Animals: The Invertebrates Chapter 26
Overview of The Animal Kingdom
- Diversity in Body Plans
- A. Two types
- 1. Vertebrates (Backbone)
- 2. Invertebrates (No Backbone)
- Body Symmetry and Cephalization
- A. Two types of Symmetry
- 1. Radial (Bike wheel)Fig. 26.2
- 2. Bilateral (Halves)Fig.26.2
- Most Animals Who Have Bilateral Symmetry: Anterior End (Head)
- B. Posterior End (Butt)
- This Evolved after forward crawling creatures
- Cephalization: Evolutionary Process where nerves and sensory structures evolved in the
head.
- Type of Gut (Region where food is digested &Absorbed) A. Saclike Gut (One Opening)
- B. Tubelike Gut (mouth & Anus)
- Body Cavities (Separate the Gut From Body Wall)
- A. Example
- 1. Coelom (Cintains distinctive lining called periotoneum)
- Segmentation(Series of Body units, may be similar or dissimilar)
- A. Example of Organism
- 1. Earth Worm
- 2. Insects (Head, thorax and abdomen)-
The Evolutionary Road Map
- Animals arose from protisanlike ancestors before Cambrian Era
- 560 million years ago all phylums were established
The One Placozoan
- Placozoan (
A soft bodied marine animal that is 3mm long)
- Trichoplax adhaerens (3mm short bodied marine animal found gliding acrossed anaqium
tank)
A. 2-layer
- B. no symmetry
- C. no organs
- D. breaks down food with enzymes
- E. Most simple Organism
Porifera
(Sponges)
- Sponges ( Invertebrate, no symmetry, no organs, and gets food throw flagellated collar
cells)
- Size
- A. Finger Nail to Chair sized
- More complex cell layers than Trichoplax
- Feed by filtering water
- Amoebocytes is where digestion and distribution of nutrients occur
- Spiccules are skeletal needles made of CaCO3 or SiO2
- Cannot form tissue because it is not organized enough
Cnidarians
- Def- radial, tentacled animals and most live in the sea.
- Over 11,00 species, fewer 50 live in fresh water
- Members of phylums (jellyfish, anemones, & hydra)
- Produce nematocysts (toxin ladden treads used to capture prey and fend off predators)
- Cnidarian Body Parts
- Two Common Body Forms, both form around a saclike gut.
- 1.Medusa look like an upside down saucer. All float in water, mouth is in middle of the
bottom of the saucer. Have oral arms.
- Gut is like a permanent food processing chamber, has a complex lining with glandular
cells that secrete digestive enzymes.
- 2. Polyp (tube like), Tentacle fringed mouth at one end and the other is attached to a
substrate.
- These organisms are like moving guts as its trichoplax drapes over the ground digesting
mounds of food.
- Epithelial tissue- found in all animals more complex than a sponge. Examples:
gatrodermis and the epidermis
- Cnidarians have a simple nervous system call a nerve net that responses to stimuli
- It is made up of nerve cell that run through the epithal tissue
- Along with sensory and contractile cells movement and shape changes are controlled
- Between epidermis and gastrodermis lays a secreted material called mesoglea
- This gives jellyfish heir buoyancy and serve as a deformable skeleton
- Not abundant in most polyps, who use their guts to propel them
- Hydrostatic skeleton-
fluid-filled cavity or cell mass, most polyps have them
Some Colonial Cnidarians
- Colonial anthozoans show variation of a basic body plan
- Examples: Corals are made up of interconnected polyps that secrete their own calcium
reinforced skeletons. They serve as the building material for reefs.
- Cniderian Life Cycles
- Most Cniderians have a polypstage or a medesa stage
- Medesa- sexual form
Comb Jellies
Phylum Ctenophera
- Marine predators that show radial symmetry
- Has eight comblike structures, made of thick, fused cilia
- All comb move together to propel it forward
- Some have feeding nets (two tentacles that branch out)
- Dont produce nematocysts, but can store it from jelly fish it has eaten
- Evolutionary gave rise to muscles and organs in the circulatory, excretory and
reproductive systems
- Resemble mesoderms
Flat Worms
Phylum Platyhelminthes
- 15,000 known species, are turbellarians, flukes and tape worms
- Have saclike gut and food usually enter through the pharynx
- Most have flat bodies
- Are bilateral and cephalized unlike sponges and Cniderians
- Simplest animals with organs, that are formed by different tissues and are organized
inspecific proportion and pattern
- Also have organ systems, two or more organs interacting to do one task
- Turbelians
- Live in the seas and fresh water
- Carnivores that eat small animals of suck from dead ones
- Herbivorous types eat diatoms
- Bodyfluid regulated by a planarian organ system
- Reproduce asexually by fussion
- Each worm is a homophrodite, contain both gonads used in sexual reproduction
- Flukes
- Parasites, live in vertebrates guts, liver, lungs, bladder, and blood vessels
- Have many life cycles
- Have a sexual and asexual phase in two different host
- Definitive host is where it reaches sexual maturity
- intermediate host is where they develop in laral stage and become encysted
- Tapeworms
- Parasites in the intestines, not no gut because it is surrounded by predigested food
- Attaches to intestinal wall by a scolex (hook and sucker)
- Behind the scolex, proglottiod form by budding
- proglottoids are homophroditic
- Older proglottooids store eggs
- Eggs leave the host through feces
- Then the eggs are carried by an intermediate host
- Tapeworms resemble planlas of Cniderians.
- Some think bilateral animals evolved from planula ancestors
Roundworms
- Live in the snowfield, deserts and hot springs
- Thousands can be found in a cup full of dirt
- Parasitize plants and animals, 30 species parasitize humans
- Body plan- bilateral, cylindrical body, and tapered at both ends
- Have cuticle- tough flexible body covering
- Simplest animals with a digestion system
- Cause trichinosis in uncooked meats
Ribbonworm
- Predators in marine habitat
- Close relatives to flatworms
- Unlike flatworms they have a complete gut and circulatory system and are not
hermaphrodites
- Have a proboscis (tubelike) to capture prey by injecting venom
Rotifera
(Rotifers)
- One millimeter long, but multicelluar and have a complex digestive tract
- Abundant in plankton
- They eat bacteria and single celled algae
- Most have crown of cilia, help it swim and waft food in its mouth
- Have salivary glands a jawed pharynx, an esophagus, digestive gland, a stomach and an
intestine and anus
- Protonephridia remove excess water
- Head is a cluster of nerves, some species have eyes
- Some have two toes that allow it to attach to substrate while feeding
- Evolutionary side step, show complexity of animals with a false colon
A
Major Divergence
- After Cambrian to distinct evolutionary lineages formed
- 1. Protostomes (Mollusks, annelids and arthropods)
- 2. Deuterostomes (Echinoderms and chordates)
- Differences appeared in embro development
- Deuterostomes embryos divide parallel and perpendicular (radial cleavage)
- The first hole in embryo becomes the anus
- Colon forms in an out pouching of the gut
- Protostomes embryos divide in oblique wedges (spiral cleavage)
- First hole is the mouth
- Colon forms on side of the gut
Mullusca
(Mollusks)
- Include snails, bivalves, octopus, and squid. Make up the second largest phylum besides
arthropods
- Most mollusks have shells and have coelomate bodies with a complete digestive tract
- Bivalves are clams and muscles (2 part shells)
- Squids have a reduce shell and it is internal
- Octopus have no shell and a highly developed nervous system along with a large complex
brain
Annelida
(segmented worms)
- Leeches, earthworms, and polychaete worms are examples of annelida. All are bilateral
and have true colons
- Leeches can be predators of small animals or blood-sucking parasites. They also have two
suckers at opposite ends of their body. They are use for attachment and movement
- Polychaete worms are found in marine environments. Some are tube builders others crawl,
burrow or swim
- Dine on small invertebrates and algae
- Sea nymphs are crawling polychaete
Arthropods
- Examples are spiders, insects, crustaceans, and other related organisms
- Have joint appendages, a well developed nervous system, specialization of body segments
and an exoskeleton made of chitin.
- Two life cycles
- 1. nymphs- small version of the adults
- Larvae is another form some arthropods are born as. (maggots)
- 2. metamorphosis- they inclose themselves in a pupa and change into adults who can
disperse gamete and reproduce
- Chelicerates have only one surviving marine animal is the horseshoe crab
- On land they are ticks, spiders, mites, and scorpions to name a few
- Spiders and Scorpions pump digestive enzymes into the guts of their prey. Some are also
venomous to humans
- Ticks can transmit lyme disease and Rocky Mountain Spotted Fever
- Spider and Scorpions have book lungs
- Crustaceans include crabs lobsters, shimp and mud puppies
- Shell of barnacles is calcified to protect themselves for predator s when are attach to
an object
- Eat tiny photosynthetic plankton
- Insects have a head, thorax and abdomen
- Also have a sensory antennae and paired mouth, use for chew biting or puncturing
Echinodermata
(echinoderm)
- Examples are sea stars, sea urchins, and sand dollars
- All are coelomate Deuterostomes and have a complex digestive tract
- Adult echinoderms are radial symmetric
- Larvae show bilateral symmetry
- Ancestors are believed to be bilateral
- Starfish have tubefeet they are used for walking, burrowing clinging to rocks or
grabbing clams or snails for a meal (Some sallow prey whole)
- Adults have no brain, but nervous system allow it to react to stimuli
Chordata
- are vertebrates
- All members show the following 4 features some time during their
life
- A notchord
- Dorsal hollow nerve cord
- Pharyngeal gill slits
- muscular tail