Animal Biodiversity

specifies the identity of a body part or segment during embryonic development.

ex. instruct the 3 thoracic segments (T1, T2, T3) each to develop a set of legs and the 2nd thoracic segment (T2) to develop wings

Hox gene clusters have been identified in a wide variety of animals with bilateral symmetry

• sponges
• contain no tissues (Parazoa), but still has specialized cells
• still considered multicellular heterotrophic animals

• porocytes: pores
• choanocytes: contains flagella to create current, also phagocytose food
• amoebocyte: shuttle food particles through the mesophyl
• spongocoel: main cavity
• osculum: exit, where current goes out
• spicules: silica or calcium carbonate skeleton

all organisms that have tissue (will either be radial or bilateral)

• diploblastic
• necessary for slow or immobile organisms because they have a 360 degree response to their environment
• ancestral to bilateral symmetry
• Cnidarians all have radial symmetry.

• radial symmetry
• diploblastic (2 embryonic tissue types): epiderm & endoderm
• can be polyp or medusa
• special features: cnidocytes (stinging cells on tentacles) and nematocysts (capture prey)

• type of cnidarian
• polyp dominant (sessile) but also has a medusa stage (mobile)
• fire coral
• portuguese man-o-war (colony of polyp)

• type of cnidarian
• true jellyfish
• exclusively medusa form

• type of cnidarian
• boxy jellyfish with extremely potent venom and highly developed eyes
• exclusively medusa form

• type of cnidarian
• include sea anemones & most corals
• strictly polyp form

• triploblastic (3 embryonic tissue types): endoderm, mesoderm, ectoderm
• coevolved with cephalization & movement
• includes protostomes & deuterostomes

• Blastopore develops into the mouth.
• spiral & determinate cleavage: Eary on, cells have a fixed destination so alteration to an embryo at an early stage is likely to be fatal.
• Mesoderm comes from solid masses of cells near the blastopore, which develop into the coelom (body cavity).
• includes mollusks, annelids, anthropods

• Blastopore develops into the anus
• indeterminate radial cleavage: Alteration to one cell early on is not likely to have an effect on the end form (totipotent)
• Folds of archenteron form coelom.
• includes echinoderms & chordates

protostomes that have a lophophore (crown of ciliated tentacles around the mouth) and a larva phase during development

• flat worms (Platyhelminthes)
• Bryozoa
• Annelids
• Mollusks

• triploblastic & bilateral
• acoelomate (no body cavity): reason they are flat

• Turbellaria: free living (does not live inside an organisms's body)
• Monogeneans: parasitic on fish
• Trematodes: parasitic flukes
• Cestoidea: parasitic tapeworms

pseudocoelomates (false body cavity): only partially lined by mesoderm

• eucoelomates (full body cavities): complete gut
• has a mantle for gas exchange, a muscular food, only real shells, gills to filter feed (secondary for gas exchange)
• radula is a tongue-like structure
• include gastropods, cephalopods, bivalve, & chitons

chiton (Polyplacophora)

• group of mollusks that include snails and slugs
• mostly hermaphrodites
• use radula to scrape algae off rocks

• group of mollusks that include squid and octopi
• "head foot"

• group of mollusks that include clams and oysters
• has 2 shells (valves)
• incurrent and excurrent siphons

• eucoelomates (full body cavities)
• segmentation
• cutaneous respiration
• has complex organ systems, mouth, esophagus

• Oligochaetes: earthworms
• Polychaetes: have parapodia (paired feet), live in oceans
• Hirudinea: leeches (parasitic)

• protostomes that shed or molt
• include nematodes & anthropods

• type of Ecdysozoan
• pseudocoelomate (false body cavity):
• has digestive & reproductive organs surrounded by a fluid-filled cavity

• group of Ecdysozoans that has jointed legs
• Hox genes important in segmented body plan giving rise to diverse appendages
• has an external skeleton made of chiton (polysaccharide)
• include chelicerates (spiders, scorpions, ticks), myriapods (centipedes & millipedes), crustaceans (lobsters, shrimp, crabs), and insects

• arthropods that include spiders, scorpions, and horse-shoe crabs
• only anthropod that lack antennae
• has a cephalothorax
• pincerlike claws called chelicerae

• arthropods that include centipedes & millipedes
• many pairs of legs

• arthropods that have branched legs
• has sensory antennae

• only arthropods to develop wings
• shed exoskeleton but cannot molt wings

• has 6 legs
• have a head, abdomen, and thorax

• group of deuterostomes that include sea stars, sea urchins, sand dollars, and sea cucumbers
• has a water vascular system for respiration & movement
• has tube feet that allow them to crawl, sense their environment, capture food, and breathe

• a pharynx with pharyngeal slits
• a dorsal nerve cord

ex. acorn worms

• cephalochordates
• urochordates (tunicates)
• vertebrates (craniates)

• notochord (stiff rod of collagen)
• dorsal, hollow nerve cord
• muscular, post-anal tail
• pharyngeal slits or clefts
• myotomes

• tunicates (sea squirts)
• has a pharynx with numerous slits
• Water and wastes are expelled through an anal siphon.
• has a larva stage with chordate characteristics that are lost in the adult stage

• chordates that lack a well-differentiated head & has no cranium or vertebrate
• Instead, it has elongated bodies with a notochord that extends the length of the body from "head to toe"

ex. lancelets (amphioxus)

• jawless vertebrates
• includes myxini (hagfish) and lampreys

Hagfish has knotting behavior.

• jawed fish
• includes chondrichthyes & osteichthyes

• cartilaginous fish
• has placoid scales (modified dermal scales)
• includes sharks and rays

• bony fish
• has dermal scales
• includes ray-finned fish and lobe-finned fish

• amphibians and all amniotes (reptiles, mammals, birds)
• Ancestors may have been lobe-finned fish

• desiccation-resistant shell
• can exchange gases while retaining water
• permit long development times
• allows organisms to be in dry terrestrial habitats

• do not have scales, absorb water directly through skin
• tetrapods but not amniotes

• scales made of alpha and beta keratin and formed from the epidermis
• Feathers of birds are modified epidermal scales that retain body heat.

• anapsids: no additional holes in the temporal region of the skull (tortoises)
• diapsids: 2 holes in the temporal region of the skull (crocodiles)

• hair (permits retention of body heat)
• mammary glands

• monotremes
• lay eggs
• don't have nipples. Instead, the young drink milk secreted from pores in the skin of the mother's belly

• marsupials
• doesn't have a placenta so uses pouch
• The young are born at an early stage of development.

• placental mammals
• Placenta enables the offspring to be larger and more quickly independent when born.