Invertebrates #19

Flagellum

• the motor appendage of motile cells

• its location defines if the organism is a Fungi or an Animal

Metazoa

• Animals

• evolved 1 bill yrs ago

• characteristics:

  • multicellular heterotrophs

  • cell that lack a cell wall, and are held together with collagen

  • embryonic development includes a blastula stage

    • many of the major evolutionary steps in animals are defined by embryology

Embryology

• the study of early organismal development

  • process of an organism growing from a zygote to a fetus

Blastula

• the stage through which all animal embryos develop

  • embryo forms a circular form that is hollow on the inside

Cambrian Period

• when all extant animal phyla evolved

• when animal diversity exploded (cambrian explosion)

• 540 mill yrs ago

• predominantly marine animals

• animals began to venture onto land

Ordovician Period

• arthropods now completely living on land

  • Arachnids, Myriapods, & Hexapods independently became land-dwelling around the same time as plants

• 460 mill yrs ago

Tetrapod

• dont make it onto land until the Devonian period (after the Ordovician Period and the Cambrian period)

Denonvian Period

• 360 mill yrs ago

• when tetrapods get to land

Porifera

• sponges

• sessile animals that lack tissues

  • cells are differentiated into different roles, but they do not work together for a specific function

  • suspension feeders

  • primarily marine

Cnidaria

• Hydras, Corals, Jellyfish

• symmetrical (1 gastrovascular cavity - mouth & anus use same hole)

• have a top and bottom but not lateral differentiation

• Predatory:

  • use tentacles tipped with spear-like stinging cells to capture prey

• 2 Subhyla:

  • Medusozoa - jellyfish & hydra

  • Anthozoa - corals & anemones

Mollusca

• evolved eyes multiple times within the phylum

• major subgroups:

  • Bivalvia - clams, mussels, scallops, oysters

  • Gastropoda - snails, slugs

  • Cephalopoda - octopus, squid, nautilus

Annelida

• segmented worms

• 3 subgroups:

  • Polychaetes, Oligoshaetes, Hirudinea

• earthworms

  • decomposers

• leeches (hirudinea)

  • parasitic or predatory

Platyhelminthes

• flatworms

• free-living predators

• parasites

• lack circulatory and respiratory systems

• species important medically:

  • trematoda

  • cestoda (tapeworms)

Nematoda

• Roundworms

• found everywhere on earth

• Hugely important to humans, both as a research subject,

  as agricultural pests, and as insect pest-control

• diverse, thread-like worms found in almost every habitat, from soil and water to parasites in plants and animals

Arthropoda

• 5 groups:

  • Chelicerata

    • spiders, scorpions, ticks

    • marine, freshwater, and terrestrial

    • predators, parasites, and decomposers

    • 8 walking legs + 2 pairs of feeding limbs

  • Myriapoda

    • millipedes - predators & 1 pair of legs per body segment

    • centipedes - decomposers & 2 pairs of legs per body segment

    • terrestrial

  • Crustacea

    • crabs, lobster, shrinp

    • marine, freshwater, and terrestrial

  • Insects

    • 3 body segments: head, thorax, abdomen

    • 3 pairs of legs & 2 pairs of wings

    • terrestrial & freshwater

    • NO MARINE bc their respiratory systems requires oxygen/air, and their exoskeletons (hardened with oxygen) aren't suited for saltwater

Echinodermata

• starfish, sea urchins, sand dollars, sea cucumbers

• strictly marine

• adults are 5-sided (pentaradial)

• larvae are bilateral (2 sided)

• have a unique water vascular system that powers their tube feet

Chordata

an animal phylum containing all vertebrates (like humans, fish, birds) and two invertebrate groups (tunicates/sea squirts & lancelets)

Bilateria

• Bilateral symmetry

• most animals

• have a top and bottom, a front and back, and a left and right

Gastrulation

• a process when the embryo starts to form a pouch

  • 3 layers of cells form in the embryo which get locked into a developmental pathway for tissues

Germ Layers

• 3 layers in embryonic development

• determine the developmental fate of tissues

Endoderm

• innermost layer (yellow) of the embryo

• will go on to become:

  • digestive system (liver, pancreas, bladder)

  • Lungs

  • Thyroid & parathyroid

Mesoderm

• middle layer (blue) of the embryo

• will go on to become:

  • muscles (cardiac, skeletal etc.)

  • bone, cartilage, and connective tissues

  • fat tissues

  • circulatory system

  • lymphatic system

  • dentine of teeth

  • spleen

  • genitals & reproductive tissue

Ectoderm

• outermost layer (brown) of the embryo

• will go on to become:

  • the external surface of the body (skin, hair, etc.)

  • the Nervous system (nerves, brain, spinal cord)

Blastopore

• the depression/pouch formed in gastrulation

Protostome

• Blastopore becomes the mouth of the organism

• & a second opening develops to become the anus

• 2 major groups:

  • Lophotrochozoa

  • Ecdysozoa

Deuterostome

• Blastopore becomes the anus of the organism

• & a second opening develops to become the mouth

Ecdysozoa

• a type of Protostomes

• have a tough cuticle that they shed in order to grow

• most diverse group of organisms on the planet