Wednesday, February 22, 2012

February 22, 2012

To start things off in class today, we turned in UP pgs. 35-36 and we got UP pg 37 stamped.
The rest of class we finished up the animal notes. Here they are:

The Evolution of Multicellularity (We might of done this before but I can't remember exactly, so I will put them in just in case)
  • Animals probably evolved from a colonial, flagellated protist that lived in Precambrian seas.
  • By the late Precambrian, animals were already diverse.
  • At the beginning of the Cambrian period, animal diversity exploded.
  • Over about 10 million years ago, all the major animal body plans existing today evolved.
Early Animals and the Cambrian Explosion
  • In the last half-billion years, animal evolution has mainly generated new variations of old "Designs" that originated in the Cambrian Seas
  • This "explosion of diversity" in the Cambrian period marked the fossil record as the beginning of the Paleozoic era.
  • The "explosion" could be due to increasingly complex predator-prey relationships that led to diverse adaptations for feeding, motility, and protection. (ex: shells or hard exoskeleton evolved vs. earlier soft-bodies.)
  • Or, the explosion could be due to variation in how and when, and where genes that control the development of animal form are exposed. (ex: placement of body parts in embryos can produce major differences int he phyla)
Animal Phylogeny
  • To reconstruct the evolutionary history of animal phyla, researchers must depend on clues from comparative anatomy and embryology
  • This diagram represents one set of hypotheses about evolutionary relationships among nine major animal phyla.
Body Symmetry
  • Radial symmetry--animals that are arranged around a central axis. A single cut through the middle of the organism in any direction should produce two equal halves (kind of like a pizza)
  • Bilateral symmetry--A single longitudinal cut only in one direction will produce two equal halves.
Body Cavities
  • A fluid filled space separating the digestive tract from the outer body wall. (Body cavity=coelom or gut)
  • Its fluid cushions the suspended organs to prevent internal injury.
  • It enables internal organs to grow and move independently of the outer body wall; makes exercise not harmful to internal organs.
  • In soft-bodied animals, it functions as a hydrostatic skeleton against which muscles can work (ex: for burrowing)
  • Ex: Flatworms lack a body cavity=acoelomate
  • Ex: Roundworms have a body cavity partially lined by mesoderm (middle layer tissue)=pseudocoelomate
  • Ex: Earthworms have a body cavity completely lined by mesoderm=coelomate
Details of Embryonic Development
  • Of the animals with a true coelom, there are 2 branches:
  • Branch 1: mollusks, annelids, arthropods: mouth develops first in embryo=Protosomes
  • Branch 2: echinoderms and chordates: anus develops first in embryo=Deuterostomes
Animalia Kingdom- 8 Major Invertebrate Phyla:
  1. Porifera
  2. Cnidaria
  3. Platyhelminthes
  4. Nematoda
  5. Mollusca
  6. Annelida
  7. Arthropoda
  8. Echinodermata
  • Invertebrates, animals w/o backbones, represent more than 95% animal kingdom!!
1. Phylum Porifera--Sponges
  • Sponges are sessile (non-moving)
  • Sponges are the simplest animals, probably evolved very early from colonial protists.
  • Range in height from about 1 cm to 2 meters
  • Have no nerves or muscles (This explains why SpongeBob is so weak ;D), and consist of about 9,000 species
  • About 100 species lives in fresh water and the rest are marine.
  • The body of a sponge resembles a sac perforated with holes.
Sponges Feeding Method:
  • Most sponges feed by collecting bacteria from the water which streams through their porous bodies (filter feeding)
  • Flagellated cells called choanocytes trap bacteria in mucus and then engulf the food by phagocytosis
  • Cells called amoebocytes pick up food from the choanocytes, digest it, and carry nutrients to other cells
2. Phylum Cnidaria--Jellyfish, Sea Anemones, Coral, and Hydras
  • Cnidarians show radial symmetry.
  • Are carnivores, with cnidocytes (stinging cells) on their tentacles.
  • Consist of more than 10,000 mostly marine species
  • Have a body plann that is a sac with a central digestive compartment, the gastrovascular cavity. This cavity functions as a mouth and an anus.
  • Two body forms: the sessile polyp attaches to a substrate, and the free-floating medusa.
3. Phylum Platyhelminthes--Flat Worms--Tapeworms, Flukes, and Planaria
  • Flatworms are the simplest bilateral animals.
  • Range from about i mm to 20 m in length.
  • Live in marine, freshwater, and damp terrestrial habitats.
  • Include many parasitic species including flukes and tapeworms
  • Tapeworms have a ribbon-like body which can be up to 20 m long in humans
  • Lack a digestive tract, so they absorb partially digested food from the intestines of their host.
  • Humans can become infected with tapeworms by eating undercooked food.
4. Phylum Nematoda-Round Worms
  • Roundworms get their common name from the cylindrical bodies tapered at both ends.
  • Roundworms are among the most diverse and widespread animals.
  • Roundworms consist of about 90,000 known species (10x more actually exist!)
  • Range in length form 1mm to 1m.
  • Live in most aquatic habitats , in wet soil, and as parasites in the body fluids and tissues of plants and animals
  • Exhibit a complete digestive tract with a mouth and anus
  • Have a body cavity: pseudocoelom
  • Humans host at least 50 parasitic species including pinworms, hookworms, and the parasite which causes trichinosis
5. Phylum Annelida--Segmented Worms--Earthworms, Polychaetes, and Leeches
  • Annelids are worms with body segmentation, the division of the body along its length into a series of repeated parts.
  • Annelids consist of about 15,000 species
  • Range in length from 1mm to 3m long
  • Live int he sea, most freshwater habitats, and damp soil
  • The three major classes of annelids are stated in the title.
  • Farmers value the earthworm because they eat their way through the soil, extracting nutrients, tilling the soil, and producing nutrients which improve the texture of the soil
  • Polychaetes are marine; crawl or burrow in the seafloor
  • Polychaetes have segmented appendages and hard bristles that help the worm move. The appendages also increase the animals surface are for gas exchange and elimination of metabolic wastes
  • Leeches include medicine, until the 20th century for blood-letting.
  • Leeches are currently used as a source or anticoagulant and to help relieve swelling in reattached fingers and toes
6. Phylum Mollusca-Snails, Slugs, Clams, Octopuses, and Squid
  • Mollusks are soft-bodied animals
  • Are usually protected by a hard shell (Although slugs, squids, and octopuses have either reduced shells, most of which are internal or none at all.)
  • Often feed by using a straplike rasping organ called a radula to scrape up food.
  • Consist of about 150,000 species that are primarily marine, although some inhabit fresh water (snails, clams) and some live on land (snails, slugs)
  • All Mollusks have a similar body plan with three main parts: a muscular foot, usually used for movement, a visceral mass containing most of the internal organs, and a fold of tissue called the mantle that drapes over the visceral mass, and secretes the shell if one is present.
  • There are three major types of mollusks:
  • Gastropods which include snails and slugs.
  • Bivalves include clams, oysters, and mussels
  • Cephalopods which include squids and octopuses
7. Phylum Arthropoda--Crustaceans, Millipedes, Centipedes, and Insects
  • Arthropods are named for their jointed appendages
  • Number more then a billion billion (1,000,000,000,000,000,000) living individuals
  • Include more than 1 billion identified species (two out of three) and are represented in nearly all habitats of the biosphere
  • Arthropods are the most successful of all animal phyla as far as species diversity, distribution, and sheer numbers
  • Arthropods are the most segmented animals with appendages that have become specialized for a great variety of functios
  • Walking
  • Feeding
  • Sensory reception
  • Copulation
  • Defense
  • The body of an arthropod covered by an exoskeleton
  • Must occasionally shed it and secrete a larger one-molting
  • Temporarily vulnerable to predators
4 Classes of Arthropods
  • Arachnids: include scorpions, spiders, ticks, and mites
  • Crustaceans: include crabs, lobsters, crayfish, shrimps, and barnacles
  • Millipedes: eat decaying plant matter, have 2 pairs of short legs per body segments and Centipedes: paralyze prey (cockroaches & flies) and have one pair of long legs per body segment
  • Insects: including bees, grasshoppers, ants, termites, and cockroaches. Outnumber all other forms of life combined
8. Phylum Echinodermata--Spiny Skin--Starfish, Sand Dollars, & Sea Cucumbers
  • Echinoderms are named for their spiny skin
  • All echinoderms are marine
  • Most are sessile or slow moving
  • Lack body segments
  • Have an endoskeleton constructed from hard plates just beneath the skin.
  • Have a water-vascular system, a network of water filled canals that circulate water throughout the echinoderm's body, facilitating gas exchange and waste disposal
  • Have tube feet connected to the water-vascular system for movement
  • Larvae form=bilateral symmetry
  • Adult form=radial symmetry
  • Share an evolutionary branch with chordates

That is all for the notes!

HW: Study Animal Notes, Nature due March 2, isopod research (if you want to), earthworm lab tomorrow

Have a good evening and the next scribe is Jack


  1. Sorry for some of the random changes of font size, Blogger was acting strange

  2. Your post was really good! I like how you put all of the notes into your post. A few suggestions are: maybe you could bold or underline the words we need to know, and, also, maybe you could explain what those words mean. Finally, you might want to make the picture a bit bigger. Other than that, though, it was a really good post!

  3. I agree with everything that Kiran said. Plus it might have helped if you discussed some of the ideas outside of notes that we discussed in class. But overall really great post!