Annelids & Arthropods
Terms
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Phylum Annelida
1. when
2. # species
3. 3 classes + examples -
1. 570mya
2. 9000 species
3. -Class Polychaeta (clamworms)
-Oligochaeta (earthworms)
-Hirudinea (leeches) - When did Phylum Annelida first evolve?
- during the Cambrian (570 MYA)
- How many species does phylum Annelida have?
- 9000 species
- Name the 3 classes in Phylum Annelida and give an example
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1. Class Polychaeta (clamworms)
2. Class Oligochaeta (earthworms)
3. Class Hirudinea (leeches) -
Characteristics Of Annelida
Metamerism -
-divided into segments (or metameres)
-externally - grooves which encircle the body
-internally - membranes (or septa) are partitions -
Characteristics Of Annelida
Hydrostatic Skeleton of Coelomic Fluid - Coelomic fluid acts as hydrostatic skeleton against which the muscles act to change body shape
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Characteristics Of Annelida
Cuticle -
-on surface, have tough skin (or cuticle)
-hard bristles -
Characteristics Of Annelida
Straight Digestive Tract - running from mouth to anus
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Characteristics Of Annelida
Closed Circulatory System -
-well-developed circulatory System
-blood is confined to vessels -
Characteristics Of Annelida
Segmented Nervous System -
-has the brain (couple of big ganglia)
-two ventral nerve cords (pair of ganglia)
-(ganglia are clumps of nervous tissue) - Name the 6 charactereistics of Phylum Annelida
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1. Metamerism
2. Hydrostatic Skeleton of coelomic fluid
3. Cuticle
4. Straight digestive tract
5. Closed circulatory System
6. Segmented nervous system - Parapodia
- fleshy lobes for gas exchange; extend from body segments.
- Chaetae (Setae)
- bristles on the parapodia. These are used for locomotion.
- Pharynx
- first part of the digestive tract leading from the mouth
- Esophagus
- narrow tube carrying food from pharynx into the crop
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Stomach/Intestine
1. function
2. animals found on -
structure where digestion and absorption takes place. Found following the esophagus.
2. clamworm (class polychaeta), earthworm (class oligochaeta) - Ventral Nerve Cord
- transmits nerve impulses to and from "brain". It lies beneath digestive tract.
- Nephridia
- tiny kidney tubes used for excretion. One pair per segment.
- Gonochoristic
- both male and female worms, and reproduce sexually. Their gonads are not distinct organs but are masses of developing gametes. Most polychaetes are gonochoristic.
- Clitellum
- swollen glandular area that secretes a slimy material to form a cover for the eggs during repoduction
- Crop
- thin-walled storage chamber for food received from esophagus
- Gizzard
- muscular chamber that grinds the food; follows the crop
- Suprapharyngeal Ganglion
- a mass of nerve cells above the pharynx and connected by nerve chords and subpharygal ganglion below. Thus, the gut passes through the "brain".
- Pseudohearts
- five pairs of lateral blood vessels that are specialized to pump the blood.
- Hermaphroditic
- have both male and female organs. All olichaetes are hermaphroditic. The earthworm has 2 pairs of testes in segments 10 and 11 and one pair of ovaries in segment 13. sperm and eggs are released via tubes out the genital pores.
- Seminal Vesicles
- the sperm passes out of the male genital pore along the seminal groove to the clitellum and enters the other worm. This has to do wit mating in earthworms.
- Phylum Arthropoda
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-most likely evolves from polychaetes
-1,000,000 species
-have similarities: metamerism, placement of appendages, basic plan of the nervous system - name main subphylum and respective classes of Phylum Arthropoda
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1. Subphylum Trilobitomorpha (trilobites-extinct)
2.Subphylum Chelicerata
-Class Merostomata (horseshoe crabs)
-Class Eurypterida (sea scorpions)
-Class Arachnida (spiders, scorpions)
3. Subphylum Crustacea
-Class Malacostraca
4. Subphylum Uniramia
-Class Insecta (=Hexapoda) (grasshoppers, bees, fruit flies) - Jointed Appendages
- arthropods; adaptable to a variety of habitats.
- Regional Specialization
- in arthropods, groups of segments have fused together to form units called the head, thorax, and abdomen. Thus, different regions of the body have specialized for different functions.
- Chitinous Exoskeleton
- arthropods are covered by a tough, horny integument called chitin. THe exoskeleton is protective w/o sacrificing mobility.
- Open Circulatory system
- blood flows from a heart and arteries into blood spaces where it bathes the tissue directly before returning to the heart.
- Segmented Nervous System
- same for arthrops as annelids.
- Sexual Dimorphism
- arthropods often show pronounced sexual dimorphism. Males and females will have different body forms.
- Carapace
- hard shell that covers the exterior of the cephalothorax
- Antennae
- sensory organs for taste and touch; found dorsally at the anterior end of the cephalothorax.
- Chelipeds
- claws or pincers for feeding and fighting, underneath the carapace of the thorax; first pair of legs.
- Walking Legs
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-four pair of legs used for locomotion
-found underneath the carapace of the thorax - Swimmerets
- 5 pairs of appendages that aid in respiration and reproduction, found on the ventral side of the abdomen; sexually dimorphic; males' first pair is stiff and red; female swimmerrets are all identical
- cardiac Stomach
- structure w/ tiny calcified teeth used for grinding food; empties into the more posterior pyloric stomach.
- Pyloric Stomach
- digestive chamber where further digestion takes place; empties into the intestine
- Intestine
- structure where absorption takes place