ch 27 Flashcards
A series of key evolutionary adaptations led to
the major animal phyla.
Sponges are the simplest kind of animals. They lack
tissues and body symmetry and live attached to the sea floor, where they filter food particles from the water.
Cnidarians have
tissues, tentacles, and radial symmetry. They digest their food extracellularly, in a digestive cavity.
Flatworms lack
a body cavity and have bilateral symmetry, simple organs, and a digestive tract with a single opening.
Roundworms have
a body cavity (pseudocoelom), muscle tissue, and a gut that is open at two ends.
Mollusks, and all animal phyla that evolved after this group, have
a coelom, which enabled the formation of advanced body systems.
Segmented worms have evolved
complex body systems, including a nervous system and a circulatory system.
Arthropods, such as spiders, scorpions, crabs, and lobsters, are characterized by
jointed appendages and an exoskeleton.
Echinoderms and chordates have similar
patterns of development and very likely share a common ancestor
Echinoderms have
an endoskeleton, radial symmetry, a simple nervous system, and a water vascular system.
All chordates develop a
hollow dorsal nerve cord, notochord, and pharyngeal slits sometime during their lifetime. Vertebrates are chordates that have a cartilaginous or bony endoskeleton that includes a vertebral column.
Animal evolutionary stages:
multicellularity,
tissues,
bilateral symmetry (body parts growing around central point or axis),
body cavity/pseudocoelum(fluid filled cavity BETWEEN mesoderm and endoderm) and one way/two opening gut,
coelom (fluid filled cavity ENTIRELY within mesoderm),
segmentation,
jointed appendages and exoskeleton or endoskeleton,
deuterostomic development,
notochord.
Animals evolved from
a heterotrophic protist
Most animals live where
in water.
Animals are
heterotrophs – most ingest food b4 digesting.
99% of animals are
invertebrates (sans backbone)
35 phyla in
the animal kingdom, most in sea less in fresh water and much less on land.
3 phyla dominate land life:
Arthropoda (spiders, insects & crustaceans), Mollusca (snails) and Chordata (most backboned).
Animals cells lack
cell wall – flexible
Cells of animals (except sponges) organized into
structural & functional units called tissues.
Ability to move by contraction of muscle cells is
outstanding characteristic of animals (except sponges).
Most animals reproduce how
sexually with motile sperm and non-motile egg (both are the only haploid cells).
Sponges
simplest animals, no symmetry, most live in salt water, no tissues or organs, digest food by endocytosis, multicellular, do have key property of animal cells – able to recognize other body cells.
Internal cavity of sponges lined with
choanocytes (AKA collar cells) that have flagella that beat and draw water through sponge pores which filter for food.
All other animals have tissues and symmetry and
are eumetazoans “true animals”.
3 tissues of eumetazoans:
Ectoderm
Mesoderm
Endoderm
Ectoderm
outer layer develops epidermis (skin) and nervous system
Mesoderm
middle layer develops skeleton and muscles
Endoderm
inner layer develops digestive system and digestive organs
Cnidaria and Ctenophora
two primitive eumetazoan phyla
Cnidaria and Ctenophora exhibit
radial symmetry, specialized tissue, extracelluar digestion of food in a digestion cavity
Cnidaria include
jellyfish, anemone, hydra and coral – all carnivores.
Stinging cells called cnidocytes have
small barbed harpoons called nematocysts which spears prey. Two forms: free floating medusae and attached polyps. Some life cycles go through both phases.
cnidocytes
Stinging cells