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