Presentation is loading. Please wait.

Presentation is loading. Please wait.

Ch. 35 – Mollusks & Annelids  Mollusks and annelids are grouped together because they were the 1 st organisms to develop a true coelom. – This suggests.

Similar presentations


Presentation on theme: "Ch. 35 – Mollusks & Annelids  Mollusks and annelids are grouped together because they were the 1 st organisms to develop a true coelom. – This suggests."— Presentation transcript:

1

2 Ch. 35 – Mollusks & Annelids  Mollusks and annelids are grouped together because they were the 1 st organisms to develop a true coelom. – This suggests that these two groups of animals may have evolved from a common ancestor.  The coelom provides space for a circulatory system to function without interference from other organs. They can contract muscles without hindering the movement of food through the gut.  Both have the same 1 st stage in larva development which is called a trochophore.

3  Phylum: Mollusca – Snails, clams, octopuses, oysters, squids – Video Video – Mollusk is Latin for “soft” – Most have a shell to protect them and are soft inside the shell. – Develop from a trochophore larva which is a free-swimmer. Cilia helps them swim.

4 Mollusk Characteristics Most are filter feeders (100,000 + species).  True coelom  3 main body parts: muscular foot, head, & visceral mass.  Circulation, respiration, digestion, excretion, reproduction, nerve impulses.

5 Body Arrangement  1. Muscular foot – used for locomotion.  2. Head – has a cerebral ganglia & mouth.  3. Visceral Mass – contains many organs.  4. Mantle – protects the visceral mass. It secretes a shell in most mollusks.  Shell is made of calcium carbonate. – How does the mollusk breathe with a shell?  Gills are used for respiration.

6 4 Classes of Mollusks  1. Class: Gastropoda – snails & slugs – Largest class of mollusks – Gastropoda means “stomach foot” – Slugs have no shell – Snails have a single shell – The body mass can turn 180 degrees this is called torsion

7 Snails  Gills for respiration  Survive in moist environments  Open Circulatory System  Hemocoel – open body cavity for blood circulation.  Radula – a saw-like tongue made of chitin.  Use foot to move with wavelike contractions.

8

9

10

11  2. Class: Polyplacophora – chitons – Polyplacophora means “many plates” – Their shells consist of 8 overlapping plates.

12

13  3. Class: Cephalopoda – squids & octopus – Cephalopod means “head foot” – They have tentacles and a sharp radula to kill prey. – Closed Circulatory System – blood circulates in vessels.

14 Squids  Largest invertebrate  Giant squid are up to 3 meters long.  Squid have the ability to squirt ink.  They have the ability to change colors. – Video Video  Squids have separate sexes  Squid & octopus use jet propulsion to move.  Video Video

15  4. Class: Bivalvia – clams & oysters – Bivalvia means “two halves” – They are sessile & filter food from the water. – They have a muscular foot – They don’t have a distinct head

16 – If a piece of sand grain gets into its shell the mantle coats the sand grain with secretion to form a pearl.  Clams – Filter feeders – Have incurrent siphon for water to enter and an excurrent siphon for water to exit. – Have separate sexes like most mollusks.

17  Body parts of a clam  Dissection  Clam Video Clam Video

18 Annelida  Phylum: Annelida – earthworms & leeches – Video Video  Characteristics – Body is divided into segments  metamerism – True coelom – Well developed organ system – Most have setae  external bristles – Some have parapodia  fleshy appendages – Video Video

19 3 Classes  1. Class: Polychaeta – marine annelids – Have setae & parapodia – Have antannae (the only class) – Some are free-swimmers

20  2. Class: Hirudinea – leeches – No setae – Live in calm bodies of freshwater – Sucker at each end – Smallest class of annelids Video

21  3. Class: Oligochaeta – earthworm – Have setae – used to anchor their segments to soil as they burrow through the soil. – Contract and expand in order to move Video

22 Main Systems of an Earthworm  Digestive system  Worms feed on organic matter in the soil.  Worms loosen & aerate soil.  Travels in the following pathway: prostomium (lip)  mouth  pharynx  esophagus  crop  gizzard  intestine  Crop  stores food, gizzard  grinds food

23  Circulatory system  Closed system – have blood vessels  Aortic arches – serve as a heart – 5 pair  Have a dorsal & ventral blood vessel

24  Respiratory & Excretory systems  No lungs or gill  directly through the skin  When it rains why do worms migrate to the surface?  Nephridia is the excretory organ that eliminates waste.

25  Reproductive system  Hermaphrodites  However, they can’t fertilize their own eggs.  They attach at the clitellum & secrete a mucus layer in which the egg & sperm are placed in.

26  Sperm is injected from the seminal receptacle.  Eggs are released from the oviducts.


Download ppt "Ch. 35 – Mollusks & Annelids  Mollusks and annelids are grouped together because they were the 1 st organisms to develop a true coelom. – This suggests."

Similar presentations


Ads by Google