Neural crest cells

Form skull bones, teeth, nerves, sensory capsules

Filter Feeders

Filter particles from water

Cnidarians

Diploblastic, radially symmetrical

Polyp

Stationary, mouth on top

Medusa

Free-swimming, mouth underneath

Gastrovascular cavity

Digestive + hydrostatic skeleton

Reptiles

Waterproof scales with keratin

Shelled eggs

Internal fertilization

Endothermic

Heat from metabolism (birds, mammals)

Ectothermic

Body temp from environment (reptiles, amphibians)

Birds

Archosaurs; evolved for flight

Primates

Grasping hands/feet, flat nails, fingerprints

Humans

Upright, bipedal

Paleontology

Paleoanthropology = study of human origins via fossil record

Invertebrates

No backbone

Porifera

Simple body with pores

Lophotrochozoans

Identified by DNA

Flatworms

Live in moist/aquatic environments

Ecdysozoans

Animals that molt external cuticle (ecdysis)

Nematodes

Cylindrical, tapered at ends, tough cuticle

Myriapods

Terrestrial arthropods with many segments